Intensity Of Light-emitting Diodes Research Articles

Photobiomodulation therapy (red/NIR LEDs) reduced the length of stay in intensive care unit and improved muscle function: A randomized, triple-blind, and sham-controlled trial.

Photobiomodulation therapy (PBMT) has been widely used to improve strength, fatigue resistance and increase muscle mass in healthy individuals. These effects could help critically ill patients admitted to intensive care units (ICUs) who show reduced mobility and muscle strength. ICU-acquired weakness lessens overall health and increases the patient's length of stay in the ICU. This study evaluated the effects of PBMT using low intensity light-emitting diodes (LEDs) on the mobility and muscle strength (functional capacity) and length of stay of patients admitted to hospital ICU. This randomized, triple-blind, sham-controlled trial was conducted in a hospital ICU. Sixty patients were randomly assigned to two equal groups: (a) PBMT and (b) Sham. PBMT was applied daily to patients until their discharge from the ICU, using a flexible neoprene array of 264 LEDs (120 at 635 nm, 1.2 mW each; 144 at 880 nm, 15 mW each) for 90s (207.36 Joules) at each site. Ten sites were located bilaterally on the thighs, legs, arms, and forearms ventrally and dorsally, 15 min totaling 2,073.6Joules per session. Outcomes were length of stay (in h) until discharge from the ICU, muscle strength by the Medical Research Council (MRC) score and handgrip dynamometry (HGD), patient mobility by Intensive Care Unit Mobility Scale (IMS) and the Simplified Acute Physiology Score 3 (SAPS 3) for predicting mortality of patients admitted to the ICU. PBMT reduced the average length of stay in the ICU by ~30% (p = 0.028); increased mobility (IMS: 255% vs. 110% p = 0.007), increased muscle strength (MRC: 12% vs. -9% p = 0.001) and HGD (34% vs. -13% p < 0.001), and the SAPS3 score was similar (p > 0.05). The results suggest that daily PBMT can reduce the length of stay of ICU patients and increase muscle strength and mobility.

Advances in the use of white light on broccoli and kale postharvest shelf life

In this work, the effect of irradiation with three different intensities of white light-emitting diodes (LED) on the quality and senescence of refrigerated broccoli and green and red kale was studied. A high increase in weight loss was observed in samples exposed to high (80 μmol m−2 s−1) and low (10 μmol m−2 s−1) LED intensity. Samples stored under mid-intensity (30 μmol m−2 s−1) significantly reduced the change of total color (∆E), hue angle, and lightness (L*) values. Broccoli florets and green kale subjected to mid-intensity illumination retained higher chlorophyll levels than the other treatments (P < 0.05), and about 30% more compared to the dark stored samples. These differences were even more evident in red kale. Mid-intensity illumination also markedly reduced sugar losses and improved carotenoid contents. As a whole, results show that the selected intensity of white light used for postharvest illumination has a key influence on treatment efficacy. Industrial relevancePostharvest shelf life of green vegetables is very limited and there is a need to use environmentally friendly tools to extend it. The use of white light during storage has been proven to be a clean and non-chemical methodology to delay vegetable senescence, but the appropriate illumination conditions to maximize the quality of unprocessed vegetables are still unknown. In the present work, the effect of different lighting conditions on the visual and nutraceutical quality of refrigerated broccoli and green and purple kale was studied, and the best condition was defined. The selected light intensity may be considered for fresh market storage.

Classification and utilization of waste electronic components based on triboelectric nanogenerator

The rapid development of the internet of things is accompanied by a large number of equipment deployment. When the equipment fails or reaches its service life, tons of e-waste will be generated. Therefore, there is an urgent need to find environmentally friendly and effective ways to recycle and treat e-waste. In this paper, a method of classification detection and resource utilization of waste electronic components based on the triboelectric nanogenerator (TENG) is proposed, which provides a novel idea for electronic waste treatment. We studied the output voltage characteristics of different kinds of TENG based on waste electronic components subject to different environmental loadings. The output characteristics of TENG are explored, reflecting the e-waste categories and processing environment. TENG is also connected with hundreds of light-emitting diodes (LEDs) through rectifier bridge circuit, and the output performance of TENG is characterized by the number and intensity of LEDs.

