Light-emitting Diode Radiation Research Articles

Supplementary Blue and Red Radiation at Sunrise and Sunset Influences Growth of Ageratum, African Marigold, and Salvia Plants

BACKGROUND: Light-emitting diodes (LEDs) with lower electric cost and the specific wavelength have been considering as a novel light source for plant production in greenhouse conditions as well as in a closed culture system. Supplementary lighting for day-length extension was considered as light intensity, light quality, and/or photoperiod control on plant growth and development. Effects of supplementary blue or red LED radiation with lower light intensity on growth of Ageratum (Ageratum houstonianum Mill., cv. Blue Field), African marigold (Tagetes erecta L., cv. Orange Boy), and Salvia (Salvia splendens F. Sello ex Ruem & Schult., cv. Red Vista) were discussed during sunrise and sunset twilight in the experiment. METHODS AND RESULTS: Supplementary lighting by blue and red LEDs for 30 (Treatment B30; R30) or 60 (Treatment B60; R60) min. per day were established in greenhouse conditions. Photosynthetic photon flux for supplementary radiation was kept at 15 μmol m-2 s-1 on the culture bed. Natural condition without supplementary light was considered as a control. The highest shoot and root dry weights were shown in African marigold exposed by red light for 60 min. per day. Supplementary blue and red lighting regardless of the radiation time significantly stimulated development of lateral branches in African marigold. Stem growth in Ageratum and Salvia seedlings was significantly promoted by red radiation as well as natural light. CONCLUSIONS: Extending of the radiation time at sunrise and sunset twilight using LEDs stimulated reproductive growth of flowering plant species. Different characteristics on growth under supplementary blue or red lighting conditions were also observed in the seedlings during supplementary radiation.

Effect of incoherent LED radiation on third-degree burning wounds in rats

The main physiological characteristics in a burn process are the increase of the capillary permeability and the occurrence of edema and exudation. Light-emitting diode (LED) has been proposed as treatment of burning. This study investigated the effects of LED on the repair process of rat skin submitted to a third-degree burning. The lesions were produced on the dorsal surface of male Wistar rats. Animals were divided into 4 groups (n = 6) as follows: L1 and L2 groups as LED-treated burned rats, and received LED therapy along 7 and 15 days with 48 hours intervals, respectively; C1 and C2 groups as control, non-treated burned rats. A red LED (640 nm, 30 mW) operating with a fluence of 4 J/cm2 was used. The wound area was measured daily after irradiation. Animals were euthanized at the 8th and 16th days after burning, and the wound fragment was submitted to histology. The inflammatory cells as well as the damaged area at the 8th day after burns were significantly lower for the LED-treated group when compared to control. Furthermore, the LED phototherapy effect on cellular migration was even more pronounced at the 16th day. Our results indicated that the treatment with a LED system was clearly effective in reducing the number of inflammatory cells and improving the healing process in an experimental model of third-degree burnings.

LEDs based on InAsSbP/InAsSb heterostructures (λ = 4.7 μm) for carbon monoxide detection

Light-emitting diodes (LEDs) operating in the 4.4–4.8-μm wavelength range have been developed for detecting the presence of carbon monoxide (CO) in air. The proposed LEDs are based on InAsSbP/InAsSb heterostructures with InAs0.85Sb0.15 active region, which were grown by metalorganic vapor-phase epitaxy. The electrolumuinescent properties of LEDs have been studied. The output power of LED operating in a pulsed mode reaches 50 μW at a current pulse amplitude of 2 A, and that in a quasi-continuous wave mode is 1 μW at a current of 200 mA. The absorption of LED radiation in a gaseous medium containing 10% CO has been studied. The proposed LEDs can be used to simultaneously detect both CO2 (absorbing at λ = 4.3 μm) and CO (λ = 4.67 μm).

A Problem of Infrared Electronic-Toll-Collection Systems: The Irregularity of LED Radiation Pattern and Emitter Design

According to our measurements, the radiation pattern of many low-cost commercial light-emitting diodes (LEDs) is not smooth. Some LEDs even have serious irregularities that affect the performance of infrared communication systems. For systems where a definite communication area is required, such as electronic-toll-collection (ETC) applications, this problem is particularly serious. In this paper, we first present our measured results for the radiation pattern of several typical low-cost commercial LEDs, showing that almost all of them are irregular to some extent. We then use the most acceptable model with a suitable half-intensity angle to construct the emitter of an ETC system. The design was calculated with the aid of an optimization algorithm to determine the mounting angle for each LED such that the system has an extended communication area in the longitudinal direction, i.e., in the vehicle traveling direction, and can withstand high signal attenuation. For a typical LED with half-intensity angle Φ1/2 = 13°, a very simple two-group structure for the emitter is obtained, and the analysis results are verified by experimental measurements.

