Intensity Of Light Flux Research Articles

Kinetics of narrow-spectrum LED glow under pulsed power

The results of experimental investigations of the glow kinetics of narrow-spectrum LEDs based on InGaN-GaN 450 and 520 nm and AlGaInP-GaAs 625 nm structures are presented. The increase and decrease of the light flux intensity under pulsed power are described by exponential dependences containing fast and slow components. The time constants of both components decrease with the increase of the pulse frequency for all three types of LED samples. The time constant of the slow component decreases with the increase of the current and voltage pulse amplitudes. The maximum light output on the frequency dependences of LED energy characteristics is observed at the frequency of 75…100 kHz. Further frequency increase results in the decrease of the LED energy efficiency. The obtained results are explained based on the LED equivalent electrical and energy circuits.

Dynamics of growth parameters of Gentiana lutea L. in vitro plants under different lighting conditions

Aim. Study of the dynamics Gentiana lutea L. plant growth processes in vitro depending on the light regime changes of their cultivation in order to develop a scheme to increase their adaptive potential. Methods. Methods of plant cultivation in vitro, biometric method, as well as ANOVA variance analysis and middle group analysis in pairs using the Tukey test (Tukey test) were used. Results. It is shown that the cultivation of G. lutea plants in vitro using 25 W/m2 light flux intensity in the region of photosynthetically active radiation and the ratio of blue (Eb): green (Eg): red (Er) ranges = 41.8%: 42.7 %: 15.5% triggers non-specific photomorphogenesis reactions for intact plants, which lead to poor root system development, stem elongation, formation of small leaves with a thin leaf blade, overall low productivity and low adaptation potential of G. lutea plants to ex vitro and in situ conditions. Increasing the light flux intensity to 44 W/m2 and increasing the red wave proportion up to 20.3% allows not only to improve the bioproductivity of G. lutea plants which are cultivated in vitro, but also to increase the coefficient of microclonal reproduction without the additional use of exogenous growth regulators. The greatest growth of the aboveground and underground parts, increase in effective leaf surface are observed in vitro plants during cultivation at 135 W/m2 light flux intensity and spectral composition Eb: Eg: Er = 29.5%: 32.5%: 38.0%. Conclusions. It is possible to improve plant bioproductivity by changing the light conditions of plant cultivation in vitro, and, accordingly, to increase the adaptive potential to ex vitro and in situ conditions.
 Keywords: Gentiana lutea L., in vitro plants, light flux intensity, spectral composition, growth parameters.

Электромеханическая модель индикаторного полимерного оптоволоконного PEL-покрытия для диагностирования механических воздействий

A mathematical model of the functioning of the indicator polymer piezoelectroluminescent (PEL) coating for diagnosing external mechanical effects - quasi-static pressing of rigid ball particles has been developed. The algorithm of numerical processing of informative intensity of light flux at the output from optical fiber built into indicator coating of optical fiber PEL-sensor is presented. A numerical analysis for the case of single mechanical effect revealed the regularities of influence of the values of the sensor spiral pitch on the informative parts of the resulting spectra of light flux intensity and pressure distribution along the length of the sensor spiral. Informative characteristic points of pressure spectra plots were revealed; these are points of maxima, abscissa and values of which make it possible to find the desired values of radius and pressing force of a rigid ball particle.

Динамическая модель управления режимом демпфирования вибраций оптоволоконным PEL-датчиком с фазовым сдвигом управляющего электрического напряжения.

