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The development of blue/green/red tricolor upconversion (UC) phosphors under invisible light irradiation has attracted significant interest in emerging applications such as anti‐counterfeiting, three‐dimensional (3D) optical data storage, and solid‐state 3D displays. In this study, a series of LiYO2:RE3+,Yb3+ (RE = Tm, Ho, Eu) phosphors are successfully prepared via first precipitation process followed by calcination, and completely optimized for efficient tricolor UC luminescence with 980 nm laser excitation. Mechanisms involving two‐ or three‐photon absorption processes and low‐phonon‐energy‐suppressed multi‐phonon relaxation have been proposed for Ho3+(Eu3+)/Yb3+ and Tm3+/Yb3+ codoping, respectively. In addition, the RE3+ (Yb3+) concentration‐induced phase transition of the LiYO2 host is discussed for interesting possibilities in spectral regulation. Based on the broad color gamut achieved by the tricolor UC phosphor mixture, homochromatic and polychromatic metamerisms are experimentally fabricated via screen printing for high‐level anti‐counterfeiting and information security. Moreover, for a proof‐of‐concept demonstration, prototypes of 3D optical data storage and volumetric displays are constructed by embedding tricolor UC mixtures and their 3D printed patterns in polydimethylsiloxane. It is believed that the continuous exploration of tricolor UC under invisible light excitation for metamerism anti‐counterfeiting and 3D displays can promote the development of high‐level information security and advanced volumetric display technologies. [ABSTRACT FROM AUTHOR]

Tristimulus values and chromaticities, which are derived using the color matching functions (CMFs), are commonly used for color characterization, calibration, and specifications, with the stimuli having the same values believed to have the same color appearance (i.e., metameric match). Many studies, however, found that the stimuli having the same tristimulus values do not appear the same (known as metameric failure) due to the failure of CMFs in accurately characterizing the color matching mechanisms. Most past work investigated the performance of different CMFs through color matching experiments, with a smaller chromaticity or calculated color difference between the reference and test stimuli suggesting a better performance. Such differences, however, may not accurately characterize the performance of the CMFs, since the color spaces or chromaticity diagrams may not be uniform, in terms of the threshold of noticeable color difference. In this study, the human observers evaluated the perceived color difference between pairs of stimuli, which were calibrated to have the same tristimulus values calculated using the CIE 1931 2° CMFs, with two sizes of field of view (FOV). The results clearly suggested that the stimuli having the same tristimulus values may not always appear the same, which depended on the primaries and the FOV. More importantly, the results clearly suggested that the chromaticity differences from color matching experiments may overestimate the metameric failure, especially when the color differences were small. [ABSTRACT FROM AUTHOR]

PURPOSE. To evaluate the metameric disparities among monolithic zirconia materials with differing yttrium compositions across various lighting conditions. MATERIALS AND METHODS. Thirty-six square-shaped zirconia samples measuring 10 × 10 × 0.5 mm were prepared from monolithic zirconia materials with three different yttrium contents. A 0.2 mm thick layer of polymerized dualpolymerizable self-adhesive resin cement was created using a silicone mold with the same dimensions as the prepared zirconia specimens. To evaluate metamerism, color measurements were conducted using a spectrophotometer device on a neutral gray background in a color measurement cabinet that offers four different illumination environments. All samples underwent aging by subjecting them to 10000 thermal cycles using a thermal cycle tester. Following thermal aging, color measurements were taken once more, and the data were recorded using the CIE L*, a*, b* color system. Two-way ANOVA and Post-hoc Bonferroni tests were employed to analyze the data. RESULTS. It was observed that there was no statistical difference among the color measurements made in different illumination environments of the monolithic zirconia ceramics used to evaluate metamerism (P > .05). This observation remained consistent both before and after thermal aging. After thermal aging, the color of monolithic zirconia materials exhibited a tendency towards red and yellow hues, accompanied by a decrease in brightness levels. CONCLUSION. It can be stated that different illumination conditions did not affect the metamerism of monolithic zirconia materials, but there was a color change in monolithic zirconia materials after a thermal aging period equivalent to one year. [ABSTRACT FROM AUTHOR]

