Chromatic Variation Research Articles

Learned phase coded aperture for the benefit of depth of field extension.

Modern consumer electronics market dictates the need for small-scale and high-performance cameras. Such designs involve trade-offs between various system parameters. In such trade-offs, Depth Of Field (DOF) is a significant issue very often. We propose a computational imaging-based technique to overcome DOF limitations. Our approach is based on the synergy between a simple phase aperture coding element and a convolutional neural network (CNN). The phase element, designed for DOF extension using color diversity in the imaging system response, causes chromatic variations by creating a different defocus blur for each color channel of the image. The phase-mask is designed such that the CNN model is able to restore from the coded image an all-in-focus image easily. This is achieved by using a joint end-to-end training of both the phase element and the CNN parameters using backpropagation. The proposed approach provides superior performance to other methods in simulations as well as in real-world scenes.

On the Role of Color in Reading and Comprehension Tasks in Dyslexic Children and Adults.

We investigated the effect of chromatic variations on the reading process with normal and dyslexic readers. We demonstrate that color can induce wholeness, parts-whole organization and phenomenal fragmentation during reading and comprehension tasks within written texts made up of words and non-words in the following conditions: monochromatic (the whole text colored with only one color), word (each word colored in different color), half word (half word colored with a color different from the one of the second half), syllable (every syllable colored with a different color) and letter (each letter with a different color). The dependent variables considered were reading time, reading errors and incorrect answers to a comprehension test. The main results demonstrated that these parameters of reading performance are all influenced by the five aforementioned chromatic conditions. These outcomes manifest similar trends in four groups of readers: children and adults combined with normal or dyslexic readers. Possible applied research and clinical applications are discussed together with some basic questions related to color vision suggesting that the main purposes of color for living beings is to generate wholeness, parts-whole organization and perceptual segmentation.

Discrimination of spectral reflectance under environmental illumination

Color constancy is the ability to recover a stable perceptual estimate of surface reflectance, regardless of the lighting environment. However, we know little about how observers make judgments of the surface color of glossy objects, particularly in complex lighting environments that introduce complex spatial patterns of chromatic variation across an object’s surface. To address this question, we measured thresholds for reflectance discrimination using computer-rendered stimuli under environmental illumination. In Experiment 1, we found that glossiness and shape had small effects on discrimination thresholds. Importantly, discrimination ellipses extended along the direction in which the chromaticities in the environmental illumination spread. In Experiment 2, we also found that the observers’ abilities to judge surface colors were worse in lighting environments with an atypical chromatic distribution.

TiO2–SiO2–PDMS nanocomposite coating with self-cleaning effect for stone material: Finding the optimal amount of TiO2

Nano-sized TiO2 is widely used as photocatalysts for many applications; however, some aspects in the application in cultural heritage conservation are still unresolved. In particular, in this research, we focused our attention on nanostructured product composed by silica, polydimethylsiloxane (PDMS) and TiO2 nanoparticles. We explored the effect of variable amounts of nanoparticles on the features of coating, since this issue still has some unclear aspects. Several samples of limestone have been treated, and then, analysed. The chromatic variations induced by the treatments have been measured by colorimetric analysis, while the hydrophobic properties of coatings have been evaluated by contact angle measurements and capillary water absorption. The photocatalytic efficiency has been evaluated by methylene blue staining. In addition, two large facilities have been involved in this study, in order to obtain accurate results in a non-invasive way. On one side, middle-UV Raman spectroscopy measurements at IUVS beamline@Elettra (Trieste), by using UV synchrotron radiation (SR) source, revealed successful, with respect to conventional set-up, in order to quantify the amount of the anatase on the surface. On the other side, neutron radiography measurements at RAD Radiography Station@BNC (Budapest) permitted a sensitive monitoring of the water absorption dynamics on untreated and treated samples.