A mathematical dynamic model of the operation of the vibration pressure optical fiber piezoelectroluminescent (PEL) sensor in the damping mode was developed taking into account the electrical conductivities and Maxwell-Wagnerian relaxation of electric fields in the phases for the case of harmonic stress (vibration pressure) on the external cylindrical surface of the sensor. Analytical solution of damping of stationary axisymmetric oscillations of optical fiber PEL-sensor is obtained and investigated by applying coherent control electric voltage to electrodes of sensor with phase shifting relative to vibration pressure. Regularities of frequency dependencies for real, imaginary parts of control, informative transfer and damping coefficients of sensor are established and studied. Analysis of influence of value and shift angle of phases of control electric voltage on results of numerical simulation for intensity of light flux at output from optical fiber of sensor under action of vibration pressure is performed. Frequency dependencies were found for the electrical impedance of the AC electric circuit of the sensor in comparison with the approximation of these dependencies by electromechanical analogy. It was revealed that in the frequency range under consideration, the electrical impedance of the sensor with satisfactory accuracy is based on consideration of an equivalent electric circuit with parallel connection of frequency-dependent active and capacitive elements. Frequency range and values of control parameters are set for effective active damping of vibration pressure through conversion to Joule heat (dissipation) of mechanical energy supplied to the sensor. The results of comparing the analytical and numerical (in the ANSYS package) approaches confirm the validity and adequacy of the decisions obtained.

Prospects for photostimulation of nisin biosynthesis

The purpose of the article was to study the effect of blue spectrum light on the nisin producer Lactobacillus lactis. It was found that photostimulation of a Lactobacillus Lactis culture with blue spectrum light (435-470 nm) with a light flux intensity of 1800 mcd for 50-60 minutes positively affects the activity of nisin (increases by 60.1%), while the titer of the Lactobacillus culture lactis is 2 times higher. At the same time, there is a slight decrease in nisin titer after 24 hours of incubation, which is explained by the peculiarities of nisin biosynthesis: nisin is less active at the beginning of biosynthesis; during the period of the exponential growth phase, an increase in the biosynthesis of nisin is noted; the greatest activity of nisin is noted at the beginning of the stationary phase; nisin synthesis is reduced in the middle of the stationary phase of the cells; self-regulation of nisin synthesis (increased nisin synthesis leads to increased competition for metabolites of the substrate and energy material, nisin molecules act as an external factor that regulates synthesis). Light treatment of the nisin producer Lactobacillus lactis increases its resistance to oxidative stress and enhances its viability. As a result of studies during storage of the Lactobacillus lactis culture in skimmed milk, the positive effect of light on the high preservation of nisin activity was proved. Thus, photostimulation of the bioproducer of nisin - Lactobacillus Lactis culture with blue light with a light flux intensity of 1800 mcd for 50-60 minutes has a positive effect on its viability and allows us to recommend the use of blue light to increase nisin production.

Development of the mathematical model of light flux intensity sensor based on the photodiode and operational amplifier

The article describes a method for interpolating the dependence of the photodiode relative spectral sensitivity on the optical radiation wavelength using a special function that provides interpolation of the experimental dependence with any asymmetry coefficient. A new version of the light flux intensity sensor mathematical model based on a photodiode and an operational amplifier using the proposed interpolation technique has been created. It was found that the interpolation error does not exceed 3–6 %, depending on the type of photodiode and the shape of its experimentally obtained spectral characteristic. The processes occurring in the equivalent circuit of the measuring channel based on the operational amplifier are analyzed. The created mathematical model can be applied to optimize the processes in the measuring channel of the light flux intensity. The research results presented in the article can be used in the design and mathematical modeling of light flux intensity sensors for the needs of various fields of science, industry and medicine.

Biotechnology for bacteriocin synthesis using photostimulation

This article presents results of a study of the effect of blue color on the bacteriocin activity. It was revealed that photostimulation of Lactobacillus Lactis with light in the blue spectrum (435-470 nm) with a light flux intensity of 1800 mcd for 50-60 minutes positively affects the bacteriocin activity (increases by 60.1%), while titer of the Lactobacillus lactis is 2 times higher. It was found that it was in the first 18 hours that the irradiated samples had a greater difference in terms of activity and titers than unirradiated samples. Oxidative stress affects the culture’s viability, both in samples treated with blue light and in the untreated cultures. However, impact intensity on the treated cultures is weaker. These outcomes indicate the possibility of using blue light for stimulating bacteriocin biosynthesis in order to use it as a food additive for prolongation of shelf life of food products.

