Possibilities of determining of the skin structural and biophysical parameters by the spectra of scattered light are estimated. The measurement schemes for the diffuse reflectance, brightness coefficients of co- and crosspolarized radiation, backscattered by biological tissue, and spatial illumination at some distance from the source are considered. Retrieval algorithms of volumetric concentrations of melanin and blood vessels, the thickness of the epidermis, the degree of blood oxygenation and the average diameter of the capillaries are proposed. It is shown that the first two schemes give approximately the same characteristics of the solution of the inverse problem, although polarization measurements are somewhat more resistant to experimental errors. An analysis of this similarity has demonstrated that it is due to the features of the spectral optical properties of the skin layers. The third experimental scheme, which is resistant to errors, has a significantly higher sensitivity to the degree of blood oxygenation and the average diameter of the capillaries and allows you to retrieve all the desired skin parameters with acceptable for practice accuracy, turned out to be the most preferred.

Evolution of photoluminescence spectra of graphitic-like carbon nitride synthesized by pyrolysis of melamine in closed oxygen containing air environment was studied in the temperature range of 10-300 K. It was shown that the oxygen concentration in the resulting material is 4-5 at. % and increases with the temperature and decreases with increasing of the synthesis process duration. Measurements at low temperatures up to 10 K made it possible to resolve several bands on the photoluminescence spectra of graphite-like carbon nitride associated with radiative recombination processes. It was found that an increase in the synthesis temperature from 500 to 600 °С as well as an increase in its duration from 30 to 240 min at a given temperature lead to a shift of photoluminescence spectrum maximum from 2.74 eV to the lower energy region of 2.71-2.67 eV. That shift is associated with the increasing role in light emission of the molecular system formed by π-bonds of carbon and nitrogen atoms with sp²-hybridization characterized by a smaller band gap. Transitions associated with recombination through oxygen-induced levels in the band gap of the semiconductor contribute to the appearance of a “tail” on the photoluminescence spectra in the low-energy region (2.4-2.33 eV). An increase in the temperature of carbon nitride synthesis to 600 °C leads to a change in the structure of energy zones and an increase in the energy of radiative transitions due to an increase in the oxygen doping level and thermal stratification.

An influence of electric field on the transmission of linearly polarized light by the composite films based on polyvinylbutyral doped with the particles of heterometallic complex (NH₄)₂{[Cu(dien)(H₂O)]₂[α-V₂Mo₆O₂₆]}∙5H₂O (dien - diethylenetriamine) was studied. Anisotropy of light absorption caused by the electrostatic field was found when of the composites were irradiated with linearly polarized light. The observed electro-optical effect was explained by the appearance of photo-induced optical anisotropy under the influence of linearly polarized light. The anisotropy was changing in space due to the reorientation of the dipole moment of the photogenerated electron-hole pairs in the composite under the action of the external electric field.

All-optical method for magnetic resonance detection (ODMR) with temperature sweep is developed. The method uses the temperature dependence of the spin Hamiltonian parameters of paramagnetic color centers in silicon carbide. The detection process is based on the natural mechanism of optical alignment of spin sublevel populations in a wide temperature range, including room temperature, and on the change of these populations during level anti-crossing or cross-relaxation processes.

This paper reports for the first time the synthesis of nano-urchin Mo-doped VO₂ particles and its degradation properties in the presence of methylene blue (MB). Nano-urchin Mo-doped VO₂ particles were synthesized by the hydrothermal method, and their microstructure was controlled by the concentration of Mo. The Mo-doped VO₂ particles showed fast degradation of methylene blue in a relatively short time of 5-10 min. These results show the potential application of Mo-doped VO₂ particles for decolorization of dyers in environmental water treatment.

The effect of the vacuum annealing temperature on the structure and functional composition of the surface of ultradispersed diamond (UDD) produced by detonation synthesis was studied using Raman scattering, IR absorption, X-ray diffraction analysis and electron paramagnetic resonance. It was established that vacuum annealing at T ≤750°C does not affect the structure of diamond nanoparticles; at higher annealing temperatures, the formation of amorphous sp²-hybridized carbon begins on the surface of the particles. Annealing at a temperature of 1050°С leads to complete graphitization of the UDD surface with preservation of the diamond structure of the nucleus of the particles. During annealing in the temperature range of 650-750°C, the minimum of functional groups is observed on the UDD surface, while the surface retains high activity.

Optical properties of CdS thin films obtained by the method of high-frequency magnetron sputtering were studied. The optical constants and the band gap of the films under study were determined (E_g = 2.39 eV). The spectral dependences of the refractive index, absorption, and extinction coefficient were obtained from the transmission spectra at room temperature. The optical parameters of the films were determined using a single-oscillator model, as well as the Cauchy and Sellmeyer equations.