Color stability of conventional and bulk fill composite resins

ABSTRACT Objective: This study compared the color stability of different dental composite resins after prolonged exposure to a coffee solution. Methods: Sixty-four cylindrical discs (10 mm diameter x 2 mm thickness) were prepared using 8 different dental composite resins (n=8, per group). The specimens were first immersed in artificial saliva for 24 h followed by immersion in a coffee solution for 14 days. The assessment of chromatic variation (ΔE) was performed with the aid of a Vita Easyshade Advanced spectrophotometer (VITA Zahnfabrik, Bad Sackingen, Germany). The color of each specimen was calculated based on the L*, a* and b* coordinates of the CIELab system. Results: Grandio SO had the lowest average chromatic variation (ΔE=7.77) after immersion in coffee solution. Durafill VS, Grandio and Z350 XT (ΔE=8.58; ΔE=9.52; ΔE=10.39, respectively) showed similar chromatic variation, with no statistical difference in relation to Grandio SO. However, the other dental composite resins evaluated showed statistically higher values of ΔE compared to Grandio SO, and Enamel HRi (ΔE=20.56) demonstrated the highest chromatic variation. Conclusion: The Bulk Fill and hybrid composite resins from the same manufacturer (Micerium, Avegno, Italy) showed greater chromatic variation than the other composite resins tested. Grandio SO (Voco, Cuxaven, Germany) had the lowest ΔE variation.

CHEMICAL PROFILES OF ESSENTIAL OILS AND FATTY ACIDS FROM Erythrina velutina

Chemical analysis involving gas chromatography coupled to mass spectrometry of the essential oils of red and orange flowers from E. velutina revealed a predominance of phenylpropanoids in both samples. However, qualitative and quantitative differences were found in the compositions. (E)-Asarone (16.22 ± 0.23%) and (E)-caryophyllene (12.22 ± 0.11%) were identified as the major constituents of the essential oil from the red flowers, whereas (E)-caryophyllene (41.72 ± 1.65%) and eugenol (20.99 ± 0.21%) were identified as the major constituents of the oil from the orange flowers. Seventeen fatty acids were characterized in the red and black seeds. The fatty acid composition in the two chromatic variations had a high degree of similarity. Oleic acid (41.56 ± 1.33% and 46.12 ± 1.90% in the red and black seeds, respectively), palmitic acid (15.39 ± 0.16% and 12.33 ± 0.41%) and behenic acid (9.95 ± 0.14% and 12.10 ± 0.42%) were identified as the main fatty acids. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) enabled identifying significant differences in the chemical profile of the essential oils from the red flower and orange flower varieties of E. velutina. In contrast, PCA and HCA analysis revealed no significant differences in the fatty acid profile of the red and black seeds.

Is nano-TiO 2 alone an effective strategy for the maintenance of stones in Cultural Heritage?

Abstract TiO2-based nanocoatings have been becoming more and more widespread during last years in Cultural Heritage: they seem to be able to keep stone surfaces self-cleaned and to prevent the formation of biofouling. However, the efficiency of these coatings is strongly dependent on the substrate (i.e.: porosity and roughness) and on the amount of TiO2. Thus, this study experimentally investigates on the self-cleaning and anti-biofouling efficiency of a nano-TiO2 dispersion (without any organic or inorganic additive) applied on six different types of natural stones (three limestones, two sandstones and one tuff) usually used in Cultural Heritage, where high porosity and roughness can be found and the TiO2 amount cannot be increased in order to avoid any chromatic variation of the substrate. Water was used as solvent so as to reduce the risk of exposition of hazardous materials and to eliminate any chemical action on stones. The self-cleaning power of the coating was evaluated by measuring its ability at discolouring organic dye Methylene Blue, while its anti-biofouling efficiency was assessed by an accelerated growth test under controlled climatic conditions of two algal microorganisms, namely Chlorella mirabilis and Chroococcidiopsis fissurarum. Results show that, even if the photocatalytic and biocide power of nano-TiO2 itself is well known in literature, its application for the maintenance of stones in Cultural Heritage does not seem to be an effective strategy, especially when stones are highly porous and rough. Roughness and porosity of stones, in fact, can limit the efficiency of TiO2, which is thus not able to powerfully keep the stone substrate cleaned or slow down algal proliferation.

Discrimination of signal carotenoid content using multidimensional chromatic information