Gene expression under laser and light-emitting diodes radiation for modulation of cell adhesion: Possible applications for biotechnology

Experimental data about the modulation of adhesion and proliferation of anchorage-dependent HeLa cells with monochromatic or quasimonochromatic radiation in red to near-infrared region are presented. Cell adhesion and proliferation can be increased by irradiation with light of certain wavelengths (maxima in action spectrum are 619, 675, 740, 760, and 820 nm) or decreased when the activity of photoacceptor (cytochrome c oxidase in mitochondrial respiratory chain) is inhibited by chemicals before the irradiation. This modality allows controlling the number of attached and/or proliferating cells. Possible biotechnology applications of this method are outlined.

Effect of Light Emitting Diode Radiation on Antioxidant Activity of Barley Leaf

Antioxidant activity of extracts of barley leaves cultivated by light emitting diode (LED) radiation such as red, far-red, blue, blue-red, green, yellow, and white light was investigated. After measuring length and weight of the leaves cultivated, barley leaves were extracted using 70% ethanol. The Hunter color value, total phenolic compounds, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salts (ABTS) radical-scavenging activities of extracts were determined. Lengths of samples cultivated by red and green light radiation were 13.7 and 13.6 cm, respectively. Hunter L* values of samples cultivated by red, far-red, and UVA radiation were 65.29, 67.55, and 67.57, respectively. The content of total phenolic compounds of samples cultivated by blue light radiation was 1.62 mg/L of sample. The DPPH radical-scavenging activities of samples cultivated by blue, green, UVA, and white light radiation were 64.28, 48.92, 55.95, and 48.72%, respectively. The ABTS radical-scavenging activity of samples cultivated by blue light radiation scored higher compared with those of samples cultivated with other LED lights. Antioxidant activities of barley leaves showed different results depending on harvest time. Application of LED radiation during re-cultivation after the first harvest showed increasing tendency on antioxidant activity of barley leaves.

Color Tone Tuning by Partial Sr2 + Substitution of Ba2 + in the White Phosphors Ba1 − ySryLa2 − xDyxZnO5 ( x = 0.01 – 0.2 , y = 0 – 0.65 )

phosphors were prepared by a solid-state reaction, and their photoluminescence properties were investigated for the conversion of the UV light emitting diode radiation to white light. The results showed that the maximum emission intensity of the samples without substitution was achieved at the doping level under the UV excitation at 388 nm, and the Commission Internationale del’Eclairage (CIE) chromaticity coordinate of the total emissions was located at (0.256, 0.334). When substituted by , the X-ray diffraction showed that the lattice constants and unit cell volumes of decreased linearly with the increasing content. The color tone of the phosphors could be tuned by the amount of substitution as the consequence of the induced lattice distortion, which resulted in a change in the local site symmetry around the ions. The CIE chromaticity coordinate of phosphors varied from bluish white (0.256, 0.334) at to near white (0.315, 0.370) at under the UV excitation at 388 nm.

Spectral effects on embryogenesis and plantlet growth of Oncidium ‘Gower Ramsey’

Embryogenic calli of Oncidium were grown under tubular fluorescent lamp (FL) or light-emitting diode (LED) arrays with different spectra to determine the effects of light quality on protocorm-like body (PLB) formation and plantlet growth from the callus. The effect of light is generated by monochromatic blue, red or mixed far-red LEDs on the photomixotrophic radiation. The light sources induced higher number of PLB formation compared with the darkness. The best condition for PLB formation was to culture on MS half salt medium supplemented with 0.1 mg l −1 NAA and 0.4 mg l −1 BA under red + blue + far-red (RBFr) LEDs and FL radiation for 8 weeks. Roughly 3000 embryos were induced in an initial culture of 1 g of fresh weight of calluses. During subculturing, PLBs had the ability to convert into plantlets. In this study also indicated the far-red LED radiation was a noticeable factor. It showed that using Fr combined with R and B (RBFr) or RFr radiation significantly enhanced leaf expansion, numbers of leave and root, chl contents, fresh and dry weight of Oncidium plantlets. Therefore, the wavelength specificity of RBFr LEDs comprising a novel illumination system is advantageous over FLs for PLB formation, resulting in higher efficiencies of plant regeneration and growth in Oncidium cultures.

Three-dimensional measurement of light-emitting diode radiation pattern: a rapid estimation

We describe a simple imaging technique that enables a three-dimensional inspection of the angular intensity distribution of a light-emitting diode (LED) over a significant part of the hemisphere. The measurement set-up is very simple: it consists of only a charge-coupled device (CCD) camera and a flat diffuse translucent screen. An LED illuminates the screen, and the CCD camera records one image from the back. The visualization algorithm takes into account the cosine-fourth law, vignetting and screen transmittance to render the far-field radiation pattern from the recorded image.

