Light-emitting Diode Light Source Research Articles

Effect of Additional Light Curing on Colour Stability of Composite Resins

AimThe objective of this study was to evaluate the effect of additional light curing on the colour stability of composite resins. Materials and methods: Four different composite resins—a nanofill, a nanohybrid, a microhybrid, and a bulk-fill composite resin—were tested. Eighty disc-shaped specimens were prepared from each material using either a quartz tungsten halogen or a light-emitting diode light source and were randomly divided into 2 groups according to the surface treatment: no polishing (nonpolished) or polishing with aluminum oxide discs (polished). Then additional light curing was applied to half of the specimens in each group. All specimens were immersed in coffee solution for 1 week. Colour was measured with a spectrophotometer at baseline and after 1 week of storage in coffee solution. Results: Statistically significant differences in colour stability were observed in the restorative materials according to the composition of composite resin, the polishing protocol, and additional light curing, whilst there were no significant differences according to the light source. Additional light curing reduced discolouration in all groups tested. Conclusions: Additional light curing may be beneficial after finishing and polishing in order to maintain aesthetics and increase the resistance of composite resins to discolouration.

NIR Irradiation Based on Low-Power LED Drive Module Design for Fat Reduction.

In this study, we designed a low-power visible ray (V) drive module based on a light-emitting diode (LED) to initiate fat reduction using light source irradiation. A chemical phantom of muscle and fat was fabricated, and the performance of the proposed LED drive module was tested using this chemical phantom. The LED light source could reduce fat by irradiating the skin 4–5 cm deep. The device exhibits a negative feedback and parallel amplification to maintain a stable circuit based on low-power consumption. Muscles have a high-water content and low impedance, whereas fats have a low water content and significant salt content. Therefore, fat exhibits high impedance. Chemical phantoms were fabricated according to these impedance values, and the fat reduction effect using the LED circuits was analyzed. When the fat phantom was irradiated by the light source, the fat impedance lowered, and we confirmed that fat reduction could be obtained. This study is expected to be applicable to family medicine and weight management health care.

Influence of spectrum characteristics on the output efficiency of LED pump laser

The absorption spectrum distribution of the gain medium and the emission spectrum of the pump light source are essential factors that affect the efficiency of light-emitting diode (LED) pump. The spectral bandwidth of the LED light source is usually 20–60 nm, covering several absorption peaks of the gain medium, which is different from the laser diodes (LD) pump with a spectral bandwidth 2–6 nm. In this study, the four-level rate equations for LED pump is established. The influence of the absorption spectral distribution on the pumping characteristics of LDs and LEDs are analyzed. Nd:YAG and Nd:YLF lasers pumped by LEDs with spectrum widths of 30 nm and LDs with spectral widths of 4 nm were calculated. Results show that the spectrum distribution may cause a 61.7% difference in photon number density of LED pumped Nd:YAG laser and the LD pumped Nd:YAG laser and 66.4% in Nd:YLF lasers. The LED pumped Nd:YAG laser and Nd:YLF laser are compared by experiment and simulation in the same experimental system. Without the resonant cavity, the output signal intensity of the laser amplifier is 87.2% of the . When there is a resonant cavity, under the pump energy of 10.3 mJ, the output of Nd:YAG laser was 749 μJ, and the output of Nd:YLF laser was 177 μJ. The output of Nd:YAG laser is about 4 times that of Nd:YLF laser.

