A plasma modeling algorithm using a two-zone light source approximation has been developed and coupled with the NLopt library for multiparametric optimization. An abstraction layer was created to streamline the initialization of both libraries in a single step, to calculate a loss function of the specified type, and to convey its value to the optimization algorithm. The proper functioning of these combined algorithms was confirmed with model data, demonstrating convergence to the plasma parameters that were used to generate a test synthetic spectrum. The CRS2-LM algorithm enables the fastest convergence to the original spectrum; hence, it has been utilized for the approximation of experimental spectra. It has been demonstrated that the application of a two-zone model provides an accurate description of both ionic and atomic lines, including those that are self-reversed during the evaporation of aluminum alloys. Furthermore, “blind” optimization methods for the loss function are effective for determining temperature and electron density in laser-induced plasma from its spectra.

We present influence of the UV-Vis and monochromatic (l = 408 nm) radiations on the reactions of copper sulphate and copper(II) oxide with β-diketones, chelators and dicarbonic acids. It has been established that the reactions of copper sulphate and copper(II) oxide with disodium dihydrogen ethylenediaminetetraacetate and amber acid in aqueous media and in the presence of urea can be achieved faster rate by using UV-Vis radiation. Monochromatic radiation hastens the reaction of copper(II) oxide with disodium dihydrogen ethylenediaminetetraacetate and ethylenediamine tetraacetic acid in aqueous and acetonitrile media. Taken as a whole it was found that the eight reactions had speeded by UV-Vis and monochromatic (l = 408 nm) radiations.

Results are presented on obtaining in a TEM laser system with an improved design of lasing having a peak output power of ³10 kW in several spectral ranges through the use of a combined gas mixture containing, in addition to CO₂ molecules, inert gases in which lasing is realized on electronic transitions.

The transmission spectra of colloidal solutions of magnetite nanoparticles in kerosene with different volume concentrations of the solid phase and the influence of an external magnetic field on them have been studied. It has been found that with increasing the magnetite concentration, a pronounced maximum in the near-infrared region of 740–760 nm appeares in the spectra. The limits of magnetite concentration have been established at which the transmission spectra are successfully described based on the Bouguer–Lambert law. It is shown that the appearance of a maximum in the transmission spectra with increasing concentration is associated with a minimum in the spectrum of the imaginary part of the refractive index of nanosized magnetite.

The possibility of using NV-defects in a diamond at room temperature on nanometer spatial scales to measure the magnetic field has been studied. For these purposes, samples with a high concentration of NV-centers are usually used, which increases the signal level but prevents the measurement of an inhomogeneous field in the scale of molecules or nanostructures. The parameters of a weak magnetic field have been measured taking into account the Earth’s field by measuring the ultrafine structure of the optically detected magnetic resonance spectrum to calibrate and determine the resolution of a magnetic field sensor on a single NV-defect.

The spectral-charge properties of the heterostructure of a 100-nm-thick n-type titanium dioxide (TiO₂) film on a p-type silicon substrate in the solar radiation wavelength range of 300–1200 nm studied by computer simulation. The presence of trap states in the TiO₂ film, which contribute to the localization of charge carriers, is taken into account. The simulation has been carried out using the Anderson model for semiconductor heterojunctions, the solution of the Poisson equation, the continuity equations for electrons and holes, and the Maxwell equations for electromagnetic waves in the Comsol Multyphysics software package. We have calculated the distribution of the generation rates and concentration of charge carriers in the heterostructure, the distribution of charge density and electric potential on the wavelength l of solar radiation incident on the TiO₂ film, and also on the energy of trap states E_t, which has been set inside the band gap, counting from the bottom of the conduction band. The integral density of solar radiation 1 kW/m² is assumed to be the same for all wavelengths. Nonmonotonic dependences of the generation rate of charge carriers in TiO₂ in the wavelength range l = 325–375 nm are revealed. It has been established that for relatively shallow traps (E_t = 0.2–0.3 eV) a positive charge with the density of 1.6 mC/cm³ is formed in the volume of a TiO₂ film, which weakly depends on the radiation wavelength l. As the trap energy increases, the volume charge density in the TiO₂ film decreases and changes sign, reaching –3.4 mC/cm³ at E_t = 0.8 eV and l = 900 nm. The surface charge density on the titanium dioxide film is negative, its value increases with increasing the trap energy E_t and the radiation wavelength l, reaching –2.8 × 10^–4 μC/cm² at E_t = 0.8 eV and l = 900 nm. We explain the results obtained by the interrelation between the interference processes in TiO₂ of the incident and reflected waves from the interface, the separation of charge carriers generated by sunlight at this interface, and also by the localization of electrons on the surface states of TiO₂.

