Influence Of Different Light Sources Research Articles

Photocatalytic degradation of methylene blue by anatase TiO2 coating

AbstractPhotocatalytic coatings have the potential to contribute to the purification of water via an advanced oxidation process (AOP). A commonly used method for analyzing the mechanism of the photocatalytic performance of a given reactor type is to document the degradation behavior in a solution containing methylene blue. However, since methylene blue is rather unstable, the degradation results should be viewed critically. In this work, the degradation behavior of a test solution with methylene blue on quartz glass surfaces coated with photocatalytic titanium dioxide (TiO2) of the anatase modification was investigated through a variety of different light sources. The coating was deposited by physical vapor deposition (PVD) with the reactive pulsed DC magnetron sputtering ion plating (MSIP) method described in the study by Desch and Lake, while the quartz glasses were coated with a 100 nm thick TiO2 coating on the outside. The same glasses were used for all experiments with TiO2. In the determination of the degradation rate, additional experiments were performed using pure quartz glass without any coating, which made it possible to examine the influence of different light sources on the degradation rate of methylene blue in general. Three different light sources, namely UV‐A, UV‐C, and simple fluorescent lamps were used in this study. The concentration of methylene blue was recorded by photo spectrometer in 10‐min increments throughout the experiment and the experiments were performed for 24 h in all cases. Our data indicates that the methylene blue test is a poor method because the degradation rate is not clearly differentiable due to the low stability of the test substance. Without including reference testing in the absence of a catalyst, data may be subject to misinterpretation.

Study of the differences among hyperspectral estimation models under different measurement light source conditions

ABSTRACT In hyperspectral remote sensing measurements, the spectral effective information extracted under different measurement light source conditions will produce differences, which in turn affects the robustness of the constructed models. Therefore, it is important to study the differences between hyperspectral estimation models under different measurement light source conditions to construct a general hyperspectral model of vegetation parameters under different light source conditions. In this paper, hyperspectral models are constructed from artificial and natural light sources, and the hyperspectral reflectance and the corresponding SPAD values of artificial and natural light sources under winter wheat, corn and tea tree were measured under the same time period and the same light measurement angle and height. The collected data were used to construct models for the four vegetation indices with better results after screening and to explore how to reduce model variability under different measured light source conditions. The results show that the difference between the artificial light source and natural light source models is significant (the coefficient of determination R2 is significantly different between the artificial light source and natural light source models), and the influence of different light sources on the construction of hyperspectral estimation models can be reduced by selecting vegetation indices. The linear regression equation model constructed by NDVI can effectively reduce the influence of different light sources on the construction of SPAD hyperspectral models and make the model more general. This study can provide new ideas and methods to investigate the differences in spectral models under different measurement light sources.

Effects of different light quality and GA3 concentration on tobacco seedling growth, root characteristics, and carbon and nitrogen metabolism

Light quality and gibberellins affect growth, development and morphogenesis of plants. In order to improve the quality of tobacco seedlings under greenhouse conditions, the influence of different light sources and their interaction with foliar-applied gibberellic acid (GA3) on key growth and metabolic parameters in tobacco were examined. Light sources included white, red and blue lights while GA3 was applied in three concentrations, i.e., 0, 50 and 100 mg L-1. The survival rate of the seedlings was observed after transplanting. Morphological parameters like plant height, stalk diameter, and length, width and number of leaves increased maximally with higher concentration of GA3 under all three light regimes, however, light sources did not show any visible difference. Further, root vitality, chlorophyll content and the activities amylase and nitrate reductase increased significantly due to GA3 application and achieved highest values with blue light + 100 mg L-1 GA3. Supplementation of red and blue light along with foliar application of GA3 significantly increased the growth parameters including seedling height, stem diameter, root-shoot ratio, leaf length and root vitality. The contents of carbon metabolites including starch, soluble sugars, and reducing sugars improved significantly in plants grown under red and blue lights in combination with foliar application of GA3. The results of the present study depict that growing tobacco under blue light and the application GA3 is beneficial in terms of achieving increased growth, root characteristics, carbon and nitrogen metabolism of tobacco seedlings.

