Mean Color Research Articles

Influence of combined hydrolyzed collagen and maltodextrin as carrier agents in spray drying of cocona pulp

Abstract This work aimed to evaluate the effect of carrier agents containing maltodextrin and protein, represented by hydrolyzed collagen on the spray drying process of cocona (Solanum sessiliflorum Dunal), and on the properties of the resulting powders. We used pre-established proportions between the solids of cocona pulp and the carrier agents (P:CA), and among carrier agents themselves, maltodextrin and hydrolyzed collagen, (MD:HC). The process was carried out in a spray dryer at an inlet air temperature of 120 ºC. We prepared twelve feed solutions containing 20% of total solids, with P:CA ratios of 1:3, 1:4, 1:5 and 1:6, and MD:HC ratios of 0:100, 50:50, and 100:0. Solids recovery was obtained for the evaluation of the spray drying process. The cocona pulp powders were analyzed for moisture content, water activity, particle size distribution, mean particle diameter, chemical structure (FTIR) and color. For a P:CA of 1:6, for the sample formulated with hydrolyzed collagen only, solids recovery (96.2%) was much higher than that of the sample with maltodextrin only (39.2%). The chemical structure of cocona powders can be considered a sign of a good encapsulation process. The color of the cocona pulp powder was similar to that of the carrier agents. The formulation with highest content of hydrolyzed collagen improved the recovery of solids, guaranteed the cocona pulp encapsulation, and obtained fruit powders with bioactive properties.

Evidence of Golden and Aesthetic Proportions in Colors of Paintings of the Prominent Artists

We introduce the color ratio concept and treat the challenge of automatically analyzing the color and width/height proportion ratios in the recognized paintings. The first time the authors, by using the computer simulations, show that majority of paintings having both proportions, the color and width/height proportion ratios are less than the Golden ratio (GR) and larger than the Aesthetic ratio. The method of color modeling is described by using color proportions similar to ratios in the Golden triangle. New methods of color modeling are presented that are based on the ratio of the well-known paintings, such as the Aivazovsky and Da Vinci coloring models. We also use the GR to generate new color models that may help to produce color images from grayscale images. Examples of processing images of art prominent painting are given, and the mean color ratio and mean of width/height proportions over 441 works of 13 artists.

Color changes induced by different staining solutions and different light curing units in dental resin composites

PurposeTo evaluate color changes induced by three different staining solutions and three different light curing devices in two different resin composites.Materials and methodsTwo different resin composites (ESTELITE Σ QUICK and ESTHET.X HD) were tested in this study. Hundred discs (5 mm diameter × 2 mm thick) of each tested material were made. Ten specimens were used as control, while other 90 specimens subdivided into three subgroups (n = 30); (a) cured with halogen-light curing-unit, (b) cured with plasma-arc unit, and (c) cured with argon laser of 488 nm. Each subgroup was further subdivided into three classes (n = 10): (a) immersed in tea for 10 min three times daily for 3 months, (b) immersed in coffee for 10 min three times daily for 3 months, and (c) immersed in Arabic coffee for 10 min three times daily for 3 months. Between staining challenges, specimens were immersed in artificial saliva. Specimens were tested for quantitative color changes using Quanta Environmental Scanning Electron Microscope. Data was statistically analyzed using three-way analysis of variance and Tukey's post-hoc test (P ≤ 0.05).ResultsThe mean color change of coffee (126.53 pixel) showed the highest value. This was followed by tea (117.96 pixel) and Arabic coffee (113.5 pixel) with no statistically significant difference between the two solutions. Meanwhile, laser showed the highest mean value (122.55 pixel) whereas; there was no statistically significant difference between QHL (117.9 pixel) and plasma arc curing (117.54 pixel). No significant difference was found between the two tested materials ESTELITE Σ QUICK and ESTHET.X HD.ConclusionThe two tested composites performed similarly under the test conditions. Curing with argon laser along with the coffee as staining solution affected the color stability of the tested materials.