Red, orange, and yellow carotenoid-based ornaments, which are widely used as sexual signals in many birds, fish, and reptiles, are known to exhibit multidimensional chromatic variation as a result of both the concentration and relative proportions of different constituent carotenoids with differing spectral properties. This is thought to reflect intrinsic variation in signaler quality, making it a useful basis for female choice. However, whether females are able to discriminate relevant variation in carotenoid concentration and/or composition independently of each other, and of other phenotypic or behavior traits, and if so, how this mediates their choice, is poorly understood. Here, female 3-spined sticklebacks (Gasterosteus aculeatus) were presented with computer-animated courting males that varied exclusively in the appearance of their carotenoid-based coloration; specifically, each male’s signal provided a perceptual match for carotenoid coloration expressed by live males with known underlying carotenoid content, thereby providing a biologically-relevant signal while precluding confounding traits influencing female choice. Females were able to discriminate between prospective mates solely on the basis of perceived variation in the allocation of carotenoids to males’ sexual signals, and exhibited a strong preference for males with coloration indicative of higher concentrations of carotenoids in their signal, rather than in response to perceived variation in the relative proportion of constituent carotenoids. This has important implications for our understanding of male signaling strategies and the information content of carotenoid-based sexual signals.

The unrepresentable and ineffable

While colour seems to communicate values that fluctuate depending on cultures and eras, the attribution of emotional correlations to chromatic variations seems on the contrary to constitute a widespread tendency among human groups. Now, is it true that every language includes the notion of colour, as well the terms referring to colours? If certain cultural contexts are devoid of any representation of colour, and consequently of a nomenclature of individual colours, can we still talk about colour semantics, or of an emotional connotation of colours? The ethnography of a population native to the Upper Amazon, who assesses the colour-related sensory experiences without using one of our main descriptive tools – colour names – will give us the opportunity to reflect on what we could call an oxymoron: defining what’s ineffable.

Parameters that influence the chromatic variation of porous face ceramic waterproofed with organosilicic products

All water repellent products, theoretically colorless, when applied superficially in the porous face ceramic, produce a chromatic variation in the color of the ceramic. The factors that influence the color variation are explored. The ceramic is selected according to its type of manufacture: manual, pressed and extruded, characterizing it considering the absorption coefficient, open porosity, absorption rate, surface finishing and initial color parameters. The water repellent products are selected on the basis of their chemical composition. The final color of the waterproofing ceramics is analysed together with the parameters obtained from the characterization of the ceramic, noting that the only color variation depends on the initial color of the ceramic, existing a linear relationship between the initial and final color of the waterproofing ceramics with each of the products. The final color of a ceramic can be predicted, depending on the composition of the water repellent product being applied.

Effect of tree architecture on fruit quality and yield attributes of nectarine (Prunus persica var. nectarina) cv. Fantasia under temperate condition

The present study was carried out at research farm of ICAR-Central Institute of Temperate Horticulture, Srinagar during the year 2009 to 2013. The nectarine cv. Fantasia grafted on wild peach rootstock and subsequently these trees were trained in six different training systems, viz. central leader system, open center system, Y shape- tatura trellis, four scaffolds, modified central leader system and modified open leader system. These six training systems were further evaluated for plant growth, fruit quality, and yield and average data of four years have been statistically analyzed. Significant chromatic variation was recorded for fruit skin color and maximum a* value was recorded in tatura trellis (44.13), similarly maximum trunk cross section area (TCSA) (54 cm2 ), fruit yield (32.72 tonnes/ha), fruit quality in terms of fruit weight (105.28 g), fruit length (65.53 mm), fruit diameter (66.85 mm), No. of fruits/plant (310) and yield efficiency (0.379 kg/cm2) were recorded in Y-shape tatura trellis system as compared to other traditional and contemporary tree architecture. Among biochemical parameters, highest TSS (14.66 0B) and ascorbic acid (15 mg/100g fresh fruit weight), titrable acidity (0.311%), TSS/acidity (60.89) was recorded in Y shape tatura trellis system, central leader system and modified open leader system respectively. Likewise total anthocyanin (6.23 mg cyanidin-3-glucoside equivalents 100/g fw), total carotenoids (8.71 mg/100 g), total phenols (575 mg GA equivalents/100 g), total flavonols (371 mg catechin equivalents /100 g), diphenyl-1-picryl hydrazyl (DPPH) (66 mg of AAE/100 g of fresh weight) and Ferric reducing antioxidant potential (FRAP) (69.16 mg of AAE /100 g of fresh weight) was recorded in Y shape tatura trellis followed by four scaffold training system. The present study emphasizes the superiority of Y shape tatura trellis system over other training system and could be exploited for higher quality and quantity nectarine production in temperate regions.

