scholarly journals A Spectrophotometric Study on Light Attenuation Properties of Dental Bleaching Gels: Potential Relevance to Irradiation Parameters

2020 ◽  
Vol 8 (4) ◽  
pp. 137
Author(s):  
Eugenia Anagnostaki ◽  
Valina Mylona ◽  
Kyriaki Kosma ◽  
Steven Parker ◽  
Marianna Chala ◽  
...  
Keyword(s):  
Light Attenuation ◽  
Spectrophotometric Study ◽  
Light Sources ◽  
Light Spectrum ◽  
Safety Hazards ◽  
Dental Bleaching ◽  
Bleaching Gels ◽  
Intensity Loss ◽  
Similar Intensity ◽  
High Absorption

Background: During in-office bleaching, appropriate light sources are applied in order to enhance the activity of the bleaching gels applied onto teeth. For this method to be effective, a high absorption of light within the gel is necessary. Variation in the light attenuation capability of the gel, the duration of application and light activation can contribute towards safety hazards associated with this procedure. Methods: In this study, seven different gels and hydrogen peroxide have been evaluated for their optical properties by means of spectrophotometry (440–1000 nm). The transmitted light spectrum was used to estimate the intensity loss for each gel. The mean intensity decreases observed were statistically analysed using an analysis of variance (ANOVA). Results: The five more-pigmented gels tested indicated a very similar intensity loss of around 80%, whereas the remaining two gels showed significantly less attenuation (predominantly, p < 10−6). Conclusions: Throughout the spectrum of wavelengths examined, and according to the underlying studies evaluated, five of the gels assessed demonstrated an attenuation high enough to possibly avoid overheating of the underlying enamel dentine and pulp. An evaluation of appropriate irradiation parameters is proposed.

scholarly journals Impact of different standard lighting sources on red jadeite and color quality grading

2019 ◽  
Vol 23 (4) ◽  
pp. 371-378
Author(s):  
Xin Pan ◽  
Ying Guo ◽  
Ziyuan Liu ◽  
Zikai Zhang ◽  
Yuxiang Shi
Keyword(s):  
Light Source ◽  
Color Space ◽  
Sample Surface ◽  
Color Temperature ◽  
Integrating Sphere ◽  
Light Sources ◽  
Light Spectrum ◽  
Fisher Discriminant Analysis ◽  
Fisher Discriminant ◽  
Quality Grading

The purpose of this paper is to investigate the standard light source for grading and displaying the color of red jadeite and to classify the color. With Raman spectrometer, ultraviolet-visible spectrophotometer and X-ray fluorescence spectrometer, the results show that, the Fe 3+ is the main chromogenic mineral of red jadeite, which negatively correlates with the tonal angle, while the color of red jadeite has a positive correlation with the hematite content. The color of 120 red jadeite samples was examined by collecting the reflective signaled from the sample surface using an integrating sphere with the portable X-Rite SP62 spectrophotometer based on CIE 1976 L*a*b* uniform color space. The color parameters of jadeite samples under D65, A and CWF standard light sources were analyzed. The light spectrum of D65 light source is continuous, relatively smoothed with high color temperature, which makes the sample color close to that under the natural light and can be used as the best evaluation light source. A light source contributes to improve the red tone of jadeite, which is the best light source for commercial display of red jadeite. CWF light source can be used as the auxiliary lighting for color evaluation. The color of red jadeite is divided into five levels from best to worst using K-Means cluster analysis and Fisher discriminant analysis under D65 light source: Fancy Vivid, Fancy Deep, Fancy Intense, Fancy dark and Fancy.

scholarly journals Optimization of Multiband White-Light Illuminants for Specified Color Temperatures

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Snjezana Soltic ◽  
Andrew Neil Chalmers
Keyword(s):  
Genetic Algorithm ◽  
Differential Evolution ◽  
White Light ◽  
Color Difference ◽  
Light Sources ◽  
Optimal Solutions ◽  
Light Spectrum ◽  
Light Spectra ◽  
Wide Acceptance ◽  
Color Rendering