Design of Photovoltaic Panel-Light-Emitting Diode Spotlight and Its Performance Analysis in Tunnel Buildings

According to the adaptive characteristics of the entrance and exit sections of tunnel buildings with the intensity of external sunlight, the cost of traditional photovoltaic panel (PV)-light-emitting diode (LED) lighting system increases due to battery. Combined with the structure of sunshine conveyor, a new PV-LED spotlight is proposed. The lighting device uses PV module as the power supply to directly drive the LED light source, which can make the brightness of the tunnel synchronized with the sunlight intensity, avoid the problem that it cannot work stably due to its weather changes, and further save the cost without battery. The main control chip adopts STC12C5A60S2 and supports multiple 10-bits precision A/D conversion channels. It can process the output signal of the light intensity detection circuit and set a threshold circuit to judge the intensity of sunlight, further control the working state of LED lighting device. The LED display module adopts 12864 liquid crystal display (LCD) with built-in T6963C driver to display five kinds of data, including the output voltage of light intensity detection circuit and the corresponding voltage value of four threshold circuits. The circuit resistance can be adjusted to change the light output voltage threshold required by the tunnel. In the test, the PV-LED lighting device is erected in the tunnel building. Compared with the traditional PV-LED lighting device and the new PV-LED spotlight designed, the new PV-LED lighting device in the morning and evening can further improve the efficiency of solar power generation. Meanwhile, the PV plate plane of the designed lighting device is perpendicular to the plane where the sunlight shines. The spectral irradiance and full band spectral irradiance of the lighting device in six bands was calculated and found that the percentage of spectral irradiance in different bands is close to the percentage requirement under AM1.5.

Macrocyclic Photoinitiator Based on Prism[5]arene Matching LEDs Light with Low Migration.

In this work, a naphthalene-based macrocycle prism[5]arene (NP5 OCH3 ) is developed as a novel kind of photoinitiator. When NP5 OCH3 is irradiated under light, the bond between methylene and naphthalene can be quickly broken owning to the existence of ring tension. The macrocycle is cleaved to linear oligomer biradicals, which can effectively initiate the free radical photopolymerization of acrylate monomers. Compared with conventional photoinitiators, NP5 OCH3 has strong light absorption in the wavelength range of 365-405nm, so it can well match the environment-friendly light-emitting diodes (LEDs) light source to realize highly efficient initiation. In addition, there is no small molecule fragment generated during NP5 OCH3 fracture, and the resulted linear oligomer biradicals can be immobilized in the polymer after initiating polymerization, so NP5 OCH3 photoinitiators show much lower migration rate and cytotoxicity. Cleavable macrocycle prismarene may provide a new idea for the design of safe and efficient photoinitiators matching long wavelength light.

Ladder-like energy-relaying exciplex enables 100% internal quantum efficiency of white TADF-based diodes in a single emissive layer

Development of white organic light-emitting diodes based on purely thermally activated delayed fluorescence with a single-emissive-layer configuration has been a formidable challenge. Here, we report the rational design of a donor-acceptor energy-relaying exciplex and its utility in fabricating single-emissive-layer, thermally activated delayed fluorescence-based white organic light-emitting diodes that exhibit 100% internal quantum efficiency, 108.2 lm W−1 power efficiency, and 32.7% external quantum efficiency. This strategy enables thin-film fabrication of an 8 cm × 8 cm thermally activated delayed fluorescence white organic light-emitting diodes (10 inch2) prototype with 82.7 lm W−1 power efficiency and 25.0% external quantum efficiency. Introduction of a phosphine oxide-based acceptor with a steric group to the exciplex limits donor-acceptor triplet coupling, providing dual levels of high-lying and low-lying triplet energy. Transient spectroscopic characterizations confirm that a ladder-like energy relaying occurs from the high-lying triplet level of the exciplex to a blue emitter, then to the low-lying triplet level of the phosphine oxide acceptor, and ultimately to the yellow emitter. Our results demonstrate the broad applicability of energy relaying in multicomponent systems for exciton harvesting, providing opportunities for the development of third-generation white organic light-emitting diode light sources.

LED light sources improved the essential oil components and antioxidant activity of two genotypes of lemon balm (Melissa officinalis L.)

