Intensity Of Light Source Research Articles

The Effect of Blue-blocking Lenses on Photostress Recovery Times.

The selective reduction in visible wavelengths transmitted through commercially available blue-blocking lenses (BBLs) is known to influence the appearance and contrast detection of objects, particularly at low light levels. This influence may impair the human retinal receptor response time to dynamic light changes during photostress events. This study aimed to assess whether BBLs selectively affect photostress recovery times (PSRTs) for chromatic and achromatic stimuli of different Weber contrasts that were viewed on a dark black background. Photostress recovery times were measured in 12 younger participants (18 to 39 years old) with no history of ocular disease or abnormal vision. Photostress recovery times were evaluated for four brands of BBLs, which were compared with a control lens. In these experiments, after exposure to an intense light source for 5 seconds, the time taken to recover vision and correctly identify a computer-generated letter stimulus viewed under low and high luminance levels was determined, which means perception is likely to be governed by mesopic and photopic conditions. Across conditions, the letter stimulus was achromatic and chromatic and could differ in luminance contrast. Under photopic stimulus conditions, although reducing luminance contrast increased PSRTs, BBLs had no significant effect on PSRTs relative to control lens. However, under mesopic stimulus conditions, BBLs significantly affect PSRTs for both achromatic (F2.006,8.02 = 61.95, P < .0001) and chromatic stimuli (F3,16 =139.01, P < .0001), particularly for blue targets, which had considerably longer PSRTs (38.40 seconds). The brand of BBL was also shown to selectively affect PSRTs, with those with transmittance profiles that block the most blue light having longer PSRTs. The present study suggests that, although the color and contrast of the target stimuli affected recovery times, the difference in recovery times between different types of BBLs was noticed only under low-light-level stimulus conditions.

Crystal-based intensive gamma-ray light sources

We discuss design and practical realization of novel gamma-ray Crystal-based Light Sources (CLS) that can be constructed through exposure of oriented crystals (linear, bent, periodically bent) to beams of ultrarelativistic charged particles. In an exemplary case study, we estimate brilliance of radiation emitted in a Crystalline Undulator (CU) LS by available positron beams. Intensity of CU radiation in the photon energy range $10^0-10^1$ MeV, which is inaccessible to conventional synchrotrons, undulators and XFELs, greatly exceeds that of laser-Compton scattering LSs and can be higher than predicted in the Gamma Factory proposal to CERN. Brilliance of CU-LSs can be boosted by up to 8 orders of magnitude through the process of superradiance by a pre-bunched beam. Construction of novel CLSs is a challenging task which constitutes a highly interdisciplinary field entangling a broad range of correlated activities. CLSs provide a low-cost alternative to conventional LSs and have enormous number of applications.

Study on Preparation of Microstructured Optical Membrane

Micro-structured optical film is one of the micro-optical elements and has a great market demand. This article studies the microstructured optical film formed by UV imprinting: The influence of embossing pressure on microstructure replication accuracy was explored. The larger the pressure, the better the material filling. When the pressure is 5N, the microstructure replication is complete; The relationship between the radiation intensity and warpage deformation was explored, and the decrease in the intensity of the UV light source can effectively reduce the warpage deformation; The influence of the material formula on the optical properties of the product was explored. When the oligomer content was 55%, the film had a high light transmittance. At the same time, the prepared film was subjected to an apparent inspection with good microstructure replication accuracy.Microstructured optical elements are widely used in optical fields such as semiconductors, lasers, beam shaping [1-2] and solar energy [3-5] due to their unique advantages such as small size and high performance. As a key component in many industries, it has a high market demand rate. However, the microstructure forming process is complicated, the manufacturing cost is high, and the accuracy is difficult to guarantee, which has restricted its development. With the advancement of science and technology and the increase in market demand, more and more researchers and enterprises have put their eyes on the research of preparing micro-structured optical elements.At present, the commonly used microstructures are mainly icrolens array [6-8], and the processing methods include micro-imprinting [9-10], etching [11], electron beam direct writing, and micro-injection [12], etc. This article studies the UV-curing embossing process in micro-embossing. This processing method has the advantages of fast molding, high efficiency, and environmental protection. And this process is conducive to mass production and has a broad market application prospect.In this paper, the forming process and material formulation of microstructured optical film prepared by light-cured micro-imprinting were investigated, and the microstructure morphology of the preparation was analyzed apparently.

