Intensity Of Light Source Research Articles

A smartphone-based ratiometric fluorescent device for field analysis of soluble copper in river water using carbon quantum dots as luminophore

Sensitive detection of copper is valuable for environment and human healthy. Herein, we reported a smartphone-based ratiometric fluorescent device for field analysis of soluble copper in river water samples, which is based on the fluorescence quenching effect of Cu2+ to N-doped carbon quantum dots. The fluorescent images in the sample and reference areas in a twin cuvette were captured by the camera in a smartphone. The non-linearity response of the image brightness to the exposure was corrected by (B−B0)/(255 −B), where B and B0 are the brightness with and without luminophore, respectively. It was shown that corrected brightness ratio is insensitive the variation in light source intensity, ambient temperature, shooting parameters and focus of the camera, which is helpful to improve the stability and reliability of the cheap portable detection device. By using a balanced calibration method, the accuracy for concentration estimation is improved further. Under optimized conditions, the proposed method was applied to detect Cu2+ in the range from 1 to 200 nM with the detection limit of 0.43 nM. This simple fluorescence device offers the advantages of portability, reliability and accuracy for field analysis.

Inter-Method Reliability of Pulse Volume Related Measures Derived Using Finger-Photoplethysmography

Abstract. Pulse volume (PV) and its related measures, such as modified normalized pulse volume (mNPV), direct-current component (DC), and pulse rate (PR), derived from the finger-photoplethysmogram (FPPG), are useful psychophysiological measures. Although considerable uncertainties exist in finger-photoplethysmography, little is known about the extent of the adverse effects on the measures. In this study, we therefore examined the inter-method reliability of each index across sensor positions and light intensities, which are major disturbance factors of FPPG. From the tips of the index fingers of 12 participants in a resting state, three simultaneous FPPGs having overlapping optical paths were recorded, with their light intensity being changed in three steps. The analysis revealed that the minimum values of three coefficients of Cronbach’s α for ln PV, ln mNPV, ln DC, and PR across positions were .948, .850, .922, and 1.000, respectively, and that those across intensities were .774, .985, .485, and .998, respectively. These findings suggest that ln mNPV and PR can be used for psychophysiological studies irrespective of minor differences in sensor attachment positions and light source intensity, whereas and ln DC can also be used for such studies but under the condition of light intensity being fixed.

Due diligence required to quantify and visualise agrichemical spray deposits using dye tracers

Dye tracers allow researchers to optimise spray application equipment and spray formulations by quantifying the amount of agrichemical spray retained and/or quantifying the area covered (including the size and number of spray deposits). This paper discusses the issues involved in selecting a dye fit-for-purpose, and outlines the experimental checks required to ensure the dye will provide accurate, reliable results of spray retention and spray coverage. This is illustrated using a pilot study to identify a dye, or combination of dyes, capable of quantifying both spray retention and spray coverage on the model species Eucalyptus fastigata H. Deane & Maiden. Due diligence in selecting a dye to quantify agrichemical spray retention requires checks to ensure the dye is quantifiable, extractable from the target surface, and stable not only in the spray formulation used, but also under the prevailing environmental conditions (sunshine, temperature and humidity), and after storage on the target surface prior to extraction and analysis. To visually quantify spray coverage and/or the number and size of deposits, tests are required to ensure the dye provides clear contrast between the dye deposits and non-covered surface. Tests are also required to ensure the dye selected does not alter the physical properties of the spray. There are numerous reasons why a dye may fail to provide accurate spray deposit or coverage results, or correct results. In this study, one dye was not representative of the formulation spread (and therefore coverage). Two others could be used to visualise spray deposits but, due to UV degradation, retention was not quantifiable. A fourth dye was too difficult to visualise on the target. A fifth dye (pyranine) was a suitable candidate; it was photo-stable in dried deposits, quantifiable and could be visualised with an intense UV light source. The plant target itself presented unexpected complications; the sampling method previously employed in retention trials enabled pyranine dye to penetrate the leaves, due to moisture from the dehydrating leaf solubilising and mobilising spray dye deposits during storage. A revised sampling method, allowing the leaves to dehydrate without condensation, was required to fully recover the dye. Using the identified methodology pyranine proved to be suitable as a dual-purpose dye capable of quantifying both spray retention and spray coverage under the anticipated experimental conditions. This paper highlights the requirement for due diligence in dye selection prior to investing in a full-scale field trial. Researchers must check every stage in the experimental process of selecting dyes as deposit tracers. If not, they may fail to get results or, more likely, unwittingly publish incorrect results.

