Journal of Applied Spectroscopy最新文献

We conducted a spectral analysis of the enamel, dentino-enamel junction, and dentin of teeth in women with and without connective tissue dysplasia (CTD) in five age groups: 14–17, 18–21, 22–26, 27–31, and 32–36. Using the principal component analysis method, 19 absorption bands in the IR spectra of hard dental tissues were analyzed and the feasibility of grouping the samples by age and the presence or absence of CTD was assessed. The greatest differences in the functional group composition of the dental hard tissues in the case of connective tissue dysplasia were found at the dentino-enamel junction and were most pronounced for the 14–17 year-old age group. In this age group in comparison with the norm, the intensity of the collagen absorption bands in dentin at 1202, 1249, and 1342 cm^–1 was reduced by 30–50%, while the intensity of the phosphate absorption bands in the enamel at 1037 and 1050 cm^–1 was reduced by 50–70%. The lower third molars in this age group erupt with an insufficient level of maturity in a hypomineralized state, which may be associated with a reduced collagen content and different collagen structure due to connective tissue dysplasia. The data obtained can serve as the basis for a review of preventive measures and prenosological diagnosis of disease in teeth and maxilla based on the connective tissue theory of eruption.

Theoretically calculated IR absorption spectra of Ti/SiO₂/Si₃N4/n⁺-Si structures with an island surface layer were used to show that the absorption maximum broadened and shifted to longer wavelength as the n⁺-Si island size increased with a constant period of their placement on the surface. This peak was probably associated with excitation of plasmon oscillations in the surface island layer. A structure with an island size of 3 μm and a period of 6 μm was shown to absorb ~99% of the incident radiation at a wavelength practically equal to the period (6.2 μm). Other absorption bands at ~4 μm and 9.0–9.5 μm arose regardless of the island size and were associated with absorption in the SiO₂ layer. A layer of undoped silicon of thickness up to 200 nm located between the Ti substrate and SiO₂ layer slightly reduced the intensity and half-width of the plasmon absorption maximum.

The pulsed cathodoluminescence spectra of zinc selenide at room temperature were recorded: feedstock and materials required for the synthesis of optical ceramics. Samples of the cubic phase ZnSe with stoichiometric composition were also studied in the presence of additional phases (hexagonal ZnSe and ZnO). Three characteristic luminescence bands were detected for single-phase cubic zinc selenide. For the cubic ZnSe with stoichiometric composition one strong line of interband luminescence with a width of 12–14 nm is observed in the region of 470 nm; with an excess of selenium, an additional broad band appears at 647 nm, and with an increased impurity content and a small excess of zinc a single band is observed at 588 nm. In two-phase materials containing cubic and hexagonal ZnSe as the main or additional phase luminescence is not observed at room temperature. In the spectrum of cubic ZnSe with an additional hexagonal ZnO phase, a strong broad doublet band of hexagonal ZnO appears at 525–900 nm in addition to the interband luminescence line with a wavelength that decreases from 470 to 466 nm with increasing ZnO content. A rapid analysis of the quality of the ZnSe material can be carried out on the basis of the presence or absence of these pulsed cathodoluminescence bands.

The energy and spectral characteristics of the most powerful AlInGaN LEDs with emission spectrum peaks at wavelengths of 440, 470, and 510 nm were studied in relation to the pumping of two laser media: Ti:Sapphire (Ti:Al₂O₃) and alexandrite (Cr:Al₂BeO₄). The absorption coefficients of the LED radiation in the laser media were studied experimentally with respect to the peak wavelength, operating mode, and excitation level. The corresponding spectral matching values (the efficiency of absorption of the pump radiation) were calculated for various combinations of the LEDs and active laser media. The energy characteristics (radiation power, pulse energy) of the LED emitters were studied over a wide range of excitation levels. The maximum energy capabilities of the LED emitters were assessed in terms of both output optical power and efficiency. The optimum combinations of LEDs and active laser media to achieve laser generation were determined.

Lead in any food is harmful even at low concentrations. In this study, a direct and highly sensitive lead analysis technique was developed for wheat flour using laser-induced fluorescence combined with laser-induced breakdown spectroscopy. Wheat flour was pressed into small pellets and ablated by a low-energy ultraviolet 266-nm laser. A tunable dye laser constructed in our laboratory was used to resonantly excite the lead. The optimized interpulse time delay was 400 ns. A calibration curve was constructed and the detection limit for lead was 73.8 ppb. This method could be used to directly and sensitively analyze wheat flour for trace concentrations of lead.