Personalized Dental Medicine: Impact of Intraoral and Extraoral Clinical Variables on the Precision and Efficiency of Intraoral Scanning

(1) Objectives: The aim is to measure the influence of different intraoral (crowding and molar inclination) and extraoral (surface material and ambient light) conditions on the efficacy and efficiency of intraoral scanning. (2) Methods: In a controlled in vitro experimental study, the samples were divided into six groups showing two types of intraoral conditions—lower incisor crowding (groups 1–3) and lower molar mesial tipping (groups 4–6). Each modified model was replicated using three types of materials with different light-absorption properties (n = 18 models). Each sample was scanned 30 times at light intensities of 0.0, 1800, or 3600 l×, yielding 3240 scans. Scanning efficiency (digital acquisition; scanning chair-time; and scanning failures) and scanning efficacy (undetected volume) were assessed using virtual superimpositions and Mecano Equate software. The intra- and interobserver error and reliability of the method were calculated and data analyses were performed using the t-test, paired t-test, and one-way analysis of variance (p < 0.05). (3) Results: Digital acquisition was influenced by the degree of crowding and molar inclination (p < 0.05). The scanning surface material affected the efficacy and efficiency, which were lower with a calcium sulfate hemihydrate A modified compound scanning surface (p < 0.05). Higher intensities of ambient light in the scanning room were associated with reduced scanning efficacy (p < 0.05). Moreover, the scanner showed greater amounts of undetected volume as the degrees of crowding and mesial tipping of the lower second molar increased over 25°, with mean error values of 0.97 mm3 and 1.12 mm3, respectively. (4) Conclusions: For scanning procedures employing digital acquisition, differences in the degrees of crowding and mesial tipping of the lower second molar, scanning surface material, and external light source intensity influence the efficacy and efficiency of the scanning procedures, scanning chair-time, scanning failures, and undetected volume.

Workflow and hardware for intraoperative hyperspectral data acquisition in neurosurgery.

To prevent further brain tumour growth, malignant tissue should be removed as completely as possible in neurosurgical operations. Therefore, differentiation between tumour and brain tissue as well as detecting functional areas is very important. Hyperspectral imaging (HSI) can be used to get spatial information about brain tissue types and characteristics in a quasi-continuous reflection spectrum. In this paper, workflow and some aspects of an adapted hardware system for intraoperative hyperspectral data acquisition in neurosurgery are discussed. By comparing an intraoperative with a laboratory setup, the influences of the surgical microscope are made visible through the differences in illumination and a pixel- and wavelength-specific signal-to-noise ratio (SNR) calculation. Due to the significant differences in shape and wavelength-dependent intensity of light sources, it can be shown which kind of illumination is most suitable for the setups. Spectra between 550 and 1,000nm are characterized of at least 40dB SNR in laboratory and 25dB in intraoperative setup in an area of the image relevant for evaluation. A first validation of the intraoperative hyperspectral imaging hardware setup shows that all system parts and intraoperatively recorded data can be evaluated. Exemplarily, a classification map was generated that allows visualization of measured properties of raw data. The results reveal that it is possible and beneficial to use HSI for wavelength-related intraoperative data acquisition in neurosurgery. There are still technical facts to optimize for raw data detection prior to adapting image processing algorithms to specify tissue quality and function.

Application of MoS2/reduced graphene oxide for photocatalytic degradation of rhodamine B in water environment

In this study, MoS2 was composited with RGO (the reduced form of graphene oxide) for enhancing the photocatalytic degradation of RhB in aqueous solution by applying visible light irradiation. A new approach to synthesize graphene was applied by reduction of graphene oxide using ascorbic acid. Factors affecting the photocatalytic degradation including pH, initial rhodamine B concentration, light source intensity and quencher existence were investigated. The results showed that MoS2/RGO composite exhibited better photocatalytic activity in the degradation of RhB (with a conversion of 80 %) compared to pure MoS2 (with a conversion of 30.8 %) under visible light irradiation. The higher photocatalytic performance of MoS2/RGO was found in slight acidic environment. Among the tested free radical killers, ammonium oxalate revealed the most significant effect on the photocatalytic degradation of RhB.This research also indicated that MoS2/RGO composite can be considered as a potential catalyst for the degradation of persistent organic dyes in wastewater.

