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The aim of this study is to measure color changes caused by two regenerative protocols over 3 months, and the effectiveness of internal bleaching. Twenty extracted human maxillary anterior teeth were used. The apex and canal were prepared to reproduce immature teeth. Teeth were divided: group 1: Triple-antibiotic-paste was applied for 3 weeks and then changed for blood until 3 months. Group 2: Blood was inoculated and sealed at cemento-enamel junction level with Biodentine for 3 months. Both groups were subjected to three sessions of internal bleaching. Color assessments were taken at baseline and at 2 and 3 weeks, 2 and 3 months, and 1, 2, and 3 weeks from the beginning the bleaching phase. Statistical significance was considered at P = .05. Both techniques produce color changes above the acceptability limit at 2 weeks. Chromatic variation caused by Triple-antibiotic-paste was intense and progressive over time. Replacement of the Triple-antibiotic-paste with blood made the color change more intense and progressive, with significant statistical differences at 2 and 3 months (T4 > T3; P = .028). The internal bleaching technique was statistically more effective in the Triple-antibiotic-paste group at 1 week (P = .002). Both techniques cause unacceptable color changes, causing Triple-antibiotic-paste more staining than Biodentine. Two sessions of internal bleaching recovered clinically perceptible color in both regenerative endodontic procedures without returning the original color.

Large effect pigments, widely used in various fields of industrial applications, produce characteristic visual textures known as sparkle and graininess, which need to be quantified by objective or subjective methods. The development of preliminary measurement scales for sparkle and graininess, whose recommendation is now under discussion in the International Commission on Illumination (CIE), is described in this article. These scales are absolute, linear and traceable to standards of optical radiation metrology. The main purpose of this article is to justify the convenience of adopting these preliminary measurements scales, showing clear evidence that they correlate well with subjective evaluations. Before standardization, these scales need to be validated with more experimental data, including different specimens and experimental systems from other research groups.

Large effect pigments, due to their strongly specular reflectance, produce a special visual texture known as sparkle. The use of these pigments in many industries (automotive, cosmetic, paper, architecture...) makes the control of this visual texture necessary. A measurement scale has to be developed, so that traceability can be provided by national metrology institutes (NMI) or designated institutes. Some of them (PTB, METAS, CMI and CSIC) have tested their existing capabilities to measure sparkle, and their results are presented. Two possible sources of systematic errors have been identified: inadequate illumination and collection full-angles, and inadequate size of the virtual aperture used to assess the luminous flux reflected on the effect pigments. The measurement scale of sparkle used in this comparison is thoroughly presented. This comparison will allow the methodology to measure sparkle to be improved.

Sparkle and graininess are textural effects that appear as intrinsic spatial features of coatings containing goniochromatic pigments, whereas others such as mottling are undesired outcomes. In this study, we present new methods for the evaluation of sparkle, graininess and mottling of automotive coatings through images acquired with a novel gonio-hyperspectral imaging system based on light-emitting diodes with extended spectral sensitivity beyond the visible range (368–1309 nm). A novel analysis of sparkle that considered the amount of sparkling spots was used. Graininess was quantified through a novel statistical descriptor based on the energy descriptor computed from the histogram. A new index was proposed for an enhanced detection of mottling based on the analysis of striping, which was better observed and quantified in the infrared range. Spectral assessments showed a strong relationship with color and spectral reflectance for graininess and mottling. In conclusion, the results showed that these new spatial and spectral methods are a suitable, alternative and potential approach for the assessment of these textural features.

In this work, we built a multi‐primary display model based on the new quantum dots (QD) technology to enlarge the display color gamut. In this way, first the emission spectral radiance curves of the three RGB channels of a commercial QD display were fitted to a four‐parameter function. From this modeling, it is possible to gain new theoretical color primaries by selecting new spectral peaks (cyan, yellow, magenta, and/or additional RGB primaries) and imposing some colorimetric conditions for the resulting white of this proposed theoretical multi‐primary display. Proper characterization to assess the performance of the display was conducted to know if the basic “gain‐offset‐gamma” (GOG) model can be used for direct and inverse color reproduction (from RGB to CIE‐XYZ, and vice versa). The GOG model was found to well characterize this display. The spatial uniformity of the display was also evaluated in luminance and color chromaticity terms. Finally, with the primaries modeling and color characterization based on the GOG model, a 5‐primary model (RGBYC) was tested. The evaluation of this theoretical RGBYC display model confirms the gamut enlargement, which can also improve goniochromatic color reproduction.

