scholarly journals Study on the Degradation of Optical Silicone Exposed to Harsh Environments

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1305 ◽  
Author(s):  
Maryam Yazdan Mehr ◽  
Willem van Driel ◽  
Francois De Buyl ◽  
Kouchi Zhang
Keyword(s):  
Light Transmission ◽  
Light Exposure ◽  
Light Emitting Diode ◽  
Salt Bath ◽  
Attenuated Total Reflection ◽  
Free Form ◽  
Harsh Environment ◽  
Significant Deterioration ◽  
Light Emitting ◽  
Swimming Water

Degradation mechanisms of silicone plates under harsh environment conditions are studied in this investigation. Environmental degradation of silicone free form, used as secondary optics in Light Emitting Diode LED lighting lamps and luminaires or any other applications requiring high quality optics being used, has negative implications for the optical performance. Degradation of silicone plates in harsh environment conditions was studied in salt bath and swimming water environments, using different light radiation and temperatures. Samples were exposed to harsh environment conditions for up to 4 months. Optical and chemical characteristics of exposed plates were studied using an Fourier transform infrared- attenuated total reflection FTIR-ATR spectrometer, an integrated sphere, and a Lambda 950 Ultraviolet-Visible UV-VIS spectrophotometer. Results show that 100 °C salt bath exposure had the most severe degrading effect on the optical characteristic of silicone plates. Increasing exposure time in the salt bath at that high temperature is associated with a significant deterioration of both optical (i.e., light transmission and relative radiant power value) and mechanical properties of silicone samples. On the contrary, silicone plates showed a great degree of stability against light exposure (UV at 360 nm and blue light at 450 nm).

The Intellectual Lighting And Data Transmission System based On RGBW Light Emitting Diodes

2021 ◽  
pp. 63-68
Author(s):  
Daniil S. Shiryaev ◽  
Olga A. Kozyreva ◽  
Ivan S. Polukhin ◽  
Sergey A. Shcheglov ◽  
Svetlana A. Degtiareva ◽  
...  
Keyword(s):  
Visible Light ◽  
Data Transmission ◽  
Light Transmission ◽  
Transmission Rate ◽  
Light Emitting Diode ◽  
Spectral Characteristics ◽  
System Component ◽  
Transmission Channel ◽  
Error Vector Magnitude ◽  
Light Emitting

The system of intellectual lighting data transmission via visible light is developed and manufactured. Spectral characteristics of a downlink which uses the red crystal of a RGBW light emitting diode for data transfer were studied. The DALI protocol-based radiation chromaticity control system which allows us to set different lighting scenarios with constant data transmission rate was developed. The radiation chromaticity range covers almost the entire colour gamut in the colour space. The system of high-frequency matching of system component impedances was developed and frequency characteristics of the suggested scheme were studied for development of the system. Optimal parameters of the signal for visual light communication such as carrier frequency, modulation type and band were determined. Observation of the constellation diagram which represents different values of the complex amplitude of the keyed signal in the form of a complex number on a quadrature plane (cosine and sine components of the carrying signal) and of fixation of the amplitude of the error vector magnitude (EVM) was selected as a method of study of the transmission channel quality. The value of EVM in the visible light transmission channel was significantly lower for signals with amplitude modulation than for phase-manipulated signals. When implementing different lighting change scenarios, radiation of other crystals of the light emitting diode crystals not used for transmission did not lead to increase of EVM by more than one percent.

scholarly journals Determination of Dental Adhesive Composition throughout Solvent Drying and Polymerization Using ATR–FTIR Spectroscopy

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3886
Author(s):  
Arwa Almusa ◽  
António H.S. Delgado ◽  
Paul Ashley ◽  
Anne M. Young
Keyword(s):  
Light Exposure ◽  
Light Emitting Diode ◽  
Attenuated Total Reflectance ◽  
Drying Time ◽  
Light Emitting ◽  
Spectral Changes ◽  
One Step ◽  
Urethane Dimethacrylate ◽  
Kinetics Of