A micromachined vector light sensor

We report the design, fabrication, and performance characteristics of a novel microfabricated light sensor designed to determine the intensity and direction of an incident light source. The device structure comprises several light sensors that are integrated onto a pyramid base. The direction to the light source is estimated using the ratios of the signals from the lights sensors that are facing different directions. We demonstrate that this “vector light sensor”, is capable of measuring both the intensity and the direction of light from a source. The three-dimensional structure of the sensor is created based on well-known silicon microfabrication techniques and uses photodiodes for the detection of visible light. The signals from the photodiodes were read and processed based on a simple algorithm to experimentally verify the device performance. In addition to the direction, the distance to a light source may be estimated by simple triangulation of data from two vector light sensors. The small size and low power consumption of the individual sensors make them suitable for applications where passive distance and direction estimation is required. Furthermore, it is envisioned that arrayed sensors can directly provide light-field information in a plane.

Photocatalytic Oxidative Degradation of Carbamazepine by TiO2 Irradiated by UV Light Emitting Diode

Here, ultraviolet light-emitting diodes (UV-LED) combined with TiO2 was used to investigate the feasibility of carbamazepine (CBZ) degradation. The effects of various factors, like crystal form of the catalyst (anatase, rutile, and mixed phase), mass concentration of TiO2, wavelength and irradiation intensity of the UV-LED light source, pH of the reaction system, and coexisting anions and cations, on the photocatalytic degradation of CBZ were studied. The mixed-phase (2.8 g/L) showed the best degradation efficiency at 365 nm among three kinds of TiO2, wherein CBZ (21.1 µM) was completely oxidized within 1 h. The results of batch experiments showed that: (i) CBZ degradation efficiency under UV-LED light at 365 nm was higher than 275 nm, due to stronger penetrability of 365 nm light in solution. (ii) The degradation efficiency increased with increase in irradiation intensity and pH, whereas it decreased with increase in initial CBZ concentration. (iii) The optimal amount of mixed-phase TiO2 catalyst was 2.8 g/L and excessive catalyst decreased the rate. (iv) The co-existence of CO32−, HCO3−, and Fe3+ ions in water significantly accelerated the degradation rate of photocatalytic CBZ, whereas Cu2+ ions strongly inhibited the degradation process of CBZ. ·OH was found to be the main active species in the UV-LED photocatalytic degradation of CBZ. UV-LED is more environmentally friendly, energy efficient, and safer, whereas commercial TiO2 is economical and readily available. Therefore, this study provides a practically viable reference method for the degradation of pharmaceuticals and personal care products (PPCPs).

Tetrahydroporphyrin-tetratosylate (THPTS)-based photodynamic inactivation of critical multidrug-resistant bacteria in vitro

BackgroundPhotodynamic inactivation (PDI) is a promising approach to treat multidrug-resistant infections. However, effectiveness of PDI is limited, particularly in Gram-negative bacteria. The use of photosensitizer (PS) 3,3′,3′′,3′′′-(7,8,17,18-tetrahydro-21H,23H-porphyrine-5,10,15,20-tetrayl)tetrakis[1-methyl-pyridinium]tetratosylate (THPTS) and laser light has led to very promising results. This study focuses on the effects of THPTS in various critical multidrug-resistant bacterial strains and explores the possibility of light-emitting diode (LED)-based activation as a clinically more feasible alternative to laser light. MethodsTHPTS was further chemically characterized and in vitro testing of PDI of different multidrug-resistant bacterial strains was performed under various experimental conditions, including varying drug concentration, incubation time, light source (laser and LED) and light intensity, by determination of viable bacteria after treatment. The effect of hyaluronic acid as an adjuvant for medical applications was also evaluated. ResultsBacterial density of all investigated bacterial strains was reduced by several orders of magnitude, irrespective of multidrug-resistance or hyaluronic acid addition. The effect was less intense in Gram-negative strains (disinfection), and more pronounced in Gram-positive strains (sterilization), even at reduced THPTS concentrations or decreased light treatment intensity. Controls without THPTS or without light treatment did not indicate reduced bacterial density. ConclusionsPDI with THPTS and laser light was effective in all investigated bacterial strains. Gram-negative strains were less, but sufficiently, susceptible to PDI. Adding hyaluronic acid did not reduce the antibacterial treatment effect. LED-based PDI is equally effective when illumination duration is increased to compensate for reduced light intensity.