BackgroundNowadays, light-emitting diodes (LEDs) as a new lighting technology, have been emerged as an alternative source of light for plants due to their wavelength specificity, the narrow width of their bands, small size, solid structure, long lifetime, and low heat generation. Here we investigated the effect of different LED light sources on the essential oil components and antioxidant activity of Melissa officinalis. Two genotypes of lemon balm (Ilam and Isfahan) were subjected to four artificial light treatments, including white, red, blue, red + blue LEDs, and greenhouse light as natural lighting.ResultsThe LED lights significantly increased shoot fresh and dry weights and leaf number in the two genotypes as compared to greenhouse condition. The results showed that the content and composition of essential oil in the two genotypes were variable under different light treatments and the total amount of compounds in the Ilam genotype was higher than the other genotype. The results of analysis of the essential oil by GC/MS indicated that the highest amount of monoterpenes in the genotypes was related to citronellal under red + blue LED lamps (15.3 and 17.2% in Ilam and Isfahan genotypes, respectively) but blue, white, and greenhouse condition had the most effect on sesquiterpenes content in both genotypes. The results showed that the observed variation between the two genotypes in the essentials oil composition was related to the relative percentage of the constituents and not to the appearance or lack of a specific component. Red + blue lighting also provided the highest radical scavenging activity in both genotypes (80.77 and 82.09% for Ilam and Isfahan genotypes, respectively). Based on principal component analyses (PCA), three main groups were identified regarding genotypes and all light treatments.ConclusionsOverall, results indicated that the essentials oil composition of two genotypes of lemon balm was affected both qualitatively and quantitatively by different LED light sources; hence, LED lights might be used to improve monoterpenes, sesquiterpenes, and antioxidant activity in the selected genotypes.

Development of a Smartphone-Based Optical Device to Measure Hemoglobin Concentration Changes for Remote Monitoring of Wounds.

Telemedicine (TM) can revolutionize the impact of diabetic wound care management, along with tools for remote patient monitoring (RPM). There are no low-cost mobile RPM devices for TM technology to provide comprehensive (visual and physiological) clinical assessments. Here, a novel low-cost smartphone-based optical imaging device has been developed to provide physiological measurements of tissues in terms of hemoglobin concentration maps. The device (SmartPhone Oxygenation Tool—SPOT) constitutes an add-on optical module, a smartphone, and a custom app to automate data acquisition while syncing a multi-wavelength near-infrared light-emitting diode (LED) light source (690, 810, 830 nm). The optimal imaging conditions of the SPOT device were determined from signal-to-noise maps. A standard vascular occlusion test was performed in three control subjects to observe changes in hemoglobin concentration maps between rest, occlusion, and release time points on the dorsal of the hand. Hemoglobin concentration maps were compared with and without applying an image de-noising algorithm, single value decomposition. Statistical analysis demonstrated that the hemoglobin concentrations changed significantly across the three-time stamps. Ongoing efforts are in imaging diabetic foot ulcers using the SPOT device to assess its potential as a smart health device for physiological monitoring of wounds remotely.

One/two-photon sensitive sulfonium salt photoinitiators based on 1,3,5-triphenyl-2-pyrazoline

Three 1,3,5-triphenyl-2-pyrazoline-based sulfonium salt photoinitiators (PIs) were synthesized, and the relationship between their molecular structures and photophysical and photochemical properties under one/two-photon irradiation were presented. The sulfonium salts had absorption peaks from 343 nm to 372 nm that overlapped the emission of 365–425 nm light-emitting diode (LED) light sources. The energy levels of molecular orbitals were closely related to the quantum yield of photoacid generation (ΦH+) as determined by the electrochemical and absorption properties of the PIs, and the introduction of an electron-pushing group could increase ΦH+ due to the enlarged energy gap between the singlet excited states S1 and S2. Interestingly, the wavelength dependence of ΦH+ was due to the nature of the transition. The π–π* transition showed high ΦH+ values (0.56–0.66) under excitation by UV LEDs, while the π–σ* transition showed low efficiency under visible LED irradiation. Intramolecular charge transfer from the pyrazoline ring to sulfonium salts induced efficient photolysis and high ΦH+. The sulfonium salts could efficiently initiate cationic polymerization and free radical polymerization. In addition, their high two-photon absorption cross-sections (δ780 nm = 75–105 GM) reduced the threshold of two-photon microfabrication. These PIs should have potential in LED photocuring and two-photon 3D microfabrication.