Comparative evaluation of shear bond strength of directly bonded brackets using three varieties of light cure systems

Context: Using Visible Light to bond orthodontic attachments is now an accepted norm, the progression being Halogens, Low and High Intensity Light Emitting Diodes (LEDs). Since, clinical use of bonded brackets is pragmatically linked with Shear Bond Strength (SBS) and chair-side time, adhesives with shorter curing time are a boon. Hence, the aforementioned facets bear a more detailed study. Settings and Design: 6 Groups (2 Halogens, 2 Low Intensity LEDs and 2 High Intensity LEDs); Each Group comprised of 10 assemblies of Metal Brackets (3M Unitek, Gemini Series) bonded to facial surface of extracted human Maxillary 1st bicuspids. Methods and Material: Brackets were directly bonded using Standard Bonding Protocol to freshly extracted Human Maxillary Premolars. Shear Bond Strength (SBS) testing was done using Universal Testing Machine, Instron. The SBS values attained in Kg/F were converted into MPa and results subjected to a comparative evaluation. Results: Mean SBS values, in MPa, for Halogen Light Cure Systems were 8.51 and 8.86; for Low Intensity LEDs were 10.50 and 10.33 while for High Intensity LEDs 15.54 and 13.85.

LED Light-Induced ROS Differentially Regulates Focal Adhesion Kinase Activity in HaCaT Cell Viability.

In this study, changes in cell signaling mechanisms in skin cells induced by various wavelengths and intensities of light-emitting diodes (LED) were investigated, focusing on the activity of focal adhesion kinase (FAK) in particular. We examined the effect of LED irradiation on cell survival, the generation of intracellular reactive oxygen species (ROS), and the activity of various cell-signaling proteins. Red LED light increased cell viability at all intensities, whereas strong green and blue LED light reduced cell viability, and this effect was reversed by NAC or DPI treatment. Red LED light caused an increase in ROS formation according to the increase in the intensity of the LED light, and green and blue LED lights led to sharp increases in ROS formation. In the initial reaction to LEDs, red LED light only increased the phosphorylation of FAK and extracellular-signal regulated protein kinase (ERK), whereas green and blue LED lights increased the phosphorylation of inhibitory-κB Kinase α (IKKα), c-jun N-terminal kinase (JNK), and p38. The phosphorylation of these intracellular proteins was reduced via FAK inhibitor, NAC, and DPI treatments. Even after 24 h of LED irradiation, the activity of FAK and ERK appeared in cells treated with red LED light but did not appear in cells treated with green and blue LED lights. Furthermore, the activity of caspase-3 was confirmed along with cell detachment. Therefore, our results suggest that red LED light induced mitogenic effects via low levels of ROS–FAK–ERK, while green and blue LED lights induced cytotoxic effects via cellular stress and apoptosis signaling resulting from high levels of ROS.

High intensity and red enriched LED lights increased the growth of lettuce and endive

Changes in plant responses have been associated with different fractions of the visible spectrum and light intensity. Advances in light-emitting diodes (LED) have enabled the study of the effect of narrow wavelengths on plant growth and antioxidant compound synthesis. LED technology also facilitates the incorporation of light sources in a controlled setting where light spectra and intensity can be regulated. The objective of this study was to compare the effect of two commercial light spectra (S1: standard white light with 32.8% blue, 42.5% green, 21.7% red, and 2.4% far-red; S2: AP67 spectrum, designed for horticultural growth, with 16.9% blue, 20.5% green, 49.7% red and 12.3% far red) at two light intensities [low intensity (78 μmol m–2s–1 of photons for S1 and 62 μmol m–2s–1 for S2, and high intensity (HI) (102 and 100 μmol m–2s–1 for S1 and S2, respectively)] on growth and antioxidant compound contents in two leafy vegetables: endive (Cichorium endivia L.) and lettuce (Lactuca sativa L.). Fresh weight (FW), dry weight (DW), and DW% of plants were taken as growth indicators. In addition, leaf number, soil plant analysis development index, leaf area (LA), and specific leaf area were also evaluated. Antioxidant synthesis was measured as total phenol content, total flavonoid content, and antioxidant activity. The results showed that S2 and HI increased the FW, DW, and LA in both species. On the other hand, antioxidant compound contents were significantly increased by HI but did not vary with the spectrum. Highlights - The spectra of LED affected leaf number in lettuce and endive. - S2 spectrum improved growth parameters of both leafy vegetables. - Light intensity improved growth parameters of both leafy vegetables. - Antioxidant compound contents were significantly increased by high intensity LED light.