The of this study aim was to develop a rapid method to determine the chemical composition, solvent evaporation rates, and polymerization kinetics of dental adhesives. Single-component, acetone-containing adhesives One-Step (OS; Bisco, USA), Optibond Universal (OU; Kerr, USA), and G-Bond (GB; GC, Japan) were studied. Filler levels were determined gravimetrically. Monomers and solvents were quantified by comparing their pure Attenuated Total Reflectance-Fourier Transform Infra-Red (ATR–FTIR) spectra, summed in different ratios, with those of the adhesives. Spectral changes at 37 °C, throughout passive evaporation for 5 min, then polymerisation initiated by 20 s, and blue light emitting diode (LED) (600 mW/cm2) exposure (n = 3) were determined. Evaporation and polymerisation extent versus time and final changes were calculated using acetone (1360 cm−1) and methacrylate (1320 cm−1) peaks. OS, OU, and GB filler contents were 0, 9.6, and 5.3%. FTIR suggested OS and OU were Bis-GMA based, GB was urethane dimethacrylate (UDMA) based, and that each had a different diluent and acidic monomers and possible UDMA/acetone interactions. Furthermore, initial acetone percentages were all 40−50%. After 5 min drying, they were 0% for OS and OU but 10% for GB. Whilst OS had no water, that in OU declined from 18 to 10% and in GB from 25 to 20% upon drying. Evaporation extents were 50% of final levels at 23, 25, and 113 s for OS, OU, and GB, respectively. Polymerisation extents were all 50 and 80% of final levels before 10 and at 20 s of light exposure, respectively. Final monomer polymerisation levels were 68, 69, and 88% for OS, OU, and GB, respectively. An appreciation of initial and final adhesive chemistry is important for understanding the properties. The rates of evaporation and polymerisation provide indications of relative required drying and light cure times. UDMA/acetone interactions might explain the considerably greater drying time of GB.

scholarly journals Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nathan Stasko ◽  
Jacob F. Kocher ◽  
Abigail Annas ◽  
Ibrahim Henson ◽  
Theresa S. Seitz ◽  
...  
Keyword(s):  
Visible Light ◽  
Blue Light ◽  
Light Exposure ◽  
Light Emitting Diode ◽  
Spectral Band ◽  
Dependent Manner ◽  
Light Emitting ◽  
Biological Surfaces ◽  
Visible Wavelengths ◽  
High Doses

AbstractThe delivery of safe, visible wavelengths of light can be an effective, pathogen-agnostic, countermeasure that would expand the current portfolio of SARS-CoV-2 intervention strategies beyond the conventional approaches of vaccine, antibody, and antiviral therapeutics. Employing custom biological light units, that incorporate optically engineered light-emitting diode (LED) arrays, we harnessed monochromatic wavelengths of light for uniform delivery across biological surfaces. We demonstrated that primary 3D human tracheal/bronchial-derived epithelial tissues tolerated high doses of a narrow spectral band of visible light centered at a peak wavelength of 425 nm. We extended these studies to Vero E6 cells to understand how light may influence the viability of a mammalian cell line conventionally used for assaying SARS-CoV-2. The exposure of single-cell monolayers of Vero E6 cells to similar doses of 425 nm blue light resulted in viabilities that were dependent on dose and cell density. Doses of 425 nm blue light that are well-tolerated by Vero E6 cells also inhibited infection and replication of cell-associated SARS-CoV-2 by > 99% 24 h post-infection after a single five-minute light exposure. Moreover, the 425 nm blue light inactivated cell-free betacoronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner. Importantly, clinically applicable doses of 425 nm blue light dramatically inhibited SARS-CoV-2 infection and replication in primary human 3D tracheal/bronchial tissue. Safe doses of visible light should be considered part of the strategic portfolio for the development of SARS-CoV-2 therapeutic countermeasures to mitigate coronavirus disease 2019 (COVID-19).