El objetivo de la experiencia educativa planteada en este proyecto es promover la autoevaluación como un instrumento de aprendizaje y motivación. El profesorado involucrado diseñó una rúbrica de evaluación mediante Corubrics. La autoevaluación fue realizada sobre un trabajo colaborativo entre los alumnos. La rúbrica está dividida en 8 ítems que evalúan tanto aspectos sobre el contenido como aspectos relacionados con su actitud (postura corporal, contacto visual, etc.). Cada categoría fue descrita con cuatro niveles, desde 4 (muy correcto) a 1 (muy flojo). En primer lugar, respecto a los resultados académicos, el 73% de los alumnos obtuvieron una calificación de notable, y el 27% restante la calificación de apto, que es un buen indicador del grado de involucración del alumnado. Cabe destacar que se encontraron desviaciones máximas del 84% y mínimas del 10% entre las calificaciones otorgados por el profesorado y los alumnos. Por ello, se creyó oportuno modular la nota final mediante diferentes porcentajes entre profesor (60%) y alumno (40%). Por último, se realizó la evaluación de la propia innovación educativa, que fue valorada de manera positiva por el alumnado. Por tanto, puede considerarse la autoevaluación como una herramienta muy útil de aprendizaje y motivación.

In order to consider 3D objects from suitable Fused Deposition Modelling (FDM) printers as prototypes for the automotive sector, this sample must be able to reproduce textural effects (sparkle or graininess) or metallic or gonio-appearance to reinforce the attractive appeal of these materials. This study worked with two different commercial filaments: grey metallic PLA (poly(lactic acid)) and ABS (acrylonitrile-butadiene-styrene copolymer) with diffractive pigments. For both materials, a statistical design of experiments (DoE) was carried out to find the printing parameters effect on the final 3D-objects gonio-appearance. The selected printing parameters were printing speed (2 levels), layer height (2 levels) and sample thickness (3 levels). Twelve smooth square objects were printed from each material. The ABS-diffractive filaments achieved the most significant flop and higher sparkle values than metallic PLA. Graininess was high when working with PLA filaments instead of ABS. Layer height was the most significant parameter to maximize PLA objects’ flop or sparkle effects. The best result was found when printing at 0.1 mm. For the ABS samples, the stronger flop and sparkle effects were achieved with the 50 mm/s printing speed, the 0.1 mm layer height and the lowest thickness level. This study shows the methodology to study the printing parameters effects and interactions to maximize the FDM-3D-objects gonio-appearance.

The first edition of the Master's Degree in "Color Technology for the Automotive Sector" was held during the last academic year. The academic results in terms of qualifications, achievement and learning were good. In spite of the good sensations, there are aspects to be improved, both in methodology and the development of the subjects, timing of the contents, organization or communication channels. Following this line, the Academic, agreed on a plan of continuous improvement based on the feedback provided by the graduate surveys. A specific survey was carried out to gather their specific experience of the course in order to be able to modify the general strategy of the master's degree at the teaching and organisational level. The objectives were to adapt the teaching methodology to facilitate a more reflexive, participative and autonomous learning with a high degree of involvement and motivation of the students, to improve the academic results in terms of learning and satisfaction, to simplify and improve the logistic management of the course, etc. Thus, the survey included questions relating to the usefulness of the master's degree, methodology, organisation and planning of teaching, as well as a final question relating to the overall satisfaction of the course. A short survey was chosen with only 10 questions that the student rated from 1 to 5 on a scale from "strongly disagree" to "strongly agree". From the analysis of the responses, some important weaknesses were detected, such as the lack of content developed in video format, and the slowness of feedback on the results obtained in the proposed tasks. Based on these results, it was proposed an improvement plan that included the incorporation of videos to teaching materials, flexibility in the deadlines for activities, and the periodic monitoring of student learning and concerns through "Adobe Connect".

