Institute of Precision Mechanics and Control

Advances in improving existing noninvasive optical diagnostic methods and creating new criteria for assessing the effects of diabetes on tissues and the vascular system are highly demanded. One of the promising, noninvasive and contactless methods for visualizing the vascular system is laser speckle contrast imaging. This study studies the possibility of using magnetic resonance contrast agents in laser speckle contrast imaging and optical coherence tomography, for the first time, on rat ears, under conditions of alloxan-induced type 1 diabetes. By combining diagnostic techniques, the study investigated the ability to differentiate between healthy rat tissue and diabetic rat tissue based on dynamic and structural changes caused by local application of magnetic resonance agents. This study explores the possibility of using magnetic resonance contrast agents for laser speckle-contrast imaging and optical coherence tomography of rat ears under conditions where alloxan-induced type 1 diabetes mellitus is developing was studied for the first time. Kinetics of scattering coefficient (µs) for healthy and diabetic rats during optical clearing were evaluated. The most significant reduction is seen with the Gadovist solution, showing decreases of 18.6% and 16.1% for healthy and diabetic rats, respectively. Magnevist induced a smaller reduction in the µs, with decreases of 12.6% and 6.8%, respectively. Data on the flow rate in the vessels of the ears of laboratory rats obtained in the diabetic group demonstrate reduced indicators, relative to the healthy group of animals. These results confirm the effectiveness of magnetic resonance contrast agents as optical clearing agents for both optical coherence tomography and laser speckle contrast imaging. For the first time, the nature of the change in the contrast of the static part with a change in scattering was studied. This is an additional application for studying the efficiency of optical clearing, and contributes to the multimodal application of speckle imaging methods.

From a structural point of view, plasmonic nanoparticles are always at least two-layer structures with a dielectric layer of stabilizing, targeting, fluorescent, Raman, or other functional molecules, often embedded in a matrix such as porous silica. To optimize the optical properties of such bioconjugates, one needs efficient analytical models based on simple physical ideas and with reasonable accuracy comparable to rigorous numerical methods requiring significant computer resources. Recently, we suggested an analytical approach ( J. Phys. Chem. C 2024, 128, 15029–15040) based on a combination of the modal expansion method (MEM) and the dipole equivalence method (DEM). The MEM+DEM method was exemplified by coated gold nanorods excited along the symmetry axis. Here, we extend the MEM+DEM approach for particles of various shapes and orientations, including random ones. To illustrate the possibilities of our method, we calculate extinction and scattering spectra of gold and silver nanorods, nanodiscs, triangle nanoprisms, bicones, and bipyramids with a dielectric coating thickness from 0 to 30 nm. For the main plasmonic peaks, we found excellent agreement between our analytical method and numerical simulations performed with COMSOL, except for some disagreement between MEM and COMSOL solutions for bicones with small rounding radii. This drawback of MEM for coated particles is explained by the unusual local field distribution with strong localization near the particle tips. To fix the point, we propose a factorized version of MEM that brings analytical spectra of coated bicones and bipyramids in good agreement with numerical counterparts. To illustrate the application of our method to real experimental colloids, we prepared 12 AuNR samples using a chemical etching with fine-tuning of the LPR over the 1020–630 nm range. By including the CTAB shell in the simulation model, we achieved excellent agreement between the calculated and measured dependence of the LPR peak position on the AuNR aspect ratio. In summary, our method makes it possible to use the MEM parameters of the original metal particles. It does not require additional numerical calculations to build analytical models for bilayered or multilayered conjugates. The presented analytical solutions depend on the particle shape, the shell thickness, and the shell refractive index, regardless of the particle size and the metal’s nature. Due to the simplicity and reasonable accuracy of the MEM+DEM analytical models, they can help apply machine learning to predict various plasmonic responses such as light absorption, scattering, surface enhanced Raman scattering (SERS), and metal-enhanced fluorescence (MEF).

For many statistical procedures, it is important to assume the source data have a normal distribution. However, if this assumption is insufficiently justified, the use of these procedures can lead to false conclusions. The problem of normality testing has therefore received much attention in the literature. This work considers normality testing in a case where the data consist of a number of small independent samples, in each of which the observations are independent and identically distributed but have different shift and scale parameters from sample to sample. In such cases, we must use statistics that are independent of the parameters. A natural way of eliminating the shift parameter is to substitute the observations in each small sample according to their differences. This work estimates the stability of such decompositions and compares the power of several normality tests based on transformed data.