Photoresist (PR) NFR 016D4 films deposited on the surface of silicon wafers by centrifugation have been studied by attenuated total reflection IR-Fourier spectroscopy. It has been established that at wave numbers <1600 cm^–1, an increase in the background absorption of the PR/Si structures is observed, due to the effect of electromagnetic radiation on the silicon substrate and scattering/reflection processes at the PR/Si interface. The asymmetry of the force field of the aromatic ring in the NFR 016D4 film has been found. It is shown that the features of the spectra of thicker NFR 016D4 photoresist films are due to the presence of residual solvent. In the irradiated films, the formation of formaldehyde has been detected as a result of the fragmentation of hydroxymethyl residues in the composition of the phenol-formaldehyde resin. Radiation-induced processes in NFR 016D4 photoresistive films at doses up to 2 ∙ 10¹⁵ cm^–1 take place mainly with the participation of residual solvent molecules or on by-products of photoresistive film synthesis.

The optical properties, morphology, and structure of coatings from nanoparticles of rare-earth metals La, Nd, Pr, and Y, obtained by laser ablation with Nd ³⁺:YAG laser in various media (air, distilled water), have been studied. It has been established that the electronic absorption spectra of colloidal solutions of the nanoparticles have maxima in the ultraviolet and visible regions of the spectrum. The optical density of the solutions varied from 0.2 to 1.6 with an absorbing layer thickness of 10 mm and the same excitation conditions at wavelength of 1064 nm. The dimensional parameters of rare-earth metal nanoparticles and the micromorphology of deposited coatings in air and water have been studied by atomic force microscopy. It has been shown that the deposited nanostructures of the studied metals have different morphologies and differ in the shape and size parameters of the nanoparticles, which depend on the deposition medium.

By the method of high-frequency repetitively pulsed f ~ 6—10 kHz laser radiation with wavelength l = 1.064 μm and power density q = 120 MW/cm² on zirconium target at a pressure in the vacuum chamber p = 2.2 Pa nanostructured thin films on a silicon substrate have been obtained. The morphology of thin zirconium films has been studied using atomic force microscopy. Transmission spectra of zirconium films have been obtained in the visible, near and mid-IR regions. The electrophysical characteristics of Zr/Si structures are analyzed.

Photoelectrochemical, structural, and electrocatalytic properties of titanium dioxide (TiO₂) nanotubes obtained by the anodization of titanium with subsequent thermal treatment in air or hydrogen were studied. It was shown that thermal treatment of TiO₂ nanotubes in hydrogen had no effect on the morphology and phase composition of TiO₂ electrodes. However, such treatment led to a high concentration of defect states in the crystal lattice of TiO₂ due to reductive doping accompanied by the conversion of Ti⁴⁺ to Ti³⁺. A rise of the defectiveness resulted in a lowering of the overpotential for oxygen electroreduction at titanium dioxide nanotubes annealed in hydrogen compared to those annealed in air. In addition, annealing in hydrogen led to a significant increase in the long-wavelength photocurrent generated under visible light irradiation.

The article describes the application of a method developed to assess the gas resistance of woody plants. With its help, it is possible to identify plants resistant to environmental pollution for further practical and breeding use. The method is based on the assessment of the level of inhibition of photosynthetic activity of leaves when exposed to toxic gases in the laboratory. As an indicator of genotype tolerance, the level of the effective quantum yield of photosystem II was used. The sensitivity of the indicator was quite sufficient to differentiate the control and experimental variants. The objects under study were ranked according to the degree of gas resistance and recommendations were given for the practical application of the new method.