Thermal coupled photocatalysis over Pt/g-C3N4 for selectively reducing CO2 to CH4via cooperation of the electronic metal–support interaction effect and the oxidation state of Pt

Pt nanoparticle-loaded g-C3N4 (Pt/CN) that consisted of integrating Pt0 and Pt2+ species was prepared for selectively reducing CO2 to CH4 with H2O by thermal coupled photocatalysis. A strong electronic metal-support interaction was constructed between Pt nanoparticles and the g-C3N4 substrate, which limited the activity for CO evolution and improved the charge transfer from g-C3N4 to Pt for selective CH4 production. The formed Pt2+ species in the Pt nanoparticles completely suppress the side reaction of H2 production from reducing H2O. Moreover, a moderate heat input in the photocatalytic reaction facilitated the transfer of the photogenerated electrons from Pt nanoparticles to CO2, which further increased the photocatalytic activity for CH4 evolution. As a result, a significant enhancement of CO2 methanation performance (∼100 % selectivity, 14.8 μmol g−1 h−1) was realized on a 2 % Pt-loaded g-C3N4 photocatalyst under low intensity light-emitting diode (420 nm, on the order of solar intensity) irradiation at 125 °C.

Visible Light-Induced Antibacterial Activity of Pigments Extracted from Dregs of Green and Black Teas.

Chlorophyll and its derivatives are potential natural sensitizers frequently applied in antimicrobial photodynamic therapy. Chlorophyll derivatives are formed naturally during tea processing, but they do not contribute to the color of tea infusions and thus are presumably left in the tea dregs. The present study aimed to investigate (i) the chlorophyll remnants in the pigments recovered from dregs of green and black teas and (ii) the antibacterial activity of pigments extracted from the tea dregs upon illumination using a light-emitting diode (LED) as the light source. Pigment analysis using high-performance liquid chromatography (HPLC) revealed the presence of main degradation products of chlorophylls, such as pheophytin and its epimers, pyropheophytin, and pheophorbides. In vitro assays demonstrated significant reductions in the number of viable bacteria in the presence of the pigments after 30 min of incubation with LED light irradiation. The descending order of bacterial susceptibility was Listeria monocytogenes > Staphylococcus aureus > Escherichia coli > Salmonella typhi. At an equivalent irradiation intensity, the blue and red LEDs could stimulate a comparable inactivation effect through photodynamic reactions. These findings demonstrated the valorization potential of tea dregs as a source of chlorophyll derivatives with visible light-induced antibacterial activity.

Systematic Review of Photobiomodulation Therapy (PBMT) on the Experimental Calcaneal Tendon Injury in Rats.

This systematic review analyzed the light parameters and the effects of photobiomodulation therapy (PBMT) through low-level laser therapy (LLLT) and/or LED (light-emitting diode) on tendon repair of rats submitted to calcaneal injury. This study was conducted in accordance with the guidelines of the Preferred Reporting Items for Meta-Analysis, and PubMed and MEDLINE databases were accessed to search eligible studies published in English. The search terms were as follows: "Achilles tendon" or "Calcaneal tendon" or "tendon injuries" or "soft tissue injuries" and "tendinopathy" or "tendinitis" and "low-level light therapy" or "low-level laser therapy" or "low intensity power therapy" or "light-emitting diode" or photobiomodulation." The SYRCLE (SYstematic Review Center for Laboratory animal Experimentation) risks of bias was used to assess the risk of bias for selected studies. A total of 225 studies were found based on the descriptors used, and only 33 studies were eligible. Light parameters identified per point of irradiation were approximately 60 mW (continuous mode at infrared spectra), 2Wcm-2 , 2J and 45Jcm-2 . Light parameters at red spectra, continuous versus pulsed mode, and PBMT combined or compared with other therapies such as ultrasound, and studies using unhealthy rats (ovariectomized and/or diabetic models) were also identified and grouped according to these similarities. The main effects found were decreased inflammatory markers and signs of inflammatory process. PBMT (laser/LED) has positive effects in reducing the inflammatory and time for tissue repair in animal models of tendon injury and/or tendinitis using parameters identified.

