Structures and orientational transitions in thin films of tilted hexatic smectics

We present detailed systematic studies of structural transformations in thin liquid crystal films with the smectic-C to hexatic phase transition. For the first time all possible structures reported in the literature are observed for one material (5 O.6) at the variation of temperature and thickness. In unusual modulated structures the equilibrium period of stripes is twice with respect to the domain size. We interpret these patterns in the frame work of phenomenological Landau type theory, as equilibrium phenomena produced by a natural geometric frustration in a system having spontaneous splay distortion.Comment: 7 pages, 6 figure

Towards simplifying assessment of athletes physical fitness: Evaluation of the total physical performance by means of machine learning

The paper describes the methodology for the evaluation of the total physical performance of athletes on the basis of simultaneously recorded signals of stabilography and heart rate variability. An objective assessment of the level of physical performance was carried out using testing on the bicycle ergometer. The use of genetic programming and linear discriminant analysis allowed obtaining the set of diagnostically significant features. The set of diagnostically significant features is able to determine the level of physical fitness using only data from stabilographic studies and heart rate variability with an accuracy of at least 97%. Strength and weaknesses of the proposed approach are discussed. © 2019 by SCITEPRESS - Science and Technology Publications, Lda. All rights reserved

Development of the decision support system in treatment of arterial hypertension application of artificial neural networks for evaluation of heart rate variability signals

The article presents first step of the decision support system development in treatment of arterial hypertension. Results of arterial hypertension diagnostic task by short-term signals of heart rate variability are presented. The tilt test study was used as the functional load. The peculiarity of this work is application of neural networks for this task. The different number of hidden layers in the neural networks and different number of neurons in hidden layers were tested in this study. The classification accuracy of the neural networks was compared with those of simple machine learning classifiers. The following steps of the decision support system development are declared. Copyright © 2018 by SCITEPRESS – Science and Technology Publications, Lda. All rights reserved

History of biomechanical research at the Ilizarov Centre (to the 100th anniversary of Academician G.A. Ilizarov)

Background. Biomechanical studies of both the Ilizarov apparatus itself and the physiological system “apparatus – limb” occupy a significant place in the history of the formation and elaboration of the Ilizarov method, developed in the middle of the last century at the Kurgan Research Institute of Experimental Traumatology and Orthopaedics (nowadays – the world-famous Centre named after its creator). The analysis of the history of biomechanical research in the formation of Ilizarov method is not without interest.The aim. To analyze the history and stages of development of biomechanical research in order to substantiate the effectiveness of the Ilizarov method of transosseous osteosynthesis.Results. The national medical industry did not produce the appropriate equipment for biomechanical research in the early 1970s. That is why a group of engineers was included into the Laboratory of Clinical Physiology and Biomechanics (established in 1971) of the Ilizarov Centre, which created equipment for studying the processes in the tissues of the limbs and in the structure of the Ilizarov apparatus itself during its traction and compression impact on biological structures. The community of physicians, scientists and engineers made it possible to overcome a number of difficulties and problems. In their scientific publications and dissertations, the laboratory staff paid great attention to biomechanical research during transosseous osteosynthesis with the Ilizarov apparatus. At present, the staff of the Ilizarov Centre continues the traditions established by G.A. Ilizarov. For the first time in our country, a computer 3D video analysis of the kinematics and kinetics of orthopedic patients gait was introduced; it was supplemented with embedded software for the preparation of a clinical report of human gait biomechanics.Conclusions. The initial stage of the biomechanical research at the Ilizarov Centre included the creation of the research equipment. Subsequently, the biomechanical studies carried out by the staff of the Centre for almost half a century have shown an applied and functional result of the realization of general biological regularities of the Ilizarov’s discovery. At present, the biomechanical research continues at a higher level with the use of modern high-tech equipment

Effect of Dipolar Interaction in Molecular Crystals

We investigate in this paper the ground state and the nature of the transition from an orientational ordered phase at low temperature to the disordered state at high temperature in a molecular crystal. Our model is a Potts model which takes into account the exchange interaction $J$ between nearest-neighbor molecules and a dipolar interaction between molecular axes in three dimensions. The dipolar interaction is characterized by two parameters: its amplitude $D$ and the cutoff distance $r_c$. If the molecular axis at a lattice site has three orientations, say the $x$, $y$ or $z$ axes, then when D=0, the system is equivalent to the 3-state Potts model: the transition to the disordered phase is known to be of first order. When $D\neq 0$, the ground-state configuration is shown to be composed of two independent interpenetrating layered subsystems which form a sandwich whose periodicity depends on $D$ and $r_c$. We show by extensive Monte Carlo simulation with a histogram method that the phase transition remains of first order at relatively large values of $r_c$.Comment: 6 pages, 7 figure