Metabolic Analysis of Root, Stem, and Leaf of Scutellaria baicalensis Plantlets Treated with Different LED Lights.

Light emitting diodes (LEDs) have recently been considered an efficient artificial light source in plant factories for enhancing plant growth and nutritional quality. Accordingly, this study aimed to review blue, red, and white LED light sources for efficiency and length of the growing period to produce seedlings of Scutellaria baicalensis with high nutritional value. The roots, stems, and leaves of S. baicalensis seedlings were grown under different LED lights and harvested after two and four weeks, and analyzed using high-performance liquid chromatography and gas chromatography time-of-flight mass spectrometry to identify and quantify primary and secondary metabolites. Roots, particularly in the seedlings treated with white LEDs were determined to contain the greatest concentrations of the representative compounds present in S. baicalensis: baicalin, baicalein, and wogonin, which show highly strong biological properties compared to the other plant organs. A total of 50 metabolites (amino acids, sugars, sugar alcohols, organic acids, phenolic acids, and amines) were detected in the roots, stems, and leaves of S. baicalensis seedlings, and the concentrations of primary and secondary metabolites were generally decreased with the increasing duration of LED illumination. Therefore, this study suggests that white LED light and a 2-week growing period are the most efficient conditions for the production of baicalin, baicalein, and wogonin.

Analysis on High-Power Seaport LED Luminaire with Uniform Light Distribution Based on Optimized Lens and Heatsink

In the case of light-emitting diode (LED) seaport luminaires, they should be designed in consideration of glare, average illuminance, and overall uniformity. Although it is possible to implement light distribution through auxiliary devices such as reflectors, it means increasing the weight and size of the luminaire, which reduces the feasibility. Considering the special environment of seaport luminaires, which are installed at a height of 30 m or more, it is necessary to reduce the weight of the device, facilitate replacement, and secure a light source with a long life. In this paper, an optimized lens design was investigated to provide uniform light distribution to meet the requirement in the seaport lighting application. Four types of lens were designed and fabricated to verify the uniform light distribution requirement for the seaport lighting application. Using numerical analysis, we optimized the lens that provides the required minimum overall uniformity for the seaport lighting application. A theoretical analysis for the heatsink structure and shape were conducted to reduce the heat from the high-power LED light sources up to 250 W. As a result of these analyses on the heat dissipation characteristics of the high-power LED light source used in the LED seaport luminaire, the heatsink with hexagonal-shape fins shows the best heat dissipation effect. Finally, a prototype LED seaport luminaire with an optimized lens and heat sink was fabricated and tested in a real seaport environment. The light distribution characteristics of this prototype LED seaport luminaire were compared with a commercial high-pressure sodium luminaire and metal halide luminaire.

Influences of Spectral Power Distribution on Circadian Energy, Visual Comfort and Work Performance

Spectral power distribution (SPD) is an essential element that has considerable implications on circadian energy and the perception of lit environments. The present study assessed the potential influences of SPD on energy consumption (i.e., considering circadian energy), visual comfort, work performance and mood. Two lighting conditions based on light-emitting diode (LED) and organic light-emitting diode (OLED) were used as proxies for SPDs of different spectral content: dominant peak wavelength of 455 nm (LED) and 618 nm (OLED). Using measured photometric values, the circadian light (CL), melatonin suppression (MS), and circadian efficacy (CE) of the two lighting sources were estimated via a circadian-phototransduction model and compared. Additionally, twenty-six participants were asked to evaluate the said lit environments subjectively in terms of visual comfort and self-reported work performance. Regarding circadian lighting and the associated energy implications, the LED light source induced higher biological actions with relatively less energy than the OLED light source. For visual comfort, OLED lighting-based conditions were preferred to LED lighting-based conditions, while the opposite was true when considering work performance and mood. The current study adds to the on-going debate regarding human-centric lighting, particularly considering the role of SPD in energy-efficient and circadian lighting practices.