Effect of Thickness on Light Transmission and Vickers Hardness of Five Bulk-fill Resin-based Composites Using Polywave and Single-peak Light-emitting Diode Curing Lights

2019 ◽  
Vol 44 (1) ◽  
pp. 96-107 ◽  
Author(s):  
GA Maghaireh ◽  
RB Price ◽  
N Abdo ◽  
NA Taha ◽  
H Alzraikat
Keyword(s):  
Vickers Microhardness ◽  
Light Transmission ◽  
Light Emitting Diode ◽  
Surface Hardness ◽  
Single Peak ◽  
Distilled Water ◽  
Light Emitting ◽  
Radiant Exposure ◽  
Light Curing ◽  
Post Hoc

SUMMARY Objectives: This study compared light transmission through different thicknesses of bulk-fill resin-based composites (RBCs) using a polywave and a single-peak light-emitting diode light-curing unit (LCU). The effect on the surface hardness was also evaluated. Methods: Five bulk-fill RBCs were tested. Specimens (n=5) of 1-, 2-, 4-, or 6-mm thickness were photopolymerized for 10 seconds from the top using a polywave (Bluephase Style) or single–peak (Elipar S10) LCU, while a spectrophotometer monitored in real time the transmitted irradiance and radiant exposure reaching the bottom of the specimen. After 24 hours of storage in distilled water at 37°C, the Vickers microhardness (VH) was measured at top and bottom. Results were analyzed using multiple-way analysis of variance, Tukey post hoc tests, and multivariate analysis (α=0.05). Results: The choice of LCU had no significant effect on the total amount of light transmitted through the five bulk-fill RBCs at each thickness. There was a significant decrease in the amount of light transmitted as the thickness increased for all RBCs tested with both LCUs (p<0.001). Effect of LCU on VH was minimal (ηp2=0.010). The 1-, 2-, and 4-mm-thick specimens of SDR, X-tra Fill, and Filtek Bulk Restorative achieved a VHbottom/top ratio of approximately 80% when either LCU was used. Conclusions: The total amount of light transmitted through the five bulk-fill RBCs was similar at the different thicknesses using either LCU. The polywave LCU used in this study did not enhance the polymerization of the tested bulk-fill RBCs when compared with the single-peak LCU.

scholarly journals Realization of a Secure Visible Light Communication System via Chaos Synchronization

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Teh-Lu Liao ◽  
Chih-Yung Chen ◽  
Hsin-Chieh Chen ◽  
Yung-Yi Chen ◽  
Yi-You Hou
Keyword(s):  
Visible Light ◽  
Light Transmission ◽  
Light Emitting Diode ◽  
Digital Signal ◽  
Visible Light Communication ◽  
Audio Signals ◽  
Light Emitting ◽  
Straight Line ◽  
Data Transmission Security ◽  
To Receive

A novel technique for transmission of information through visible light communication (VLC) is developed in this study. A light-emitting diode is used as the light source at the transmitting side to send the encrypted information. At the receiving side, a light sensor, OPT-101, is used to receive the light signals that carry the encrypted information. The Arduino Due microcontroller board is used for digital signal processing at both the transmitting and receiving sides. Furthermore, to prevent the transmitted message from being intercepted, two chaotic systems, a master and a slave, with a synchronization controller are designed to obtain the transmitted audio signals. The design enables not only a VLC system with the light transmission path as a straight line (so that data cannot be stolen) but also the encryption of the audio signals with the chaotic system (Rössler system) to enhance data transmission security. The effectiveness of this system is then experimentally verified.

scholarly journals Inactivation of Escherichia Coli and Salmonella Using 365 and 395 nm High Intensity Pulsed Light Emitting Diodes

Foods ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 679 ◽  
Author(s):  
Amritha Prasad ◽  
Michael Gänzle ◽  
M. S. Roopesh
Keyword(s):  
Escherichia Coli ◽  
Foodborne Pathogens ◽  
High Intensity ◽  
Light Exposure ◽  
Light Emitting Diode ◽  
Antibacterial Efficacy ◽  
Pulsed Light ◽  
Light Emitting ◽  
E Coli ◽  
Novel Approach