The pursuit of aesthetic excellence in dentistry, shaped by societal trends and digital advancements, highlights the critical role of precise shade matching in restorative procedures. Although conventional methods are prevalent, challenges such as shade guide variability and subjective interpretation necessitate a re-evaluation in the face of emerging non-proximity digital instruments. This systematic review employs PRISMA protocols and keyword-based search strategies spanning the Scopus®, PubMed.gov, and Web of ScienceTM databases, with the last updated search carried out in October 2023. The study aimed to synthesise literature that identified digital non-proximity recording instruments and associated colour spaces in dentistry and compare the clinical outcomes of digital systems with spectrophotometers and conventional visual methods. Utilising predefined criteria and resolving disagreements between two reviewers through Cohen's kappa calculator, the review assessed 85 articles, with 33 included in a PICO model for clinical comparisons. The results reveal that 42% of studies employed the CIELAB colour space. Despite the challenges in study quality, non-proximity digital instruments demonstrated more consistent clinical outcomes than visual methods, akin to spectrophotometers, emphasising their efficacy in controlled conditions. The review underscores the evolving landscape of dental shade matching, recognising technological advancements and advocating for methodological rigor in dental research. [ABSTRACT FROM AUTHOR]

Insect attraction to artificial light can potentially facilitate disease transmission by increasing contact between humans and vectors. Previous research has identified specific wavelength bands, such as yellow and red, that are unattractive to biting flies. However, narrow‐band, non‐white lights are unsuitable for home lighting use as their very poor color rendering is often considered aesthetically undesirable. The creation of a white light that is unattractive to insects has so far remained elusive. White light can be created by combining a number of narrow‐band light‐emitting diodes (LEDs). Through choice chamber experiments on Culex pipiens (Cx. pipiens) mosquitoes, we examine whether combining specific wavelength bands has an additive, subtractive or synergistic effect on insect attraction. We show that a white light created by combining narrow‐band red, green and blue (RGB) LEDs is less attractive to Cx. pipiens than a broad‐spectrum white light; and that a white light created by combining narrow‐band blue and yellow LEDs is more attractive than a broad‐spectrum white light. White light produced by RGB combinations could therefore serve as a safer and cheaper light in countries where phototactic vectors and vector‐borne disease are endemic. [ABSTRACT FROM AUTHOR]

In this article we explore some prospects and problems of the dispositional analysis of colors as a compromise between physicalism and eliminativism. For physicalism, colors can be identified with physical properties of objects, while for eliminativists such as Galileo, colors are mere names for sensations. Going through the ideas of Barry Stroud, David Hilbert and Joshua Gert, we think that the phenomenon of color constancy can be better understood from the idea that objective color is a disposition to produce apparent colors in varied circumstances. Finally, we point out the reason why the fact that common sense does not regard color as a disposition can be explained by a difference between dispositions to produce appearances and the more common dispositions of the physical world such as solubility and malleability. Unlike these, colors, as dispositions to produce appearances, have broad and everyday conditions of manifestation, with a small temporal gap between the existence of the conditions of manifestation and the manifestation itself. [ABSTRACT FROM AUTHOR]

The common ancestor of Ambulacraria was a mobile bilaterally symmetrical organism. Its body was subdivided into a preoral (proboscis) region, a perioral (collar) region with ciliated tentacles, and a trunk region with a metameric coelom and metameric gill slits. Like in other Bilateria, the preoral and tentacular regions of Ambulacraria are free of Hox gene expression, which begins in the area of the first pair of gill slits in compliance with the colinearity. The axial complex is a synapomorphy of the Ambulacraria clade. A bilaterally symmetrical ancestor of Echinodermata lay on its dorsal side, so its anus was shifted to the ventral side as in present-day echinoderm larvae. This stage of evolution corresponds to the Early Paleozoic bilaterally symmetrical forms, such as Protocinctus, Ctenocystis, and Ctenoimbricata. The common ancestor of echinoderms had a symmetrical tentacular apparatus consisting of five ciliated tentacles on each side of a collar. At the next stage, the ancestors of echinoderms lay on the right side that resulted in the reduction of the tentacles on the right side and the right hydrocoel. This evolution stage includes various Early Paleozoic forms (Cothurnocystis, Dendrocystoides, Syringocrinus, Castericystis, Coleicarpus, Rhenocystis, etc.). The next stage is related to the sedentary lifestyle. During this stage, the mouth and tentacles occupied an apical position, the anus has shifted up, and thus an intestinal loop was formed. The five primary tentacles of the left side of the ancestor of Ambulacraria predestined the formation of pentaradial symmetry of echinoderms. The primary tentacles remained only in Holothuroidea. The secondary ciliary grooves were formed between the primary tentacles. These grooves were accompanied by hydrocoelic canals, which gave rise to the water-vascular (ambulacral) system. The present-day echinoderms are characterized by several metameric rings formed by the derivatives of the left somatocoel. They derive from the coelomic segments of the left side of the trunk of the ambulacrarian ancestor and, thus, the echinoderms retain coelomic metamerism. The attachment of the crinoid larvae by the preoral lobe reflects the ancient method of locomotion of deuterostomes using the proboscis, but, in reality, the Pelmatozoa stalk is homologous to the Pterobranchia stalk, i.e., the posterior end of the body, because the right somatocoel grows into it. During metamorphosis, the internal coelomic complex of the larva is inverted by 180°. The significance of this inversion for the translocation of the anterior genes of the Hox cluster is discussed. The ancestors of Eleutherozoa began to crawl on the oral surface, which led to a shift of the anus to the aboral side. Thus, the ontogeny and phylogeny of echinoderms exhibits a change from bilateral symmetry to dissymmetry, and then the development of pentameric symmetry. [ABSTRACT FROM AUTHOR]