Guaiacol is a model compound of one of the most common lignin biopolymers. The results of the analysis of the dependences of the components of the complex dielectric permittivity and specific electrical conductivity in the frequency ranges of 10^–2–10⁷ Hz and temperatures of 213–433 K of guaiacol are presented. Three groups of relaxators are identified. Their characteristics (relaxation time, activation energy) are defined. The change in the activation energy depending on the aggregate state is shown. The similarity of the processes of dielectric relaxation and conductivity of lignin and its model compounds in an alternating electric field are established.

The influence of six experimental light sources (lamps) based on LEDs with different emission spectra, simulating optical radiation close to solar radiation, on the photochemical activity of photosystems (PS) of leaves of purple basil, as well as on the redox state of the P700 reaction center, has been studied. The studied spectra differ in the distribution of photon flux over the main emission spectrum ranges, correlated color temperature (CCT) and general color rendering index (R_a). As a result of a comparative analysis of PAM fluorometry parameters, spectral regions have been identified that ensure more efficient photosynthetic processes in the leaf cells of basil plants at the stages of technical ripeness and flowering. In particular, basil plants grown on a spectrum with a CCT of 5260 K and R_a 98 have a fairly low F₀ level, one of the highest F_v/F_m ratios, characteristic of plants under non-stressful conditions, one of the highest quantum yields of both PS Y(I) and Y(II), as well as high electron flow rates. The spectra with CCT 4550 K, R_a 91, CCT 2820 K, R_a 81 also look promising in terms of PAM fluorimetry parameters. The spectrum with CCT 2990 K and R_a 97 has the worst performance in terms of the studied PSI and PSII parameters.

Elemental chemical analysis of aquatic organisms is necessary for biochemical and ecological studies, as well as for pollution monitoring. To this end, mainly wet analytical methods are used. However, direct analysis is possible by techniques such as X-ray fluorescence spectroscopy (XRF) and laser-induced breakdown spectroscopy (LIBS), which are mutually complementary in terms of analytical capabilities. Our study deals with the comparison of LIBS and XRF performance in the calibration-based determination of macroand microelements (P, Cl, K, Ca; B, Mn, Fe, Cu, Zn, and Sr) in organs and tissues of fishes and aquatic plants (bream, pike, horsetail, and hornwort). It has turned out necessary to normalise the signals of elements to the intensity of incoherently scattered radiation (in XRF) and to that of Balmer H-alpha emission line (in LIBS) to account for matrix effects. The comparison of the obtained data with the results of reference analysis by inductively coupled plasma optical emission spectroscopy has shown that LIBS is superior to XRF in terms of trueness for relatively light elements (P, K, Ca, Mn, Fe, and Cu). For heavier elements (Zn and Sr), this advantage moves to XRF. The combination of LIBS and XRF makes it possible to broaden the range of measurable elements, and in some cases (determination of P, K, Mn, Fe, Zn, and Sr), wet chemical decomposition becomes unnecessary, which is important for the simplification of analytical procedures.

The filtering of optical signals and the transformation of information using a stimulated echo hologram in the presence of external spatially inhomogeneous electric fields in the case when it is excited using an object laser pulse carrying information and a pulse acting as a frequency filter are considered. It is shown that the reproducibility of information embedded in the temporal form of an object laser pulse depends on the duration, amplitude, area of exciting pulses, and magnitudes of gradients of external spatially inhomogeneous electric fields. Varying the magnitudes of gradients of external spatially inhomogeneous electric fields makes it possible to control the efficiency of conversion and filtering of information recorded in a stimulated echo hologram, which can be used to create an echo holographic processor.