A validation of the graininess attribute was made by means of a psychophysical experiment and the multidimensional scaling algorithm. A visual experiment was designed to obtain graininess differences to be used like the dissimilarity matrix in the MDS algorithm. The results revealed that two dimensions are needed to characterize the graininess effect. The BYK-mac-i instrument and a gonio-hyperspectral imaging system were employed to evaluate the statistical dimensions. On one hand, the first dimension correlated well with the graininess value provided by the BYK-mac-i (r2 = 0.9566). However, we were unable to find a relationship with dimension 2 and any parameter measured by this instrument. Furthermore, the images captured by the gonio-hyperspectral imaging system were processed. A good relationship with the correlation parameter was observed (r2 = 0.8958). However, no relationship was established with dimension 2. Based on these conclusions, further research is necessary that focuses on the new imaging processes and a new visual experiment.

Several different instruments have been introduced into the market to obtain good color characterization for different measurement configurations. These commercial instruments have different optical and working configurations, however, the measurement data provided by each instrument should be similar to have good consistency when comparing them to each other measuring the same sample material. Therefore, the purpose of this work was to apply an inter‐model agreement study of spectral and colorimetric data of three instruments (CM‐M6, BYK‐mac‐I, and MA98). Two different statistical tests were applied following ASTM recommendations. In general, the measurement geometries close to the specular direction and the flop direction showed greater deviations. In addition, the partial color differences calculated for the comparison of MA98 versus CM‐M6 were larger than the BYK‐mac‐i versus CM‐M6 comparison. Finally, it can be concluded that most of the measurement geometries were statistically significantly different from each other which means that these differences were due to systematic or bias errors and not exclusively to random errors.

Effect pigments in coatings produce eye-catching colour and texture effects and are widely used in automotive, cosmetics, coatings, inks, flooring, textile or decoration. One of these texture effects is graininess, which is the perceived texture exhibited when the effect coating is observed under diffuse illumination. To date there is not a standard procedure to measure graininess from reflectance measurements. The objective of this work is to propose a methodology for traceable graininess measurements, similarly as it was proposed for colour in 1931. In this article, the relevant reflectance-based quantities are clearly defined, and a formal relation with data from visual experiments is given. This methodology would allow a measurement scale of graininess and a difference formula to be agreed once conclusive visual data become available.

Color tolerances of curved gonio‐apparent panels have been studied in this work. To achieve that, an experimental set‐up of the illumination and tilt variation of two identical coated panels was designed for simulation of curved panels with both concave and convex borders and with and without effect pigments (perceived as solid and gonio‐apparent colors, respectively). Finally, visual and instrumental measures were collected with both curvatures. The results show that the relationship of the instrumental color difference with the tilt angle can be modeled by a second‐order and the vertex did not depend on illumination, but on coating type. The critical angles (the angle marked when the color discrepancy between two identical samples is merely perceived) assessed by the observers showed that they were not equal according to border, nor according to coating type. The color tolerances at these angles were clearly higher than the conventional chromatic thresholds of industrial color comparisons.

Alumosilicate materials of different morphologies, such as platy and tubule nanoclays, may serve as an efficient, protective encasing for colored organic substances and nanoparticles. The adsorption of dyes onto the nanoclays increases their stability against thermal, oxidative, and acid–base‐induced decomposition. Natural organic dyes form stable composites with clays, thus allowing for “green” technology in production of industrial nanopigments. In the presence of high‐surface‐area alumosilicate materials, semiconductor nanoparticles known as quantum dots are stabilized against agglomeration during their colloid synthesis, resulting in safe colors. The highly dispersed nanoclays such as tubule halloysite can be employed as biocompatible carriers of quantum dots for the dual labeling of living human cells—both for dark‐field and fluorescence imaging. Therefore, complexation of dyes with nanoclays allows for new, stable, and inexpensive color formulations.