Analysis of structural features of a LED searchlight

We come up with the design of an illumination device with point light sources, which are arranged on three different-level surfaces. Werely upon the visualization and light flux analysis to identify reflective surface shapes and the number of point light sources (LEDs). With a view of optimizing the illuminator's design, we look into its ability to withstand deformations (rigidity) at different vibration frequencies. For the design with highest rigidity, we study the impact of the reflective surface roughness on the illuminator's performance. We conduct the ray tracing for each optical surface with due account for its roughness, with the illuminator vibrating on an Eigenfrequency. Based on the ray tracing, we find the light flux intensity pattern from the illuminator. We argue that following the study stages proposed it is possible to:-choose an optimal illuminator's design for specific service conditions;-choose a fabrication procedure for the reflecting surfaces.The results obtained will be of use when designing navigation lights, floodlights for tall building cranes, and aircraft landing lights.

Study features of the change of the fluorescence signal of the sensor element based on porous glass on the concentration of labeled insulin

Nonmonotonic calibration dependence has been found during the fluorescent detection when performing the competitive immune analysis of insulin in a microfluidic device with the integrated sensor element based on silicate porous glass. A possible version of the interpretation of the observed effect has been discussed. The effect of the light flux intensity of the source radiation on the fluorescence of the sensor element has been studied experimentally.

Simulation of conversion profiles inside a thick dental material photopolymerized in the presence of nanofillers

In dental composites, the presence of inorganic fillers in the organic matrix leads to a light-scattering phenomenon that modifies the light intensity and, consequently, the ultimate polymerization yield. In this study, we aimed to characterize the impact of light scattering on the photopolymerization profiles inside thick materials. First, the photopolymerization kinetics of dental composites containing alumina or zirconia nanofillers were studied. An optimal formulation based on 75 wt% Bis-GMA, 25 wt% triethyleneglycoldimethacrylate and 1 wt% camphorquinone/dimethylaminoethylmethacrylate (1/1) was determined. The compatibility between the organic matrix and the fillers was enhanced by grafting a silane coupling agent onto the surfaces of the nanoparticles. This grafting improved the mechanical properties of the final composites without modifying the photopolymerization kinetics. The presence of nanofillers leads to a light-scattering phenomenon that influences the photoinitiated polymerization yield inside the composite. Thus, to characterize this phenomenon, a four-flux radiative transfer theory was applied to calculate the decrease in the light intensity crossing the dental composite. The conversion profiles were then calculated and compared with experimental ones. Photopolymerization of thin layers of a 75/25 (w/w) Bis-GMA/TEGDMA mixture exposed to a 465-nm monochromatic light radiation was first investigated. The final methacrylate conversion was measured by FTIR spectroscopy for different light intensities I0. Then, the variation of the light flux intensity φ inside thick samples of the previous mixture containing mineral nanofillers (Al2O3 or ZrO2) was calculated by means of a numerical model by taking into account the light scattering induced by the fillers. The obtained results permit the determination of the conversion profiles inside the loaded material and the maximal thickness that can be photopolymerized without consequent alteration of the polymerization yield and of the mechanical properties.

Multivariable feedback linearizing control of Chlamydomonas reinhardtii photoautotrophic growth process in a torus photobioreactor

