Russian Journal of Biomechanics

22 мая 2022 г. на 87 году ушел из жизни Ю.И. Няшин - известный в России и за её пределами ученый, организатор науки и педагог, заслуженный деятель науки РФ, доктор технических наук, профессор, почетный профессор Института механики металлополимерных систем им. В.А. Белого НАН Белоруссии в Гомеле (Беларусь), почетный профессор университетов в Пизе и Падуе (Италия), академик РАЕН. Он 45 лет руководил кафедрой теоретической механики в Пермском государственном техническом университете. Юрий Иванович - признанный крупный ученый в области биомеханики, механики деформируемого твердого тела, математического моделирования и оптимизации технологических процессов. Им создана Пермская научная школа по биомеханике, которая известна в России и за рубежом. С 1997 года является создателем и главным редактором единственного в России международного научного журнала «Российский журнал биомеханики». Он неоднократно выступал на международных конференциях по механике и биомеханике в различных странах мира (США, Германия, Австрия, Италия, Франция, Дания, Болгария, Польша, Украина, Беларусь, Грузия, Япония, Китай и др.). Под его руководством защищены более 40 кандидатских диссертаций и 9 докторских диссертаций.

Heart failure remains one of the leading causes of death especially among people over the age of 60 years worldwide. To develop effective therapy and suitable replacement materials for the heart muscle it is necessary to understand its biomechanical behaviour under load. This paper investigates the passive mechanical response of the sheep myocardia excised from three different regions of the heart. Due to the relatively higher cost and huge ethical demands in acquisition and testing of real animal heart models, this paper evaluates the fitting performances of six different constitutive models on the myocardial tissue responses. Ten sheep were sacrificed, and their hearts were excised and transported within 3 hours to the testing biomechanical laboratory. The upper sections of the hearts above the short axes were carefully dissected out. Tissues were dissected from the mid-sections of the left ventricle, mid-wall and right ventricle for each heart. The epicardia and endocardia were then carefully sliced off each tissue to leave the myocardia. Stress-strain curves were calculated, filtered and resampled. The results show that Choi-Vito model was found to provide the best fit to the left ventricle, the polynomial (anisotropic) model to right ventricle, the Four-Fiber Family model to right ventricle, Holzapfel (2000) to right ventricle, Holzapfel (2005) to right ventricle and the Fung model to left ventricle.

On the basis of a course of functional electrical stimulation (FES) in 9 patients with multiple sclerosis (MS), the authors revealed peculiarities of the method of artificial correction of movements in this cohort of patients. The authors found that the main features of the FES method, characteristic of other diseases, also remain in patients with MS. However, these patients have specific requirements for the method application, connected with their increased fatigability. Authors suppose, that the following peculiarities may be assumed as the specific ones: short duration of the session (no more than 20 minutes), small number of sessions (8-9), modest quantity of the correctional influences (no more than 4 muscles), low intensity of contraction; session termination with the appearance of minimal fatigue; necessity of complete rest for 1.5 hours before and after the session of FES. Following 76 sessions of FES in 9 patients with MS, the authors revealed the main correctional influences, necessary for this cohort of patients, peculiarities of the temporal and amplitude programs of FES, advantages of multichannel FES over the traditional single-channel FES, usually applied in patients with MS. The example of a certain patient helped the authors to find out, that as long as these conditions can be ensured, considerable improvement of the biomechanical structure of walking is observed in this patient only after 6-7 sessions of FES. This is revealed in a remarkable increase of the mean walking velocity, cadence and double step length, in the growth of stability, the diminution of the temporal, kinematic and dynamic asymmetry, in a decrease of recurvation at the knee joint, in an increase of flexion angle at the knee and hip joints, in the appearance of a new element in the curve of knee angle - flexion at the knee joint in the stance phase, in a remarkable strengthening of heel-strike and push-off of the vertical component Rz of the ground reaction force.

Modern photopolymer filling (restorative) materials are important tools for practicing dental clinicians when treatment cannot be limited to non-invasive or minimally invasive dentistry methods. In this work, using X-ray computed microtomography (micro-CT), an ex vivo non-destructive study of the density of fillings from glass ionomer cement and composite resin on human teeth was carried out. Using the technique of segmenting regions of interest on tooth microtomograms before and after dental intervention, the advantages of a composite material over glass ionomer cement were revealed, and the microstructure features of each material were studied. The density of the composite filling turned out to be closer to natural enamel compared to the density of the glass ionomer cement filling, it also contains a smaller number of artifacts, and the artifacts themselves are smaller in size. A separation of a filling from a composite resin into an outer and an inner layer was found during dental intervention. On the surface of a filling made of glass ionomer cement, several regions of integrity violations in the form of large cavities were found. After the preparation of longitudinal sections of tooth samples, a study of the microgeometrical characteristics of fillings was carried out using atomic force microscopy (AFM). Analysis of the results showed the closeness of both the average roughness values and the maximum roughness height for a composite filling to those for natural sound enamel.

It is crucial to conduct research on clinical parameters of different body systems in gastric cancer as it is one of the most serious diseases in the modern world. The aim of our work was to study the rheological properties of blood in gastric cancer, along with the electrophysical properties of blood and iron metabolism in patients with gastric cancer. The research methods were modern and innovative. The study included patients with stomach cancer and a control group of healthy volunteers. The average age in the studied groups was similar. In all cases participants’ informed consent was obtained. In patients with gastric cancer before surgery the iron and hemoglobin levels were low, transferrin and ferritin remained within normal limits. On the 7th day after the operation, ferritin increased twice, hemoglobin was close to control values. Transferrin and iron remained reduced on the 7th postoperative day. The erythrocyte aggregability index in patients with gastric cancer before surgery was 1.5 times higher compared to the control group. On the 7th day after the operation, the erythrocyte aggregability index improved and increased by only 30 % compared to the control. The index of electrophysical properties in gastric cancer before surgery was changed compared to control values, on the 7th day after surgery, it was also changed. This approach, along with a thorough study of these routine analyzes in gastric cancer, is very important. It turned out that the seven-day postoperative interval was insufficient to normalize the studied parameters. The analysis of such data will make it possible to personalize the therapy of patients with stomach cancer, which is very important for each patient and public health in general.