Photobactericidal activity activated by thiolated gold nanoclusters at low flux levels of white light

The emergence of antibiotic resistant bacteria is a major threat to the practice of modern medicine. Photobactericidal agents have obtained significant attention as promising candidates to kill bacteria, and they have been extensively studied. However, to obtain photobactericidal activity, an intense white light source or UV-activation is usually required. Here we report a photobactericidal polymer containing crystal violet (CV) and thiolated gold nanocluster ([Au25(Cys)18]) activated at a low flux levels of white light. It was shown that the polymer encapsulated with CV do not have photobactericidal activity under white light illumination of an average 312 lux. However, encapsulation of [Au25(Cys)18] and CV into the polymer activates potent photobactericidal activity. The study of the photobactericidal mechanism shows that additional encapsulation of [Au25(Cys)18] into the CV treated polymer promotes redox reactions through generation of alternative electron transfer pathways, while it reduces photochemical reaction type-ІІ pathways resulting in promotion of hydrogen peroxide (H2O2) production.

Simple Photometer Development For Educational Purposes in Natural Pigment Analysis

In this paper we will discuss the making of the simple photometer instrument to measure the absorbance of natural pigment crude extract. To make simple photometer, cuvette holder was printed using 3D Printing Machine, the development of simple photometer instrument also uses some components such as LED light (633 nm) as the light source, Photodiode-TSL250 as a detector and a variable resistor to set the initial intensity of light source. In this development, Arduino Uno was also used as USB data acquisition device to capture the signal from the instrument. The results of sample measurements between simple photometer instrument and UV-Vis 1800 spectrophotometer showed 98% regression coefficient of determination and simple photometer has a LOD and LOQ absorbance at 0.0267 and 0.0344. Simple photometer instrument was able to show similar response as commercial instrument. Through the development of simple photometer, student can easily understand the working principles of a spectrophotometer in natural pigment analysis that difficult to studied in detailed before.

Identifying Light Pollution Sources at Two Major Observatories in Malaysia

A spectral observation and analysis were conducted in order to identify the main contributor of sky brightness at two of Malaysia’s most active observatories. The light pollution observations were carried out under moonless clear night sky with a 90 mm refractor telescope and SBIG’s Self Guiding Spectrograph. We found that the main contributor to Balai Cerap Teluk Kemang (BCTK) sky brightness is High Pressure Sodium (HPS) street lighting due to its number and density used within 5 km radius of the observatory. HPS spectral lines dominate the spectrum between 556 - 640 nm, agrees with the orange hue visible to the naked eye. The intensity due to HPS lighting is so high that there was no trace of the concerned white LED spotlight less than 1 km away. However, some traces of elements from Mercury Vapor (MV) lamps at 3.6 km distance managed to reach the observatory in the green spectrum. The finding concludes that the nearby LED spotlight does not affect the night sky brightness over BCTK. Meanwhile, Langkawi National Observatory (LNO) sky profile was also observed during heavy fishing season as comparison. The sky spectra for LNO was similar to BCTK in the reds except for a very distinct peak in green region corresponding highly with green MV (532 - 547 nm) with peaks at 536 nm and 546 nm, matches the lamps used for squid fishing around the island. The intensity of the green MV light matches the intensity of HPS light sources, during the observation period of peak squid season in January. This made LNO a far less favorable condition for astronomical observing site compared to BCTK. We also found that LNO sky has brightened 3.767 times compared to finding of 2013.