The objective of this paper is to design and to validate a nonlinear multivariable controller, based on the exact feedback linearization technique, which has the capacity to stabilize the photoautotrophic microalgae growth in photobioreactor regardless of the operation point or the transient trajectory. Two measurable outputs were selected, namely the biomass concentration and the pH, whose simultaneous control can be realized by manipulating the dilution rate and the injected carbon dioxide gas flowrate. A mechanistic dynamical model describing the interactions between physicochemical and biological phenomena inside the photobioreactor was used as a starting point for the controller design. Given its complexity, the model was reduced by differentiating the states with slow dynamics from the ones with fast dynamics that were converted into algebraic expressions. In addition, a dynamic time-varying expression was derived for the concentration of hydrogen ions (negative antilogarithm of pH) thus obtaining an appropriate I/O model for control purposes. The degree of interaction between I/O channels was determined through a relative gain array analysis, in order to establish if the system allows the implementation of decentralized SISO controllers or requires a centralized MIMO controller. The feedback linearization method was associated with a model based technique to furnish the immeasurable variables required by the nonlinear control algorithm. The nonlinear controller was implemented on a laboratory torus photobioreactor piloted at constant incident light flux intensity throughout the photoautotrophic growth of a Chlamydomonas reinhardtii culture, its efficiency being proved under several operating points.

Mechanisms of nonlinear transmission in solutions and thin films of the COANP-C70 fullerene system

The process of nonlinear optical transmission in solutions and thin films of 2-cyclooctylamine-5-nitropyridine (COANP) sensitized by C70 fullerene additions has been studied. Possible mechanisms responsible for the attenuation of light flux intensity are considered. Comparative DSC data for a pure COANP and one sensitized by C70 fullerene are presented that confirm the existence of one of these mechanisms.

Photoconductivity of poly-p-xylylene + CdS nanocomposite films over a wide temperature range

For poly-p-xylylene + CdS (PPX + CdS) nanocomposite films, the dependences of the photo-conductivity σph(T) on the concentration C of CdS nanoparticles, intensity and wavelength of exciting light, and temperature T within 15–300 K are examined. An appreciable photocurrent appears at C ≥ 10 vol %, when a large percolation cluster of CdS nanoparticles is formed. The photocurrent spectrum is compared to the absorption spectrum of the film. The photocurrent Iph(P) increases with the intensity of light flux P in a wavelength range near 435 nm according to the Iph(P) ∼ Pn power law, where n 11.5 vol %, the σph(T) dependence at low T exhibits a metal-like character (σph(T) decreases with increasing temperature). Atomic force microscopy is used to examine the surface topography of PPX + CdS films, which is found to be strongly dependent on the concentration of nanoparticles. The dark conductivity and photoconductivity of nanocomposite films arise due to the thermo- and photoexcitation transfer of electrons from the CdS nanoparticles to the PPX matrix with the formation of an electronic double layer at the PPX matrix-large percolation CdS cluster interface, a process that populates the phenyl rings of the adjacent PPX layer with excess electrons. As a result, various mechanisms of electron transfer in the polymer matrix can be realized: Mott’s hopping conduction mechanism with variable-range hopping in the matrix between CdS clusters and the metal-like behavior of the conductivity in the polymer shell of the large cluster at low temperatures. The polymer shell contains excess electrons on the phenyl rings -C6H4- in the composition of anion-resonances -C6H4−-.

Orange-red light attenuates inhibition of proliferation of rat fibroblasts induced by ultraviolet-A