The main theme of the paper was focussed on the preparation, structural, optical, and photoluminescence studuies of p(-n-decyloxy) benzoic acid (10OBA) liquid crystalline (LC) compounds with 1 wt.% dispersed ZnO nanoparticles (NPs). The prepared samples were subsequently characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical polarizing microscopy (POM), differential scanning calorimetry (DSC), UV-Visible spectroscopy, and photoluminescence (PL) studies. From the XRD, the diffraction peaks observed at 36.2, 42.5, 61.3, and 73.2° were well resolved, indicating the presence of ZnO NPs and the particle size was found to be 65 nm. SEM studies revealed the uniform dispersion and the presence of ZnO NPs in the samples. The textural images of different phases (nematic, smectic) of liquid crystalline compounds of 10OBA pure and 10OBA with 1 wt.% dispersed ZnO NPs were observed through the POM with reduced temperature. From the DSC thermograms, the phase transition temperatures and the correponding enthalpy values were estimated. The bandgap reduces for 10OBA LC compound with the dispersion of 1 wt.% ZnO NPS and it is estimated as 3.25 eV compared with 4.25 eV for the undoped 10OBA LC compound. PL studies showed the presence of the peak at 616 nm owing to the presence of point defects within the bandgap-like vacancies and interstitials known as deep-level emission.

Statistical characteristics of data from coordinated lidar and radiometric sounding of the atmosphere carried out by ground-based solar radiometers and satellite lidar CALIOP were used as an input dataset for retrieving the altitude profiles of aerosol parameters. The signal-to-noise ratio of input satellite lidar signals increased when averaged over a general ensemble of experimental data. An algorithm and software package were developed for collecting and statistical processing of combined lidar and radiometric sounding datasets and calculating average aerosol optical parameters of an atmosphere model. Altitude profiles of average concentrations of aerosol fractions in the region of Belarus were calculated based on results of radiometric measurements at the Minsk site of the AERONET/PHOTONS network and lidar sounding data from CALIOP collected during the observation period from 2015 to 2019. A statistical approach to the synergy of satellite lidar and ground-based radiometric sensing data was effective for studying the long-term and large-scale aerosol changes in regions with low and medium contents of aerosol matter in the atmosphere.

A study was carried out on the spectralluminescent properties of fl uorescein after its reaction with various reactive oxygen and halogen species (({O}_{2}^{bullet-},) H₂O₂, HOCl, HOBr, HOSCN, N-chloramine, taurine N-chloramine, and taurine N-bromamine) as well as in the myeloperoxidase (MPO)–H₂O₂–Cl^–/Br^–/SCN^– system. Reaction with only HOBr or with the MPO–H₂O₂–Br system turns fluorescein into a compound with an absorption maximum at 518 nm. The fluorescence maximum is recorded at 540 nm when excited at 520 nm, corresponding to eosin Y (brominated fluorescein). Conditions with phosphatebuffered saline (PBS) at pH 7.4 containing 137 mM NaCl, 5 mM fluorescein, 15–30 mM NaBr, and 25–50 mM H₂O₂ were found to be optimal for detecting HOBr in solution. A qualitative method for determining the brominating activity of MPO in vitro has been proposed. This method was used to study the effect of physiological and synthetic inhibitors as well as reactive oxygen and halogen species scavengers on the brominating activity of MPO. Our results indicate that fluorescein holds promise for use in a fluorescent method for detecting the brominating activity of mammalian hemecontaining peroxidases.

High-performance liquid chromatography (HPLC) and Raman spectroscopy have been used to study the thermal degradation of amoxicillin trihydrate. Heating this compound at 60°C for 6 h led to an increase in the impurity contents, each not exceeding 1%. HPLC and Raman spectroscopy can be used to evaluate the quality of an amoxicillin sample obtained after thermal degradation at 80°C.

Attenuated total internal reflection (ATR) spectra of polyimide PI-2610 films deposited on single-crystal silicon wafers by centrifugation were studied after irradiation with 5-MeV electrons in a linear accelerator at doses of 1∙10¹⁴–2∙10¹⁵ cm^–2. The strongest bands in the spectrum of the PI-2610 polyimide films were attributed to vibrations of the imide ring C–N–C_st (1349 cm^–1) and aromatic ring (1517 cm^–1), stretching vibrations of the imide ring C=O_str (1700 cm^–1) and CO–C_st-group C–C bonds (1074 cm^-1), and bending vibrations of C–H bonds with maxima at 734 and 828 cm^–1. The spectral shape and intensities of bands with maxima at 1700 and 1349 cm^–1 due to C=O and C=N–C_str vibrations were observed to change at an initial dose of 1∙10¹⁴ cm^–2. It was assumed that this was due to relaxation of metastable states of these groups. The intensities of bands corresponding to asymmetric and symmetric stretching vibrations of C–H₂ bonds decreased at a dose of 2∙10¹⁵ cm^–2. The intensities of ATR bands due to vibrations of C=O and C–N bonds and aromatic and imide rings practically did not change.