Comparison of Crime-lite® 82S, Polilight® PL400 and Polilight® PL500 for the detection of semen and saliva stains

ABSTRACT Alternative light sources (ALS) are widely employed in forensic investigations for the identification of biological fluids, such as saliva and semen. While metal halide arc lamps are a common light source for many ALS, high intensity light-emitting diode (LED) globes are a more energy efficient alternative. To date, ALS operating with different light sources have not been evaluated against each other, and this study is the first to complete a side-by-side comparison of the arc lamps, Polilight® PL400 (PL400), Polilight® PL500 (PL500) and the LED-based Crime-lite® 82S (blue) (CL82S) for the detection of semen and saliva dilutions on various fabric materials. The absence or presence of fluorescence were scored independently by four experienced item examination scientists to reduce bias. The number of fluorescence stains detected using the CL82S (244 observations) was higher and brighter in intensity compared to those visualized using PL400 and PL500 (183 and 202 observations, respectively). Notably, dilutions of saliva which were not visible under PL400 and PL500 on a range of fabrics were detected under CL82S, which was statistically significant (p < 0.003). Taken together, CL82S is a better screening tool than the PL400 and PL500 for detection of dilute semen and saliva stains on various fabric types.

Small-sized irradiation structures for intensive year-round cultivation of green vegetable crops

Full and healthy human nutrition is characterized by the presence of green vegetable crops in the diet, which are rich in vitamins and useful components for humans. The need for them is observed year-round and all-season. Therefore, green vegetable products must be grown not only using traditional industrial technologies, but also in small businesses and private households. The realization of technology is ubiquitous, year-round cultivation of leafy vegetable crops in an artificial environment is possible using small-sized forms of cultivation facilities – irradiation chambers and boxes, grow boxes, phytotrons, etc. In this case, the main technological operation is the necessary light mode for plants: with the spectrum necessary for plants development and growth, with the necessary intensity and mode of irradiation. The developed irradiation units (camera and box) allow growing green vegetables at any time of the year, in any territory allotted for this, in the quantity necessary for consumption, etc. These units allow automatically monitoring the parameters of the air environment and soil, and, if necessary, adjusting it to create a comfortable environment for plant development. Experimental studies and processing of the results allowed concluding that by varying the spectrum and intensity of light-emitting diodes in the developed structures of irradiation units depending on the growth phase of green vegetable crops, it is possible to obtain products of higher consumer and commercial quality, with the necessary biochemical composition and characteristics.

Improving the luminous efficiency of gallium nitride-based light-emitting diodes using Ag nanograting structure

In order to improve the traditional gallium nitride (GaN)-light-emitting diode (LED) luminous efficiency, a structure of the GaN-LED is designed based on the local field enhancement of surface plasmon (SP). The principle of improving LED luminous properties using the SP features is described in detail. The factors that affect the light extraction efficiency of this LED structure are simulated with the COMSOL software. The thickness of p-GaN layer, the thickness of indium tin oxide (ITO) layer, the grating period T , the duty ratio r , as well as the shape of the interface between p-GaN and ITO are studied. The normalized radiated powers, the normalized absorbed powers, and the electric field distribution of this structure under different structure parameters have been achieved. The results show that when the thickness of p-GaN layer is 110 nm, the thickness of ITO buffer layer is 120 nm, the period T is 370 nm, the duty ratio is 0.5, and the value of D 1 / T is 0.6. The luminous intensity of LED is higher than that of the traditional LED nearly 43 times and is nearly 36 times higher than that of the Ag nanosphere structure, and SPs can be coupled with the active layer effectively to improve the luminous efficiency of LED, providing a theoretical guide for the preparation of high-performance GaN-LED chips.