The Right Light: Tiger Salamander Capture Rates and Spectral Sensitivity

ABSTRACTKnowledge of population dynamics is critical for species of conservation concern so wildlife researchers need to take advantage of biases in animals' behaviors that could help them monitor populations. This is particularly important for amphibians because many populations are declining and difficult to observe. Attraction of vertebrates to light is a well‐known navigational cue and some fisheries strategies utilize light sources to increase catch success. To optimize population monitoring of state‐endangered eastern tiger salamanders (Ambystoma tigrinum), we tested the utility of colored glow sticks (green, orange, pink, or yellow) as bait in traps in Maryland and Delaware, USA, during 2015–2016. We then measured intensities of the colored glow sticks and estimated photoreceptive quantum catches of each color according to the spectral sensitivities of eastern tiger salamanders. We found that eastern tiger salamanders' photoreceptors had greater quantum catches of photons from green and yellow glow sticks. However, traps baited with orange glow sticks were more than twice as likely to capture eastern tiger salamanders than were traps baited with green or yellow. There were no differences in the number of salamanders caught per successful trap among glow stick colors, perhaps due to attraction of salamanders to motion from previously captured salamanders. Our results indicate that biases other than perceived intensity of light sources may drive behavioral preferences. © 2020 The Wildlife Society.

Functional Charge Transfer Plasmon Metadevices.

Reducing the capacitive opening between subwavelength metallic objects down to atomic scales or bridging the gap by a conductive path reveals new plasmonic spectral features, known as charge transfer plasmon (CTP). We review the origin, properties, and trending applications of this modes and show how they can be well-understood by classical electrodynamics and quantum mechanics principles. Particularly important is the excitation mechanisms and practical approaches of such a unique resonance in tailoring high-response and efficient extreme-subwavelength hybrid nanophotonic devices. While the quantum tunneling-induced CTP mode possesses the ability to turn on and off the charge transition by varying the intensity of an external light source, the excited CTP in conductively bridged plasmonic systems suffers from the lack of tunability. To address this, the integration of bulk plasmonic nanostructures with optothermally and optoelectronically controllable components has been introduced as promising techniques for developing multifunctional and high-performance CTP-resonant tools. Ultimate tunable plasmonic devices such as metamodulators and metafilters are thus in prospect.

Theoretical calculations on photoelectron angular distribution of sequential two-photon double ionization for Ar atom

With the development of the intense light source, such as free electron lasers, the experiments on the nonlinear process in atomic photo absorption in the XUV and X-ray region became more and more feasible. As one of the simplest possible nonlinear processes, the sequential two-photon double ionization, in which the first photon produces an ion which is subsequently ionized by the second photon, attracts increasing attention of theorists and experimentalists. Study on the angular distributions and angular correlations of the photoelectrons in the sequential two-photon double ionization process are especially attractive, which provides valuable information about the electronic structure of atom or molecule systems and allows the obtaining of additional information about mechanism and pathway of the two-photon double ionization. In this paper, the expression for the photoelectron angular distribution in a sequential two-photon process is given based on the multi-configuration Dirac-Fock method and the density matrix theory. And then, the relativistic calculation program for photoelectron angular distribution is further developed with the help of the program packages GRASP2K and RATIP which are based on the multi-configuration Dirac-Fock method. By using this code, the sequential two-photon double ionization of the 3p shell in atomic argon is studied theoretically. The cross section, magnetic cross section, alignment of residual ions and the asymmetry parameter of the photoelectron angular distribution, each as a function of photon energy, for the first and the second step of sequential two-photon double ionization of argon are presented. The calculations predict that the alignment has a maximum value and the asymmetry parameter has a minimum value in the region of the cooper minimum. The angular distribution of the first step ionization for Ar atom and the second step ionization for Ar&lt;sup&gt;+&lt;/sup&gt; ion are given at 33.94 eV and 55.34 eV photon energy, respectively. In addition, the difference in property between the angular distributions of the first photoelectron in sequential two-photon double ionization and in conventional one-photon single ionization is discussed. The present calculated results are compared with other available results, showing that they are in good agreement with each other. The results of this paper will be helpful in studying nonlinear processes in the XUV range.