This paper has been written from the standpoint of the phylogenetic tetrad method which includes comparative anatomy, evolutionary developmental biology ("evo–devo"), paleontology, and molecular phylogenomics. The Bilateria consists of two sister groups such as Cnidaria and triploblastic Bilateria. Their common ancestor was a bilaterally symmetrical diploblastic organism with two circles of tentacles, labial and marginal, around a slit-like mouth. Anthozoa retains a primary bilateral symmetry. Medusozoa develops a secondary radial symmetry as a result of adaptation to a sedentary lifestyle. The common ancestor of the triploblastic Bilateria had a through gut formed by amphistomy, a coelom, segmentation, and metameric limbs. The marginal circle of tentacles gave rise to metameric limbs, the labial circle of tentacles gave rise to perioral ciliated tentacles, ventral ciliated sole (neurotroch), and telotroch. The homology of the ciliated tentacle apparatus in Trochozoa, Lophophorata, and Deuterostomia is substantiated. The ciliary armament of the triploblastic Bilateria larvae follows the general structural plan and includes the adoral ciliary field (a homologue of the ciliary tentacles of adult forms), neurotroch, and telotroch. The homology of pre-oral and oral (=tentacular) segments in triploblastic Bilateria is substantiated. The origin of Ecdysozoa as primarily semi-aquatic organisms is discussed. The chitinous cuticle of Ecdysozoa is homologous to the chitinous theca attached to the epidermis. The primary biramous limbs of Ecdysozoa resulted from the integration of tentacles of the marginal and labial circle of the common bilaterian ancestors. Tentacles of the marginal circle gave rise to exopods, and those of the labial circle gave rise to endopods. Examples of a primary biramous limb in Cambrian Ecdysozoa and recent Chelicerata are considered. The secondary biramous limb of Crustacea is a result from the secondary splitting of the endopod of the primary biramous limb into exopodite and endopodite. The problem of Hexapoda wings homology is discussed. Lobopoda is an Ecdysozoa lineage which adapted to life in loose substrate and acquired a worm-like body shape; the primary endopods became lobopods, while the primary exopods gave rise to metameric dorsolateral spines. Habitation in the sediment (Palaeoscolecida and Cephalorhyncha) caused a complete reduction of limbs and segmentation. The role of progenesis in the nematode origin is discussed. [ABSTRACT FROM AUTHOR]

The pursuit of aesthetic excellence in dentistry, shaped by societal trends and digital advancements, highlights the critical role of precise shade matching in restorative procedures. Although conventional methods are prevalent, challenges such as shade guide variability and subjective interpretation necessitate a re-evaluation in the face of emerging non-proximity digital instruments. This systematic review employs PRISMA protocols and keyword-based search strategies spanning the Scopus®, PubMed.gov, and Web of ScienceTM databases, with the last updated search carried out in October 2023. The study aimed to synthesise literature that identified digital non-proximity recording instruments and associated colour spaces in dentistry and compare the clinical outcomes of digital systems with spectrophotometers and conventional visual methods. Utilising predefined criteria and resolving disagreements between two reviewers through Cohen’s kappa calculator, the review assessed 85 articles, with 33 included in a PICO model for clinical comparisons. The results reveal that 42% of studies employed the CIELAB colour space. Despite the challenges in study quality, non-proximity digital instruments demonstrated more consistent clinical outcomes than visual methods, akin to spectrophotometers, emphasising their efficacy in controlled conditions. The review underscores the evolving landscape of dental shade matching, recognising technological advancements and advocating for methodological rigor in dental research.