Los resultados académicos de la primera edición del Máster en “Tecnología del Color para el sector de automoción” fueron buenos a nivel de calificaciones y aprendizaje, con un alto grado de satisfacción con sus contenidos y su organización. Sin embargo, siempre hay aspectos que mejorar y para tal fin se elaboró una encuesta dirigida a los alumnos egresados para recoger su experiencia y poder modificar la estrategia general del máster a nivel docente y organizativo para maximizar el rendimiento académico del nuevo alumnado. En particular, se diseñó una encuesta con 10 cuestiones relativas a la utilidad del máster, la metodología, la planificación docente y una pregunta final sobre su satisfacción general. La valoración era de 1 a 5 en una escala desde “totalmente en desacuerdo” a “totalmente de acuerdo”. A partir del análisis de las respuestas, se detectaron algunos puntos débiles tales como la falta de contenidos desarrollados en formato video, y la lentitud en la retroalimentación de los resultados obtenidos en las tareas propuestas. A partir de estos resultados, se propuso un plan de mejora que incluía la incorporación de vídeos, flexibilización en los plazos de presentación de actividades, y el seguimiento periódico mediante conexión por “Adobe Connect” del aprendizaje del alumnado.

Los elementos fundamentales en el desarrollo de las asignaturas de un plan de estudios son las competencias, los objetivos, los contenidos y bibliografía y la evaluación. Todos estos apartados son desarrollados en cada asignatura cuando se propone un nuevo plan de estudios. Sin embargo, es necesario realizar un seguimiento para mantener el plan de estudios actualizado y acorde con las necesidades del título que se oferta. Desde la implantación del Máster en Optometría Avanzada y Salud Visual de la Universidad de Alicante se han creado redes docentes dentro del programa de Redes de Investigación en Docencia Universitaria de la Universidad de Alicante que han trabajado en el seguimiento del Máster, contribuyendo a la mejora de la coordinación de todas las asignaturas y al análisis de las herramientas utilizadas para desarrollar las distintas actividades. Como continuación de este trabajo es necesario analizar el proceso de evaluación llevado a cabo en todas las asignaturas del plan de estudios. Por ello, los profesores coordinadores de estas asignaturas nos planteamos la necesidad de crear un grupo de trabajo que permitiera analizar los procesos de evaluación, su relación con el resto de elementos de las asignaturas y sus posibilidades de mejora para el curso 2018-19.

For improving color reproduction accuracy of mobile displays, we recently developed a generic model for device-specific display characterization model that also accounts for the influence of illuminance from ambient light. In the present article, this MDCIM model (Mobile Display Characterization and Illumination Model) is applied to a Samsung Galaxy S4 display, representing OLED displays. The performance of the model was tested by determining the values of all model parameters using publicly available technical data only. We organized visual tests under various ambient illuminance levels from 600 to 3000 lux. Seven observers compared the color of displayed images with the color of physical samples. With the MDCIM method, the quality of the color match was shown to improve considerably as compared to using only device-independent encoding color space. On a five-point scale to quantify color reproduction accuracy, the MDCIM resulted in more than 1 unit improvement at 1000 lux illuminance. At lower and higher illuminance, the improvement was even larger. Color reproduction accuracy was found to be at least reasonable, according to the subjective assessment of visual observers, for more than 75% of the samples when using the MDCIM method, but only 20% or less when using the common device-independent encoding color space.

Effect pigments in coatings produce eye-catching colour and texture effects and are widely used in automotive, cosmetics, coatings, inks, flooring, textile or decoration. One of these texture effects is graininess, which is the perceived texture exhibited when the effect coating is observed under diffuse illumination. To date there is not a standard procedure to measure graininess from reflectance measurements. The objective of this work is to propose a methodology for traceable graininess measurements, similarly as it was proposed for colour in 1931. In this article, the relevant reflectance-based quantities are clearly defined, and a formal relation with data from visual experiments is given. This methodology would allow a measurement scale of graininess and a difference formula to be agreed once conclusive visual data become available.