Laser ignition (1064 nm, 120 μs) of mixed compositions of brown coal particles of ≤ 0.1 mm in size with the addition of pentaerythritol tetranitrate (PETN) was investigated. It was found that with an increase of the PETN additives in the range of 0-50 wt.%, the critical density of the ignition energy of mixtures monotonously decreases from 2.9 to 2.0 J/cm². Using spectral pyrometry, it was determined that temperature of the flame of the mixed composition increases from 1800 to 2100 K.

The interaction between emodin, frangulin-A (obtained from Ventilago leiocarpa Benth) with bovine serum albumin (BSA) and calf thymus DNA (ct-DNA) has been investigated. The fluorescence spectrum and molecular docking methods are used to investigate the interaction between emodin, frangulin-A, and BSA. The UV spectrum revealed interaction between emodin, frangulin-A, and ct-DNA. The fluorescence spectrum confirmed that the compounds of emodin-BSA and frangulin-A-BSA were formed showing fluorescence quenching and a decrease of the maximum emission wavelength. The simulated molecular docking showed stable combinations of emodin-BSA and frangulin-A-BSA. Thus, molecular interactions mainly occur due to hydrophobic forces and hydrogen bonds. According to the UV spectrum, emodin and frangulin-A interacted with ct-DNA via electrostatic interaction.

In this study, we used eight millet varieties and took visible-near infrared hyperspectral images of 480 millet samples. Spectral and image characteristics, including texture and color features, of the millet samples, were extracted from the hyperspectral images. Support vector machine (SVM) models for millet variety identification were established using the extracted spectral and image characteristics. An attention-Convolutional recurrent neural network (attention-CRNN) model with attention mechanism was introduced for the identification of millet varieties, and the SVM and attention-CRNN models for millet variety identification were established using an image and spectral features fusion method. We found that the highest mathematical transformation method was the reciprocal logarithmic method. The identification accuracy of the SVM cultivar classification model with the reciprocal logarithmic spectral characteristics curve was 73.13%. The overall identification accuracy of the SVM model for the eight millet varieties using the image features was only 61.25%. The identification accuracy of the SVM model using the image and spectral information fusion method greatly improved the overall accuracy rate to 77.5%, and the minimum discrimination accuracy of the millet varieties increased from 50 to 65%. The overall identification accuracy of the attention-CRNN model was 87.50%, which is 10% higher than that of the SVM model, and the minimum discrimination accuracy of the millet varieties increased from 65 to 90%. The results show that the attention-CRNN model improved the overall identification accuracy of the eight millet varieties and greatly improved the minimum identification accuracy. The attention-CRNN model shows great potential for the nondestructive identification of millet and possibly other small grain varieties.

This paper presents wetland aquatic vegetation remote sensing data using laboratory experiments on irises (Iris tectorum Maxim) and a simulation of the wetland aquatic vegetation growth environment. The spectral reflectance of the iris canopy under the background of different substrates was monitored. Experimental results show that under different backgrounds of wetland aquatic vegetation, the canopy spectral characteristics are different and present a certain regularity.

This article presents the results of the assessment of carbon dioxide fluxes through the Naroch lake surface during the vegetative season (May-September) of 2017, obtained by the method of closed chambers and IR spectroscopy. The results show that the average daily runoff values are 0.409 mg C/m² in the pelagic zone and 0.647 mg C/m² in the littoral zone. The carbon dioxide fluxes balance indicates the runoff over emission prevalence. The total seasonal carbon runoff into the lake from the atmosphere is 128.6 t C, including 26.3 t C and 102.3 t C received through the surfaces of the littoral and pelagic zones, respectively.

This article describes a modification of the spectrophotometric method for the determination of chlorophyll a in seston (suspended matter), which is convenient for hydroecological monitoring. It is proposed to use nuclear filters, as they have a number of advantages over fiberglass and bulk filters. An important difference of our approach from the standard methods is the use of the short-term (up to 30 min) drying of nuclear filters with seston in a desiccator at a temperature of 50-55°C immediately after the suspended matter is deposited on the filter. A comparative analysis of the assessment of the chlorophyll and phaeopigments content by the standard method and the proposed modification is carried out using the laboratory cultures of algae (Euglena gracilis, Chlorella vulgaris) and plankton from a natural water body.