Purpose: To assess the illuminant metamerism of three different pigments used for maxillofacial prostheses under three different illumination sources and to standardize subjective shade-matching and observation protocols.Materials and Methods: Nine silicone shade tabs were constructed for three volunteers who had light, medium, and dark skin tones using make-up, oil paint, or silicone pigments (three shade tabs per volunteer). A shade recipe was recorded during session one, and further tabs were constructed by following the recipe at two subsequent sessions. Using an observation protocol, expert examiners rated the shade match under three different illuminants.Results: The intra-rater and inter-rater reliability revealed acceptable reliability (ICC > 0.6). Two-way analysis of variance revealed significant differences (P < .05) for pigments and illuminants and for the interaction of pigments with illuminant on the raters' scores.Conclusion: Illuminant metamerism affected the appearance of the silicone shade tabs. Oil paint with fluorescent or incandescent illumination had the worst effect. It was found possible to construct a consistent shade guide and to recommend an observation protocol, which should be repeatable if similarly experienced examiners are used. [ABSTRACT FROM AUTHOR]

Both pleiotropic connectivity and mutational correlations can restrict the decoupling of traits under divergent selection, but it is unknown which is more important in trait evolution. To address this question, we create a model that permits within-population variation in both pleiotropic connectivity and mutational correlation, and compare their relative importance to trait evolution. Specifically, we developed an individual-based stochastic model where mutations can affect whether a locus affects a trait and the extent of mutational correlations in a population. We find that traits can decouple whether there is evolution in pleiotropic connectivity or mutational correlation, but when both can evolve, then evolution in pleiotropic connectivity is more likely to allow for decoupling to occur. The most common genotype found in this case is characterized by having one locus that maintains connectivity to all traits and another that loses connectivity to the traits under stabilizing selection (subfunctionalization). This genotype is favored because it allows the subfunctionalized locus to accumulate greater effect size alleles, contributing to increasingly divergent trait values in the traits under divergent selection without changing the trait values of the other traits (genetic modularization). These results provide evidence that partial subfunctionalization of pleiotropic loci may be a common mechanism of trait decoupling under regimes of corridor selection. [ABSTRACT FROM AUTHOR]

Within all major taxa of Bilateria, there are forms with coelomic metamerism. This suggests that coelomic metamerism was characteristic of the common ancestor of Bilateria. Among deuterostomes, metamerism is clearly expressed in chordates, and elements of metamerism are present in hemichordates. Do echinoderms have remnants of coelomic metamerism that was inherited from the common ancestor of Bilateria? The coelomic system of echinoderms includes several metameric coelomic rings located along the oral-aboral axis, namely: the axocoelomic ring, the hydrocoelomic ring, 2 to 6 coelomic rings originating from the left somatocoel, and one epigastric ring originating from the right somatocoel. Thus, in echinoderms, there is a dissymmetrical metamerism, derived from the original metamerism of the common ancestors of Deuterostomia and, possibly, the common ancestors of Bilateria. The problem of dexiothetism as the cause for the formation of coelomic dissymmetry in echinoderms is discussed. [ABSTRACT FROM AUTHOR]

As display technology advances in color gamut, the potential of experiencing higher degree of observer metamerism is more likely with narrow bandwidth stimuli display devices. In previous studies, it is confirmed that observer metamerism was introduced in soft proofing with monitor and color grading with projector scenarios, and also led to serious implications. Hence, it is desired to investigate whether laser‐based projection system would introduce observer metamerism compared to halogen‐based projection system. In this study, a two‐part experiment was designed and conducted. Experiment 1 was based on color patches and experiment 2 was based on test images. Intra‐observer and inter‐observer variability were calculated and analyzed. Both experiments had illustrated observer metamerism was introduced in laser‐based projection system. Comparison to CIE Standard Observers was also conducted for each experiment, and the results had suggested that the CIE Standard Observers were not suitable for laser‐based projection system. A new observer category was required at least for the group of observers participating the experiments. A quick method to transform the content from the CIE 1964 Standard Observer for color patches or the CIE 1931 Standard Observer for images has been established in experiment 1, and this quick method could help to facilitate the growth of personalized color management system. [ABSTRACT FROM AUTHOR]

Object color space is highly structured due to optical constraints (radiant power non-negative, reflectance factors between zero and unity) and ecological context (daylight illuminant). In this setting trichromacy induces a natural geometry through a unique spectral tripartition. Different from null-context colorimetry, one gains two desirable relations: The colorimetric coordinates are coarse-grained spectral reflectance factors and there is a direct link to color experiences, since RGB–coordinates provide ostensive definitions. The framework allows one to deal with subtractive color mixture, source variation, effects of metamerism and relations between scenes and image data in a unified, structured manner. In ecological contexts, colors are effectively object properties. The formal framework is linear algebra and convex geometry. Applications in human biology, computer graphics, design, etc., are immediate.

