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The paper proposes a modified method for measuring the refractive index of a triangular prism using an autocollimation angle measuring system designed to measure angles formed by flat surfaces of objects. The method involves using a fixed mirror to reflect the refracted beam, measurement of the angles of incidence of the beam on the face of the prism corresponding to the autocollimation positions and calculating the refractive index of the prism material using the solution of a system of equations. The paper presents the experimental study results for a triangular prism made of K8 optical glass using the proposed method, and a comparison of the results with the readings obtained using the State Primary Standard of the Refractive Index Unit GET 138-2021. The proposed method makes it possible to simplify the process of measuring the refractive index since there is no need to measure the angle of deviation of the beam.

Methods for measuring the refractive index of optically transparent dielectric materials are considered. Modified methods based on the methods of minimum deviation and constant deviation are proposed and allow determining the refractive index of triangular prisms with unknown apex angles. In the proposed methods, the angles of light deviation on three faces of the prism are measured, and the refractive index of the material and the prism angles are determined from the solution of a system of equations. To implement the proposed methods, a goniometric system is used. That system was designed to measure angles between the flat surfaces of objects in manual and automated modes. Reference prism samples made of N-SF 1 optical glass, and a hollow prism filled with distilled water are studied. The proposed methods are compared and the measurement error is estimated. It is shown that the modified methods can be used for high-precision measurements of the refractive index in cases where the angles of the prism are unknown, or their measurement is associated with technical difficulties.

When developing oil fields, there is an urgent task to quickly determine the type of pumped formation fluid, which includes formation gas, formation oil and formation water. In this paper, we propose a new type of a sensor element designed for flow refractometry of formation fluid based on the effect of total internal reflection. The sensor element is a taper tip of a conical shape made of sapphire and is 20 mm in length and 20 mm in diameter. The original shape of the sensor element is determined by a modified ray tracing method, taking into account analytical relations that determine the conditions for providing a larger dynamic range of measurements under specified physical, technological and design constraints. The conversion dependence of the tip is obtained for the wavelengths of 405 nm, 1064 nm and 3300 nm and allows determining the type of formation fluid (gas/water/oil). The proposed method enables the development of conical sensor elements based on the total internal reflection for downhole monitoring systems and optical threshold sensors of the refractive index.

In this work, the splitting of resonance lines in a Fabry-Perot resonator formed by a section of a standard curved single-mode fiber with metal-coated ends is investigated numerically and experimentally. It is shown that this splitting is similar to the Autler-Townes splitting and results from a strong coupling between the fundamental mode of the core and the whispering gallery mode of the cladding of the curved fiber. The influence of all basic parameters of the curved resonator on the splitting of its resonance lines in the reflection and transmission spectra is considered. Prospects for the practical application of the effects studied for high-resolution optical refractometry, as well as the direction of further research are outlined.

Morphological and physico-chemical properties of erythrocytes encapsulated by terpenoindol alkaloids (TIA) by nephelometry and osmotic resistance of erythrocytes in a medium with low concentrations of sodium chloride have been studied. Changes in the morphological and physico-chemical parameters of TIA-loaded erythrocyte carriers and freshly isolated erythrocytes have been studied. It was found that during the process of encapsulation of TIA by a modified hypotonic swelling method, the morphological and physicochemical parameters of erythrocytes change insignificantly in comparison with the control.

Methods of tissue-simulative phantoms and capillaries fabrication from PVC-plastisol and silicone for application as test-objects in optical coherence tomography (OCT) and skin and capillary emulation are considered. Comparison characteristics of these materials and recommendations for their application are given. Examples of phantoms visualization by optical coherence tomography method are given. Possibility of information using from B-scans for refractive index evaluation is shown.

The elliptical polarization of He-Ne laser radiation reflected by plant leaves (Begonia Fista and Hedera Helix) was investigated. It was supposed that the elliptic polarization component of reflected radiation is caused by the acts of total reflection of incident radiation on cuticle inhomogeneities. By using the model of the phase-shifting ability of a scattering layer, the cuticle refractive index and the mean angle of inclination of cuticle roughness microfacets to leaf surface was evaluated.

A new alcohol oxidase-peroxidase method of determination of ethanol content in fermented musts and wine products is described and compared to conventional methods routinely used in winemaking. The sensitivity, accuracy, and reliability of this method were determined. The results of ethanol determination in fermented musts and wines correlated well with the data obtained by refractometry (correlation coefficient R = 0.9595, p < 0.0001) and densitometry (correlation coefficient R = 0.9384, p < 0.0001). This method is less time- and labor-consuming and allows simultaneous testing a series of wine samples.

The paper describes results of experimental studies of changes in the refractive index of the live cell (human erythrocyte) substance. The measurements were carried out using automated interference microscope. Oscillations of the refractive index were detected with the amplitude 5-10% and period 1 x 10(3)-3 x 10(3). In other words, oscillations with a near one hour period is equal to 10-45 min. It is supposed that these oscillations may result from coherent changes in the state of protein molecules.