Review of fully coherent free-electron lasers

Generation of intense, fully coherent radiation with wide spectral coverage has been a long-standing challenge for laser technologies. Several techniques have been developed in recent years to extend the spectral coverage in optical physics, but none of them hold the potential to produce X-ray laser pulses with very high-peak power. Urgent demands for intense X-ray light sources have prompted the development of free-electron lasers (FELs), which have been proved to be very useful tools in many scientific areas. In this paper, we give an overview of the basic principle of FELs, techniques for realizing fully coherent FELs, and the development of fully coherent FEL facilities in China.

Extension of water-window harmonic cutoff by laser defocusing-assisted phase matching.

We extend a recently demonstrated scheme [Optica4, 976 (2017)OPTIC82334-253610.1364/OPTICA.4.000976] to overcome the limit of conventional harmonic cutoff for different pulse durations, laser wavelengths, and gas targets. By tuning the truncation of long wavelength lasers, we show that the defocusing-assisted phase matching (DAPM) can be achieved in a tightly focused beam and highly ionized short gas cell, and can be used to effectively extend the harmonic cutoff energy and optimize its yield. An analysis of phase matching reveals that at longer wavelengths, greater cutoff extension to the water window region is achieved because of the larger harmonic intrinsic phase (proportional to the cube of laser wavelength), and because DAPM works at relatively higher laser intensities using a Ne target. This scheme provides a promising method for efficiently generating intense attosecond light sources in the extreme ultraviolet to x-rays.

Trigger performance verification of the FlashCam prototype camera

FlashCam is a camera proposed for the medium-sized telescopes of the Cherenkov Telescope Array (CTA). We compare camera trigger rates obtained from measurements with the camera prototype in the laboratory and Monte-Carlo simulations, when scanning the parameter space of the fully-digital trigger logic and the intensity of a continuous light source mimicking the night sky background (NSB) during on-site operation. The comparisons of the measured data results to the Monte-Carlo simulations are used to verify the FlashCam trigger logic and the expected trigger performance.

Self-marked HCN gas based FBG demodulation in thermal cycling process for aerospace environment.

The thermal cycling process experienced by spacecraft during orbital operation would lead to deterioration of the demodulation performance of fiber Bragg grating (FBG). A new demodulation method based on Fabry-Perot (F-P) filter and hydrogen cyanide (HCN) gas is proposed to improve the performance. The method skillfully utilizes the self-marked HCN absorption lines as absolute wavelength references. In the thermal cycling environment whose temperature ranging from 5°Cto 65°C,the fluctuation of demodulation wavelength reduces to ± 2.6 pm, which is improved by 3.1 times compared with traditional method. The proposed method also shows a good robustness in the cases of weak light source intensity and poor signal-to-noise ratio (SNR) of HCN spectrum.

A novel nano-superparamagnetic agent for photodynamic and photothermal therapies: An in-vitro study.

