Publications by authors named "Alexander Bykov"

In this work, a series of boronated amidines based on the -dodecaborate anion and amino acids containing an amino group in the side chain of the general formula [BHNHC(NH(CH)CH(NH)COOH)CH], where n = 2, 3, 4, were synthesized. These derivatives contain conserved α-amino and α-carboxyl groups recognized by the binding centers of the large neutral amino acid transporter (LAT) system, which serves as a target for the clinically applied BNCT agent para-boronophenylalanine (BPA). The paper describes several approaches to synthesizing the target compounds, their acute toxicity studies, and tumor uptake studies in vivo in two tumor models.

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We explore the propagation of structured vortex laser beams-shaped light carrying orbital angular momentum (OAM)-through complex multiple scattering medium. These structured vortex beams consist of a spin component, determined by the polarization of electromagnetic fields, and an orbital component, arising from their spatial structure. Although both spin and orbital angular momenta are conserved when shaped light propagates through a homogeneous, low-scattering medium, we investigate the conservation of these angular momenta during the propagation of Laguerre-Gaussian (LG) beams with varying topological charges through a turbid multiple scattering environment.

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Recent advancements in wavefront shaping techniques have facilitated the study of complex structured light's propagation with orbital angular momentum (OAM) within various media. The introduction of spiral phase modulation to the Laguerre-Gaussian (LG) beam during its paraxial propagation is facilitated by the negative gradient of the medium's refractive index change over time, leading to a notable increase in the rate of phase twist, effectively observed as phase retardation of the OAM. This approach attains remarkable sensitivity to even the slightest variations in the medium's refractive index (∼10).

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This study introduces a novel approach in the realm of liquid biopsies, employing a 3D Mueller-matrix (MM) image reconstruction technique to analyze dehydrated blood smear polycrystalline structures. Our research centers on exploiting the unique optical anisotropy properties of blood proteins, which undergo structural alterations at the quaternary and tertiary levels in the early stages of diseases such as cancer. These alterations manifest as distinct patterns in the polycrystalline microstructure of dried blood droplets, offering a minimally invasive yet highly effective method for early disease detection.

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We utilize Laser Speckle Contrast Imaging (LSCI) for visualizing cerebral blood flow in mice during and post-cardiac arrest. Analyzing LSCI images, we noted temporal blood flow variations across the brain surface for hours postmortem. Fast Fourier Transform (FFT) analysis depicted blood flow and microcirculation decay post-death.

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Significance: Phase retardation of circularly polarized light (CPL), backscattered by biological tissue, is used extensively for quantitative evaluation of cervical intraepithelial neoplasia, presence of senile Alzheimer's plaques, and characterization of biotissues with optical anisotropy. The Stokes polarimetry and Mueller matrix approaches demonstrate high potential in definitive non-invasive cancer diagnosis and tissue characterization. The ultimate understanding of CPL interaction with tissues is essential for advancing medical diagnostics, optical imaging, therapeutic applications, and the development of optical instruments and devices.

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Significance: The study of the effect of aging on the optical properties of biological tissues, in particular polarization, is important in the development of new diagnostic approaches.

Aim: This work aims to provide a comprehensive analysis of the factors and mechanisms that contribute to the alteration of skin polarization properties caused by aging, using polarization-sensitive hyperspectral imaging measurements and Monte Carlo simulation.

Approach: Our investigation involved both experimental studies of human skin of volunteers of different ages and computational modeling that accounted for changes in the absorption and scattering properties of the skin model.

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Significance: Mueller-matrix polarimetry is a powerful method allowing for the visualization of malformations in biological tissues and quantitative evaluation of alterations associated with the progression of various diseases. This approach, in fact, is limited in observation of spatial localization and scale-selective changes in the poly-crystalline compound of tissue samples.

Aim: We aimed to improve the Mueller-matrix polarimetry approach by implementing the wavelet decomposition accompanied with the polarization-singular processing for express differential diagnosis of local changes in the poly-crystalline structure of tissue samples with various pathology.

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Plasmonic nanoparticles (NP) possess great potential in photothermal therapy and diagnostics. However, novel NP require a detailed examination for potential toxicity and peculiarities of interaction with cells. Red blood cells (RBC) are important for NP distribution and the development of hybrid RBC-NP delivery systems.

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Purpose: Terahertz (THz) medical imaging is a promising noninvasive technique for monitoring the skin's conditions, early detection of the human skin cancer, and recovery from burns and wounds. It can be applied for visualization of the healing process directly through clinical dressings and restorative ointments, minimizing the frequency of dressing changes. The THz imaging technique is cost effective, as compared to the magnetic resonance method.

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Article Synopsis
  • A study focused on creating disubstituted carboxonium derivatives of the -decaborate anion [2,6-BHOCCH] was conducted, proposing a method involving the reaction of [BH] with benzoic acid.
  • The synthesis occurs through a two-step process, starting with a mono-substituted product, but a quicker one-step method is also suggested.
  • The structure of the resulting tetrabutylammonium salts was confirmed using X-ray analysis, and the reaction mechanism was explored with DFT calculations, revealing the importance of intermediate anionic species and the regioselectivity for the 2,6-isomer.
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A multimode optical fiber supports excitation and propagation of a pure single optical mode, i.e., the field pattern that satisfies the boundary conditions and does not change along the fiber.