[EN] Alumosilicate materials of different morphologies, such as platy and tubule nanoclays, may serve as an efficient, protective encasing for colored organic substances and nanoparticles. The adsorption of dyes onto the nanoclays increases their stability against thermal, oxidative, and acid¿base-induced decomposition. Natural organic dyes form stable composites with clays, thus allowing for ¿green¿ technology in production of industrial nanopigments. In the presence of high-surface-area alumosilicate materials, semiconductor nanoparticles known as quantum dots are stabilized against agglomeration during their colloid synthesis, resulting in safe colors. The highly dispersed nanoclays such as tubule halloysite can be employed as biocompatible carriers of quantum dots for the dual labeling of living human cells¿both for dark-field and fluorescence imaging. Therefore, complexation of dyes with nanoclays allows for new, stable, and inexpensive color formulations.

The field of spectral radiance factor (SRF) measurements has seen growing interest in recent years. Scale conformity has so far only been established between the national metrology institutes (NMIs) of Germany and the USA. This study aims at a bigger, multilateral scale comparison. For this purpose, a total of six NMIs participated in a scale comparison of goniospectrophotometers based on neutral and colored diffusely reflecting ceramics samples. In addition, two universities, providing a home-built gonioreflectometer and two widely used commercially available color measurement instruments, respectively, were involved. The wavelength range of the scale comparison covers the visible wavelength range from 380 nm to 780 nm. Results indicate systematic issues and that the uncertainty evaluation of the NMIs requires further work; although for the greatest part of the covered spectral range the agreement is good.

El Máster en Tecnología del Color para el Sector Automoción (ColTAS) se oferta en modalidad semipresencial mediante Moodle. La metodología de aprendizaje está basada en una metodología adaptativa que combina b-learning y flipped classroom considerando diferentes estilos de aprendizaje para obtener el máximo rendimiento y la máxima satisfacción. En este proyecto se ha trabajado en la implementación de esta metodología mediante la elaboración de actividades, tanto grupales como individuales. Las actividades individuales han sido diseñadas con tres perfiles de participación: básico, medio y alto. Así, se incentiva la motivación del alumnado y se tiene en cuenta su objetivo. Las actividades grupales permiten combinar alumnos con diferentes características, de esta forma los grupos se complementan para alcanzar mejores resultados. El primer análisis de los resultados obtenidos tras la finalización del curso indican una gran satisfacción por parte del alumnado. Su participación ha sido activa, tanto en los foros planteados, como en la realización de las tareas, ya que todos ellos completaron los tres niveles de dificultad planteados. La evaluación de los resultados obtenidos mediante esta metodología ha aportado datos válidos para mejorar esta metodología para futuras ediciones y conseguir así un mayor éxito de esta titulación propia.

Continuamente se están desarrollando nuevas herramientas docentes que permiten elaborar materiales que facilitan el proceso de aprendizaje de los alumnos. En el Máster en Optometría Avanzada y Salud Visual de la Universidad de Alicante, que comenzó a impartirse en el curso 2015-16, esto es cada vez más necesario y demandado por los alumnos, sobre todo por aquellos que no pueden hacer un seguimiento del máster totalmente presencial. Con este fin, se ha creado un grupo de trabajo formado por todos los profesores del Máster, que pretenden analizar las herramientas de innovación docente utilizadas actualmente para desarrollar las distintas actividades y valorar la utilización de estas u otras en el resto de asignaturas.

Solar thermal coatings are designed to achieve the highest incident solar flux into the receiver of a tower solar plant. These materials are subjected to extreme working conditions of temperature and solar concentrated radiation. Much effort is being made to develop a durable and high absorptive coating that can provide an excellent solar to heat conversion efficiency. Complex deposition techniques (PVD, CVD, electrodeposition, etc.) are developed and tested to achieve solar selectivity. High solar absorptance paints are an alternative technique, that is, easy to apply and implement in the field. In paint, pigments are the compound that provides high absorptance values, whose stability impacts the durability of optical properties. The search for new selective solar pigments for solar receivers is a promising route to improve the efficiency of this technology. In this work, novel nanocomposites were synthesized from low-cost organic materials such as table sugar. Promising results were obtained when intercalated and calcined in the laminar structure of montmorillonite, a type of smectite clay. The pigments were tested in a paint format on metallic coupons at different temperatures to obtain absorptivities above 96% of absorptance after 24 h at 700 °C. Further experiments are still needed to obtain optimum conditions to maximize the coating's absorptivity and durability at high temperature.