Metamerism is a critical color phenomenon which can cause serious problems for products assembled by various parts. Customers generally expect all parts are color‐matched under different observing conditions. This article extends the concepts of illuminant and observer metamerism to observing‐condition metamerism, that is, objects are color‐matched under one observing condition but not under others. The color inconstancy of a single object is also expanded to be evaluated under multiple observing conditions. Moreover, four Waypoint (Wpt) Shift Manifold difference metrics are proposed to evaluate not only observing‐condition metamerism of metamers and paramers but also observing‐condition color inconstancy of single objects: The Mean Object Inconstancy Index (MOII), The Mean Object Color Difference (MMOCD), Object Metamer Index (OMI), and Object Hue Similarity Index (OHSI). Existing indices of metamerism and color inconstancy employ appearance matching using a Chromatic Adaptation Transform (CAT) and color difference formulas such as CIEDE76 or CIEDE2000. The proposed metrics utilize material matching based upon the Waypoint Material Adjustment Transform (Wpt‐MAT) and Euclidian color difference in the perceptually uniform Material Color Equivalency Space WLab. Conceptual comparisons between these approaches are discussed and evaluated. Additionally, computational evaluation results under observing conditions composed by 99 illuminants and 70 observers show that MOII provides a measure of color inconstancy for single objects, MMOCD provides a measure of metamerism between metamers and paramers with a generalized assessment of color difference between two objects, OMI provides a measure of paramers, and OHSI provides a quantitative measure of hue characteristics for different observing conditions. [ABSTRACT FROM AUTHOR]

• Hemodynamic responses in the visual cortex were measured to investigate the contribution of ipRGCs in migraine under visual stimulation. • Statistically significant changes in fNIRS signals dependent on stimulation intensity applied to ipRGCs were observed in patients with migraine. • No such changes were observed in healthy participants. • ipRGCs, in addition to photometric values related to cones, may be associated with migraine. To clarify whether photoreception of intrinsically photosensitive retinal ganglion cells (ipRGCs) is related to migraine, we investigated the relationship between hemodynamic responses related to neural activity and visual stimulation of ipRGCs. It has been established that photoreception in ipRGCs is associated with photophobia in migraine. However, the relationship between visual stimulation of ipRGCs and hemodynamic responses in the visual cortex has not been clarified. Hemodynamic responses in the visual cortex were measured using functional near-infrared spectroscopy (fNIRS) as signals reflecting changes in oxygenated and deoxygenated hemoglobin concentrations. Different types of visual stimulation generated by a metamerism method were applied to the peripheral field of the eye of patients with migraine (N = 20) and healthy participants (N = 21). The stimulation intensity on the retina was controlled using an artificial pupil. In the primary visual cortex of patients with migraine, statistically significant changes in fNIRS signals dependent on visual stimulation intensity applied to ipRGCs were observed (p < 0.01), while no such changes were observed in healthy participants. These results reveal that visual stimulation of ipRGCs projecting to the primary visual cortex is involved in hemodynamic responses in patients with migraine, suggesting that ipRGCs, in addition to photometric values related to cones, are associated with migraine. [ABSTRACT FROM AUTHOR]

Abstract Debonding, staining and wear are usually the reasons for denture teeth replacement by new ones from same or different brands. Objective This study investigates the possible differences in color of denture teeth of the same or different brands under different illuminations, since their metameric behavior in color under specific illumination may become unacceptable. Methodology For the purpose of this study, 10 denture teeth (#11), shade A3, of 4 different brands were selected (Creopal/KlemaDental Pro, Executive/DeguDent, Cosmo HXL/DeguDent, Ivostar/Ivoclar-Vivadent). Teeth stabilized in white silicone mold and the CIELAB color coordinates of their labial surface under 3 different illumination lights (D65, F2, A) were recorded, using a portable colorimeter (FRU/WR-18, Wave Inc). ΔE*ab values of all possible pairs of teeth of the same brand (n=45) or pair combinations of different brands (n=100) under each illumination light, in a dry and wet state were calculated. Data were analyzed statistically using 3-way ANOVA, Friedman’s and Wilcoxon’s tests at a significance level of α=0.05. Results The results showed that brand type affected significantly L*, a* and b* coordinates (p0.05). Intra-brand color differences ranged between 0.21-0.78ΔΕ* units with significant differences among brands (p

A method is proposed to generate categorical colour observer functions (individual colour matching functions) for any field size based on the CIE 2006 system of physiological observer functions. The method combines proposed categorical observer techniques of Sarkar et al with a physiologically‐based individual observer model of Asano et al and a clustering technique to produce the optimal set of categorical observers. The number of required categorical observers varies depending on an application with as many as 50 required to predict individual observers' matches when a laser projector is viewed. However, 10 categorical observers are sufficient to represent colour‐normal populations for personalized colour imaging. The proposed and recommended categorical observers represent a robust and inclusive technique to examine and quantify observer metamerism in any application of colorimetry. [ABSTRACT FROM AUTHOR]