This paper presents some results of the measurements and processing of spectra and images by the spectrometric scientific equipment from the ISS in the frame of the Uragan space experiment. As a result of many years of measurements, we describe the database of the surface reflectance of natural objects. Examples of using the database for searching various underlying surfaces on multispectral and hyperspectral satellite images are given.

We studied the prevalence of heavy metals and metalloids (HM) in forest park zones of Tver on the basis of ecological monitoring using ICP-AES-analysis. We detected the presence of 14 heavy metals in the samples of two lichen species (Hypogymnia physodes, Xanthoria parietina) and 13 HM in the soil specimens. The spectra of heavy metals in both species in all the investigated model territories are similar. However, the differences in the level of content of the abovementioned metals in lichens and the components of the environment are revealed. They are due to the specific processes of ecotoxicant absorption by living objects. The cumulative features of HM and the indicator abilities of the studied lichens depend on the anthropogenic transformation of territory and the ecotype features and specificity of the chemical composition of lichens species. For the anthropogenically transformed territories Hypogymnia physodes has the largest indicator value, and for undisturbed phytocenosis this indicator has a maximum for Xanthoria parietina. Each of these species allows us to diagnose zinc, manganese, copper, cadmium, vanadium, and lead. Xanthoria parietina actively absorbs tin and chrome, whereas Hypogymnia physodes absorbs nickel and cobalt. It should be considered during monitoring.

We developed a technique and selected the optimal parameters for solving the inverse problem of determining the total content of R-11 freon (CCl₃F) from ground-based spectrometric measurements of solar radiation at the NDACC St. Petersburg station using a IFS125HR Fourier interferometer and SFIT4 software. The main features of the technique: the used spectral interval is 830-860 cm^-1, the previously measured spectral sensitivity function of the device is taken into account, and the continuum absorption of radiation by water vapor and attenuation of radiation by amorphous ice deposited on the receiver are also taken into account. Moreover, when solving the inverse problem to compensate the variability of the thickness of the ice film, the shape of the baseline of the spectrum is corrected by a polynomial of the second degree and the vertical distribution of water vapor is specified. Using the technique, the total content of R-11 was determined in the period 2009-2019, and an estimation of measurement errors was obtained: the average systematic error was 7.4% and the random error was 2.9% for the entire observation period. The assessment of the long-term total content trend is -0.29 ± 0.07%/year, and the mean molar fraction trend is -0.31 ± 0.07%/year.

The dynamic Raman spectra of a brand of red wine (aa) as the main research object were collected over a range of laser integration times (1–5 s) to observe the changing trends of molecules in the wine under experimental conditions. The three-dimensional Raman characteristic spectrum of this wine was then constructed further by two-dimensional correlation fusion analysis. The fluctuations of the three-dimensional Raman spectra were also evaluated using a similarity algorithm. The correlation coefficients were 0.977 ± 0.011 and 0.990 ± 0.006 based on synchronous and asynchronous two-dimensional correlation Raman spectroscopy, respectively. These results suggested that the samples of wine aa were highly self-similar and could be effectively distinguished from two different brands of red wine (bb and cc) based on their different spectral responses. Therefore, this method has the potential to supplement existing methods for the classification analysis of red wine.

A method is proposed for determining the optical characteristics of glass plates after physicochemical surface treatment, based on measuring the spectra of ellipsometric angles at incidence angles equal to the Brewster angle. It is found that from the coordinates of the minima on the spectra of ellipsometric angles, one can determine the dispersion dependence of the refractive index and estimate the thickness of the surface layers during the process of the plate manufacturing. The refractive index spectra calculated by the Brewster formula for KU-1 optical quartz plates in the region with no absorption are in satisfactory agreement with the spectra determined by known numerical methods using the DeltaPsi2 software of the UVISEL 2 spectral ellipsometer (Нoriba). The relative error in determining the refractive indices of the quartz plates by the proposed method does not exceed 0.1%.

We have modeled various configurations of fiber optic probes and analyzed the fluorescence spectra from a model of human skin tissue. The stochastic Monte Carlo method implemented in the TracePro software package is used to simulate the propagation of light in the tissue and optical fiber. Endogenous fluorophores-riboflavin and protoporphyrin IX serve as fluorescence sources of the skin model. They have a minimal intersection of the emission spectra and provide fluorescence of human skin when excited by laser radiation with a wavelength of 405 nm. The assumption about the possibility of selecting the fluorescence signal by the tissue depth using specific parameters of optical fiber probes is tested. For the first time, model spectra were obtained using six configurations of fiber optic probes for the selective recording of skin autofluorescence.