Biosensor technologies in medicine, as in many other areas, are replacing labor-intensive methods of monitoring human health. This paper presents the results of experimental studies on label-free sensors based on a hollow core microstructured optical waveguide (HC-MOW) for human blood serum analysis. The MOWs with a hollow core of 247.5 µm in diameter were manufactured and used in our work. These parameters allow the hollow core to be filled with high-viscosity solutions due to the capillary properties of the fiber. Calculations of the spectral properties of the HC-MOW fiber were carried out and experimentally confirmed. Twenty-one blood serum samples from volunteers were analyzed using standard photometry (commercial kits) and an experimental biosensor. The obtained transmission spectra were processed by the principal component analysis method and conclusions were drawn about the possibility of using this biosensor in point-of-care medicine. A significant difference was shown between the blood serum of healthy patients and patients with confirmed diagnoses and a long history of cardiovascular system abnormalities. Algorithms for spectra processing using the Origin program are presented.

The effects of optical clearing of implantable collagen materials were studied using optical clearing agents (OCAs) based on aqueous glucose solutions of various concentrations. By measuring the kinetics of the collimated transmission spectra, the diffusion D and permeability P coefficients of the OCAs of collagen materials were determined as D = (0.22 ± 0.05) × 10-6 to (1.41 ± 0.05) × 10-6 cm2/c and P = (0.55 ± 0.04) × 10-4 to (1.77 ± 0.07) × 10-4 cm/c. Studies with optical coherence tomography (OCT) confirmed that each of the OCAs used had an effect on the optical properties of collagen materials, and allowed us to quantify the group refractive indices of the collagen of various samples, which turned out to be in the range from nc = 1.476 to nc = 1.579.

Regular quaternion differential equations of the perturbed orbital motion of a cosmic body (in particular, a spacecraft, an asteroid) in the Earth’s gravitational field are considered, which take into account zonal, tesseral and sectorial harmonics of the field. These equations, unlike classical equations, are regular (do not contain special points such as singularity (division by zero)) for perturbed orbital motion in the central gravitational field of the Earth. In these equations, the main variables are four-dimensional Kustaanheim–Stiefel variables (KS-variables) or four-dimensional variables proposed by the author of the article, in which the equations of orbital motion have a simpler and symmetric structure compared to equations in KS-variables. Additional variables in the equations are orbital energy and time. The new independent variable is related to time by a differential relation containing the distance from the cosmic body to the Earth’s center of mass (the Sundman differential time transformation is used). Regular equations of perturbed orbital motion in quaternion osculating (slowly changing) variables are proposed. The equations are convenient for using methods of nonlinear mechanics and high-precision numerical calculations, in particular, for forecasting and correcting the orbital motion of spacecraft. In the case of orbital motion in the Earth’s gravitational field, the description of which takes into account the central and zonal harmonics of the field, the first integrals of the equations of orbital motion of the eighth order are given, changes of variables and transformations of these equations are considered, which made it possible to obtain closed systems of differential equations of the sixth order for the study of orbital motion, as well as systems of differential equations of the fourth and third orders, including a system of differential equations of the third order with respect to the distance from the cosmic body to the center of mass of the Earth and the sine of geocentric latitude, as well as a system of two integro-differential equations of the first order with respect to these two variables.

Diabetes mellitus (DM), a chronic metabolic disorder that adversely affects the blood-brain barrier (BBB) and microglial function in the central nervous system (CNS), contributing to neuronal damage and neurodegenerative diseases. However, the underlying molecular mechanisms linking diabetes to BBB dysfunction and microglial dysregulation remain poorly understood. Here, we assessed the impacts of diabetes on BBB and microglial reactivity and investigated its mechanisms. We found diabetes severely disrupted the BBB integrity and microglial response to vascular injury. We also revealed a potential relationship between BBB disruption and impaired microglial function, whereby increasing BBB permeability led to a downregulation of microglial P2RY12 expression, thereby impairing microglial protection against cerebrovascular injury. Understanding these mechanisms may contribute to the developing of therapeutic strategies for diabetes-related neurological complications.

The article considers the problem of continuous production management. The technological process of sheet glass production is chosen as an example. We have analyzed the process of sheet glass forming. We have described the main stages of production. They propose a model based on situational control to develop a control system for glass production.

In this study we have analyzed the change in the intensity distribution of three-wavelength transillumination images of human interphalangeal joints under the action of the optical clearing agent. RheumaSens medical scanner prototype with the following wavelengths: 660, 850, and 905 nm, has been tested. A water solution of glycerol (70%) and DMSO (5%) has been used as an optical clearing agent, and sonophoresis has been applied for enhance of skin permeability. Eight healthy volunteers and a volunteer with rheumatoid arthritis have been investigated. As a result, we have obtained an increase in the contrast of joint images within 10 min: 1.2±0.14, 1.16±0.15, and 1.16±0.02 folds at the wavelengths of 660, 850, and 905 nm, respectively. It has been shown an effect of skin optical clearing on the enhancement of the images of joint with rheumatoid arthritis in the transillumination mode.