A new method for detection of hepatitis B surface antigen (HBsAg) has been developed. It employees IAsys optical biosensor registration kinetics of HBsAg complexes with monoclonal antibodies. Detection of intermolecular interactions is accompanied by changes of the light refraction coefficient in the sensitive layer of the biosensor cuvette. The main advantage of this diagnostic technique consists in rapid registration of these interactions in real time, without any introduction of special labels into analysing molecules. The optical biosensor method was successfully employed for the detection of HBsAg in human blood serum. A comparative study of HBsAg detection by the optical biosensor and by immunoenzyme analysis demonstrated high specificity of HBsAg detection by this new method.

Changes in clinical refraction parameters were followed up in 343 students of school of pilots in the town of Burguruslan in the course of vocational training. Skiascopy and laser refractometry methods were used. Dynamic follow-up of clinical refraction showed its increase in 24.3% of the examinees both with emmetropia and hypertropia or myopia. The most noticeable increase of refraction was observed during the first two years of training, which may be explained by intensive exercise of the eyes because of theoretical studies and flights. The results evidence practical advantages of laser refractometry in comparison with skiascopy.

Changes in the properties of natural actomyosin suspensions, such as turbidity, light scattering, volume concentration, particle size and particle size distribution during superprecipitation (SPP) of actomyosin in media of different compositions have been investigated. Two sets of changes indicating the existence of two SPP types--the "immediate" SPP characterized by a rapid one-step rise in turbidity and the "spontaneous" SPP, when the slow increase in turbidity follows the clear phase, have been revealed. In both cases the mechanism of the increase in the suspension turbidity is assumed to be similar and is conditioned by an increase in the refraction index (density) of the particles; however, the ways of formation of dense particles are different. During the "immediate" SPP, the particle density increases due to particle striction, whereas during the "spontaneous" SPP dense particles are formed as a result of ordered lateral association of myosin and actin filaments.

The influence of sulphuric magnesium on the molecular regulation processes in lecithin-water systems was investigated by the optical methods of polarized microscopy, refractometry and infrared spectroscopy. The obtained changes of structure parameters are interpreted by the modification role of Mg2+ cations and SO4(2-) groups.

Experiments on millimeter wave radiation (range 37.5-78.5 Ghz incident radiation power density 1-10 mVt/cm2) upon index refraction of 2-10% water solution of human blood plasma are presented. Investigations were carried out by holographic interferometry with sufficient sensitivity for estimating the index refraction -10(-6). Index refraction variations in 2% water solution of human blood plasma are detected to be equal to 10(-4). Such index refraction variations upon millimeter wave is one order greater than that of the temperature effect and two order greater than the sensitivity of settlement. The mechanism of these phenomena is discussed.

The authors analyze the results of surgical correction of hypermetropic and mixed astigmatism, carried out by two methods: clinoid resection of the cornea and clinoid resection of the cornea with tangent autoclinoplasty (i. e. implantation of the resected site to the tangent incision in strongly refracting meridian). Surgical technique has been mastered in experiments with isolated eyes and the mechanism of changes in corneal refraction, resultant from its resection, studied. Experiments with rabbit eyes have shown that after corneal resection cicatrization is over by the third month after surgery. 17 operations with classical clinoid resection and 17 ones with that and tangent clinoid autoclinoplasty were carried out in patients with corneal astigmatism of 2.0 to 6.25 diopters, the follow-up periods being from 6 months to 4 years. The mean reduction of astigmatism after the use of the aforesaid methods has made up 2.47 and 4.8 diopters respectively (according to the data of subjective examination of refraction).

A calculation of the refractive index of particles of a disperse perfluorochemical-based (PFC-based) blood substitute has been made taking into account particular features of the structure of PFC emulsion particles and the equations earlier obtained by one of the authors in the studies on light interaction with optically inhomogeneous 2- and 3-layer spheres. The possibility of averaging by volume the refractive index of 2-layer emulsion particles has been shown. The refractive index of PFC particles has been experimentally determined using independent optical methods, and the thickness of the particle shell formed by a surfactant has been evaluated.

A method of determination of molecular masses of globular proteins based on microcolumn size-exclusion HPLC on modified silica sorbent (TSK-GEL 3000 SW) with refractometric detection has been developed. Molecular masses in the range 10 to 200 kD were determined with the accuracy of +/- 3%.

A simple method is proposed to calculate bilayer lipid membrane (BLM) thickness using measurements of BLM reflectivity. BLM is considered to be nonhomogenous with the refractive index n = n(z)--a function of coordinate z normal to the membrane plane. The membrane thickness obtained with this method is 4 divided by 6% less than that obtained with the standard method.

The kinetics of form change (flattening) of Chinese hamster fibroblast cell surface facing the glass has been studied during attachment of fibroblasts to the glass using the effect of frustrated total reflection. Two stages of the process were shown to exist. The first one is characterized by a rapid (5 min) partial flattening and requires no serum in the medium. The second stage occurs only in the presence of serum in the medium, it lasts no longer than one hour and ends in a complete flattening. After the second stage is completed, spreaded cells appear.