Visualization of Lighting Quality and Object Appearance When Using Multichannel Light Sources

ABSTRACT The availability of quasi-monochromatic Light Emitting Diodes (LEDs) with peak wavelengths distributed over the visible spectrum has opened the way to the development of multichannel LED light sources generating tunable illumination spectra. As the color appearance of an object is strongly influenced by the spectral power distribution of the light source, these multichannel light sources are also commonly used as a research tool in color quality studies. In a number of studies, spectrum optimization algorithms are applied in order to generate a target spectrum directly. Other papers report on the calculation of an illumination spectrum with the aim to optimize one or a set of general quality metrics such as the luminous efficacy of radiation and the color rendering index Ra or Rf. The approach followed in this paper is to explore and visualize, for a given multichannel LED light source, the lighting quality parameters which can be reached within the chromaticity gamut for a selected object. For any predefined target white point chromaticity, the illumination metamers are calculated analytically within the constraints defined by the multichannel LED light source under consideration. The solution space is sampled with a brute force method and the values of any general or specific color quality index can be evaluated. For a predefined object spectral reflectance (or one typical spectral reflectance representative for a set of objects), the object chromaticity gamut is derived. Several object chromaticity targets within the gamut, such as the memory color of familiar objects, can be selected and the impact of “local” variations of the hue and chroma within this gamut on the general and special lighting quality indices and on the user preference can be checked. This can simplify the selection of an object-based optimum illumination spectrum. The approach is illustrated in practice using a five-channel LED light source which was developed in-house.

LED Excitation of an Imaging Cytometer for Bead-Based Immunoassay

We present and demonstrate a light-emitting diode (LED)-excited imaging cytometer for the detection of bead-based immunoassay samples. A broad area green LED illuminates the specimen plane using a set of aspheric lenses and an excitation filter. The imaging module was comprised of an objective lens, filters, tube lens, and camera. To demonstrate the multiplex capability of the presented system, a panel of three sets of beads with varying classification fluorescence intensity was employed. Experimental results revealed that the LED light source provides uniform illumination across the specimen plane, and therefore permits the multiplex detection of three biomarkers. Detection of a sepsis biomarker, procalcitonin, was used to demonstrate the detection sensitivity and measurement range of the system. The imaging cytometer can detect the concentration of procalcitonin as low as 24.4 pg/mL and it holds the potential for being developed for point-of-care testing applications.

Effect of Irradiation with Visible Light (Green, Red, Blue) on Inhibition of Melanin Biosynthesis

Purpose: This study aims to investigate the inhibitory effect and regulatory mechanism of melanin biosynthesis in mouse-derived B16 melanoma cells (B16F10), using a light emitting diode (LED) light source irradiation device of three single wavelengths (630, 470, 525 nm) for irradiation of visible light (green, red, blue). Methods: Using three single-wavelength LED light sources, cytotoxicity, tyrosinase activity, and melanin biosynthesis were measured. Results: LED irradiation with green, red, and blue wavelengths did not show cytotoxicity or changes in melanin content at each wavelength. When the wavelength was irradiated alone, the blue and green LED wavelengths caused a decrease in tyrosinase activity, blocking the intracellular signaling mechanism that caused the increase in tyrosinase activity induced by α-melanocyte-stimulating hormone (α-MSH). In addition, protein kinase A cascade, an intracellular signaling mechanism that causes an increase in tyrosinase activity induced by α-MSH, was blocked, as it was inhibited with cyclic adenosine monophosphate (cAMP). Red series wavelength LED did not lead to any reaction. Conclusion: The irradiation of blue and green series wavelength LEDs among visible lights controls the mechanism involved in melanin formation in skin cells and results in skin whitening, which suggests that it can be effective in the whitening and cosmetic industry using LED in the future.