Supervised Machine Learning–Based Detection of Concrete Efflorescence

The development of automated systems for detecting defects in and damage to buildings is ongoing in the construction industry. Remaining aware of the surface conditions of buildings and making timely decisions regarding maintenance are crucial. In recent years, machine learning has emerged as a key technique in image classification methods. It can quickly handle large amounts of symmetry and asymmetry in images. In this study, three supervised machine learning models were trained and tested on images of efflorescence, and the performance of the models was compared. The results indicated that the support vector machine (SVM) model achieved the highest accuracy in classifying efflorescence (90.2%). The accuracy rates of the maximum likelihood (ML) and random forest (RF) models were 89.8% and 87.0%, respectively. This study examined the influence of different light sources and illumination intensity on classification models. The results indicated that light source conditions cause errors in image detection, and the machine learning field must prioritize resolving this problem.

Influence of Different Light Sources on the Biochemical Composition of Arthrospira spp. Grown in Model Systems.

Arthrospira platensis and Arthrospira maxima are prokaryotic microalgae commercially marketed as spirulina. The pigments extracted from these algae are widely used for cosmetic and nutraceutical applications. This work aimed to evaluate the influence of three light-emitting lamps (white, orange and blue) on the growth and biomass composition of two strains of A. platensis (M2 and M2M) and one of A. maxima. The obtained data show strain- and light-dependent responses of the microalgae. In addition, white and orange lights led to a similar overall effect by increasing the levels of chlorophyll a and carotenoids. However, exposure to orange light resulted in the highest dry weight (5973.3 mg L−1 in M2M), whereas white light stimulated an increase in the carbohydrate fraction (up to 42.36 g 100 g−1 in A. maxima). Conversely, blue light led to a constant increase in the concentration of phycocyanin (14 g 100 g−1 in A. maxima) and a higher content of proteins in all strains. These results provide important environmental information for modulating the growth of different spirulina strains, which can be used to address the synthesis of biochemical compounds of strategic importance for the development of new nutraceutical foods.

Influence of different light sources on the production process of tomato in intensive photoculture

Introduction. The development of ideas about the influence of the light environment - the radiation spectrum, intensity and duration of exposure, on the physiology of plants, serves as the basis for the creation of effective light sources for protected ground.Purpose. Comparative test of the influence of a light environment with different spectral composition on the productivity and quality of tomatoes in conditions of intensive photo culture.Methods. Investigations were made under controlled conditions of intensive photoculture when growing dwarf tomatoes of the variety Natasha selections of the “Federal Scientific Vegetable Center” on thin-layer soil analogs with the supply of a nutrient solution to the plant roots through a slit capillary in vegetative light installations developed at the ARI. The light sources were high-pressure sodium lamps and LED lamps SD1, SD2, and SD3 with different emission spectra. Results. Tomatoes of the Natasha variety, illuminated during development with HPS lamps, formed almost the same yield with an average fruit weight of 42.5 kg/m2 per layer per year. Natasha tomato grown under LED lamps showed a tendency to lower productivity by 29% under SD1 and by 8% under SD2 and higher by 19% under underSD3 compared to that under HPS lamps. A comparative assessment of the biochemical composition of tomato fruits indicates their high quality under all tested light sources.Conclusion. Cultivation of dwarf tomato varieties on thin-layer soil analogs showed the best results in terms of productivity with good quality plant products under LED lamps SD3 with a radiation spectrum close to sunlight.

Research on urban landscape planning method based on GIS

The traditional urban landscape planning method for complex terrain and environment factor analysis is relatively vague, resulting in low planning efficiency and high spatial accuracy error. Therefore, a landscape planning method considering environmental pollution is proposed. Firstly, the geographic information system (GIS) technology platform is introduced. Through vector data and raster data, the terrain and terrain are analysed. Considering the light pollution of the garden night scene, the night scene lighting mode is designed, the influence of different light sources on the surrounding environment is analysed, plant species are analysed, and according to the characteristics of the plant landscape design, the design of urban landscape planning methods is completed. The experimental results show that the total score of the final design method is higher, and the spatial accuracy error is less than 4%, which verifies the feasibility of the landscape planning method.

Photo-ammonification of low molecular weight dissolved organic nitrogen by direct and indirect photolysis