The effect of in-office bleaching applications on the color and translucency of composite resins

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Labor and birth outcomes in term low-risk adolescent pregnancies

Aim: The study aimed to evaluate the relationship between the caries frequency, which was determined using different caries indexes Objective: The aim of this study was to investigate the effect of in-office bleaching agents on the color and translucency of different resin composites. Materials and Methods: Twenty-four disk-shaped specimens with 1 mm thickness and 8 mm diameter were fabricated from five different resin composites. The specimens were then divided into three subgroups, two office bleaching groups (40% Opalescence Boost, 38% Whitesmile Power Whitening) and one control group (n=8). All specimens were polymerized for 40 s with a LED light-curing unit. Color measurement was performed using a spectrophotometer. Bleaching agents were applied to the experimental groups in accordance with the manufacturer's instructions for 14 days, while the specimens in the control group were kept in distilled water only. Translucency parameters of the specimens before and after bleaching and the color changes after bleaching were calculated using CIE L*a*b* color coordinates. Data were analyzed using the paired sample t-test and ANOVA (α=0.05).Results: Statistically significant differences were found between the control group and the bleached groups according to color change values (p0.05). The highest mean color change value was observed in the Ceram-X / Opalescence Boost group. The Ceram-X / Opalescence Boost, Majesty Esthetic / Opalescence Boost, and Ceram-X / Whitesmile Power specimens showed clinically non-acceptable color changes. Translucency parameter values in each group between baseline and the end of the 14th day revealed no statistically significant difference (p>0.05).Conclusions: The office bleaching agents may affect the color and translucency parameters of composite resins depending on the structural properties.

Management of white spot lesions using resin infiltration and microabrasion: a comparative in vitro study.

ABSTRACTStudy objective: White spot lesions are unwelcomed side effects of fixed appliances that compromise the treatment outcome. Recently the infiltration of white spot lesions has been introduced as a viable treatment alternative and the objective is to evaluate the colour improvement, stability against discolouration and abrasion resistance following resin infiltration and resin infiltration following Microabrasion..Materials and methods: This study design is an in vitro prospective study that included 45 teeth extracted for orthodontic purposes. Artificial white spot lesions were created in the enamel and teeth were randomly allocated to three groups, then the teeth were treated with infiltration (Icon) and infiltration following Microabrasion (Opalustre) or remained untreated (control). The three groups were then subjected to Thermocycling, tooth brush abrasion and discolouration then visible colour change and abrasion resistance were measured.Results:When ΔE was calculated between the baseline measurements and those after white spot lesions there was a clinical and statistical color change in the three groups, in group II (the combined treatment group) the calculated ΔE between baseline measurements and those taken after treatment and after aging the mean color difference was less than that in group III (only resin infiltration group). Under SEM after aging all the treated surfaces of the specimens in group II were smooth with no microcracks while in group III the treated surfaces showed smooth areas and other areas showed microfissures and microcracks.Conclusions:When microabrasion preceded resin infiltration in the treatment of WSLs, it improved the color matching immediately after treatment application and showed better performance after aging procedures. It also produced smooth surface free from microcracks under SEM.

Effect of Hydrothermal Aging and Beverages on Color Stability of Lithium Disilicate and Zirconia Based Ceramics.

Background and Objectives: All-ceramic prosthesis is widely used in modern dental practice because of its improved physico-mechanical and optical properties. These restorations are exposed to coloring agents from various nutrition and beverages in the oral cavity. Long-term color stability is critical for the success of these restorative materials. The purpose of this in vitro study was to assess the effect of common beverages and mouthwash on the color stability of lithium disilicate (LD), monolithic zirconia (MZ) and bilayer zirconia (BZ) surfaces. Materials and Method: Thirty disc-shaped specimens from each material were fabricated; each group was subdivided (n = 10) according to coffee, green tea and chlorhexidine immersion solutions. The baseline color of ceramic discs was recorded according to the CIE L*a*b* system with a portable spectrophotometer. The second measurement was recorded after 3000 thermocycling and immersion in coloring agents for 7 days. The mean color difference was calculated and data were compared with Kruskal-Wallis and Mann-Whitney post hoc tests (0.05). Results: ΔE values for LD with the immersion of coffee, tea, and Chlorhexidine gluconate (CHG) were 1.78, 2.241 and 1.58, respectively. Corresponding ΔE values for MZ were 5.60, 5.19, and 4.86; marginally higher than the clinically acceptable level of 3.5. Meanwhile, BZ showed better color stability compared to MZ with ΔE values of 4.22, 2.11 and 1.43. Conclusions: Among the ceramics evaluated, LD ceramic was found to be more color stable, while MZ ceramics displayed a higher susceptibility to discoloration. MZ and BZ ceramic colors were significantly altered with coffee immersion, while LD ceramics were more affected by green tea.