New (linear and non-linear) integro-functional equations are derived. The solutions of these equations are truncated spectral characteristics of fourth-order mutual coherence function of a laser beam propagating in a turbulent medium. The linear integro-functional equation includes some function W on which the solution of this equation does not depend (that is, it is invariant under any choice of function W). Firstly, formally rigorous and fairly simple representations for the fourth-order mutual coherence function and its truncated spectral characteristics are obtained. In finding these and other representations for these functions, we used, in particular, the property of invariance of solutions of a second-order partial differential equation for fourth-order mutual coherence function and new linear integro-functional equation with respect to any choice of function W. It is shown that by means of a special choice of this function and the parameters that determine the positions of the observation points and the cross sections of the laser beam, it is possible to obtain various exact, asymptotic, and semi-analytical representations for the truncated spectral characteristics, integral characteristics of the fourth-order mutual coherence function, and this function itself. In addition, semi-analytical representations are understood as representations that contain information about unknown values in a partially implicit form, but at the same time allow them to be found in an analytical (or numerical) form through the use of any (for example, iterative) constructive procedures. In particular, a semi-analytical representation is the recursive formula obtained in the article. It can be used to effectively find analytical expressions or numerical values for the above-mentioned functions on various cross sections of a laser beam propagating in a turbulent medium.

We investigated the influence of three factors on the formation of a Bessel light beam (BLB) in the scheme of transforming a Gaussian beam by an axicon: the ellipticity of the incident light beam, the ellipticity of the axicon, and the presence of a round tip of the axicon. For this purpose we used the methods of Fourier optics via numerical simulation. The results of the influence of each factor on the structure, quality parameters k_c, k_r, <R²> of the formed BLB and its Fourier spectrum (FSBLB) are shown. We introduced quality parameters of the FSBLB k_Is, k_ws, k_rs, which characterize the spread of amplitude, half-width and average frequency of the conical component of the FSBLB, as well as the parameter η, which determines the ratio of the energy in the conical component to the total energy of the beam. The quality of the FSBLB was analyzed with help of these parameters. The ellipticity of the Gaussian beam incident on the axicon leads to a reduction of the length of the region of existence of the BLB. In this case with increase of longitudinal coordinate all quality parameters decrease and the coefficient of constancy k_c drops most quickly. With increasing eccentricity of the half-widths of the Gaussian beam ε_b, the quality parameters of the FSBLB k_Is, k_ws, which characterize the spread of the intensity and half-width of the conical component of the beam, decrease. The ellipticity of the axicon affects all parameters of the quality of the BLB; most clearly, with an increase in the eccentricity of the axicon ε_a, the coefficient of constancy k_c and the average value of R² decrease. This happens due to oscillations in the ring closest to the axis of the BLB. The shape of the FSBLB with increasing ε_a also changes, moving from circular to elliptical. Because of this the coefficient of constancy of the frequency of the spectrum of the conical component decreases. Regularities in the transverse distributions of the intensity of the BLB, formed in the presence of azimuthal modulation of the cone angle were considered for the case when the number N of complete periods of oscillation of the cone angle is greater than 2. The number of intensity minima in the paraxial ring at a small value of the axicon base angle modulation amplitude B (≤0.05) in the case of odd N is equal to N, and in the case of even N is equal to 2N. For large values of B (>0.05) as in the case of even N, so in the case of odd N, the number of minima in the paraxial ring of the beam is equal to 2N. The spherical tip of an otherwise conical axicon leads to the formation of a separate non-conical component in the spectrum. In the case of a hyperbolic axicon, the conical component of the spectrum broadens in the direction of low spatial frequencies. The results obtained can be used to form special light fields, as well as to assess the quality of manufacturing of axicons and the ellipticity of the beam incident on the axicon.

The variation of the Voigt convolution contour in a spectrometer for measuring of weak absorption consisting of a frequency-tunable laser and an external analytical resonator is studied. It is established how the characteristics of the convolution and the parameters of the resonator affect the reproduction of the shape and width of the absorption line. The effect of absorption saturation on the accuracy of measuring the weak absorption coefficient is discussed.

The aspect of the detection of hydrogen isotopes in nuclear materials was analyzed in this review. Particular attention was paid to the spectroscopic methods for the detection of hydrogen isotopes in fusion reactor materials since their presence can induce severe problems in terms of material degradation and shortening of its lifetime. The main focus is on laser-induced breakdown spectroscopy, an optical emission method that is efficient, reliable, and fast. Recent results obtained at the VINCA Institute will also be presented.