In this study, iron oxide nanoparticles (SPIONs) were synthesized and coated by GA (SG) and then SG was encapsulated by ICG (SGI). After identifying specifications and cytotoxicity of the agents, the potential of SGI for photodynamic therapy (PDT) and photothermal therapy (PTT) was studied. An SGI size of 12-13 nm was determined by TEM images and its zeta potential was measured at -23.8 ± 5.8 mV. MCF-7 and HT-29 cells were exposed to a non-coherent light source at a wavelength of 730 nm and a range of 3.9-124.8 J/cm2 under two different concentrations of agents. The viability of treated cells was determined via MTT assay. To analyze the effects of different irradiation conditions, some indices such as Coefficient of Light Effect, Synergism Index, Addition Ratio, Treatment Efficacy and ED50 were defined. Cell survival at the highest power of irradiation in the absence of any agent was decreased to 93% and 73% for HT-29 and MCF-7, respectively. In both cell lines, the cellular survival dropped by increasing the light source intensity. The maximum cell death recorded for SG, ICG and SGI was 63 ± 2%, 63 ± 2% and 21 ± 2% for MCF-7 cells and 67 ± 2%, 78 ± 1% and 53 ± 1% for HT-29 cells, respectively. SGI had a significant photodynamic and photothermal effect on cells. This is a promising outcome, which can help enhance the effectiveness of a minimally invasive treatment. Moreover, SPIONs can be used to apply magnetic hyperthermia or act as a contrast agent in MRI images.

Artificial light in baited pots substantially increases the catch of cod (Gadus morhua) by attracting active bait, krill (Thysanoessa inermis)

Abstract The use of pots in the north Atlantic finfish fisheries is negligible because this fishing method typically has a low capture efficiency. Large numbers of individuals encounter baited pots, but the proportions of fish that enter the pot and become caught are low. Krill, which constitutes an important prey for cod (Gadus morhua), is attracted by light. The catching efficiency of baited cod pots with three light sources with different colours and intensities (white: 9744 mW m−2, white: 23 mW m−2, green: 8 mW m−2) were tested in coastal waters in northern Norway. Pots with the light source of highest intensity gave a 17 times higher catch rate of cod than that of control pots (with bait only). The light source of medium intensity gave about a five times higher catch rate, whereas the weakest light did not influence the catch. Cod caught in pots with light had more krill and arrowworms in their stomach and were observed feeding on these preys inside the pot. We concluded that light sources of increasing intensity attract more krill, and that cod were attracted into the pot by the dense swarms of prey and not the light per se.

All-optical control of surface plasmons by second-harmonic generation

Light with light control of surface plasmon polaritons is theoretically demonstrated. A barely simple and compact source of these waves consists in a finite number of slits (evenly spaced) perforating a metal film. The system scatters electromagnetic fields in one side of the metal film when it is illuminated from the opposite side by a polarized light source. High intensity light sources moreover efficiently generate light at second harmonic and higher frequencies in the metal led by optical nonlinearities. It is shown how the mixing of fields scattered by the slits from a weak beam at $\lambda$ wavelength, with the second harmonic fields generated by a high intensity $2 \lambda$ beam, creates a destructive interference of surface plasmons in one of the two possible directions of emission from the slits, while these are enhanced along the opposite direction. The unidirectional launching of surface plasmons is due to the different properties of symmetry at $\lambda$ whether they are linearly or nonlinearly generated. It is envisaged a nanodevice which might allow sending digital information codified in the surface plasmon field or be used to build ultra-narrow bandwidth surface plasmon frequency combs.

Estimation of Position and Intensity of Multi-Light Sources Based on Specular Sphere

Illumination estimation is an important research content in mixed reality technology. This paper presents a novel method for locating multiple point light sources and estimating their intensities from the images of a pair of reference spheres. In our approach, no prior knowledge of the location of the sphere is necessary, and the center of the sphere can be uniquely identified with the known radius. The sphere surface is assumed to have both Lambertian and specular properties instead of being a pure Lambertian or specular surface, which guarantees a higher accuracy than the existing approaches. The position estimations of multiple light sources are based on the fact that the specular reflection is highly dependent on highlights. One sphere is utilized to determine the directions of the light sources, and two spheres are used to locate the positions. The images of reference spheres are sampled and partitioned with multiple light sources in different positions. An illumination model is used to calculate the intensities of the ambient light and multiple light sources. Experiments on both simulation and synthetic images show that this method is feasible and accurate for estimating the positions and intensities of the multiple light sources.