Efficacy and Adverse Effects of Whitening Dentifrices Compared With Other Products: A Systematic Review and Meta-analysis.

Whitening dentifrices (WDs) are widespread and accessible worldwide, claiming to whiten teeth. Therefore, this systematic review aimed to assess the extrinsic stain removal (ESR), the whitening potential, and the adverse effects of WDs. Randomized controlled trials comparing WDs with regular dentifrices (RDs) and other home-based whitening products were searched at NCBI-PubMed, Cochrane-CENTRAL, EBSCO-Host, and clinicaltrials.gov. The studies were screened and had data extracted by two independent researchers. Eligible studies presented outcomes of ESR, color change, and adverse effects, with no restriction of publication date. Data were meta-analyzed using RevMan 5.3, and the level of evidence was rated according to GRADE criteria. Eleven studies (n=1962) assessed reduction of stain area and intensity through Lobene Stain index, with a mean difference (MD) of -0.33 ([-0.41;-0.25]; p=0.00001) and -0.34 ([-0.44;-0.25]; p=0.00001), respectively. When the modified Lobene Stain index was used (six studies; n=2576), MD was -0.42 ([-0.58;-0.25]; p=0.00001) and -0.30 ([-0.39;-0.21]; p=0.00001), respectively. Mean color change through shade guide tabs (three studies; n=1322) was -1.80 ([-2.33;-1.26]; p=0.00001). All differences were in favor of the WDs, which also produced a risk of adverse effects (RR=1.74; [1.20, 2.52]; p=0.003; four studies; n=1322). The comparison of WDs with paint-on gel (two studies; n=58) yielded similar efficacy and adverse effects (p>0.05), whereas the comparison of WDs with white strips (two studies; n=87) yielded higher efficacy of the latter (p=0.00001) and similar adverse effects (p=0.52). The quality of evidence varied from low to moderate. WDs are more effective in reducing extrinsic stain and producing a whitening-like effect in teeth than RDs, although they also produce more adverse effects. Whitening efficacy of WDs is similar to paint-on gel and lower than white strips. Higher-quality evidence demands larger, well-conducted, independent studies.

Adding trans-abdominal elastography to the diagnostic tool for an ileal gastrointestinal stromal tumor: a case report

BackgroundDiagnosis of gastrointestinal stromal tumors (GISTs) in the distal small intestine is difficult by endoscopic ultrasound. This is the first reported case of an ileal GIST, which is diagnosed by transabdominal sonography and strain elastography.Case presentationA 75 y/o woman presented with tarry stool and dizziness. No definite bleeder could be identified by esophagogastroduodenoscopy and colonoscopy. The transabdominal sonography revealed a large heterogeneous tumor involving the muscular layer of the ileum. Strain elastography showed the strain ratio was 6.51. Strain histogram was skewed to the blue side, and mean color value was 230.5, signifying a stiff tumor. GIST was highly suspected. The patient underwent laparoscope-assisted tumor excision and the histological examination confirmed a malignant GIST. The patient was discharged without postoperative event.ConclusionTransabdominal strain elastography could play a role to discriminate small bowel GISTs and other submucosal tumors, especially in the location with difficulty in endoscopic ultrasound.

The Color Difference between Differentiated Early Gastric Cancer and Suspicious Mucosal Areas on Linked Color Imaging

Background: Image enhanced endoscopy (IEE) contributes to the early detection of gastrointestinal cancer. IEE enhances the color between a lesion and the background mucosa. Linked color imaging (LCI), a novel form of IEE, is a unique system for enhancing color and some studies have demonstrated the efficacy of LCI in the diagnosis of early gastric cancer (EGC) based on the color difference between cancer and the background mucosa. However, the effect may increase the area in which cancer is suspected and lead to an increase in false-positive results. Summary: We conducted a retrospective study of linked color images of differentiated EGC and suspicious mucosal areas to compare the colors between each lesion. Images of 38 EGCs and 23 suspicious areas were analyzed. The mean color values of EGC were as follows; L*(lightness), 61.7; a*(green to red), 41.2; and b*(blue to yellow), 27.1. Those of suspicious mucosal areas were as follows; L*, 56.1; a*, 44.2; and b*, 21.3. EGC had significantly higher L*, b* values and lower a* values in comparison to suspicious mucosal areas. EGC and suspicious mucosal areas had significantly higher a* values in comparison to the background mucosa. Key Messages: EGC had higher b* values in comparison to suspicious mucosal areas, and was not only reddish but also mixed with yellow, with an orange-like color.