The photo-ammonification process plays a crucial role in the transformation of dissolved organic nitrogen (DON) to dissolved inorganic nitrogen (DIN). However, previous studies have primarily focused on DON biotransformation than on abiotic processes. This study investigated the photo-ammonification process of nine model low molecular weight (LMW) DON molecules (e.g., amino acids, nucleotides, and urea) under the influence of different light sources. The results showed that photo-ammonification of model DON was mainly induced by UV light, while negligible contribution by visible light was found. Depending on their molecular structures, amino acids yielded different ammonia amounts, whereas negligible photo-ammonification was observed for nucleotides and urea. As for the reactive species, OH promoted ammonia yields of all the model amino acids; 3CDOM⁎ contributed to the photo-ammonification of six amino acids; 1O2 only had a positive impact on ammonification of tryptophan, histidine, and tyrosine; and CO3− accelerated ammonia generation from histidine and methionine. In natural water samples, tryptophan, tyrosine, histidine, and methionine generated significant ammonia. OH and 1O2 were speculated as the contributing reactive species based on kinetic studies as well as significant fluorescent humic-like and tyrosine-like substances degradation in irradiated samples compared to the raw samples characterized by the EEM-PARAFAC analysis. The negative linear correlations between photo-ammonification rates and the ELUMO–EHOMO of the amino acids emphasized the importance of the role of the molecular structure. Overall, these results revealed the LMW DON photo-ammonification mechanism in sunlit surface waters and highlighted its significance in the nitrogen biogeochemical cycle as well as water quality management.

Effect of indoor light on quail meat productivity

We investigated the effect of LED lamps and incandescent lamp bulbs on the productivity and slaughter quality of Pharaoh breed meat quaility. LED lamps had power output of 16 W, luminous flux of 1400 Lm, and color temperature of 4200 K. Incandescent lamp bulbs had power output of 40 W, luminous flux of 500 Lm, and color temperature of 2300-2900 K. From the 6th day of rearing the light, the intensity was 10-15 Lk within the level of live weight. We established a positive influence of LED lamps on quail slaughter qualities. The quails of experimental group (with LED lamps) had the advantages in terms of live weight (it was higher by 21.5 g or 8.23%, P> 0.999), the gains, feed conversion ratio (higher by 0.2 kg, or 5, 08%), quail liveability (higher by 4%). According to the results of the control slaughter, we admited a striking privilege in the level of slaughter weight and the eviscerated carcass of the poultry of the experimental group. The difference between groups is significant (P> 0.95…0.999). The advantages of the quails from experimental group towards the output of thigh muscles (higher by 0.02%), the drumstick muscles (0.12%), and the liver (by 1.02%) were obvious. The anatomical indices confirmed the influence of indoor lighting source on quali slaughter quality, i.e. the index of carcass food part and leg meat from experimental group were higher, the same was true with the indices of muscle and muscle breast of the quail of the control group with incandescent lamp bulbs. Keywords: Quails; LED lamps; Rearing; Productivity; Slaughter features References Cahaner, A. (1990). Genotype by environment interactions in poultry. Poultry Science, 81 (10), 1454-1462. Chu, T.T., Bastiaansen, J.W.M., Berg, P., Rome, H., Marois, D., Henshall, J. & Jensen. J. (2019). Use of genomic information to exploit genotype-by-environment interactions for body weight of broiler chicken in bio-secure and production environments. Genetics Selection Evolution, 51(50). Guidelines for the anatomical cutting of carcasses and organoleptic assessment of the quality of meat and eggs of poultry and egg morphology (2004). Sergiev Posad: VNITIP (in Russian) Kochish, I., Fedkina, T., Kovinko, V. (2010). Genotype, environment and productivity of broiler. Animal husbandry of Russia, 9, 11-12 (in Russian) Lewis, P.D., Morris, T.R. (1998). Responses of domestic poultry to various light sources. World's Poultry Science Journal, 54, 7-25. Lukanov, H. (2019). Domestic quail (Coturnix japonica domestica), is there such farm animal? World's Poultry Science Journal, 75 (4), 547-558. Manser, C.E. (1996). Effects of lighting on the welfare of domestic poultry: a review. Animal Welfare, 5, 341-360. Melnyk, V.O. (2015). Modern science on the effects of light on birds. Melnyk, V.V., Prokopenko, N.P., Bazyvolyak, S.M. (2019). Poultry farming in Ukraine: poultry and egg and meat production in 2018. Modern poultry, 3-4, 2-8 (in Ukrainian) Melnyk, Yu.F., Kovalenko, V.P., Uhnivenko, A.M. (2008). Selection of farm animals. Kyiv: Intas (in Ukrainian) Minvielle, F. (2004). The future of Japanese quail for research and production. World's Poultry Science Journal, 60 (4), 500-507. Mohov B.P., Krasota, V.F. (1998). Ecological and genetic assessment of the livestock system. Zootechniya, 1, 20-22 (in Russian) Nelson, J.R., Bray, J.L., Delabbio, J., Archer G.S. (2020). Light emitting diode (LED) color and broiler growth: effect of supplementing blue/green LED to white LED light on broiler growth, stress, and welfare. Poultry Science, 99 (7), 3519-3524. Olanrewaju, H.A. , Miller, W.W., Maslin, W.R., Collier, S.D., Purswell, J.L., Branton, S.L. (2018). Influence of light sources and photoperiod on growth performance, carcass characteristics, and health indices of broilers grown to heavy weights. Poultry Science, 97, 1109-1116. Shanawany, M. M. (1994). Quail Production Systems: A Review. Rome: Food and Agriculture Organization of the United Nations. Sultana, S., Hassan, M.R., Chow, H.S., Ryu K.S. (2013). Impact of different monochromatic LED light colours and bird age on the behavioural output and fear response in ducks. Italian Journal of Animal Science, 12 (2013), e94, 573-579. Vakulenko, Yu. (2014). Influence of different light sources on the quality of products of laying hens. Animal husbandry of Ukraine, 8-9, 15-18 (in Ukrainian).