We investigated the utility of machine-learning-enabled LIBS for direct rapid analysis of selected fission products (FPs), namely Y, Sr, Rb, and Zr in surrogate high-level nuclear waste mimicking three hypothetical but realistic scenarios: post-detonation glass debris, post-detonation powders, and microliter liquid drops from a radiological crime scene (RCS). Artificial neural network calibration strategies for trace quantitative analysis of the FPs in these materials were developed and achieved >95% prediction for all sample types. Owing to a lack of appropriate certified reference materials synthetic reference standards materials were used to perform method validation to accuracies ˃91%. Based on the spectral responses of the FPs, principal component analysis successfully differentiated nuclear from non-nuclear waste, demonstrating the method’s potential for RCS nuclear forensic and attributive analysis.

This research presents a theoretical analysis based on structural and spectral data to elucidate the molecular interaction mechanism of propiconazole, a fungicide. The optimization, vibration bands, and electronic structure analysis were conducted using the B3LYP level density functional theory with the aug-ccpVDZ basis set. Additionally, molecular docking simulations were performed to uncover the mechanism and modes of interaction between the propiconazole pesticide and DNA (PDB ID: 1BNA). The investigation revealed that the compound exhibits reactivity and polarizability, as indicated by the HOMO-LUMO energy range. The analysis of the molecular electrostatic potential surface (MEPS) and electrostatic potential surface (ESPS) demonstrated that the N6 and N7 atoms possess negative potential and serve as active sites for nucleophilic attacks. Similar observations were made for the oxygen and chlorine atoms. The molecular docking analysis indicated a preference for the propiconazole ligand to bind to DNA at sites involving nitrogen, oxygen, and chlorine atoms, specifically with guanine (G)-cytosine (C) interactions. Notably, the remarkable concordance between the MEP and molecular insertion results further supports these findings. These results provide valuable insights into the mechanism of DNA damage and the toxicological effects of the pesticide. Furthermore, the molecular docking analysis led to observations of changes in the optimized structure of the propiconazole molecule. For instance, the bond length between Cl1–C15, which was initially determined as 1.73 Å in the optimized structure, was recalculated as 1.77 Å following the molecular docking analysis.

Eu³⁺/Tb³⁺ co-doped CaWO₄ phosphors were synthesized by a simple green co-precipitation process. The structure of the samples was investigated by X-ray diffraction. The photoluminescence spectra and fluorescence decay lifetimes of the samples were measured to investigate the luminescence properties. We analyzed the energy transfer process between Eu³⁺ and Tb³⁺ co-doped-CaWO₄. As the Tb³⁺ to Eu³⁺ energy transfer process was confirmed, Eu³⁺ and Tb³⁺ co-doped-CaWO₄ phosphors showed a color-tunable emission from green to red under a 365 nm UV lamp.

We discuss new features of Sm3⁺ doped LaCePO₄ phosphor as a potential candidate for display applications. Mainly, the traditional modified solid-state synthesis technique was used to prepare the samples. The X-ray diffraction technique was used for the structural studies. LaCePO₄:Sm³⁺ phosphor production was verified by Fourier transform infrared studies. It was customary to use scanning electron microscopy to learn more about the morphology of the prepared samples. Additionally, photoluminescence (PL) analysis of the phosphor samples was presented for different doping ion concentrations with various excitations. In the presence of Sm3⁺, LaCePO₄ emits powerful blue and orange emissions. In-depth research was carried out on the transitions between the concentration quenching effect and the doping ion. The distribution of the spectral region estimated from PL emission spectra was shown in the 1931 Commission International de l'Éclairage (x,y) chromaticity coordinates and was located (0.20,0.22) in the blue region. According to our research, as-prepared phosphor may find useful application in display devices, especially because of its blue and orange content.