Quantitative evaluation of digital-image enhancement during heads-up surgery

Image-processing is an advantage of heads-up surgery and expected to facilitate ophthalmic surgeries. To evaluate image-processing quantitatively, we analyzed the surgical images of twenty eyes that underwent vitrectomy with internal limiting membrane (ILM) peeling assisted by Brilliant Blue G (BBG). Still images of the peeling procedure were obtained from the surgical video, and the color difference was calculated between two adjacent spots inside and outside the ILM-peeling contour, i.e., without and with BBG staining, respectively. The color differences were compared between the two settings with and without image-processing, delivered by an algorithm to enhance the color and contrast. Color differences were calculated using two methods: the Euclidean distance based on RGB values (RGB distance) and the Delta-E00 formula provided by the International Commission on Illumination. In five cases, minimum light intensities required to recognize the contour of ILM-peeling were compared during surgeries between the two settings with and without enhancement. Image-processing increased the mean color difference significantly (P < 0.001) from 15.47 and 4.49 to 34.03 and 8.00, respectively, for the RGB distance and Delta-E00. The minimum light intensity was reduced from 15 to 5 on average by image-enhancement. These results showed image-processing enhances color differences and reduces light intensities during vitrectomy.

Stain Removal Through Color Normalization of Haematoxylin and Eosin Images: A Review

Histopathology images are used for the diagnosis and examination of cancer cells. Preparing and scanning histopathology slides consist of numerous steps of which staining are an important process. But these staining procedures cause multitude problems as there may be variations in the slides due to multiple reasons. Color variations in histopathology images can occur due to inconsistent staining of biopsy tissue, color responses of different scanners or difference in raw materials and manufacturing techniques used by stain. These factors hamper the generalization of automatic image analysis method. Hence there is a need for standardizing the image before analysis by performing stain normalization which is achieved by removing the stains for visual enhancement. Color normalization techniques play a vital in the developing computerized decision support system. In this paper, a detailed study and performance evaluation of various color normalization techniques such as Histogram Specification, Macenko Method, Reinhard Method on histopathology images are presented. In these normalization procedures the mean color of the target image is transferred onto the source image. Quality performance of different stain normalization techniques is evaluated based on Entropy and Structure Similarity Index Measure (SSIM). In this work, we record the time complexity of the color normalization algorithms. The normalization techniques are tested on histopathological images from UCSB dataset and Mitosis Atypia 2014 dataset. This article reviews and summarizes the color normalization techniques on histopathological images for visual improvement.

Three-Dimensional Evaluation on Accuracy of Conventional and Milled Gypsum Models and 3D Printed Photopolymer Models.

The aim of this study was to evaluate the accuracy of dental models fabricated by conventional, milling, and three-dimensional (3D) printing methods. A reference model with inlay, single crown, and three-unit fixed dental prostheses (FDP) preparations was prepared. Conventional gypsum models (CON) were manufactured from the conventional method. Digital impressions were obtained by intraoral scanner, which were converted into physical models such as milled gypsum models (MIL), stereolithography (SLA), and digital light processing (DLP) 3D printed photopolymer models (S3P and D3P). Models were extracted as standard triangulated language (STL) data by reference scanner. All STL data were superimposed by 3D analysis software and quantitative and qualitative analysis was performed using root mean square (RMS) values and color difference map. Statistical analyses were performed using the Kruskal–Wallis test and Mann–Whitney U test with Bonferroni’s correction. For full arch, the RMS value of trueness and precision in CON was significantly smaller than in the other groups (p < 0.05/6 = 0.008), and there was no significant difference between S3P and D3P (p > 0.05/6 = 0.008). On the other hand, the RMS value of trueness in CON was significantly smaller than in the other groups for all prepared teeth (p < 0.05/6 = 0.008), and there was no significant difference between MIL and S3P (p > 0.05/6 = 0.008). In conclusion, conventional gypsum models showed better accuracy than digitally milled and 3D printed models.