Axial super-resolution using a double-zone pinhole in a confocal microscope

A double-zone pinhole intensity ratio measurement method is proposed for confocal microscopy based on the inverse phase characteristics of the axial response between the central and annular portions of the spot. The simulation and experimental results show that when the normalized optical radius of the central region is 3.2 and the peak values of the axial response of the two regions are similar, the central lobe of the axial characteristic curve can be compressed by 72.8%, without changing the original structure of the system. This simple method can effectively suppress both the light-source intensity drift and changes in the measured surface reflectance.

Baseline-free quantitative absorption spectroscopy based on cepstral analysis.

The accuracy of quantitative absorption spectroscopy depends on correctly distinguishing molecular absorption signatures in a measured transmission spectrum from the varying intensity or 'baseline' of the light source. Baseline correction becomes particularly difficult when the measurement involves complex, broadly absorbing molecules or non-ideal transmission effects such as etalons. We demonstrate a technique that eliminates the need to account for the laser intensity in absorption spectroscopy by converting the measured transmission spectrum of a gas sample to a modified form of the time-domain molecular free induction decay (m-FID) using a cepstral analysis approach developed for audio signal processing. Much of the m-FID signal is temporally separated from and independent of the source intensity, and this portion can be fit directly with a model to determine sample gas properties without correcting for the light source intensity. We validate the new approach in several complex absorption spectroscopy scenarios and discuss its limitations. The technique is applicable to spectra obtained with any absorption spectrometer and provides a fast and accurate approach for analyzing complex spectra.

The qualification and training of laser/intense pulse light hair removal operators within South Africa.

Lasers and intense pulse light (IPL) sources are powerful devices that can cause skin burns, pigmentary changes, and scarring if used incorrectly. Adequate training is essential, and regulations are required to limit complications. The purpose was to investigate the qualifications and training obtained by laser hair removal operators in South Africa. Questionnaires were distributed and information gathered from owners/managers of laser clinics, suppliers of laser devices in South Africa, individuals in the workplace performing laser hair removal procedures, and accredited tertiary institutions. A majority of clinic owners/managers (94.45%) felt that more emphasis should be placed on laser hair removal training at a tertiary level, and 66.67% outsource additional training provided by the manufacturer of laser devices. Based on the survey to manufacturers, 50% did not require any formal qualification as a minimum requirement, while 33.33% indicated laser hair removal training is incorporated at a NQF level 4 (National/Senior Certificate). The majority of individuals (68.89%) received training from tertiary institutions; however, they did not receive any practical training, and 60.87% felt the amount of training was insufficient. According to the survey sent to tertiary institutions in South Africa, only 27.78% offer laser hair removal training, and of these, 20% offer no practical training and 50% indicated that no practical examination is provided. There is a clear lack of training in laser hair removal in South Africa. The industry should have standard requirements in terms of minimum practical and theoretical hours with regards to the therapy.

Electromagnetic and gravitational waves conversion in a nonlinear dielectric medium by intense light source irradiation

Various types of gravity wave sources were considered in this paper. It is proposed to use the effect of mutual conversion of electromagnetic and gravitational waves in a nonlinear optical dielectric medium irradiated by an intensive light source as a perspective method of generating gravitational-wave radiation.

Photoelectric detection of crop fungi resistance based on microfluidic

In view of the defects such as long time-consuming and large limitation in the detection of pesticide resistance of crop pathogens at present. A novel photoelectric detection method based on enriched microfluidic chips is proposed for the detection of pesticide resistance of crop fungal disease. First, according to the aerodynamics characteristics of microbial aerosol particles and optical detection technology, a special enrichment microfluidic chip was designed to achieve high efficiency enrichment and high precision concentration detection of fungal spores. On this basis, based on the theory of pesticide resistance sensitivity baseline, the relationship among spore germination, systematic enrichment concentration, and optical detection concentration of Botrytis cinerea in strawberry treated with Pyrimethanil was studied, and the pesticide resistance detection model of uncultured pathogens was established. The light intensity of light source was 1.1 × 103 cd, and the wavelength was 620 nm as the optimum parameters for optical detection. The correlation coefficient between the microscopic examination of spores’ concentration and the results of optical detection is 0.9792. It has good linearity and reliability, which provides a theoretical basis for the research and development of portable equipment for detecting pesticide resistance of crop diseases.