Phenyl boronic acids (PBAs) form stable complexes with fluoride. The effect of type (methoxy-, formyland acetyl-) and position (ortho-, meta- and para-) of electron-donating substitutions on the hydrolytic stability and acidity of PBAs, as well as their spectroscopic and physicochemical properties and their usage in spectrofluorimetric fluoride determination, were investigated. Thermal stabilities, relative predisposition and resistance to dehydroboronation of related PBA isomers were investigated in detail and compared with the use of thermogravimetric analysis and differential scanning calorimetry profiles. Dehydroboronation reaction leads to the synthesis of related new cyclic anhydric forms – specifically named boroxines – which are clearly distinguished by Fourier transform infrared spectroscopy. PBAs were used for the complexation of fluoride for spectrofluorimetric fluoride determination in dental formulations (toothpastes (TPs) and mouth rinses (MRs)) and beverages (mineral waters (MiWs)). Determination was done by fluorescence quenching of PBAs in response to increasing fluoride concentration. The regression equation was y = –15.336x+983.17 (R² = 0.9931), and was linear in the 1.4-3.0-mM range. Determinations were performed with relative errors (%) in a range of –5.60 to +1.23, –2.01 to +5.69 and –4.16 to +2.54 for MRs, TPs and MiWs, respectively relative to fluoride levels of commercial samples. Chemometric analyses (cluster analysis, CA, principal component analysis, PCA) were performed on the same real samples. Raw fluorescence data was investigated by PCA to check their significance in chemometric discrimination. Dendograms and score plots successfully discriminated samples in related groups. This is the first demonstration of spectrofluorometric fluoride determination based on the quenching of related isomers of PBAs thus far, also the potential of raw fluorescence data of these PBAs for chemometric discrimination studies on related pharmaceutical samples was highlighted for the first time.

The objective of this study was to investigate the photoluminescence properties of Al₄B₂O₉:M (M = =Dy³⁺ , Sm³⁺ , and Tb³⁺ ). The solution combustion method was employed to prepare Al₄B₂O₉ doped with M ions. The synthesized aluminum borates were subjected to phase analysis using X-ray diffraction, while their photoluminescence properties were evaluated using a spectrofluorometer. Under excitation at 352 nm, Al₄B₂O₉:Dy³⁺ exhibited emission peaks at 484, 578, and 701 nm. Similarly, when excited at 402 nm, Al₄B₂O₉:Sm³⁺ emitted light at 563, 599, 645, and 702 nm. Finally, upon excitation at 238 nm, Al4B2O9:Tb3+ emitted light at 489, 544, 588, and 622 nm.

Trandolapril is an oral angiotensin-converting enzyme (ACE) inhibitor approved by the USFDA for the therapy of hypertension and congestive heart failure. This paper describes the validation of zero- and firstorder derivative UV spectrophotometric methods for the estimation of trandolapril in bulk and in its marketed tablet formulation. Preliminary spectrophotometric determination of the drug was carried out in phosphate buffer pH 2.0 or 0.1 N HCl. A total of 17 parametric method variants were investigated out of which three variants employing peak–zero (P–0) and peak–peak (P–P) techniques were validated with respect to linearity, accuracy, precision, and robustness. The developed methods were also assessed for stability indicating potential in force degraded solutions. Linearity was observed in the concentration range of 1.0–70.0 μg/mL with an excellent correlation coefficient (r²) ranging from 0.9981–0.9998. The limits of assay detection values were found for the range of 0.88–1.23 μg/mL, and quantitation limits ranged from 2.66–6.09 μg/mL for the proposed methods. The proposed methods were extended to the quantification of the drug in its marketed tablet formulation with good recoveries (90–98%).