Holistic quaternion vector convolution filter for RGB-depth video contour detection

A quaternion vector gradient filter is proposed for RGB-depth (RGB-D) video contour detection. First, a holistic quaternion vector system is introduced to synthetically express the color and depth information, by adding the depth to its scalar part. Then, a convolution differential operator for quaternion vector is proposed to highlight edges with both depth and chromatic variations but restrain the gradient of intensity term. In addition, the quaternion vector gradients are adaptively weighted utilizing depth confidence measure and the quadtree decomposition of the coding tree units in the video streaming. Results on the 3-D high-efficiency video coding test sequences and quantitative simulated experiments on Berkeley segmentation datasets both indicate the availability of the proposed gradient-based method on detecting the semantic contour of the RGB-D videos.

Nanotechnology on wood: The effect of photocatalytic nanocoatings against Aspergillus niger

Abstract Fungi play a primary role in wood decay, including building and historical surfaces. Over the last years, nanotechnology has been used to preserve different type of surfaces from biodeterioration caused by the development of biological contaminants. In this study, photocatalytic titanium dioxide (TiO 2 ) based nanocompounds (also containing silver and copper) were brushed on wood surfaces to evaluate biocidal ability against the development of soft-rot fungus Aspergillus niger . Five different nanotreatments were applied on two types of wood (softwood and hardwood). Compatibility with wooden substrates has been assessed using colorimetry. Antifungal capability of metallic nanotreatments was quantitatively evaluated considering different parameters: microscopic observation, chromatic variation, reflectance change and mould extent. Even though photocatalytic nanotreatments inhibited A. niger development only partially, they seem to be a promising tool to reduce harmful mould development and to better preserve wooden artefacts.

파장변화에 매우 안정한 시준렌즈 설계

특정한 파장대역에서 파장변화에 따른 굴절능의 변화를 1차, 2차 미분까지 보정하여 기준파장과 그 인근 파장 대역에서 굴절능의 변화가 매우 적도록 안정화된 광학계를 설계하는 방법에 대하여 연구하고, 이를 적용하여 회절한계의 시준렌즈를 설계하였다. 설계된 광학계는 파장 변화에 대하여 매우 안정하였고, 파장 360~410 nm 대역에서 유효초점거리의 변화가 0.002% 이내로 매우 적었다. To minimize chromatic variations across a wavelength band, we suggest a new design that corrects the first- and second-order wavelength derivatives of the refractive power. Based on this method, a diffraction-limited collimator is designed. The design is very stable against wavelength change, as expected. The chromatic change of the effective focal length is less than 0.002% in the wavelength range from 360 to 410 nm.

Morphological and Genetic Differentiation within the Southernmost Vector of Chagas Disease: Triatoma patagonica (Hemiptera - Reduviidae).

The epidemiological importance of Chagas disease vectors largely depends on their spreading ability and adaptation to domestic habitats. Triatoma patagonica is a secondary vector of Chagas disease endemic of Argentina, and it has been found colonizing domiciles and most commonly peridomiciliary structures in several Argentine provinces and morphological variation along its distribution range have been described. To asses if population differentiation represents geographic variants or true biological species, multiple genetic and phenotypic approaches and laboratory cross-breeding were performed in T. patagonica peridomestic populations. Analyses of chromatic variation of forewings, their size and the content of C-heterochromatin on chromosomes revealed that populations are structured following a North-South latitudinal variation. Cytochrome c oxidase I mitochondrial gene (COI) nucleotide analysis showed a mean genetic distance of 5.2% between the most distant populations. The cross-breeding experiments suggest a partial reproductive isolation between some populations with 40% of couples not laying eggs and low hatching efficiency. Our findings reveal phenotypic and genetic variations that suggest an incipient differentiation processes among T. patagonica populations with a pronounced phenotypic and genetic divergence between the most distant populations. The population differentiation here reported is probably related to differential environmental conditions and it could reflect the occurrence of an incipient speciation process in T. patagonica.

