Methods of absorption and fluorescent spectroscopy and fluorescent chronoscopy are used to investigate aqueous fluorescein solutions with pH values increasing from 1.79 to 11.67. For each method, the calibration curves are drawn for the fraction of dianion fluorescein species, quantum fluorescence yield, and amplitude dianion contribution to the fluorescence intensity on the pH values of aqueous solutions. The calibration curves allow the pH values of aqueous fluorescein solutions with gelatin (pH = 6.4 ± 0.1, 6.6 ± 0.2, and 6.6 ± 0.1), starch (pH = 6.3 ± 0.1, 6.3 ± 0.2, and 6.4 ± 0.1), and acid-soluble chitosan additions (pH = 5.4 ± 0.1, 5.6 ± 02, and 5.8 ± 0.1) to be estimated by these three methods. The pH values of biopolymer solutions obtained by the potentiometer method for starch (6.51) and gelatin (6.69) and by the three spectral and fluorescent methods are close; they are significantly underestimated (3.85) for chitosan solutions.

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The purpose of this work was to study the qualitative and quantitative composition of the main groups of biologically active substances in the fresh fruits of five different varieties of black chokeberry (Aronia melanocarpa (Michx.) Elliot), carried out within the framework of the search for available and cost-effective raw materials for food product fortification. Samples of aronia chokeberry were grown at the Federal Scientific Center named after I.V. Michurin in the Tambov region of Russia. Using a modern chemical–analytical methodology, the contents and profiles of anthocyanin pigments, proanthocyanidins, flavonoids, hydroxycinnamic acids, organic acids (malic, quinic, succinic, and citric), monosaccharides, disaccharides, and sorbitol were determined in detail. Based on the results of the study, the most promising varieties were determined in terms of the content of the main biologically active substances.

The article discusses the issues of mathematical modeling and processing of cardiointervalogramms of cows with different vegetative regulation. An analysis of the sinus rhythm with subsequent mathematical processing of statistical parameters is presented. The work examines the variational pulsograms of an experimental group of animals, using correlation rhythmography, analyzes the scattergrams, autocorrelation clouds in cows with different levels of vegetative regulation. Studies of heart rate variability indicators for Jersey breed cows are relevant. This is a unique method that allows one to take into account the breed characteristics of cattle, predict milk productivity and increase the period of economic use. The stress index is an indicator that most fully informs about the degree of tension of the body's compensatory mechanisms, as well as about the level of functioning of the central circuit of the regulation of heart rhythm. Based on the stress index, the initial vegetative tone was calculated.