Three simple and affordable UV spectrophotometric methods have been proposed for the simultaneous determination of chlorthalidone and nebivolol in a synthetic mixture, as well as a combined dosage form. Method I use the simultaneous equation methodology and has a linearity range of 5–25 µg/mL for chlorthalidone at 233 nm and 5–90 µg/mL for nebivolol at 280 nm respectively. The linearity ranges for chlorthalidone at 228–238 nm and nebivolol at 275–285 nm were found to be 5–60 and 5–100 µg/mL respectively, using method II, the area under the curve method. The linearity range for method III, the first derivative method, is 10–35 µg/mL for chlorthalidone at 227 nm and 10–35 µg/mL for nebivolol at 275 nm. The two diagnostic plot residuals normal probability plot and residuals versus expected values plot are utilized for the verification of outcome data and found to be optimal for three methods. The method has been validated for accuracy, precision, recovery studies, linearity, specificity, and stability studies according to the International Council of Harmonisation guideline Q2R1. These developed methods have been utilized in routine analysis for the simultaneous determination of chlorthalidone and nebivolol without pre-extraction.

An ultra-sensitive kinetic spectrophotometric method has been carried out to determine ceftriaxone in a simple and cost-effective manner. The method utilized the catalytic behavior of the drug in accelerating the reaction between iodine and sodium azide. The fixed time method was exploited to select the optimum reaction time and it was found to be 7.0 minutes after the addition of iodine at pH 2.0 using 0.1 M phosphate buffer. Experimental variables that affect the formation of the reaction product were studied and optimized. The method was validated following ICH guidelines and showed excellent linearity within 0.25–2.50 μg/mL at 348 nm. Kinetics of the reaction were investigated and the reaction rate constant was calculated. The method was successfully applied for the analysis of the drug in dosage forms with high selectivity. Comparing the results of the developed approach with the results of the reported spectrophotometric method showed no significant difference with respect to accuracy and precision. The developed method reached a sensitivity 20 folds greater than the reported method. Being selective and sensitive in analysis makes the method a suitable candidate for quality control monitoring of the cited drug.

The study developed a simple, sensitive and robust method for the estimation of curcumin in bulk drug form and in nanoemulsion formulation. Mobile phase consisting of acetonitrile and 20 mM potassium dihydrogen orthophosphate (pH 3.0) in ratio 55:45 was selected. A flow rate of 1 mL/min and an injection volume of 20 μL was injected to develop a chromatogram using a 516 C₁₈ DB reversed-phase column. The detection wavelength was adjusted at 420 nm and the retention time of curcumin was found to be 9.78±0.5 min. The method was validated as per ICH guidelines and can be used for the quantification of curcumin even at a very low concentration.

Theoretical investigation on self-focusing of an elliptical q-Gaussian laser beam carrying an intensity ripple over its cross section, in plasma with an axial density ramp has been presented. The optical nonlinearity of plasma has been modeled by the relativistic mass nonlinearity of plasma electrons in the field of a laser beam. Using the variational theory approach, semi-analytical solutions of the wave equations for the fields of the main beam and that of the ripple have been obtained. Emphasis has been put on the evolutions of the beam widths of the main beam and that of the ripple.

Terahertz time-domain spectroscopy (THz-TDS) and hyperspectral technology were used for wood recognition. As wood is a valuable national resource, it is essential to utilize it efficiently and reasonably by classifying the species of wood. To accomplish this, ten distinct species of wood, including five types of softwood (Pinus sylvestris, Pinus tabulaeformis, Pinus massoniana, Larix gmelinii, and Pinus koraiensis) and five types of hardwood (Xylosma racemosum, Populus davidiana, Fraxinus rhynchophylla, Betula platyphylla, and Tilia tuan Szyszyl), were selected as experimental samples. Four hundred groups of data for terahertz absorption coefficient spectra and four hundred groups of hyperspectral data were acquired using THz-TDS and hyperspectral technology, respectively, and then examined for their spectral features. Three spectral preprocessing techniques, including the Savitsky–Golay smoothing algorithm, standard normal variable transformation, and multivariate scattering correction, were employed to preprocess the spectrum. Support vector machine recognition models were then created to compare and analyze the effects of recognition. The results demonstrated that both THz-TDS and hyperspectral approaches could successfully identify five different species of hardwood from various families and genera, with the highest accuracy rates of 92 and 94%, respectively. THz-TDS achieved a 92% recognition rate for five different species of softwood from the same family, indicating good recognition effects, while hyperspectral technology did not achieve such results.