Far-field condition for light-emitting diode arrays

In practice, any cluster of light-emitting diodes (LEDs) can be modeled or measured as a directional point source if the detector is far enough away from the cluster. We propose a far-zone condition for measuring or modeling propagation of light from an LED array. An equation gives the far-field distance as a function of the LED radiation pattern, array geometry, and number of LEDs. The far field is shorter for high packaging density clusters, and the far field considerably increases with increasing beam directionality of LEDs. In contrast with the classical rule of thumb (5 times the source size), the near zone of an array with highly directional LEDs can extend to more than 60 times the array size. We also analyze the effect of introducing random variations of light flux among LEDs of the array, which shows that far-field variability is low in high packaging density arrays.

Color distribution from multicolor LED arrays

We describe a fully-analytical, simple yet sufficiently accurate method to compute the color pattern of the light emitted from multicolor light-emitting diode (LED) assemblies. Spatial distributions for both color variation and correlated color temperature (CCT) as a function of typical parameters of influence, such as LED spectrum, spatial distribution of LED radiation, target distance, LED-to-LED spacing, and number of LEDs, are shown. To illustrate the method, we simulate and analyze the color patterns of linear, ring, and square RGB (red, green, and blue) arrays for Lambertian-type, batwing, and side emitting LEDs. Our theory may be useful to choose the optimal value for both the array configuration and the array-diffuser distance for lighting systems with color mixing devices.

Influence of mixed LED radiation on the growth of annual plants

We investigated the effect of mixed radiation from light-emitting diodes (LEDs) on the growth and flowering of ageratum, marigold, and salvia bedding plants. Blue, red, and far-red lights were applied under controlled environmental conditions for 28 d. Both the combination of blue-plus-red radiation as well as fluorescent lighting treatment (control) caused increases in dry weights, but shoot lengths were shortest when plants were exposed to blue plus red light compared with either red or blue plus far-red treatments. The number of floral buds as well as the occurrence of flower opening for ageratum and salvia plants was also enhanced under the blue plus red mixture. Likewise, carbohydrate accumulation was stimulated by that combination compared with the other radiation treatments.

A comparative study of the effects of laser and light-emitting diode radiation on superoxide dismutase activity and nitric oxide production in rat wound fluid

The effect of laser and light-emitting diode radiation in the visible region of the spectrum on the content of reactive nitrogen species and superoxide dismutase activity in rat wound fluid was studied. The efficiency of action of coherent laser radiation and incoherent light-emitting diode radiation in the red region of the spectrum on the parameters analyzed was compared. The study was performed using the model of cut aseptic wounds proposed by L.I. Slutskii. A He-Ne laser (632 nm) or an U-332B light-emitting diode (630 nm) was used as the source of radiation. It was shown that (1) exposure of wounds to visible light of both laser and light-emitting diode causes dose-dependent changes in superoxide dismutase activity and nitrite production and that (2) radiation coherence does not play a significant role in the changes in superoxide dismutase activity or nitric oxide production by wound fluid phagocytes.

40.5L: Late‐News Paper: 18.1‐inch XGA TFT‐LCD with Wide Color Reproduction using High Power LED‐Backlighting

AbstractWe develop 18.1‐inch XGA TFT‐LCD using high power Light Emitting Diodes (LEDs) as light sources for backlighting. By matching the transmissive spectra of color‐filter to LEDs radiation, the higher brightness and the wider color reproduction of 95%‐NTSC are achieved on the front‐of‐screen.

Methods of temperature stabilization of light-emitting diode radiation

Some problems of temperature stabilization of light-emitting diode (LED) radiation have been discussed in the paper. Temperature–electrical characteristics of LED have been discussed and a way has been suggested to use them for the improvement of techniques for the temperature stabilization of their radiation power. There exists a possibility of developing one common monolithic LED-compensation system, and at the same time, a thermally compensated electroluminescence diode. The compensation system presented in the paper, in which an LED is a source of radiation and a temperature sensor, is not complicated and is practical in measurements where thermal conditions undergo fast changes. The presented system for the thermal stabilization can be adapted for impulse work, which allows for a considerable increase of LED radiation power. It has been proved in the paper that LED is an original source of radiation which can be applied to a construction of photometers of different kinds, working in real field conditions.

Importance of `Blue' Photon Levels for Lettuce Seedlings Grown under Red-light-emitting Diodes

Light-emitting diodes (LEDs) with high-intensity output are being studied as a photosynthetic light source for plants. High-output LEDs have peak emission at approximately 660 nm concentrated in a waveband of +/- 30 nm. Lettuce (Lactuca sativa Grand Rapids') seedlings developed extended hypocotyls and elongated cotyledons when grown under these LEDs as a sole source of irradiance. This extension and elongation was prevented when the red LED radiation was supplemented with more than 15 micromoles m-2 s-1 of 400- to 500-nm photons from blue fluorescent lamps. Blue radiation effects were independent of the photon level of the red radiation.

Temperature stabilisation of light-emitting diode radiation

Some problems of temperature stabilisation of light-emitting diode (LED) radiation have been discussed in the paper. Designs of electronic circuits for automatic compensation of the temperature variations in LED radiation flux have been presented.