Noise reduction in computational ghost imaging by interpolated monitoring.

An interpolation computational ghost imaging (ICGI) method is proposed and demonstrated that is able to reduce the noise interference from a fluctuating source and background. The noise is estimated through periodic illuminations by a specific assay pattern during sampling, which is then used to correct the bucket detector signal. To validate this method simulations and experiments were conducted. Light source intensity and background lighting were randomly varied to modulate the noise. The results show that good quality images can be obtained, while with conventional computational ghost imaging (CGI) the reconstructed object is barely recognizable. The ICGI method offers a general approach applicable to all CGI techniques, which can attenuate the interference from source fluctuations, background light noise, dynamic scattering, and so on.

Intraoperative thermal safety of endoscopic ear surgery utilizing a holder

PurposeDespite the ever-growing popularity of endoscopic ear surgery (EES), there are still concerns regarding the potential thermal risk associated with the use of light sources and also questions raised about the thermal safety of extended stationary applications of endoscopes with holders that allow the use of both hands in the middle ear. The temperature changes witnessed during EES when using different calipers on static endoscopes fitted with camera holders during true operations were measured, and effects of varying light source intensities, as well as the cooling effect of irrigation and suction, were investigated. MethodsThis study included 12 patients with chronic otitis who were scheduled to undergo myringoplasty surgery. Two of five different endoscopes with xenon light sources (4 mm–0°, 3 mm–0°, 2.7 mm–0°, 3 mm–45° and, 2.7 mm–30°) were used on each patient. Following irrigation and aspiration, gradually increasing heat measurements were recorded at two-minute intervals using a thermocouple thermometer for the entire period the endoscope remained in the ear. Three measurements obtained within the final 6 min, all of which were the same and reached a plateau, were considered to be the peak heat value. Measurements were repeated twice in each patient at 100% and 50% light intensities. ResultsThe highest heat was recorded by the 4 mm–0° endoscope, with heats at 100% and 50% light intensity recorded as 48.4 °C and 43.2 °C, respectively. The highest heat was measured by the 2.7 mm–0° endoscope, and heats recorded at 100% and 50% light intensities were 37.8 °C and 35.3 °C, respectively. ConclusionStationary use of endoscopes with 3 mm and smaller calipers without irrigation or aspiration, the heat in the middle ear would appear to be safe, and at a level that does not cause thermal trauma to tissue. The present study demonstrates that frequent aspiration or intermittent irrigation may prevent potential thermal damage, even in procedures performed using endoscopes of a 4 mm caliper. Light intensity settings of 50% can be adopted as a further safety measure against potential thermal risk without compromising visual acuity.

An Inexpensive, Pulsed, and Multiple Wavelength Bench-Top Light Source for Biological Spectroscopy

Since signal/noise ratios are proportional to the square root of the intensity, high intensity light sources are advantageous for many forms of UV–Vis and IR spectroscopy particularly with very low or high absorbance samples. We report the construction of a low-cost (≈ £6500 GBP, ca. 2016) bench-top spectrometer suitable for biological spectroscopy, which utilizes a hot plasma, generated with a pulsed Nd:YAG laser (λ = 1064 nm). The properties (reliability, intensity, and spectral profiles) of light generated with the plasma in different gaseous media (helium, neon, argon, and krypton) were investigated. Argon provided high intensity broadband light and was the most cost effective. The instrument was compared for spectral accuracy to a commercially available spectrometer (Thermo Scientific, GENESYS 10S) by measurement of the absorbance spectrum of the UV–Vis calibration standard holmium (III) oxide (4%, w/v) in perchloric acid (10%, w/v) and accurately replicated the results of the commercial spectrometer. This economical instrument can record consecutive absorbance spectra (between λ = 380 and 720 nm) for each laser pulse (6 Hz; ~160 ms/pulse), evinced by investigations into lysozyme aggregation in the presence of heparin. This instrument is suitable for use with lasers of a higher pulse power and repetition rates that would induce higher temperature plasmas. Higher temperature plasma sources offer increased signal to noise ratios due to the higher intensity emission generated.