BIOHEAT EQUATION WITH FOURIER AND NON-FOURIER HEAT TRANSPORT LAWS: APPLICABILITY TO HEAT TRANSFER IN HUMAN TISSUES

The paper is dedicated to mathematical problem formulations for the heat propagation in biological tissues based on the Fourier and non-Fourier laws at different boundary conditions. The heating of the tissues is provided by external heat sources like low intensity lasers or light-emitting diodes which are widely used in contemporary medical care. Numerical computations on the standard Pennes bioheat equation with Fourier heat conduction give the temperature curves for both heating and thermal relaxation processes that do not correspond to the in vivo measurement data on human skin tissue. It is shown the modified bioheat equation based on the Guyer-Krumhansl heat conduction with correct formulation of the boundary conditions produces realistic temperature curves when the distributed heat sources and sinks in the tissue are accounted for. The former corresponds to the metabolic heat and temperature dependent chemical reactions, while the latter is provided by the heat convection with blood microcirculation system. The proposed model gives realistic two time temperature curves. The perspective applications of the novel mathematical formulation are discussed.

Optical System for Led Luminaire

Lighting devices are an important element of a large number of technical systems, including road, living, industrial lighting, lighting systems of vehicles. It is known that the light instrument must fulfill two basic lighting tasks: to redistribute the light source of light source in the right way and to limit its dazzling effect. The introduction of light-emitting diodes (LEDs) for lighting necessitated a completely new quality in the construction of luminaires. The different production technology required new methods and designing tools. It also challenged designers with new problems to solve. LEDs are light sources emitting in one hemisphere, which requires a special approach to designing an LED lighting unit. However, for the illumination of premises with high spans or streets, roads such a light distribution is not suitable. For luminaires with solid-state light sources, other materials and new technology must be used; moreover, light distribution needs to be formed using different methods.&#x0D; This paper presents the design process of a LED luminaire from concept to implementation, exemplified by road lighting, and describes the methods and procedures used by the designer. Also, technological problems influencing the quality of the above lighting are addressed. Optical systems for LEDs are considered. The peculiarities of the use of secondary optical elements in the form of lenses for purpose of obtaining different diagrams of the spatial distribution of light intensity of light-emitting diodes are analyzed. Features and problems of calculation of secondary optical systems are considered. Massive collimators do not have to be elements that focus a narrow beam of light. They are able to form a beam in accordance with any accepted distribution that is appropriate for a given application. They are also able to form a beam in a specific way that is required for outdoor lighting luminaires. The stages of a project for designing a road luminaire require the application of the knowledge and experience gained in various research projects. The design methods described in this paper have been developed designing activity and are also to be used successfully in lighting production.&#x0D;

Study of the influence of wavelengths and intensities of LEDs on the growth, photosynthetic pigment, and volatile compounds production of Lippia rotundifolia Cham in vitro

Lippia rotundifolia Cham. is in the family Verbenaceae and is endemic to the Cerrado. This species is aromatic and characterized by the presence of glandular trichomes on its leaves that are rich in monoterpenes. The objective of this study was to evaluate the growth, photosynthetic pigment production, and chemical composition of L. rotundifolia grown in vitro under different light wavelengths and intensities. The light intensities consisted of five treatments using cool white fluorescent lamps at 20, 54, 78, 88, and 110 μmol m−2 s−1. The light quality consisted of six treatments using light-emitting diodes (LEDs) in different light wavelengths, namely, white, red, blue, and their interactions: 1R:1B, 2.5R:1B, and 1R:2.5B. After 45 days, the biometric parameters, photosynthetic pigment content, and volatile compounds were evaluated. The lower light intensities of 20 and 54 μmol m−2 s−1 generated higher growth, photosynthetic pigment content, and biomass accumulation. Myrcene and pentadecane were highest under light intensities of 88 and 110 μmol m−2 s−1, respectively. The highest limonene and ocimenone levels were obtained at 20 and 54 μmol m−2 s−1 intensity, respectively, and the highest myrcenone content was obtained at 78 μmol m−2 s−1 intensity. Regarding the light wavelengths, the combination of red and blue spectra further stimulated plantlet growth, and the 2.5R:1B combination obtained the best biometric data and total chlorophyll content. The z-ocimenone chemical compound contents were highest under the 1R:2.5B light spectrum. The monochromatic blue spectrum increased the myrcene and limonene content but decreased the myrcenone content, which was increased by red light. The highest pentadecane contents were obtained with the white spectrum and the red and blue combinations.

Robust Genetic Transformation System to Obtain Non-chimeric Transgenic Chickpea.