Evaluation of the Effect of Household Cleansers on the Color Change of Two Types of Permanent Soft Liners: An In Vitro Study

Many patients use household cleaners to clean denture which can cause discoloration and damage soft liners. The purpose of this study was to evaluate the effect of household cleansers on the color change of two types of permanent soft liners. Methods: In this interventional study, 80 permanent silicone soft liners, including 40 heat-cured liners (Molloplast-B, Detax Gmbh & Co. KG, Ettlingen, Germany) and 40 self-cure liners (Mucopren soft, Kettenbach GmbH & Co. KG, Eschenburg, Germany) were made in brass molds with dimensions of 15×2 mm in accordance with the manufacturer's instructions. The samples were immersed in distilled water for 24h and the initial color was determined using a colorimeter. Then, each group (n=10) was immersed for 8h daily in 2.5% vinegar, 2.5% hypochlorite, 2.5% hand washing liquid, and distilled water (control). Color measurements were performed after 7 and 30 days of immersion in solutions and data were analyzed using ANOVA, independent t-test, and Tukey's post hoc tests. Results: In distilled water, hypochlorite, and vinegar, the mean color change after one month was significantly lower in Molloplast-B than Mucopren (P=0.042, P<0.001, P=0.002); however, in Hand washing, the difference was not significant (P=0.780). Conclusion: The mean color change in Mucopren in all cleansers was higher than Molloplast-B, and the highest change in color was observed in both liners in hypochlorite.

VIRTIS-H observations of the dust coma of comet 67P/Churyumov-Gerasimenko: spectral properties and color temperature variability with phase and elevation

We analyze 2–5μm spectroscopic observations of the dust coma of comet 67P/Churyumov-Gerasimenko obtained with the Visible InfraRed Thermal Imaging Spectrometer (VIRTIS-H) instrument on board Rosetta from 3 June to 29 October 2015 at heliocentric distancesrh= 1.24–1.55 AU. The 2–2.5μm color, bolometric albedo, and color temperature were measured using spectral fitting. Data obtained atα= 90° solar phase angle show an increase in bolometric albedo (0.05–0.14) with increasing altitude (0.5–8 km), accompanied by a possible marginal decrease in color and color temperature. Possible explanations include dark particles on ballistic trajectories in the inner coma and radial changes in particle composition. In the phase angle range 50°–120°, phase reddening is significant (0.031%/100 nm deg−1) for a mean color of 2%/100 nm atα= 90°, which might be related to the roughness of the dust particles. Moreover, a decrease in color temperature with decreasing phase angle is also observed at a rate of ~0.3 K deg−1, consistent with the presence of large porous particles, with low thermal inertia, and showing a significant day-to-night temperature contrast. Comparing data acquired at fixed phase angle (α= 90°), a 20% increase in bolometric albedo is observed near perihelion. Heliocentric variations in dust color are not significant in the time period we analyzed. The measured color temperatures vary from 260 to 320 K, and follow arh−0.6variation in therh= 1.24–1.5 AU range, which is close to the expectedrh−0.5value.

Effect of accelerated staining and bleaching on chairside CAD/CAM materials with high and low translucency.

The aim of the study was to assess the effect of staining and bleaching on CAD/CAM materials with high (HT) and low translucency (LT or T). Samples were stored in coffee and subsequently bleached. CIELAB parameters were recorded at baseline, after coffee immersion, after bleaching. Translucency parameter (TP), whiteness index (WID) and color changes were calculated (ΔE00). Influence of staining and bleaching was analyzed with repeated-measures ANOVA and color differences between materials were analyzed with one-way ANOVA (α=0.05). Staining and bleaching significantly affected CIELAB parameters and WID for all materials (p<0.001). TP was significantly influenced by staining and bleaching for Crios and Enamic (p<0.05). Mean color differences were significantly different between materials (p<0.001). The greatest color changes due to staining were observed for Lava Ultimate while the lowest for e.max CAD. Both coffee staining and bleaching induced greater color changes for HT materials of the same brand compared to LT.