In Vivo Measurements of Middle Ear Temperature During Transcanal Endoscopic Ear Surgery

The light emitted from the endoscope during transcanal endoscopic ear surgery (TEES) heats the intratympanic space. This heat may potentially be dangerous to nearby important structures, as documented by in vitro and by animal and cadaveric studies. The aim of our work was to monitor middle ear temperatures during TEES in vivo. Cohort study. Tertiary referral hospital. Four patients (15-69 yrs old) underwent transcanal endoscopic tympanoplasties for chronic perforation or retraction. After elevating the tympanomeatal flap, a thermocouple was placed in the middle ear to measure the heat generated by a 30° Hopkins rod telescope (11 cm long, 2.7 mm wide) and fiberoptic light emitting diode light source. Middle ear temperature in the retrotympanum was monitored under these conditions: at 50 and 100% light intensity, after removing and wiping the endoscope tip, during suctioning and following middle ear irrigation. Maximum middle ear temperature ranged from 36.26-37.30°C. Pulling out and wiping the endoscope caused no change or minimal decrease of 0.16°C. Middle ear irrigation caused a temperature drop of 2.05°C to 5.11°C. Suctioning was associated with a drop from 0.24°C to 3.91°C that was dependent on the depth of the endoscopic tip. Middle ear temperatures during TEES using a Hopkins rod telescope and light-emitting diode light source reach values corresponding to physiological body temperature, and do not reach dangerous levels.

The Influence of Light Wavelength on Resveratrol Content and Antioxidant Capacity in Arachis hypogaeas L.

The quality and intensity of light can have a huge influence on plant growth and bioactive compound production. Compared to conventional lighting, very little is known about the influence of light emitting diodes (LED) irradiation on the antioxidant and antimicrobial properties and resveratrol content of peanut sprouts. This study was aimed at understanding the effects of LED light on the growth and antioxidant capacity of peanut sprouts. The resveratrol concentration was determined by liquid chromatography–tandem mass spectrometry. Peanut sprouts grown under blue LED light exhibited a higher total resveratrol content grown than those under fluorescent light and other LED light sources. The highest total phenolic content was recorded in the case of blue LED. The 1,1-diphenyl-2-picrylhydrazyl and 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid radical scavenging values of blue LED‒treated and micro-electrodeless light-treated sprouts were significantly (p < 0.05) higher than that of sprouts grown under lights with other wavelengths. A Pearson correlation analysis revealed a strong association of the resveratrol, total phenolic, and flavonoid contents of peanut sprouts with 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS), indicating its contribution to antioxidant activities. The anti-tyrosinase activity increased with an increase in the concentration of the tested sample. Blue LED-irradiated peanut extracts at a selected concentration range showed moderate cytotoxicity. Furthermore, the antimicrobial activity of peanut sprouts grown under blue LED was effective against Escherichia coli, Klebsiella pneumonia, and Vibrio litoralis. The present study revealed that the application of LEDs during the peanut sprouts growth improves the antioxidant activity, resveratrol concentration, and metabolite accumulation.

Construction of a Simple USB Powered LED Light Source for Illuminating Optical Microscopes

Tungsten and halogen lamps are normally used for microscope illumination. However, if there is an electrical fault in any of these lamps, extra money to purchase a new one and the sacrifice of a long time for its arrival may be required to get the lamp replaced, especially in some developing countries. The aim of this study therefore is to develop a cheap and easily obtainable light source, built with Light Emitting Diodes (LEDs) to replace a faulty tungsten or halogen lamp. The LEDs are cheap to buy, easily available and operate at a much lower voltage. A light source, using LEDs, was designed and constructed to fit easily into the space previously occupied by the tungsten or halogen lamp. An integrated switching low power DC-DC converter, having a microcontroller unit at its heart and powered from a 5 Volt source, was also constructed to control the LED light source. It was observed that the contrast of the sample image obtained with the halogen lamp was reproduced by the LED light source. In this study, a replacement LED based light source for illuminating optical microscopes was constructed, and it gave a reasonable result compared to that obtained by using the halogen lamp. This work will be very useful in those places where it may be very difficult to get a quick replacement halogen or tungsten lamp or where electric power is not always available.