This article describes a way to distinguish between two distinct components of light source–induced color shifts, base color shift and metameric color shift, to provide a more complete understanding of color rendition. Working within the existing framework of IES TM-30-18 and CIE 224:2017, it shows that base color shift varies smoothly with location in color space in a pattern that is determined by the spectral power distribution (SPD) of the light source. Patterns of smooth variation can often be approximated well with a low-order polynomial function. Here, a vector field model is presented, based on a second-order polynomial function. The polynomial coefficients are adjusted, for a given light source, to provide a least squares fit to the calculated color shifts of a standard set of color samples. The adequacy of this model was verified by comparing it to another approach for characterizing base color shift that is based on discretization of color space and a much larger set of color samples. Once the vector field model of base color shifts for a given light source is determined, the metameric color shifts can be calculated from the residuals and the distribution of those shifts can be statistically summarized. Based on this information, a metameric uncertainty index (Rt) is proposed to provide new information about a light source. In particular, it can be used to estimate the likelihood of noticeable metameric mismatches induced by a given light source, which could lead to improved predictions of the perceived color quality of light. [ABSTRACT FROM AUTHOR]

Metamerism phenomenon can be used in illuminant detection to ensure the accuracy of light source. A method based on Long‐, Middle‐, Short‐ wavelength cones(LMS) weighting algorithm to evaluate metamerism degree is proposed. The chromatic relationship between the degree of metamerism mismatch and the light source is studied. Herein, the consistency between the metameric indices (MIs) and CIE1976 L*a*b* color difference ranking is analyzed by SRCC, KRCC, PLCC and RMSE. A statistically sampling method to obtain practical LMS cone fundamentals to evaluate metamerism degree is employed. The analysis results obtained show that the method based on LMS weighting algorithm has good evaluation ability and stability in simulation experiments and statistically sampling experiments, which are in line with visual characteristics of human. Proposed method meets the requirements of selecting metameric pairs used in light source detection. The analysis results have certain guiding significance. [ABSTRACT FROM AUTHOR]

The discovery of melanopsin as a third type of retinal photoreceptor, contributing to both perceptual vision and reflex light responses, represents a new opportunity to optimise the design of artificial light sources for practical applications and to generate experimental stimuli. In the case of emissive displays, multiprimary designs incorporating a cyan primary could be used to allow melanopic radiance to be controlled independent of colour and luminance. Here we explore the performance a five-primary (violet, cyan, green, yellow, red) display device and find an anomaly in colour appearance when the cyan primary is employed. The anomaly took the form of a reddish/pinkish tinge in the central visual field, consistent with descriptions of Maxwell's spot. This effect was apparent in some full colour images and in uniform discs over a range of chromaticities. Its appearance in coloured discs correlated with differences in calculated colour coordinate between central and peripheral vision. A simulation indicated that inclusion of any primary with predominant output in the 470-500 nm range has the potential to produce such a discrepancy in central vs peripheral appearance. Applying an additional constraint in colour processing to reproduce naturally occurring differences in central vs peripheral colour coordinate eliminated appearance of the spot and produced acceptable colour images. [ABSTRACT FROM AUTHOR]

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This article deals with cationization of cotton during mercerization and its effects on trichromatic vat dyeing. If cationization is carried out during the after-treatment, regardless of cotton pretreatment, the reaction takes place on the surface and blocks cellulose groups, subsequently resulting in uneven coloration. However, when cationization is carried out with an epihalohydrin during the mercerization process, new cellulose is formed in which the cationic compound is uniformly distributed and trapped between cellulose chains, resulting in uniform coloration after the dyeing process. The reaction time for the process during mercerization is 24 h, thus a more favorable process was researched. Based on electrokinetic analysis, it was found that 5 h was sufficient for the reaction with 3-chloro-2-hydroxypropyltrimethyl ammonium chloride (CHPTAC). The cationization of cotton contributed to the processes of vat dyeing. The change in charge upon cationization resulted in very high adsorption of vat-dye anions, indicating that ionic bonding occurred in addition to van der Waals forces. The color depth improved by more than 10 times. It should be emphasized that the colors with higher chroma and targeted color hue, especially in trichromatic dyeing, were obtained on cationized cotton, in contrast to standard cotton fabrics. The color differences obtained under the different light sources indicate the occurrence of metamerism. Considering the color fastness to laundering, vat-dyed cationized fabrics of all colors may be used in hospitals or other environments where high hygiene and oxidative bleaching are required.