A new quadruple gravitational lens from the Hyper Suprime-Cam Survey: the puzzle of HSC J115252+004733

We report the serendipitous discovery of a quadruply lensed source at $z_{\rm s}=3.76$, HSC~J115252+004733, from the Hyper Suprime-Cam (HSC) Survey. The source is lensed by an early-type galaxy at $z_{\rm l}=0.466$ and a satellite galaxy. Here, we investigate the properties of the source by studying its size and luminosity from the imaging and the luminosity and velocity width of the Ly-$\alpha$ line from the spectrum. Our analyses suggest that the source is most probably a low-luminosity active galactic nucleus (LLAGN) but the possibility of it being a compact bright galaxy (e.g., a Lyman-$\alpha$ emitter or Lyman Break Galaxy) cannot be excluded. The brighter pair of lensed images appears point-like except in the HSC $i$-band (with a seeing $\sim0.5"$). The extended emission in the $i$-band image could be due to the host galaxy underneath the AGN, or alternatively, due to a highly compact lensed galaxy (without AGN) which appears point-like in all bands except in $i$-band. We also find that the flux ratio of the brighter pair of images is different in the Ks-band compared to optical wavelengths. Phenomena such as differential extinction and intrinsic variability cannot explain this chromatic variation. While microlensing from stars in the foreground galaxy is less likely to be the cause, it cannot be ruled out completely. If the galaxy hosts an AGN, then this represents the highest redshift quadruply imaged AGN known to date, enabling study of a distant LLAGN. Discovery of this unusually compact and faint source demonstrates the potential of the HSC survey.

Image Quality under Chromatic Impairments

The influence of chromatic impairments on the perceived image quality is studied in this article. Under the D65 standard illuminant, a set of hyperspectral images were represented into the CIELAB color space, and the corresponding chromatic coordinates were subdivided into clusters with the k -means algorithm. Each color cluster was shifted by a predefined chromatic impairment Δ E * ab with random direction in a * b * chromatic coordinates only. Applying impairments of 3, 6, 9, 12, and 15 in a * b * coordinates to five hyperspectral images a set of modified images was generated. Those images were shown to subjects that were asked to rank their quality based on their naturalness. The Mean Opinion Score of the subjective evaluations was computed to quantify the sensitivity to the chromatic variations. This article is also complemented with an objective evaluation of the quality using several state-of-the-art metrics and using the CIEDE2000 color difference among others. Analyzing the correlations between subjective and objective quality evaluation helps us to conclude that the proposed quality estimators based on the CIEDE2000 provide the best representation. Moreover, it was concluded that the established quality metrics only become reliable by averaging their results on each color component.

Modified Savart polariscope with wide field of view and achromatic lateral displacement

A modified Savart polariscope with wide field of view and achromatic lateral displacement is presented. The modified Savart polariscope can be made from two different birefringent crystal materials. The principle of the element is described and the impacts of systematic errors are analyzed. The achievement and performance of the modified Savart polariscope is demonstrated with numerical simulations. The maximum acceptable angle of incidence can be increased by an order of magnitude and the chromatic variations in lateral displacement are inhibited obviously across the specified spectral range 0.4μm to 0.9μm.

Variation of the surface chromatic properties of exposed concrete façades treated with anti-graffiti products

The research analyses the variation of the surface chromatic properties, hue and brightness, sustained by the Portland cement mortar support, due to the application of anti-graffiti protective treatments. The test specimens were digitally analysed using a methodology based on the RGB model, which resulted in the image histogram values of each test specimen treated. The same mortar type without protection was used as the base to quantify the modification. Surface chromatic variation is determined by the type of anti-graffiti treatment used and by the base material on which it is applied. The result is that all the anti-graffiti products studied cause the variation of the supports’ hue and brightness, with the mortar made from grey Portland cement type CEM II/B-M(V-L) 32,5 N (Mb) being the one with less variation of its surface chromatic characteristics once treated. In addition, the fluorinated acrylate component (A4) causes the smalles deviation of the absolute hue and brightness values obtained from the samples analysed.

Synthetic white pigments (white titanium and white zinc) in different binding media. Influence of environmental agents

This work concerns the behaviour of white pigments of white titanium and white zinc in different media both of natural and synthetic binders. In addition, a study was made of the impact that time, high-energy UV radiation, heating by infrared radiation, or saturation processes of relative humidity exert on stability and chromaticity of the samples. The composition of pigments and binders as well as the time course of their samples were studied by X-ray diffraction, mass spectrometry, electron microscopy, and instrumental colour measurement. The effect of the aging, UV, and infrared exposure together with moisture saturation were found to result in losses in elasticity and cracking of the film generated by the binder, the latter two factors causing the most severe losses. The greatest variations were detected in the colorimetric study, reflecting the utility of instrumental colour measurements for these types of studies. The chromatic variations detected consist fundamentally of loss in luminosity (ΔL) and chroma (ΔC) as well as a slight yellowing tendency. In general, the samples based on natural binders were more affected that those based on synthetic products.