The Effect of Antimicrobial Photodynamic Therapy Using Chlorophyllin–Phycocyanin Mixture on Enterococcus faecalis: The Influence of Different Light Sources

The purpose of this study was to evaluate the in vitro effect of the chlorophyllin–phycocyanin mixture (Photoactive+) as a photosensitizer (PS) during antimicrobial photodynamic therapy (aPDT) on the count of Enterococcus faecalis (E. faecalis) using different light sources. The antimicrobial effect of aPDT with chlorophyllin–phycocyanin mixture using different light sources including diode laser (λ = 660 nm), diode laser (λ = 635 nm), LED (λ = 450 ± 30 nm) alone or in combination was assessed using microbial cell viability assay against E. faecalis. In addition, the cell cytotoxicity of Photoactive+ was assessed on human gingival fibroblast (HuGu) cells by MTT assay; E. faecalis growth when treated by both red wavelengths (635 nm, 660 nm) and combination of LED (420–480 nm) and red wavelengths (635 nm, 660 nm), significantly reduced compared to the control group (p < 0.05). There was no significant reduction in the number of viable cells exposed to Photoactive+ compared to the control group (p < 0.05). This study shows that the application of chlorophyllin–phycocyanin mixture and irradiation with emission of red light achieved a better result for bacterial count reduction, compared to a control. This component can be applied safely due to very negligible cytotoxicity.

Proposed light sources for illuminating in Xuan paper and silk artwork with organic and inorganic pigments by evaluating color shifts in museum

AbstractArtworks based on Xuan paper or silk and painted by organic or inorganic pigments are highly responsive to light due to their materials and manufacturing technologies. They belong to the highest level of light responsive exhibits stipulated by International Commission on Illumination (CIE) and are vulnerable to fading and discoloration caused by radiation from light sources. The choice of light sources is the key of protection for artworks. It is indispensible and urgent to choose the lowest damage light sources according to the material characteristics of artworks. In this article, long‐term irradiation of typical light sources on various substrates and pigments was used as experimental method, and CIE DE2000 color difference formula was used as the evaluation index. The laws of the influence of different light sources on the color change of various materials were obtained, and the relative damage coefficients of light sources were calculated. Finally, eight kinds of light sources suitable for illuminating responsive artworks with typical material combinations were proposed. However, there are some limitations in the study, because the ancient Chinese Xuan paper and silk used as experimental objects in the experiment are yellowish. Thus, the models derived in this article are not suitable for choosing reasonable display light sources for other works of art. However, suitable light sources for different materials could be obtained by the calculation method used in this article.

Spectral damage model for lighting paper and silk in museum

Abstract Paper and silk are the artworks with the highest light sensitivity. They are very vulnerable to photochemical reactions caused by the radiation of light sources in museum lighting, resulting in irreversible permanent damage such as color fading and discoloration. The basis of lighting protection for these artworks is to clarify the influence of different light sources on paper and silk materials. In this study, 10 kinds of narrow band monochrome light in the visible light range were used as experimental light sources, real cultural relics paper and silk materials were used as experimental samples, and long-term irradiation experiments were carried out under constant temperature and humidity conditions. The color parameters of paper and silk irradiated by different light sources were detected periodically, and the curve of color difference with exposure was drawn. The relative influence coefficients of different spectral bands on the color of paper and silk were obtained by curve analysis. By fitting data regularity and regression analysis, the “relative damage-spectral composition” function was established. The effect of light source on color damage of paper and silk is described by mathematical language, and the influence formula of different spectrum on color damage of paper and silk is obtained.