Analysis of kinematic and kinetic parameters of pace in cerebral palsy patients with internal torsion hip deformity

Literature data on the correlation between femoral torsion during clinical examination and during walking are different. Aim of the study was to compare kinetics and kinematics in cerebral palsy patients with iatrogenic crouch gait pattern with and without clinically diagnosed internal femoral torsion. Material and methods. Comparative analysis of clinical examination and three-dimensional gait analysis (3DGA) was performed in 61 subjects (122 limbs), GMFCS II with iatrogenic crouch gait pattern. The average age was 14.5 ± 2.5 years. This sample was formed in 2018–2021. Kinetic and kinematic data were recorded by Qualisys 7+ optical cameras (8 cameras) with passive marker video capture technology, synchronized with six KISTLER dyno platforms (Switzerland). The analysis was performed in the QTM (Qualisys) and Visual3D (C-Motion) programs with automated calculation of values. Based on the clinical data, all the patients were divided as follows: I – no clinically detected internal femoral torsion – 50 limbs, II – clinically detected internal femoral torsion – 68 limbs. Results. Comparison of the values of kinematics and kinetics in groups of patients according to the criterion of clinically detected/not detected had statistically significant differences in kinematics – the maximum and minimum values of femur and tibia torsion relative to the norm. Differential diagnosis of compensated/decompensated internal femoral torsion was represented by multidirectional values of the angle of foot positioning relative to the motion vector. The kinetic parameters in the groups were statistically doubtful, because they depended on the walking speed of patients, their ability to move. Conclusions. The values of maximum femoral torsion angle up to 22° were not clinically interpreted as internal femoral torsion, those from 22° to 28° can be interpreted both with clinically revealed femoral torsion (68 %) and with the absence of femoral torsion (22 %), which corresponds to the risk group, those more than 28° fell into the group of clinically diagnosed internal femoral torsion

Evaluation of the effectiveness of the decision support algorithm for physicians in retinal dystrophy using machine learning methods

Electroretinography is a method of electrophysiological testing, which allows diagnosing dis-eases associated with disorders of the vascular structures of the retina. The classical analysis of the electroretinogram is based on assessing four parameters of the amplitude-time representation and often needs to be specified further using alternative diagnostic methods. This study proposes the use of an original physician decision support algorithm for diagnosing retinal dystrophy. The proposed algorithm is based on machine learning methods and uses parameters extracted from the wavelet scalogram of pediatric and adult electroretinogram signals. The study also uses a labeled database of pediatric and adult electroretinogram signals recorded using a computerized electrophysiological workstation EP-1000 (Tomey GmbH) at the IRTC Eye Microsurgery Ekaterinburg Center. The scientific novelty of this study consists in the development of special mathematical and algorithmic software for analyzing a procedure for extracting wavelet scalogram parameters of the electroretinogram signal using the cwt function of the PyWT. The basis function is a Gaussian wavelet of order 8. Also, the scientific novelty includes the development of an algorithm for analyzing electroretinogram signals that implements the classification of adult (pediatric) electro-retinogram signals 19 (20) percent more accurately than classical analysis. © 2023, Institution of Russian Academy of Sciences. All rights reserved.Ministry of Education and Science of the Russian Federation, MinobrnaukaAcknowledgements: The research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged

Ophthalmic Bioengineering. Review

This article published the materials of the round table “Bioengineering in ophthalmology” (OphthalmicBioengineering), held on May 13, 2021 as part of the international conference Ural Symposium on Biomedical Engineering, Radioelectronics and Information Technology (USBEREIT). USBEREIT is held under the auspices of the IEEE Engineering in Medicine and Biology Society. The article presents reports on: metrological aspects of registration of tonometric and electrophysiological signals in ophthalmic diagnostics; approaches to modeling the processes of pulse blood filling of the eye with the determination of hemodynamic parameters; retinotoxicity based on electrophysiological signals; analysis of electrophysiological signals in the frequency-time domain and its application in clinical practice; extraction and analysis of specialized data obtained from the electrophysiological medical device; as well as diagnosing retinal diseases based on optical coherence tomography using machine learning. © 2023 Ophthalmology Publishing Group. All rights reserved