Gesture Recognition Using Ambient Light

There is a growing interest in the scientific community to develop techniques for humans to communicate with the computing that is embedding into our environments. Researchers are already exploring ubiquitous modalities, such as radio frequency signals, to develop gesture recognition systems. In this paper, we explore another such modality, namely ambient light, and develop LiGest, an ambient light based gesture recognition system. The key property of LiGest is that it is agnostic to lighting conditions, position and orientation of user, and who performs the gestures. The general idea behind LiGest is that when a user performs different gestures, the shadows of the user move in unique patterns. LiGest first learns these patterns using training samples and then recognizes unknown samples by matching them with the learnt patterns. To capture these patterns, LiGest uses a grid of light sensors deployed on floor. While the general idea behind LiGest seems straightforward, it is actually very challenging to put it into practice because the intensity, size, and number of shadows of a user are not fixed and depend highly on the position and orientation of a user as well as on the intensity, position, and number of light sources. We developed a prototype of LiGest using commercially available light sensors and extensively evaluated it with the help of 20 volunteers. Our results show that LiGest achieves an average accuracy of 96.36% across all volunteers.

Modeling the interaction of a heavily beam loaded SRF cavity with its low-level RF feedback loops

A superconducting radio frequency (SRF) cavity provides superior stability to power high intensity light sources and can suppress coupled-bunch instabilities due to its smaller impedance for higher order modes. Because of these features, SRF cavities are commonly used for modern light sources, such as the TLS, CLS, DLS, SSRF, PLS-II, TPS, and NSLS-II, with an aggressive approach to operate the light sources at high beam currents. However, operating a SRF cavity at high beam currents may result with unacceptable stability problems of the low level RF (LLRF) system, due to drifts of the cavity resonant frequency caused by unexpected perturbations from the environment. As the feedback loop gets out of control, the cavity voltage may start to oscillate with a current-dependent characteristic frequency. Such situations can cause beam abort due to the activation of the interlock protection system, i.e. false alarm of quench detection. This malfunction of the light source reduces the reliability of SRF operation. Understanding this unstable mechanism to prevent its appearance becomes a primary task in the pursuit of highly reliable SRF operation. In this paper, a Pedersen model, including the response of the LLRF system, was used to simulate the beam-cavity interaction of a SRF cavity under heavy beam loading. Causes for the onset of instability at high beam current will be discussed as well as remedies to assure the design of a stable LLRF system.

Two-Dimensional, Hierarchical Ag-Doped TiO2 Nanocatalysts: Effect of the Metal Oxidation State on the Photocatalytic Properties

This paper reports the synthesis of two-dimensional, hierarchical, porous, and (001)-faceted metal (Ag, Zn, and Al)-doped TiO2 nanostructures (TNSs) and the study of their photocatalytic activity. Two-dimensional metal-doped TNSs were synthesized using the hydrolysis of ammonium hexafluorotitanate in the presence of hexamethylenetetramine and metal precursors. Typical morphology of metal-doped TNSs is a hierarchical nanosheet that is composed of randomly stacked nanocubes (dimensions of up to 5 μm and 200 nm in edge length and thickness, respectively) and has dominant (001) facets exposed. Raman analysis and X-ray photoelectron spectroscopy results indicated that the Ag doping, compared to Zn and Al, much improves the crystallinity degree and at the same time dramatically lowers the valence state binding energy of the TNS and provides an additional dopant oxidation state into the system for an enhanced electron-transfer process and surface reaction. These are assumed to enhance the photocatalytic of the TNS. In a model of photocatalytic reaction, that is, rhodamine B degradation, the AgTNS demonstrates a high photocatalytic activity by converting approximately 91% of rhodamine B within only 120 min, equivalent to a rate constant of 0.018 m–1 and ToN and ToF of 94 and 1.57 min–1, respectively, or 91.1 mmol mg–1 W–1 degradation when normalized to used light source intensity, which is approximately 2 times higher than the pristine TNS and several order higher when compared to Zn- and Al-doped TNSs. Improvement of the crystallinity degree, decrease in the defect density and the photogenerated electron and hole recombination, and increase of the oxygen vacancy in the AgTNS are found to be the key factors for the enhancement of the photocatalytic properties. This work provides a straightforward strategy for the preparation of high-energy (001) faceted, two-dimensional, hierarchical, and porous Ag-doped TNSs for potential use in photocatalysis and photoelectrochemical application.