The coexistence of various spatial distributions of the laser intensity in a multimode VCSEL for fixed DC values has been experimentally demonstrated. These structures are characterized by different integrated intensities, polarization states, and a set of wavelengths. It is shown that the presence of spatial multistability leads to the appearance of multistability in the laser intensity and polarization multistability. The spatial multistability leads to a strong local dependence in the hysteresis behavior of the laser intensity on the pump current. The effect of the temperature of a laser diode on the manifestation of multistability is also investigated.

PVA passivated ZnSe nanorods have been synthesized using the solvothermal method. XRD analysis of the synthesized nanorods validates the cubic zinc blende structure with average particle size of 14 nm, and SEM analysis confirms the formation of rods having a wide range of lengths. A twin nanorod along with a typical nanostructure of rods has been observed in SEM micrographs. The optical characterization of the synthesized nanorods has been made using UV-Vis and photoluminescence spectroscopy. An energy gap of 3.89 eV has been observed, which is blue shifted from the bulk ZnSe. The dielectric study of ZnSe nanorods has been also made and reported.

The optical properties of the non-oxidized surface of a polycrystalline ytterbium film were investigated by an ellipsometric method in the spectral range of 0.4-2.6 μm. The dispersion dependences of optical conductivity s, reflectivity R, imaginary and real parts of the dielectric permittivity ε₁ and ε₂, and the function of characteristic losses of electron energy Im(ε^-1) were calculated from the measured values of refractive index and absorption coefficient. Using the results of measurements in the infrared spectral region and a two-band conductivity model, the electronic characteristics of ytterbium in the solid and liquid states were calculated.

The potassium sulfate crystals with a copper content of 1.7% were synthesized and their dispersion dependences of the refractive indices n_i(λ) and birefringence Δn_i(λ) were studied. It was found that in the spectral range of 300-700 nm, the dispersion n_i(λ) is normal, and the introduction of the impurity leads to a decrease in n_i and in the electron polarizability. The band energy structure of the potassium sulfate crystal doped with 1.7% of Cu²⁺ was calculated. The introduction of an impurity leads to a decrease in the band gap (E_g = 5.3 and 4.9 eV for pure and doped crystals, respectively). The optical functions of doped potassium sulfate crystals were calculated.

This study verified the applicability of Raman spectroscopy for the detection and classification of disease in citrus leaves. The Raman spectra of citrus leaves were collected using a SENTERRA confocal microprobe Raman spectrometer and divided into five types, Huanglongbing (HLB), moderate HLB, serious HLB, nutrient deficiency, and normal. The backgrounds of the spectra were deducted by different methods, and partial least squares discrimination analysis (PLS-DA) and extreme learning machine (ELM) were used to build the mathematical model. At the same time, the data dimension was reduced using principal component analysis (PCA) and successive projection algorithm (SPA) in order to optimize and improve the classification accuracy of the model. The experiments showed that the predictive ability of the PLS-DA model with 1850 input variables by 2 times polynomial fitting deducted backgrounds was better, the recognition correct rate being 100%. The results show that Raman spectroscopy has potential for rapid diagnosis of citrus HLB.

Four simple, precise, accurate, and eco-friendly spectrophotometric methods manipulating ratio spectra were used for the determination of acefylline piperazine (AC) and bromhexine hydrochloride (BR) in the presence of two dosage form additives - methylparaben (MP) and propylparaben (PP). The dual wavelength in ratio spectra (DWRS) and derivative of double divisor of ratio spectra (DD-RS) methods were used for the simultaneous determination of AC and BR. The first derivative ratio zero crossing method (¹DD) was used for the determination of BR. AC can be determined using sequential spectrophotometry, where the ratio subtraction method was applied to remove the extended spectrum of BR followed by applying the dual wave length method. The linearity of the proposed methods was investigated in the ranges 5.00-60.00 and 4.00-60.00 µg/mL for AC and BR, respectively. The selectivity of the developed methods was investigated by analyzing laboratory-prepared mixtures containing different ratios of the cited drugs and additives in addition to the analysis of their pharmaceutical dosage form. The validity of the proposed methods was further assessed using the standard addition technique. The obtained results were statistically compared with those obtained by the reported method, showing no significant difference with respect to their accuracy and precision at p = 0.05.

A direct and in situ digestion technique is reported for electrothermal atomic absorption spectrometric analysis of Cd in dairy products. In situ digestion methods offered high sensitivity due to the absence of sample dilution and minimum risk of contamination or analyte loss. Under optimized conditions, the calibration graph was linear in the range of 0-5 ng/mL, with a limit of detection of 0.012 ng/mL. The method was successfully applied in dairy product samples including milks, yogurt, and milk beverages, with spiked recoveries of 91 to 111%. The accuracy of the proposed method was also validated by wet digestion-based method.