Excessive UV radiation suppresses processes important for normal functioning of tissues [1, 2]. Therefore, a topical problem is studying the factors which protect cells from the negative effects of UV radiation. One of such factors may be illumination with light of orange-red range of the spectrum [2‐4]. The primary skin-muscular fibroblasts were isolated from 15-day-old embryos of SHR rats with the SPF status (the nursery of Shemyakin‐Ovchinnikov Institute of Bioorganic Chemistry (Pushchino Branch), Russian Academy of Sciences, Pushchino). The suspension of fibroblasts was placed in tissue culture flasks impermeable to UV-A and orange‐red light (ORL). After one day of incubation, the medium with unadhered cells was removed and the adhered fibroblasts were cultured untill formation of a monolayer in DMEM (ICN) supplemented with glutamine, HEPES, and fetal calf serum. The cells were kept in an incubator at 37°C in a 5% CO 2 atmosphere. The fibroblasts of the 4th to 8th passages were used in the experiments. The adhered cells were detached with the use of a mixture of trypsin and Versen (Pan Eko), counted, and placed in flasks for illumination with ORL (0.9‐3.6 J/cm 2 ) or UV-A (0.27‐1.08 J/cm 2 ) or their combinations. A matrix with light-emitting Luxeon Star diodes (Lumileds) with λ m = 625 nm and a light flux intensity of 5.5 mW/cm 2 was used as source of ORL. An MD-108 irradiator (Germany) with λ M = 365 nm and a light flux intensity of 2.5 mW/cm 2 was used as a UV-A source. The suspension of fibroblasts was distributed with the use of pipette in 96-well plates for analysis of the proliferation rate. Each well with culture medium contained 10 4 cells. The fibroblasts were stained with thiazolyl blue 48 and 72 h after illumination. The cells were additionally incubated for 1 h and, then, the medium in the wells was replaced with dimethylsulfoxide. The optical density of the cells was determined with the use of a Spectra Count spectrophotometer (Packard, Germany). Analysis of the fibroblast proliferation 48 h after illumination showed that ORL had a stimulatory effect at a dose of 0.9 J/cm 2 (Fig. 1), which is in agreement

Spatial distribution of the radiation in the far zone of InAsSb/InAsSbP mesastrip lasers as a function of current

The far-zone directional pattern of diode mesastrip lasers with a 10 µm wide strip has been investigated as a function of the current. The directional pattern in the plane of the p-n junction contains one longitudinal mode, whose width depends on the current. It is shown by comparing the theoretically computed and experimentally measured spatial modes that this dependence is determined by the variation of the light flux intensity and the free-carrier density distributions over the strip width as a function of the current. In the case when the distributions are close to uniform the maximum narrow spatial longitudinal mode and a unimodal radiation spectrum are observed.

On the information content of the light backscattering and transmittance curves in aerosols

Propagation of laser light in droplet aerosol media was studied numerically and experimentally. In optically tenous aerosols the backscattering signal intensity is much weaker than the transmittance, but exhibits a specific substructure and is very sensitive to optical properties of aerosols and their size. Measurements show an excellent agreement of the experimental and theoretical curves for single scattering conditions. In optically dense aerrosol media with optical depths of the order of unity and above, the backscattered light-flux intensity becomes comparable with the transmitted light-flux intensity. Experimental data indicate that this intensity enhancement is dominated by multiple sccattering and can provide important information regarding the backscatter-to-extinction signal ratio in various aerosol media.

Analysis of transient phenomena in GaAs within the metastable model

AbstractTransients of the diode capacitance Cd, optical absorption coefficient α, and EPR signal in GaAs are studied within the framework of the metastable model. The spectral behavior of transients is studied theoretically in the 0.9 to 1.3 eV range. It is shown that the occupancy factor F (electron occupancy of EL2 defect) plays an important role in the observation of the characteristic ‘fingerprint’ signals. It significantly influences both the amplitude and the shape of the transient as well as its spectral behavior. A novel way for the determination of the value of F from the experimental results is proposed. It is discussed why the variation of F among the samples leads to the sample dependence of the results which is frequently experimentally observed. The appearance of ‘non‐quenchable’ and ‘EL2‐like’ defects is also discussed. The experimentally observed results can be modeled even with the assumption of a constant value of σ* (capture cross section for the metastable transition). The light flux intensity and the time of illumination should be specified for a meaningful comparison of various experimental results.

A high-precision optical level gauge

Optical devices are widely used for this purpose because of their simple design, which particularly involve double coordinate (level) transformation, first to angle and then from the angle to a coded signal [I, 2]. A disadvantage of such a device is the change in the light-flux intensity incident on the detector when the liquid level changes, which alters the parameters of the signal passing from the detector to the recorder and reduces the accuracy. This deficiency has been eliminated in a gauge described in [3], which has been upgraded by introducing an additional detector scanner, which rotates with angular velocity m2, which differs from the angular velocity of the source scanner ml.