This manuscript presents a preliminary investigation on the applicability of hyperspectral imaging technology for nondestructive and rapid analysis to reveal covered original handwritings. The hyperspectral imager Nuance-Macro was used to collect the reflected light signature of inks from the overlapping parts. The software Nuance1p46 was used to analyze the reflected light signature of inks which shows the covered original handwritings. Different types of black/blue ballpoint pen inks and black/blue gel pen inks were chosen for sample preparation. From the hyperspectral images examined, the covered original handwritings of application were revealed in 90.5%, 69.1%, 49.5%, and 78.6% of the cases. Further, the correlation between the revealing effect and spectral characteristics of the reflected light of inks at the overlapping parts was interpreted through theoretical analysis and experimental verification. The results indicated that when the spectral characteristics of the reflected light of inks at the overlapping parts were the same or very similar to that of the ink that was used to cover the original handwriting, the original handwriting could not be shown. On the contrary, when the spectral characteristics of the reflected light of inks at the overlapping parts were different to that of the ink that was used to cover the original handwriting, the original handwriting was revealed.

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

International Commission on Illumination (CIE) is an international organization working on the fundamental and scientific issues that can be applied to the evaluation of wide colour gamut (WCG) and high dynamic range (HDR) imaging. A model to estimate cone sensitivity with respect to age and field‐of‐view can be used to evaluate metamerism for WCG displays. CIE is developing new uniform colour space applicable for it in consideration of adaptations. [ABSTRACT FROM AUTHOR]

Copyright of Cotton Textile Technology is the property of Cotton Textile Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study investigates observer metamerism in cross‐media colour reproduction (CMCR) between monitor and physical colours. An LCD display was placed inside a viewing cabinet. The cabinet had a mid‐grey interior. Observers were asked to match a colour displayed on the monitor to a printed colour patch, which was also inside the viewing cabinet in two configurations, one consisting of two samples separated by a hairline gap (Configuration 1), and the other consisting of two samples separated by a large gap (Configuration 2). Eleven observers were asked to first match the background colour and then 10 test colours for each configuration, and this was repeated five times. The observers' variability results showed little difference between inter‐ and intra‐variability, and between the two configurations. Comparing the observers' results with the CIE 1964 standard colorimetric observer, Configuration 1 and Configuration 2 each showed similar agreement. In both configurations, the results of observer variability were smaller than those obtained by Oicherman et al. in 2008. In addition, each configuration's results showed better agreement with the CIE standard colorimetric observer than Oicherman et al.'s results. This implies that both configurations, one with two samples having a hairline gap and with two samples separated by a large gap in a viewing cabinet, could be recommended for future CMCR systems. However, if choosing between the two, then Configuration 2 is recommended rather than Configuration 1. [ABSTRACT FROM AUTHOR]

Abstract Interference thin film based on metamerism is the latest means in the field of optical anti-counterfeiting. In this paper, we propose a pair of metal-dielectric metameric interference thin films that could create a hidden image for optical security devices. To improve color match tolerance of the metameric pair, the angle insensitive metal-dielectric Fabry-Perot structure was designed as the metameric pair background film B; The logo film A adopts the five-layer angle sensitive structure to enhance the contrast. The film B is designed to have a weak color-shift effect as the observation angle is increased. When the observation angle increases from 0° to 15°, the reflectance spectrum of film B changes smoothly, and the color difference indexes between film A (0°) and film B (0°, 5°, 10°, 15°) are 0.968, 0.988, 1.798 and 3.778, respectively. This design is less sensitive to manufacturing errors and has a good color match effect. Color target optimization optimac method is utilized in the design process and remote plasma sputtering is used in the deposition process. The color difference index of the experiment is 2.753, which shows good hidden image effect for the optical security devices. Highlights • Metal-dielectric metameric thin films were created for optical security devices. • The angle-insensitive metal-dielectric structure was designed as background film. • The thin films exhibition identical appearance by the same material and PVD. • The lion pattern was created in printing which shows good hidden image effect. [ABSTRACT FROM AUTHOR]

Olaf Müller presents a supposedly empirically equivalent theory to Newtonian optics, which in his view is therefore threatened by underdetermination. This threat could even be expanded to modern physics, since this branch of physics is partly based on Newton’s theory. In this paper, I will show that Müller’s alternative theory contains an ill-defined concept, viz. the definition of whiteness as the absence of optical causal factors. This results from a fundamental property of whiteness: for every source of white light there exist metameric sources. I further argue that this cannot be reconciled by borrowing other concepts from modern physics, as is, I will show, tacitly presupposed in Müller’s argument. As a consequence, his alternative theory is not empirically equivalent to Newtonian optics and his argument in favour of underdetermination fails. [ABSTRACT FROM AUTHOR]