Chewing ability and desaturation during chewing in patients with COPD

Chewing ability is essential to maintain nutrition status and can be associated with oral conditions, sarcopenia, and lung function in patients with chronic obstructive pulmonary disease (COPD). Herein, our pilot study investigated the chewing ability and degree of desaturation during chewing in patients with COPD (n = 41) and control subjects (n = 22). Subjects chewed a color-changing chewing gum for 1 minute and chewing ability was assessed by the color of the chewed gum, which was scored from 1 (very poor) to 5 (very good). Arterial oxygen saturation (SpO2) was monitored using a pulse oximeter and the difference in SpO2 was determined by comparison between before and during chewing. The mean color score of the chewed gum was lower in the COPD group than in the control group (3.1±0.7 vs 4.2±0.9, p<0.0001). Muscle mass loss (p<0.05), <20 remaining teeth (p<0.005), and COPD (p<0.001) were risk factors for poor chewing ability. The mean SpO2 decreased by 0.78±1.46% during gum chewing for 1 min. The mean SpO2 during gum chewing (95.1±2.4%) was lower than before gum chewing (95.9±1.7%) (p<0.05). The reduction of SpO2 was greater in COPD patients who had fewer remaining teeth (p<0.05). COPD patients with SpO2 reduction >4% during the 6-minute walk test showed greater reduction during gum chewing (p<0.05). Our results suggest that COPD patients with fewer remaining teeth exhibit poor chewing ability and greater desaturation during chewing.

Computational Intelligence Model for Estimating Intensity of Blast-Induced Ground Vibration in a Mine Based on Imperialist Competitive and Extreme Gradient Boosting Algorithms

In this paper, we developed a novel hybrid model ICA–XGBoost for estimating blast-produced ground vibration in a mine based on extreme gradient boosting (XGBoost) and imperialist competitive algorithm (ICA). For comparison, we used another hybrid model combining particle swarm optimization and XGBoost [i.e., particle swarm optimization (PSO)–XGBoost] as well as other models, namely classical XGBoost, artificial neural network (ANN), gradient boosting machine (GBM), and support vector regression (SVR). We compared these techniques using 136 blasting events data gathered at an open-pit coal mine in Vietnam. The models’ performance evaluation criteria were the determination coefficient (R2), root-mean-square error, mean absolute error, ranking, and color intensity. Based on the results, our ICA–XGBoost model is the most robust in predicting blast-produced ground vibration. The PSO–XGBoost model provided a slightly poorer performance. The classical XGBoost model showed a lower performance than the hybrid models (i.e., ICA–XGBoost and PSO–XGBoost). The SVR and ANN models gave average performances, whereas the GBM model yielded the worst performance. The results also reveal that the maximum explosive charge capacity, the elevation between blast sites and monitoring points, and the monitoring distance are the most critical variables that should be used in predicting the intensity of blast-induced ground vibration in a mine.

Towards the design of a blending system for precoloured fibres

AbstractIn order to create a commercial system for blending precoloured fibres that will appear visually solid once combined, it is necessary to understand the maximum colour difference required between the blend components. Based on this understanding, the lowest number of primaries required to populate a given colour gamut can be determined. A series of psychophysical experiments was carried out to explore the colour difference between fibre‐blend components and whether the resulting blended samples are perceived as visually solid. Experiments were carried out with loose stock fibre, yarn and knitted samples. Generally, it was found that the likelihood a blend appeared as visually solid increased as the average colour difference between the blend components, or primaries, decreased. The value of the mean colour difference at which 50% of participants viewed the blend as being visually solid was found to be 20.8, 20.5 and 18.0 for fibre, yarn and knitted samples, respectively. Consequently, it was found that it was more difficult to obtain a solid shade with the knitted form than with the loose stock fibre form.

Identification of representative segment of root for colour determination of carrot

The aim of the work was to verify hypothesis that colour of longitudinal section of carrot root may be represented by a selected segment of root or a cross-section. An image analysis was based on image data obtained for longitudinal sections of carrot roots using flatbed scanner and graphics editing software. Colour images were acquired into sRGB colour space and converted to CIE Lab. Sixteen segments of equal height were separated over whole length of root image. The colour difference metric was determined to present how colour of each segment differs from the mean colour of whole root. The root section was considered to be representative for whole root if colour difference metric was the least. The analysis of results confirmed a research hypothesis and allowed for finding representative section which was located at 10⁄16 of total root length measuring from the carrot root head.