This paper describes an effective approach for the optimization of multiband spectra to produce prospective white-light spectra having specific color temperatures. The optimization process employs a genetic algorithm known as differential evolution, which aims to minimize the color rendering differences between a prospective white-light spectrum and its corresponding reference illuminant. Color rendering is assessed by calculating the CIEDE2000 color difference (ΔE00) for 14 CIE test colors under the two sources. Optimized white-light spectra were matched to three CIE standard illuminants, that is, A (2856 K), D50 (5003 K), and D65 (6504 K). Optimal solutions for three- and four-band 25 and 50 nm Gaussian spectra are presented and analyzed, together with mixed 4-LED spectra that were optimized in the same way. In all cases, the simulated sources were shown to provide color rendering of such quality that ΔE00av ≤ 2.24 units. Such white-light sources would likely find wide acceptance in numerous lighting applications.

scholarly journals Photopolymerization of dental materials: Types and characteristics of the light sources

2009 ◽  
Vol 56 (4) ◽  
pp. 207-212 ◽  
Author(s):  
Gorjana Popovic ◽  
Roze Djokic
Keyword(s):  
Absorption Spectrum ◽  
Light Source ◽  
Uv Light ◽  
Dental Materials ◽  
Life Time ◽  
Source Spectrum ◽  
Light Sources ◽  
Light Spectrum ◽  
Visible Part ◽  
Short Time

Light from the polymerization source which initiates photopolymerization in the material has its determined wavelength. Photoinitiator, such as camphorhinone, excited by light, can be activated with any of the wavelength from its absorption spectrum. To obtain successful photopolymerization, light source should emit waves of adequate wavelength; light intensity has to be optimal, to have sufficient time of exposure and material up to 2 mm thickness. Photoinitiator inside the material should match light source spectrum and work regime. Halogen lamps have wide spectra of wavelengths in the visible part of the light spectrum. Their spectra are similar to absorption spectrum of camphorhinone. Plasma (xenon) lamps emit blue light. Though their diapason is low, spectra have great intensity. Adequate diapason and easy excitation allow them to have short time of exposure. LED lamps have blue diodes as light source. They do not need filters due to narrow emission spectrum. Laser (argon) lamps are the only that emit linear spectra. Ultraviolet (mercury) lamps are not in use any more in dentistry; theirs initiators were activated by UV light. LED lamps have longer life time; do not change the spectra during time, warm less, do not need filters, allow change of the source for more powerful, more efficient and more advantageous two steps or impulse illumination mode. However, LED lamps can not be used for a material that has photoinitiator(s) activated by light with wavelength above the maximum of the LED spectra.

Fluorescence Microscopy Light Sources

2012 ◽  
Vol 20 (4) ◽  
pp. 22-28 ◽  
Author(s):  
Kavita Aswani ◽  
Tushare Jinadasa ◽  
Claire M. Brown
Keyword(s):  
Fluorescence Microscopy ◽  
Visible Light ◽  
White Light ◽  
Fluorescent Proteins ◽  
Life Sciences ◽  
Light Sources ◽  
Light Spectrum ◽  
Physical Sciences ◽  
Light Emitting ◽  
Microscopy Techniques

Fluorescence microscopy techniques are now prevalent throughout the life sciences and many of the physical sciences. These techniques are often dependent on white light sources that have evolved from the more traditional mercury arc lamp to metal halide sources to the more recent light emitting diodes (LEDs). The newer light sources show more uniform power across the visible light spectrum, allowing for the use of fluorophores and fluorescent proteins outside of the peak wavelengths associated with the more traditional light sources.

Effect of daylight LED on visual comfort, melatonin, mood, waking performance and sleep

2019 ◽  
Vol 51 (7) ◽  
pp. 1044-1062 ◽  
Author(s):  
C Cajochen ◽  
M Freyburger ◽  
T Basishvili ◽  
C Garbazza ◽  
F Rudzik ◽  
...  
Keyword(s):  
Light Exposure ◽  
Memory Performance ◽  
Light Sources ◽  
Visual Comfort ◽  
Light Spectrum ◽  
Young Males ◽  
Beneficial Effects ◽  
Light Spectra ◽  
Psychomotor Vigilance ◽  
Circadian Physiology