A set of well-controlled electrospinning devices was established by a traditional UV-Vis spectrometer in order to produce different electrospun nanofiber membranes (ENMs) quickly and purposefully. Optimal fabrication conditions for 2-acrylamide-2-methylpropane sulfonic acid (AMPS) modified polyvinylidene fluoride (PVDF) ENMs, named PVDF/AMPS ENMs, were achieved by experiments. The results presented in radical electric focusing solid phase extraction (REFSPE) confirm that PVDF/AMPS ENMs have an outstanding ability to adsorb metal ions in water under optimal conditions with an extraction voltage of 9 V and an operation time of 23 min. The UV-Vis spectra of the heavy metal ions, which were eluted from the absorption materials by supersonic elution, were regressed using the self-established PLS model, and the concentration of each ion could be calculated accurately. The combined method using REFSPE enrichment through PVDF/AMPS ENMs, ultrasonic eluting, UV-Vis detection, and PLS calculation provides a practical and effective solution for the determination of trace charged compounds.

A new method for determining lead by resonance Rayleigh scattering (RRS) has been proposed and its operation mechanism has been discussed. In pH 5.0 HAc-NaAc buffer solution, Pb(II) reacted with xylenol orange (XO) to form a chelating anion ([Pb (H₂In)]^2-), which further reacted with crystal violet (CV) to form ternary ionic complexes, resulting in the enhancement of RRS intensity. The RRS intensity increases linearly with the concentration of Pb(II) in the range of 2.00×10^-3-2.00×10^{- 2} mg/L under optimal experimental conditions along with the detection limit of 9.2×10^-5 mg/L. This method is a promising approach for the selective and sensitive determination of Pb(II) in tea.

This study utilized hyperspectral imaging technology to identify eight tree species at the leaf level. The successive projections algorithm (SPA), information gain (IG), and Gini index (Gini) were used to select the feature bands. Furthermore, the binary particle swarm optimization (BPSO) algorithm was used to optimize the feature bands selected by SPA, IG, and Gini. The particle swarm optimization-extreme learning machine (PSO-ELM), linear Bayes normal classifier (LBNC), and k-nearest neighbor (KNN) recognition models for tree species were established based on all bands, feature bands, and optimized feature bands, respectively. The experimental results show that the recognition rates of the PSO-ELM, LBNC, and KNN models based on all bands were 98.45, 99.10, and 83.67%, respectively. The SPA, IG, and Gini can all effectively select spectral bands on tree species discrimination and greatly reduce the dimension of spectral data, in which the recognition effects of the models based on the feature bands selected by Gini were the best, and the recognition rates of the PSO-ELM, LBNC, and KNN models reached 97.55, 96.53, and 80.5%, respectively. Additionally, BPSO-SPA, BPSO-IG, and BPSO-Gini can all further reduce the dimension of spectral data on the basis of ensuring the recognition accuracy of models, in which the models established based on the optimized feature bands selected by BPSO-Gini achieved the best recognition effect and the recognition rates of the PSO-ELM, LBNC, and KNN models reached 96.53, 96.68, and 81.05%, respectively. In general, the recognition performance of the PSO-ELM model was better than those of the LBNC and KNN models.

Thirteen trace metals (Li, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Nb, and Mo) and two toxic metals (Cd and Pb) in two kinds of garlic bulbs have been quantified. Following the dehydration process, the garlic residues are digested using 10.0 mL of an acid mixture of HNO₃:H₂O₂:HCl (3:1:1, v/v/v). The trace metal assay is accomplished by inductively coupled plasma mass spectrometry (ICP-MS). Results reveal that the metal levels for the garlic bulbs with purple skin in dry weight are 14.5, 1.32, 3.03, 3.88, 13.0, 2.50, 1.00, 64.1, 139.6, 13.6, 18.4, 0.29, 0.11, 1.60, and 0.52 mg/kg for Li, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rb, Sr, Nb, Mo, Cd, and Pb, respectively, while the corresponding metal concentrations in the garlics with white skin are 22.9, 2.70, 3.95, 6.60, 19.7, 3.72, 1.16, 79.9, 149.8, 19.7, 24.0, 0.33, 0.43, 0.84, and 0.30 mg/kg, respectively. In general, the trace metals in both varieties are clearly under the FAO/WHO maximum permissible limits. However, it is observed that the garlics with white skin show higher quantities of essential/possible essential metals and lower levels of toxic metals, demonstrating the garlics with white skin exhibit a higher nutrition quality and are a better source of essential minerals.