Effect of Different Standard Light Sources on the Red Color of Rhodochrosite

Based on the uniform color space CIE1976L*a*b* system, the color of rhodochrosite is characterized by three elements: lightness L*, chroma C* and hue angle ho. On the basis of the color analysis of rhodochrosite, the standard D65 light source, A light source and CWF light source were used as experimental light sources to explore the influence of different light sources on the three color elements of rhodochrosite, and comprehensively analyze the influence of different light sources on rhodochrosite color. The conclusion is that A light source can improve the L* value and C* value of rhodochrosite to make it more bright and brilliant, which is suitable as the display light source of rhodochrosite; and CWF is not suitable as the illumination light source of rhodochrosite.

Influence of Different Light Sources, Light Intensities, and Water Flow Lens (WFL) System on Dye-Sensitized Solar Cell Performances

Recently, dye-sensitized solar cells demonstrated a superior performance under ambient light conditions. In this study, the influence on dye-sensitized solar cell performances was investigated under different light sources, light intensity, spectra, and water flow lens (WFL) system. Three types of light sources (xenon, halogen, and tungsten) with various spectral distributions (spectra) were used. Dyes-sensitized solar cells with varied sensitizers and co-sensitizers were tested depending on the light sources. Higher efficiency was obtained under irradiance of tungsten and halogen lamp in comparison to the xenon lamp, specifically at lower light intensities. Additionally, a new way of spectral adjustment was demonstrated. The use of a WFL system changes the distribution of spectra and remarkably influence for better performances of solar cells and efficiency values up to 30%. The results revealed that at lower light intensity, the influence of spectra was dominant and by changing spectral distribution various values of efficiency can be obtained. Also, a great influence on solar cells characteristics had a light source used for measurements.

Influence of light sources on body characteristics of female Japanese quail (Coturnix coturnix japonica) in different reproductive ages

The aim of the study was to evaluate the influence of different light sources on organ characteristics, bone development, chemical body composition and hepatic function of female Japanese quail (Coturnix coturnix japonica) in different reproductive ages. In total, 210 female 1-day-old birds were housed in a brick shed, which was divided into six rooms during 12 weeks. Each room was equipped with a different type of light bulb (incandescent; compact fluorescent; and white, blue, red and green light-emitting diodes (LEDs)) and contained seven cages with five birds in each. The light intensity was 15 lx and the photoperiod was 23 h light and 1 h dark (23L:1D) during the first week, 10 L:14D from the second to the fifth week, and 17L:7D until the end of the experiment. The experimental design was completely randomised, with six treatments and seven replicates of each bird. The morphophysiological conditions of the birds were evaluated at the beginning (8 weeks) and during peak production (12 weeks). At 8 weeks, a higher intestine weight and length and liver weight were observed in birds maintained in white LED (P < 0.05). Lower breast weight (P < 0.01) was also observed with this type of lamp. White and red LEDs decreased (P < 0.05) the percentage of ash in the tibia, but this reduction did not affect (P > 0.05) bone resistance. At 12 weeks, higher bone resistance was obtained (P < 0.01) with white LED and higher eye diameter was observed (P < 0.05) with incandescent and white LED lamps. There was no influence (P > 0.05) of light sources on the circulating levels of aspartate aminotransferase and alanine aminotransferase. Fluorescent bulbs resulted in the highest (P < 0.05) level of γ-glutamyltransferase, while blue LED resulted in the lowest level. There was no influence (P > 0.05) of light sources on chemical body composition in any of the evaluated ages. It was concluded that the photostimulation of Japanese quail with white LED is more efficient to stimulate their organ development, especially the intestine, until 8 weeks of life, resulting in birds with better bone development during peak production.

Study for standardization of the lighting system in fruit sorting

Sorting is a very important step in the fruit processing. The attributes definition and characterization are important for both marketing and end user, making it necessary to establish regulations for classification and standardization in order to unify the language of the market and enabling a more efficient market and also increase consumer awareness. For this end, it is necessary to standardize the technical criteria that can change the perception of the product. Studies have been developed in order to standardize a methodology to determine the subclass of fruit ripening, evaluating the influence of different light sources in the subclass evaluation.