LED *Shared senior authors. light sources have a discontinuous light spectrum with a prominent ‘blue’ peak between 450 and 470 nm that influences non-image forming responses in humans. We tested an LED lighting solution mimicking a daylight spectrum on visual comfort, circadian physiology, daytime alertness, mood, cognitive performance and sleep. Fifteen young males twice spent 49 hours in the laboratory under a conventional-LED and under a daylight-LED condition in a balanced cross over design flanked by a baseline and a post-light exposure night. Despite different light spectra, the photopic lux and the correlated colour temperature of the lighting were the same for both LEDs. The colour rendering index and the melanopic strength were 25.3% and 21%, respectively, higher for the daylight LED than the conventional LED. The volunteers had better visual comfort, felt more alert and happier in the morning and evening under daylight LED than conventional LED, while the diurnal melatonin profile, psychomotor vigilance and working memory performance were not significantly different. Delta EEG activity (0.75–4.5 Hz) was significantly higher after daylight-LED than conventional-LED exposure during the post-light exposure night. We have evidence that a daylight-LED solution has beneficial effects on visual comfort, daytime alertness, mood and sleep intensity in healthy volunteers.

scholarly journals In vitro analysis of the pH stability of dental bleaching gels during in-office procedures

2021 ◽  
pp. e22-e29
Author(s):  
R. de Mendonça ◽  
J. Baliza ◽  
A. Burey ◽  
L. Cavalcante ◽  
A. Loguercio ◽  
...  
Keyword(s):  
Ph Stability ◽  
Dental Bleaching ◽  
Vitro Analysis ◽  
Bleaching Gels ◽  
Office Procedures ◽  
In Vitro Analysis

Effect of different soldering temperatures on the properties of COB light source

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhao Wang ◽  
Yuefeng Li ◽  
Jun Zou ◽  
Bobo Yang ◽  
Mingming Shi
Keyword(s):  
Light Source ◽  
Void Ratio ◽  
Light Attenuation ◽  
Luminous Flux ◽  
Luminous Efficiency ◽  
Junction Temperature ◽  
Light Sources ◽  
Content Type ◽  
Soldering Temperature ◽  
Practical Engineering

Purpose The purpose of this paper is to investigate the effect of different soldering temperatures on the performance of chip-on-board (COB) light sources during vacuum reflow soldering. Design/methodology/approach First, the influence of the void ratio of the COB light source on the steady-state voltage, luminous flux, luminous efficiency and junction temperature has been explored at soldering temperatures of 250°C, 260°C, 270°C, 280°C and 290°C. The COB chip has also been tested for practical application and aging. Findings The results show that when the soldering temperature is 270°C, the void ratio of the soldering layer is only 5.1%, the junction temperature of the chip is only 76.52°C, and the luminous flux and luminous efficiency are the highest, and it has been observed that the luminous efficiency and average junction temperature of the chip are 107 lm/W and 72.3°C, respectively, which meets the requirements of street lights. After aging for 1,080 h, the light attenuation is 84.64% of the initial value, which indicates that it has higher reliability and longer life. Originality/value It can provide reference data for readers and people in this field and can be directly applied to practical engineering.

THE EVALUATION METHOD FOR THE EFFICIENCY OF PHOTOSYNTHESIS DEPENDING ON THE COMPOSITION AND INTENSITY OF LIGHT ON THE EXAMPLE OF CUCUMIS SATIVUS L.

2019 ◽  
pp. 86-96
Author(s):  
S. I. Supelnyak ◽  
V. G. Kosushkin
Keyword(s):  
Cucumis Sativus ◽  
Evaluation Method ◽  
Early Stage ◽  
Dry Weight ◽  
Measured Parameter ◽  
Light Sources ◽  
Light Spectrum ◽  
Cucumis Sativus L ◽  
Efficient System ◽  
Stage Of Development