An analysis of early coelom development in the echinoid Holopneustes purpurescens yields a deuterostome body plan that explains the disparity between the pentameral plan of echinoderms and the bilateral plans of chordates and hemichordates, the three major phyla of the monophyletic deuterostomes. The analysis shows an early separation into a medial hydrocoele and lateral coelomic mesoderm with an enteric channel between them before the hydrocoele forms the pentameral plan of five primary podia. The deuterostome body plan thus has a single axial or medial coelom and a pair of lateral coeloms, all surrounding an enteric channel, the gut channel. Applied to the phyla, the medial coelom is the hydrocoele in echinoderms, the notochord in chordates and the proboscis coelom in hemichordates: the lateral coeloms are the coelomic mesoderm in echinoderms, the paraxial mesoderm in chordates and the lateral coeloms in hemichordates. The plan fits frog and chick development and the echinoderm fossil record, and predicts genes involved in coelomogenesis as the source of deuterostome macroevolution.

An indoor positioning method based on metameric white light sources and subpixels on a color image sensor is proposed in this paper. Metameric white light sources are obtained by merging multiple-color light-emitting diode (LED) chips with different intensity ratios. The output intensity ratios of subpixels on color image sensor at the receiver are employed to identify the respective metameric white light sources. Proof of concept experiments demonstrates that the average error of 2-D indoor positioning is 1.50 cm and 3-D indoor positioning is 3.58 cm. The indoor positioning system with the proposed method is cost effective and convenient because image sensors in nowadays available mobile devices can be utilized.

A new camera metric is proposed based, in concept, on the vision test devised by Davidson and Hemmendinger. The "D&H Color Rule" is a set of two linear patch arrays containing at most one match for near-normal color observers. The match selected by an observer can provide an indication of how that observer's color vision relates to others. Comparisons may be made to a group of interest, or more commonly, to a CIE Standard Observer. For this research, two image targets have been created, one physical and one virtual, each with a family of spectra related in much the same way as the colors in the original D&H Rule. These targets can be physically imaged or virtually modeled to predict camera RGB, and then CIELAB with a color profile. The camera can then be judged as to what degree its output matches that of a CIE Standard Observer [ABSTRACT FROM AUTHOR]

We present an efficient and scalable pipeline for fabricating full-colored objects with spatially-varying translucency from practical and accessible input data via multi-material 3D printing. Observing that the costs associated with BSSRDF measurement and processing are high, the range of 3D printable BSSRDFs are severely limited, and that the human visual system relies only on simple high-level cues to perceive translucency, we propose a method based on reproducing perceptual translucency cues. The input to our pipeline is an RGBA signal defined on the surface of an object, making our approach accessible and practical for designers. We propose a framework for extending standard color management and profiling to combined color and translucency management using a gamut correspondence strategy we call opaque relative processing. We present an efficient streaming method to compute voxel-level material arrangements, achieving both realistic reproduction of measured translucent materials and artistic effects involving multiple fully or partially transparent geometries. [ABSTRACT FROM AUTHOR]

Molecules that can tautomerize are a challenge to scientists because one must consider the possible tautomers in most tasks involving chemical structures: for example, searching databases, interpreting experimental property measurements, calculating properties, virtual screening, and analyzing structure-bioactivity relationships. The challenge in interpreting property measurements such as p K a values feeds into the general lack of extensive information not only of the relative tautomer stability in water but also the properties of the individual tautomers. This lack of information results in the lack of reliability of computational predictions of tautomer stability or properties. In spite of these problems, p K a calculations are reliable enough that they can be used to filter out high-energy tautomers from databases used for virtual screening. Continuous improvements in both p K a prediction software and theoretical calculations promise further improvements in solving the challenges of tautomers. The expected availability of high-resolution structures of many more tautomer-protein complexes will help guide the selection of the bioactive tautomer when the structure of the complex is not known. [ABSTRACT FROM AUTHOR]

The dentist-laboratory technician restorative team has been challenged over the last 50 years to find a suitable restorative material to treat the extensive tooth staining, born out of the late 1960s and early 1970s, from the ingestion of tetracycline. For milder cases, combinations of bleaching and/or a variety of direct and indirect materials could be effective. However, truly dark teeth necessitated finding a balance between blocking out the darkened tooth structure and the ability to provide lifelike dental restorations with suitable optical metamerisms. This article discusses the properties of dental zirconia and its performance in fixed dental prostheses. A case study illustrating how monolithic, gradient zirconia can provide beautiful, lifelike restorations for even the darkest tetracycline-stained teeth is provided. [ABSTRACT FROM AUTHOR]

Metamerism failure between LCD and OLED arises due to their very different spectral power distributions. In order to visually match the colors in LCD, a matrix‐based method of color correction was derived to predict the chromaticity offsets in OLED, followed by a psychophysical match experiment to verify the feasibility. [ABSTRACT FROM AUTHOR]