In this study, a novel gonio-hyperspectral imaging system based on light-emitting diodes for the analysis of automotive coatings was validated colorimetrically and spectrally from 368 to 1309 nm. A total of 30 pearlescent, 30 metallic, and 30 solid real automotive coatings were evaluated with this system, the BYK-mac and X-Rite MA98 gonio-spectrophotometers, and also with the SPECTRO 320 spectrometer for further comparison. The results showed very precise correlations, especially in the visible range. In conclusion, this new system provides a deeper assessment of goniochromatic pigments than current approaches due to the expansion of the spectral range to the infrared.

A general procedure for developing stable solar absorptive coatings at both high temperature and a high solar radiation concentration is presented. In order to generally improve thermal efficiency, a coating with high solar absorptance is applied all over the surface of receiver tubes that is subjected to extreme working conditions. Consequently, a durable coating with high absorptivity for sunlight is needed. An alternative paint formulation research and development line to Pyromark-2500, the paint currently used in many commercial solar thermal power plants (CSP) is proposed. Pigment synthesis is developed by intercalating metallic salts into laminar or tubular clay structures. Metallic oxides, which provide paint with its color properties, are obtained by a calcination process. Addition of silane or surfactants during the pigment synthesis is also optimized. Once dried and ground to a precise size, pigments are mixed with a commercial binder and applied to a metallic substrate to study their properties. Thermal stability to high temperature is studied with different tests. The results showed that laminar structure was preferred to intercalate larger amounts of metallic salt into the clay structure, and no significant differences were found when using silane or surfactant modifiers. Although the highest absorptivity value was 85% after 24 h at 600 °C, samples presented very good adherence to the metallic substrate. Addition of a small quantity of commercial black pigment to the paint composition could improve the absorptivity and maintain the excellent adhesion shown. Furthermore, montmorillonite clay, modified with a surfactant before adding metallic salt, and without silane, resulted in a black pigment in a powder form. This pillared clay could be used in future paint formulations.

Our purpose was to improve the thermal, mechanical and optimal properties of an epoxy bioresin using optimum hybrid natural pigments previously synthesised in our lab. Next, we searched for the best combinations of factors in the synthesis of natural hybrid nanopigments and then incorporated them into the bioresin. We combined three structural modifiers in the nanopigment synthesis, surfactant, coupling agent (silane) and a mordant salt (alum), selected to replicate mordant textile dyeing with natural dyes. We used Taguchi’s design L8 to seek final performance optimisation. We selected three natural dyes, chlorophyll, beta-carotene and beetroot extract, and used two laminar nanoclay types, montmorillonite and hydrotalcite. The thermal, mechanical and colorimetric characterisation of the composite obtained by mixing natural hybrid nanopigments (bionanocomposite) was made. The natural dye interactions with both nanoclays improved the thermal stabilities, colour performance and UV–VIS light exposure stability of natural dyes and bioresins. The best bionanocomposite materials were found in an acidic pH [3, 4] environment and by modifying nanoclays with mordant and surfactant during the nanopigment synthesis process.

The default method for color representation on displays involves sRGB as device-independent encoding color space. For improving color reproduction accuracy, we develop a device-specific display characterization model for the Apple iPad Air 2. In separate articles, we will evaluate the same method for other devices and for other display technologies. This model is combined with an easy-to-implement new method to account for the influence of illuminance from ambient light. The combination is called the mobile display characterization and illumination model (MDCIM) for the iPad Air 2, representing modern liquid crystal displays. Seven observers performed psychophysical tests at ambient illuminance levels from 600 to 3000 lx. They visually compared colors of calculated images with those of physical samples. The MDCIM model achieves similar color reproduction accuracy as when using the default method involving sRGB encoding at 1000 lx, while considerably improving color accuracy at other illuminance levels. At 600 lx, 98% of the observers prefer images directly generated with the MDCIM model over those created using the default method. The average color reproduction accuracy improves by two categories on a five-point scale. At 3000 lx, the percentage of colors that is represented at least reasonably well, according to the subjective assessment of visual observers, increased from 0% to 60%.