C at the belfry

In 1849, Hippolyte Fizeau determined the speed of light in a famous experiment. The idea was to measure the time taken for a pulse of light to travel between an intense light source and a mirror about 8 km away. A rotating cogwheel with 720 notches, that could be rotated at a variable speed, was used to chop the light beam and determine the flight time. In 2017, physicists and technicians of the University of Mons in Belgium reproduced the experiment with modern devices to allow members of the public to measure the speed of light themselves. The light source used was a low power laser, and the cogwheel was replaced by an electrically driven chopper, but the general spirit of Fizeau’s experiment was preserved. The exhibition was organised in the belfry of Mons, a baroque-style building classified as a UNESCO World Heritage site. The solutions found for the main problems encountered are presented here to help colleagues intending to reproduce the experiment.

The earthworm Dendrobaena veneta (Annelida): A new experimental-organism for photobiomodulation and wound healing.

Photobiomodulation (PBM) is a manipulation of cellular behavior using non-ablative low intensity light sources. This manipulation triggers a cascade of metabolic effects and physiological changes resulting in improved tissue repair, of benefit in the treatment of tissue injury, degenerative or autoimmune diseases. PBM has witnessed an exponential increase in both clinical instrument technology and applications. It is therefore of benefit to find reliable experimental models to test the burgeoning laser technology for medical applications. In our work, we proposed the earthworm Dendrobaena veneta for the study of nonablative laser-light effects on wound healing. In our preliminary work, D. veneta has been shown to be positively affected by PBM. New tests using D. veneta were set up to evaluate the effectiveness of a chosen 808 nm-64 J/cm2–1W-CW laser therapy using the AB2799 hand-piece with flat-top bean profile, on the wound healing process of the earthworm. Effective outcome was assimilated through examining the macroscopic, histological, and molecular changes on the irradiated posterior-segment of excised-earthworms with respect to controls. Three successive treatments, one every 24 hours, were concluded as sufficient to promote the wound healing, by effects on muscular and blood vessel contraction, decrement of bacteria load, reduction of inflammatory processes and tissue degeneration. D. veneta was demonstrated to be a reliable experimental organism that meets well the 3Rs principles and the National Science Foundation statement. Through their genetic and evolutionary peculiarity, comparable to those of scientifically accredited models, D. veneta allows the effect of laser therapies by multidisciplinary methods, at various degree of complexity and costs to be investigated.

Study on the luminous characteristics of a natural ball lightning

According to the optical images of the whole process of a natural ball lightning recorded by two slit-less spectrographs in the Qinghai plateau of China, the simulated observation experiment on the luminous intensity of the spherical light source was carried out. The luminous intensity and the optical power of the natural ball lightning in the wavelength range of 400–690 nm were estimated based on the experimental data and the Lambert-Beer Law. The results show that the maximum luminous intensity was about 1.24 × 105 cd in the initial stage of the natural ball lightning, and the maximum luminous intensity and the maximum optical power in most time of its life were about 5.9 × 104 cd and 4.2 × 103 W, respectively.