Chickpea transformation is an important component for the genetic improvement of this crop, achieved through modern biotechnological approaches. However, recalcitrant tissue cultures and occasional chimerism, encountered during transformation, hinder the efficient generation of transgenic chickpeas. Two key parameters, namely micro-injury and light emitting diode (LED)-based lighting were used to increase transformation efficiency. Early PCR confirmation of positive in vitro transgenic shoots, together with efficient grafting and an extended acclimatization procedure contributed to the rapid generation of transgenic plants. High intensity LED light facilitate chickpea plants to complete their life cycle within 9 weeks thus enabling up to two generations of stable transgenic chickpea lines within 8 months. The method was validated with several genes from different sources, either as single or multi-gene cassettes. Stable transgenic chickpea lines containing GUS (uidA), stress tolerance (AtBAG4 and TlBAG), as well as Fe-biofortification (OsNAS2 and CaNAS2) genes have successfully been produced.

Short communication: Mycosporine-like amino acids protect natamycin against photodegradation in milk exposed to fluorescent or light-emitting diode light

Natamycin has been used as a natural antimicrobial in dairy products, but the poor light stability of natamycin can limit usefulness in food products. Mycosporine-like amino acids are strong UV absorbers and might be useful as an additive to decrease light-induced degradations. Therefore, the objective of this study was to evaluate the photoprotective effect of mycosporine-like amino acids (MAA) in cow milk stored under 2 lighting conditions in retail commercial display cabinets with fluorescent and high intensity light-emitting diode illumination. When milk was exposed to both fluorescent and light-emitting diode light, natamycin degradation was very fast, and only 17.1 ± 0.9% of its original concentration was observed after 8 d at 4.0°C. On the other hand, by adding MAA into milk, natamycin was retained at 82.2 ± 0.9% and 92.2 ± 0.9% when low and high MAA levels were used, respectively. However, high MAA levels resulted in color changes. Therefore, MAA at low levels had a photoprotective effect for natamycin stability in cow milk exposed to light in refrigerated glass containers.

Light quality and intensity of light-emitting diodes during pre-cultivation of Picea abies (L.) Karst. and Pinus sylvestris L. seedlings – impact on growth performance, seedling quality and energy consumption

ABSTRACTThree different LED lamps with continuous spectra were compared against commonly used fluorescent lights. The lamps were characterized by light output, energy consumption and spectral quality for plant growth. The biological effects of light quality were compared by pre-cultivating seedlings of Picea abies (L.) Karst. and Pinus sylvestris L. under each spectrum for 35 days in a growth chamber with controlled temperature, humidity and photoperiod. The seedlings were then transplanted and cultivated for one vegetation period at the nursery, then planted outdoors on a forest field trial and followed for three years. The seedlings showed similar growth performance for all spectra tested. LED lamps have several advantages to fluorescent light such as energy consumption, longer life span and adjustable light intensity. Regarding light intensity the effects on growth performance were studied for both species using the most promising LED spectra. The photosynthetically active radiation (PAR) was maintained at 50, 100, 200 and 400 μmol m−2 s−1. Unlike energy consumption, seedling development did not display a linear relationship to light intensity. Instead, the results show an optimum light level between 100 and 200 μmol m−2 s−1 for the shade tolerant Picea abies seedlings and a level of around 200 μmol m−2 s−1 for the more shade intolerant Pinus sylvestris seedlings.

Comment on “Charge Carrier Extraction in Organic Solar Cells Governed by Steady‐State Mobilities”

Comment on “Charge Carrier Extraction in Organic Solar Cells Governed by Steady‐State Mobilities”

The effect of the curing time of an ultra-high intensity LED curing unit on diametral tensile strength of packable composite resin

This study aimed to evaluate the influence of the curing time of a light emitting diode (LED) curing unit on the diametral tensile strength of packable composite resin with 1 second–3 seconds from an ultra high intensity LED (Flash Max, intensity 4000 mW/cm2) and 20 seconds from a conventional LED (Ledmax 450, intensity 450 mW/cm2). We used an universal testing machine and the results showed a diametral tensile strength of 31.19 ± 6.84 MPa; 42.91 ± 8.26 MPa; and 52.53 ± 7.52 MPa. The result of an independent t-test was statistically significant (p < 0.05). We concluded the curing time of an ultra high intensity LED curing unit influences the diametral tensile strength of packable composite resin