Broadband cavity enhanced absorption spectroscopy for measuring atmospheric NO<sub>3</sub> radical

NO<sub>3</sub> radical is the most important oxidant in atmospheric chemistry at night, and it controls the oxidation and removal of various trace gas components in the atmosphere. The understanding of the chemical process of NO<sub>3</sub> radical is of great significance for studying the atmospheric pollution processes such as haze. The NO<sub>3</sub> radical has a low concentration and strong activity, so it is relatively difficult to measure accurately. We report here in this paper an instrument for unambiguously measuring NO<sub>3</sub> based on broadband cavity enhanced absorption spectroscopy (BBCEAS). To achieve the robust performance and system stability under diverse conditions, this BBCEAS instrument has been developed, with efficient sampling, and resistance against vibration and temperature change improved, and the BBCEAS instrument also has low-power consumption. The 660-nm-wavelemngth light-emitting diode (LED) is used as a light source of the BBCEAS system. The sampling gas path with low loss and suitable for domestic high-particle environment is designed. Through the LED light source test, the optimal working current and temperature can be obtained to achieve the acquisition of NO<sub>3</sub> absorption spectrum with high signal-to-noise ratio. Considering the fact that the water vapor absorption is an important interference factor for the measurement of NO<sub>3</sub> radical by BBCEAS, the daytime atmospheric measurement spectrum is used as a background spectrum, and participates in spectral fitting of NO<sub>3</sub> to reduce the effect of water vapor. The mirror reflectivity and effective cavity length are calibrated, and the Allan variance analysis is also carried out. The reflectance of the mirror can reach about 0.99993 at 662 nm (NO<sub>3</sub> absorption peak), and the corresponding theoretical effective optical path can reach more than 7 km, which can meet the measurement requirements of atmospheric NO<sub>3</sub> radicals. The detection limit (1σ) of 0.75 pptv for NO<sub>3</sub> is achieved with an acquisition time of 10 s and a total measurement error of about 16%. The atmospheric NO<sub>3</sub> radical observation is carried out in Hefei. During the observation period, the highest NO<sub>3</sub> concentration is 23.4 pptv, demonstrating the promising potential applications in in-situ, sensitive, accurate and fast simultaneous measurements of NO<sub>3</sub> in the future by using the developed broadband cavity enhanced absorption spectroscopy.

Effect of Light Emitting Diode (LED) Light on Growth and Flowering of Pot-mum ‘Orange Egg’ during Cultivation

This study was carried out to investigate the effect of the LED light source on the growth and flowering characteristics in potted chrysanthemum ‘Orange Egg’ during cultivation in a closed growth chamber with a constant temperature of 22℃ and a photoperiod consisted of 11 hours light and 13 hours darkness. Each LED light source of blue (444 nm), red (652 nm), or mixed LED (blue:red:white=2:5:1) was supplied separately. As a result, the plant height of the pot-mum 'Orange Egg' grown in red LED was longest with an average of 9.43 cm. And the plant height in blue LED was shorter than in mixed LED, but there was not statistically significant between them. The plant width and leaf width were also largest in plants grown under red LED similar to the growth response of the plant height. But the number of leaves and leaf lengths were more and longer in monochromatic LED such as blue or red than mixed LED. Flower bud differentiation was completed around 16 to 17 days after short-day treatment regardless of LED light source. However, pot-mum plants grown in red and blue LED did not develop flower buds normally and reach final flowering although those grown in mixed LED were fully flowered around 5 weeks after short-day treatment. Therefore, it is considered that the mixed LED consisting of blue, red and white is useful as LED light source for producing potted chrysanthemums in plant factories.