English

The color constancy is a procedure that measures the influence of different light sources on a digital image. The goal of the computational color constancy is to account for the effect of the illuminate.Many traditional methods such as Grey-world method, Max RGB and learning-based method were used to measure the color constancy of digital images affected by light source. All these methods have an obvious disadvantage that the light source across the scene is spectrally uniform. This assumption is often violated as there might be more than one light source illuminating the scene. This paper has proposed a modified edge based color constancy using non local means and the adaptive histogram equalization. The proposed algorithm has ability to reduce the uneven illuminate problem of edge based color constancy and also non-local means has produced sharper results. The proposed algorithm is designed and implemented in the MATLAB using image processing toolbox. The comparison among the modified edge based color constancy and the edge based color constancy has shown that the proposed algorithm is quite effective over the available methods.

Effect of different light sources on degree of conversion, hardness and plasticization of a composite

Clinical performance of composite resins depends largely on their mechanical properties, and those are influenced by several factors, such as the light-curing mode. The purpose of this study was to evaluate the influence of different light sources on degree of conversion (DC), Knoop hardness (KHN) and plasticization (P) of a composite resin. Disc-shaped specimens (5 x 2 mm) of Esthet-X (Dentsply) methacrylate-based microhybrid composite were light-cured using quartz-tungsten-halogen (QTH) Optilight Plus (Gnatus) or light-emitting diode (LED) Ultraled (Dabi Atlante) curing units at 400 and 340 mW/cm2 of irradiance, respectively. After 24 h, absorption spectra of composite were obtained using Nexus 670 (Nicolet) FT-IR spectrometer in order to calculate the DC. The KHN was measured in the HMV-2000 (Shimadzu) microhardness tester under 50 g loads for 15 s, and P was evaluated by percentage reduction of hardness after 24 h of alcohol storage. Data were subjected to t-Student test (alpha = 0.05). QTH device showed lower P and higher KHN than LED (p < 0.05), and no difference between the light-curing units was found for DC (p > 0.05). The halogen-curing unit with higher irradiance promoted higher KHN and lower softening in alcohol than LED.

Influence of different light sources on the conversion of composite resins

The purpose of this paper was to evaluate the influence of different light curing units on the conversion of four composite resins with different compositions (Durafill VS - Heraeus-Kulzer, Tetric Ceram - Ivoclar/Vivadent, Filtek Supreme XT - 3M ESPE e Aelite LS Packable - Bisco), using differential scanning calorimetry. A stainless steel matrix was used to prepare 48 cylindrical composite test samples (n=6), measuring 3 mm in diameter and 1 mm in thickness. The samples were photoactivated using a halogen lamp (Optilux 500 - Demetron/Kerr) and three different generations of light-emitting diodes (LEDs) (LEC-470 I - MMOptics, Radii Plus - SDI and Ultra-Lume LED 5 - Ultradent). After removal of the matrix, each sample was weighed and hermetically sealed in an aluminum pan and analyzed. The amount of heat liberated by thermopolymerisation of residual monomers after photoactivation was measured in Joules/gram (J/g). The data were submitted to Analysis of Variance (ANOVA) test (P ≤ 0.002) and the Tukey test (P < 0.05). The Ultra-Lume LED 5 was superior on degree of conversion for all resins. The Radii Plus was equal to the Ultra-Lume LED 5, except for the resin Tetric Ceram , were the Optilux 500 was superior. The LEC-470 I was inferior for the conversion of all resins. The study proves the importance of the compatibility of the different photoinitiators in resin composites with the different light sources.

Effect of light units on tooth bleaching with visible-light activating titanium dioxide photocatalyst

This study evaluated the influence of different light sources on the efficiency of an office bleaching agent containing visible-light activating titanium dioxide photocatalyst (VL-TiO(2)) using an artificial discoloration tooth model. Extracted bovine teeth were stained by black tea. The CIE L*a*b* values were measured before and after nine consecutive treatments by the VL-TiO(2)-containing bleaching agent (TiON in Office, GC, Tokyo, Japan). A halogen light unit (CB; CoBee, GC) or an LED unit (G-light, GC) with two modes (blue and violet: GL-BV, blue: GL-B) were used to activate the bleaching agent in three groups (n=8). Brightness (ΔL) and color difference (ΔE) increased as bleaching repeated in all groups. Two-way ANOVA showed that both number of treatments and light sources significantly affected ΔE (p<0.05). GL-BV showed better bleaching effect than GL-B. In measurement of irradiation spectra, CB showed a wide spectrum (380-530 nm), GL-B had a sharp peak at 470 nm and GL-BV showed an additional peak at 405 nm. It was concluded that the light source influenced the efficiency of the tooth bleaching with VL-TiO(2).