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Ischemic disease has severe impact on patients which makes accurate diagnosis vital for health protection. Improving the quality of prediction of patients with ischemic extremity disease by using hybrid fuzzy model allows for early and accurate prognosis of the development of the disease at various stages. The prediction of critical ischemia of lower extremity (CLI) at various disease stages is complex problem due to inter-related factors.

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A Mueller matrix imaging approach is employed to disclose the three-dimensional composition framework of optical anisotropy within cancerous biotissues. Visualized by the Mueller matrix technique spatial architecture of optical anisotropy of tissues is characterised by high-order statistical moments. Thus, quantitative analysis of the spatial distribution of optical anisotropy, such as linear and circular birefringence and dichroism, is revealed by using high-order statistical moments, enabling definitively discriminate prostate adenoma and carcinoma.

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A new series of compounds based on perbrominated disubstituted sulfonium derivatives of the -decaborate anion (-BuN)[2-BBrSR] (R = -Pr, -Pr, -Bu, -CH, -CH, -CH) was obtained, characterised by modern physicochemical methods of analysis. According to the results of an X-ray diffraction study, some of the anions and solvate molecules were disordered. The cations (-BuN) and anions [2-BBrSR] were associated via C-H…Br and H…H contacts.

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In optogenetics, as in nature, sensory photoreceptors serve to control cellular processes by light. Bacteriophytochrome (BphP) photoreceptors sense red and far-red light via a biliverdin chromophore and, in response, cycle between the spectroscopically, structurally, and functionally distinct Pr and Pfr states. BphPs commonly belong to two-component systems that control the phosphorylation of cognate response regulators and downstream gene expression through histidine kinase modules.

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Growing anthropogenic activities are significantly influencing the environment and especially aquatic ecosystems. Therefore, there is an increasing demand to develop techniques for monitoring and assessing freshwater habitat changes so that interventions can prevent irrevocable damage. We explore an approach for screening the temperature-induced stress experienced by aquatic organisms owing to environmental variations.

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Last decades the effects of localization and focusing of light in turbid randomly inhomogeneous tissue-like scattering medium have been attracting a particular attention. Weak localization of light in disordered and weakly ordered biological tissue, polarization memory effect, correlations in transmission matrices, focusing light by wavefronts shaping have been widely exploited. Here, we represent an experimentally observed and theoretically confirmed new type of spatial localization of light within biological tissues.

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Nowadays, photonics-based techniques are used extensively in various applications, including functional clinical diagnosis, progress monitoring in treatment, and provision of metrological control. In fact, in the frame of practical implementation of optical methods, such as laser Doppler flowmetry (LDF), the qualitative interpretation and quantitative assessment of the detected signal remains vital and urgently required. In the conventional LDF approach, the key measured parameters, index of microcirculation and perfusion rate, are proportional to an averaged concentration of red blood cells (RBC) and their average velocity within a diagnostic volume.

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Article Synopsis
  • The protonation of [2,6-BHOCCH] was studied theoretically and experimentally, determining optimal conditions for the reaction.
  • The process utilized trifluoromethanesulfonic acid in dichloromethane at room temperature, resulting in the complex [2,6-BHOCCH*H].
  • The structure of the complex was analyzed using NMR data and DFT calculations, revealing the location of an additional proton atom and the characteristics of the B-H bond through advanced theoretical methods.
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Photo-acoustic imaging, also known as opto-acoustic imaging, has become a widely popular modality for biomedical applications. This hybrid technique possesses the advantages of high optical contrast and high ultrasonic resolution. Due to the distinct optical absorption properties of tissue compartments and main chromophores, photo-acoustics is able to non-invasively observe structural and functional variations within biological tissues including oxygenation and deoxygenation, blood vessels and spatial melanin distribution.

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Proper rheological properties of red blood cells (RBC) including flexibility and aggregability are essential for healthy blood microcirculation. Excessive RBC aggregation has been observed to be associated with many pathological conditions and is crucial in acute circulatory problems. Low-level laser radiation (LLLR) has been found to have positive effects on the rheology of human blood, however, the detailed mechanisms of blood photobiomodulation remains unclear.

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As a result of our study on the interaction between the octahydrotriborate anion with nucleophiles (Nu = THF, PhP, PhP-(CH)-PPh (dppe), PhAs, EtN, PhNH, CHN, CHCN, PhCHCN)) in the presence of a wide range of Lewis acids (Ti(IV), Hf(IV), Zr(IV), Al, Cu(I), Zn, Mn(II), Co(II) halides and iodine), a number of substituted derivatives of the octahydrotriborate anion [BHNu] are obtained. It is found that the use of TiCl, AlCl, ZrCl, HfCl, CuCl and iodine leads to the highest product yields. In this case, it is most likely that the reaction proceeds through the formation of an intermediate [BH-HMXn], which was detected by NMR spectroscopy.

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