The article calculates potentially effective for photobiological processes density light fluxes arc tube sodium lamps (HPS) and 250 watt Light Emitting Diode (LED) lamps 46 watts. The concept of light utilization for photobiological reactions is proposed to evaluate the energy component of the light spectrum suitable for optimal activation of plant photoreceptor systems that control the shaping process by changing the orientation of the biological system in space at an early stage of development in order to achieve maximum photosynthetic response. The calculations used the experimentally obtained values of the absorption coefficients of the leaf ofCucumis sativus L. Based on the data on the linear dimensions of the leaf of the plant and the dependence of the absorption spectrum on the age of the plant, as well as the action spectra of photobiological reactions (photosynthesis, dissipation of excess energy as heat, phototropic reaction, chlorophyll, photomorphogenesis) and emission spectra of light sources, we have calculated the mass of accumulated carbohydrates at an early stage of developmentCucumis sativus L. In order to test the reliability methods of analytical evaluation, an experimental study of the effect of radiation data illuminators was carried out. For HPS 250, the weight of carbohydrates and the dry weight of the plant were0.24 g and0.20 g, respectively, for LED 46, the weight of carbohydrates and dry weight of the plant were0.05 g and0.05 g, respectively. The proposed system for assessing the efficiency of the spectrum and the intensity of radiation by the linear parameters of a plant is an intelligent basis for creating an energy-efficient system for automatically controlling LED lighting of a greenhouse with feedback on a measured parameter of a plant.

scholarly journals Light-Quality Manipulation to Control Plant Growth and Photomorphogenesis in Greenhouse Horticulture: The State of the Art and the Opportunities of Modern LED Systems

2021 ◽  
Author(s):  
Roberta Paradiso ◽  
Simona Proietti
Keyword(s):  
Plant Growth ◽  
State Of The Art ◽  
Control Plant ◽  
Spectral Composition ◽  
Environmental Parameters ◽  
The State ◽  
Light Sources ◽  
Light Spectrum ◽  
Light Emitting ◽  
Greenhouse Horticulture

AbstractLight quantity (intensity and photoperiod) and quality (spectral composition) affect plant growth and physiology and interact with other environmental parameters and cultivation factors in determining the plant behaviour. More than providing the energy for photosynthesis, light also dictates specific signals which regulate plant development, shaping and metabolism, in the complex phenomenon of photomorphogenesis, driven by light colours. These are perceived even at very low intensity by five classes of specific photoreceptors, which have been characterized in their biochemical features and physiological roles. Knowledge about plant photomorphogenesis increased dramatically during the last years, also thanks the diffusion of light-emitting diodes (LEDs), which offer several advantages compared to the conventional light sources, such as the possibility to tailor the light spectrum and to regulate the light intensity, depending on the specific requirements of the different crops and development stages. This knowledge could be profitably applied in greenhouse horticulture to improve production schedules and crop yield and quality. This article presents a brief overview on the effects of light spectrum of artificial lighting on plant growth and photomorphogenesis in vegetable and ornamental crops, and on the state of the art of the research on LEDs in greenhouse horticulture. Particularly, we analysed these effects by approaching, when possible, each single-light waveband, as most of the review works available in the literature considers the influence of combined spectra.

scholarly journals Dental Bleaching Techniques; Hydrogen-carbamide Peroxides and Light Sources for Activation, an Update. Mini Review Article

2015 ◽  
Vol 8 (1) ◽  
pp. 264-268 ◽  
Author(s):  
Leandro Féliz-Matos ◽  
Luis Miguel Hernández ◽  
Ninoska Abreu
Keyword(s):  
Correct Diagnosis ◽  
Treatment Decision ◽  
Past Century ◽  
Light Sources ◽  
Light Activation ◽  
Dental Bleaching ◽  
International Agencies ◽  
The Past ◽  
Essential Knowledge ◽  
Peroxide Activation

Hydrogen and carbamide peroxides have been successfully used for many years; in the past century the dental bleaching technique suffered several changes and almost 10 years before new millennium the technique was finally recognized by the international agencies of regulation. It is important that Dentists handle the peroxides with the essential knowledge, because it is demonstrated that satisfactory final results of this technique depend on the correct diagnosis of stains, management of the substrates (enamel and dentin) and as well sensitivity. Dentists are exposed to several dental bleaching techniques, products and brands, and in the last 2 decades the devices for light activation of the peroxides have become an extensive catalog. Today, the technique is also suffering changes based on the effectiveness of the different light sources for peroxide activation and its relation to satisfactory final results of the technique. The purpose of this literature review is to explain the determinant factors that influence satisfactory final results of the techniques and provide a general overview, in order to achieve a treatment decision based on evidence.

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