Human visual system is exposed to high levels of natural and artificial lights of different spectra and intensities along lifetime. Light-emitting diodes (LEDs) are the basic lighting components in screens of PCs, phones and TV sets; hence it is so important to know the implications of LED radiations on the human visual system. The aim of this study was to investigate the effect of LEDs radiations on human retinal pigment epithelial cells (HRPEpiC). They were exposed to three light-darkness (12 h/12 h) cycles, using blue-468 nm, green-525 nm, red-616 nm and white light. Cellular viability of HRPEpiC was evaluated by labeling all nuclei with DAPI; Production of reactive oxygen species (ROS) was determined by H2DCFDA staining; mitochondrial membrane potential was quantified by TMRM staining; DNA damage was determined by H2AX histone activation, and apoptosis was evaluated by caspases-3,-7 activation. It is shown that LED radiations decrease 75-99% cellular viability, and increase 66-89% cellular apoptosis. They also increase ROS production and DNA damage. Fluorescence intensity of apoptosis was 3.7% in nonirradiated cells and 88.8%, 86.1%, 83.9% and 65.5% in cells exposed to white, blue, green or red light, respectively. This study indicates three light-darkness (12 h/12 h) cycles of exposure to LED lighting affect in vitro HRPEpiC.
The use of non-invasive spectral measurements to control the conservation status is a part of the preventive conservation of artworks which nowadays is becoming increasingly interesting. This paper describes how to use a spectral measuring device and an illumination system specifically designed for such a task in a very large dimension artwork painting (7.8 m wide × 3.5 m high). The system, controlled by a Cartesian robot, allows spectral measurements in a spectral range of 400-780 nm. The measured data array has a total of 2201 circular regions with 5.5 mm spot diameter placed on a square grid. Colorimetric calculations performed from these spectral measurements may be used to characterize color shifts related to reflectance changes in specific areas of the paint. A color shifting from the expected gray has been shown.
Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices, just to name some representative. However, it seems to be a certain lack of adequate techniques for the assessment of the performance of final fabricated devices. As applications are more exigent this characterization is a must. We provide a technique to characterize the performance of Fresnel lenses, as light collection devices. The basis for the method is a configuration where a camera images the Fresnel lens aperture. The entrance pupil of the camera is situated at the focal spot or the conjugate of a simulated solar source. In this manner, detailed maps of the performance of different Fresnel lenses are obtained for different acceptance angles.
Background: Over the recent years, several researches have speculated about the effects of Light Emitting Diodes (LEDs) radiation on retinal epithelium cells (RPE). Worldwide, most people live exposed to LEDs irradiation incorporated in screens of PCs, phones and TV sets. These lights give rise to the formation of reactive oxygen species and induce mutagenic mechanisms which lead to apoptosis and consequently to degenerative eye diseases, such as age-related macular degeneration (AMD). Thus, it is a priority interest to develop appropriate solutions for the growing industry field of LED light phototoxicity. The aim of this study was to investigate the protective effects of blue light absorbing filters in order to decrease induced apoptosis on human retinal pigment epithelial cells. Methods: Human retinal pigment epithelial cells were exposed to 3 light-darkness (12 hours/12 hours) cycles of white (Tª5400°K), blue (468 nm), green (525 nm) and red (616 nm) LED light. Light irradiance was 5 mW/cm 2. Oxidative stress was evaluated by H2DCFDA staining, mitochondrial membrane potential by TMRM staining, DNA damage by H2AX histone activation, apoptosis by caspase-3 activation, and cell viability by DAPI. Results: Our results have shown that the use of a blue light absorbing filter decreased cellular apoptosis by 56-89% and DNA damage by 57-81%. A decrease in ROS level production and an increase in cellular viability was also obtained. Conclusion: This study suggests that blue light absorbing filters may protect against LED lighting photo toxicity and, consequently, provides a photo protector effect.
This article aims to find an optimal solution for illuminating cave art, based on the improvement of color reproduction and minimizing the damage caused by visible radiation on the painting. To improve visual perception, a light source with optimal spectral distribution has been calculated. This spectral distribution minimizes the damage, maximizes the colorimetric distance between the color of the rock paintings and the closer stone, and takes into account how it was lit by the author. A mathematical function has been used to optimize the spectral distribution of the light source. With this aim, a tunable red-green-blue (RGB) light emitting diode (LED) luminaire has been used. It has been found that the new calculated lighting of the cave does not alter the environmental conditions by performing a test of algae growth and thermographic measurements.
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