High intensity pulsed light emitting diode (LED) treatment is a novel approach to inactivate foodborne pathogens. The objective of this study was to evaluate the antibacterial potential of high intensity 365 (UV-A) and 395 nm (NUV-Vis) LED treatments against Escherichia coli and Salmonella enterica at high and low water activity (aw) conditions, and to understand the influence of different process parameters on their antibacterial efficacy. Bacteria at high (in phosphate buffer saline, PBS) and low aw (aw = 0.75) conditions were treated with both the LEDs with specific doses at a fixed distance from the LEDs. The 365 nm LED showed more effectiveness in reducing the dried bacteria compared to 395 nm LED. The dry E. coli showed more resistance to LED treatments compared to Salmonella. The 365 and 395 nm LED treatments with ~658 J/cm2 dose resulted in reductions of 0.79 and 1.76 log CFU/g of Salmonella, respectively, on 0.75 aw pet foods. The LED treatments increased the surface temperature, resulting in water loss in the treated samples. This study showed that the dose, duration of light exposure, bacterial strain, and aw played a major role in the antibacterial efficacy of the 365 and 395 nm LEDs.

Spectroscopic Sensing with a Highly Transparent, Ion-Exchangeable Polymer Blend

1997 ◽  
Vol 51 (11) ◽  
pp. 1745-1752 ◽  
Author(s):  
Letian Gao ◽  
Carl J. Seliskar ◽  
Lisa Milstein
Keyword(s):  
Light Source ◽  
Polymer Blend ◽  
Fiber Optic ◽  
Light Emitting Diode ◽  
Fiber Optic Sensor ◽  
Poly Vinyl Alcohol ◽  
Significant Deterioration ◽  
Light Emitting ◽  
Optic Sensor ◽  
Kinetics Of

A polymer blend formulation originally patented by the National Aeronaticautical and Space Administration (NASA) has been modified for use in spectroscopic sensing. The cured polymer blend is a mixture of poly(acrylic acid) in glutaraldehyde cross-linked poly(vinyl alcohol). We have optimized the composition and the casting of the blend for optical sensing. The blend has clear ultraviolet (UV) and visible spectral regions for direct spectroscopic sensing, and it is an excellent absorber of many inorganic and organic cations from aqueous solution. The kinetics of the uptake of [Ru(BiPy)3]2+ and rhodamine 620 are presented as examples of complex ion preconcentration by the blend. With only the polymer blend directly applied as a fiber-optic cladding, aqueous Cu2+ ion can be detected as low as 10−6 M by using a light-emitting diode at 810 nm as a light source. A blend-clad fiber-optic sensor can be regenerated at least 25× without significant deterioration. The polymer blend can also trap hydrophobic compleximetric reagents added during the curing of the cross-linked blend. A prototype compleximetric dye-based evanescent-wave fiber-optic sensor using 1-(2'-pyridylazo)-2-naphthol was developed to detect aqueous Co2+ with a red HeNe laser light source. The Co2+ ion could be detected as low as 10−7 M.

scholarly journals Polymerization quality testing of composite resins cured by led light source

2003 ◽  
Vol 50 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Larisa Blazic ◽  
Slavoljub Zivkovic ◽  
Dejan Pantelic ◽  
Vladimir Pipic
Keyword(s):  
Light Source ◽  
Light Exposure ◽  
Light Emitting Diode ◽  
Composite Resins ◽  
Curing Time ◽  
Light Emitting ◽  
Led Light ◽  
Depth Of Cure ◽  
Dental Tissues ◽  
Hard Dental Tissues

The quality of interface between composite resin materials and hard dental tissues is highly dependent on the polymerization light source. Newly developed blue light- emitting diode units for light polymerization of dental restorative materials are the most innovative light source technology in dentistry nowadays. The aim of this work was to estimate the depth of cure of five different light-activating composite resins exposed to different irradiation times (5s, 10s, 20s and 40s) when the experimental LED light source was used. The tested materials were: Tetric Ceram (Vivadent), Point 4 (Kerr), Admira (VOCO), Filtek Z250 (3M) and Diamond Lite (DRM Lab., Inc). The depth of cure testing was determined using a penetrometer. Results after 40s curing time were as following: the deepest depth of cure was achieved after application of Filtek Z 250, Diamond Lite Point 4 and Tetric Ceram. For the restorative material Admira was found the lowest depth of cure for the light exposure of 40s. An experimental LED light source achieved a sufficient depth of cure (over 2 mm) for all tested materials after curing time of 10s. The polymerization light source spectral distribution should be considered in addition to irradiance as a depth of cure indicator.

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