The results showed that compared with the expert archers, the elite archers had stronger functional coupling in beta1 and beta2 bands, and the difference was evident in the frontal and central regions; in terms of global characteristics of brain network topology, the average clustering coefficient and global efficiency of elite archers were significantly higher than that of expert archers, and the eigenvector centrality of expert archers was higher; for local characteristics, elite archers had higher local efficient; and the brain network characteristics of expert archers showed a strong correlation with archery performance. This suggests that compared with expert archers, elite archers showed stronger functional coupling, higher integration efficiency of global and local information, and more independent performance in the archery process. These findings reveal the differences in brain electrical network topologies between elite and expert archers in the archery preparation stage, which is expected to provide theoretical reference for further training and promotion of professional athletes.It is not only difficult to be a sports expert but also difficult to grow from a sports expert to a sports elite. Professional athletes are often concerned about the differences between an expert and an elite and how to eventually become an elite athlete. To explore the differences in brain neural mechanism between experts and elites in the process of motor behavior and reveal the internal connection between motor performance and brain activity, we collected and analyzed the electroencephalography (EEG) findings of 14 national archers and 14 provincial archers during aiming and resting states and constructed the EEG brain network of the two archer groups based on weighted phase lag index; the graph theory was used to analyze and compare the network characteristics  PreviouIn the history of sports science, exploring the physiological differences among athletes at different competitive levels has always been a topic of interest . From thPrevious research on the EEG neural mechanism of athletes with different skill levels in fine motion mainly focused on comparing experts and novices. However, few studies have discussed the differences in the brain function of professional athletes from the perspective of comparing experts and elites. Archery is characterized by fine motion and a set of action sequences such as holding the bow and drawing, anchoring, loading, aiming, sustaining release, and follow-through of the arrow . PerfectTo further examine the neural mechanism of archers with different competitive levels during aiming, this experiment adopted the most popular brain network analysis to reveal the differences in functional connections and network characteristics between elite and expert athletes using a data-driven method. We collected EEG findings of 14 national archery athletes (elite group) and 14 provincial archery athletes (expert group) during the targeting stage. Using weighted phase lag index (WPLI) algorithm to evaluate the function of the EEG findings in different band connectivity, this phase-based method reduces the volume conduction effect to a certain extent and prevents the mixing of phase and amplitude factors . Unlike p > 0.05, sex: p > 0.05).This study included a total of 31 experimental subjects who were categorized into elite and expert groups. The elite group comprised 16 archers from the Chinese national archery team , and their average training age was 8.1 years. The expert group comprised 15 archers from the Beijing archery team , and their average training age was 6.1 years. We employed the one-way ANOVA to examine the age and sex differences between the groups and found no significant difference between the two archer groups in terms of age and sex , which is portable and meets the mobility requirements of this experiment. Electrode placement was in accordance with the international 10–20 system, comprising 30 electrodes. The electrode positions were Fp1, Fpz, Fp2, F7, F3, Fz, F4, F8, FC5, FC1, FC2, FC6, T7, C3, Cz, C4, T8, CP5, CP1, CP2, CP6, P7, P3, Pz, P4, P8, POz, O1, Oz, and O2, with a ground electrode placed at the forehead and the reference electrodes placed at the left and right mastoid. Detailed electrode placement is presented in In the experiment, all subjects completed the EEG signal acquisition of the same task. As shown in The collected EEG signals were transmitted to a computer for offline processing, as shown in To reduce individual differences among the subjects, we used the individual alpha frequency (IAF) method for determining the frequency division of different subjects. IAF refers to the frequency band between 8 and 13 Hz . First, The data analysis process is summarized in In this study, we used the WPLI method to calculate the functional coupling between EEG signals. WPLI method is an algorithm to measure the degree of connection by calculating the phase synchronization relationship between signals . CompareBefore WPLI calculation, to obtain the same phase and amplitude of EEG signals of the two archer groups, first, according to the divided frequency band obtained by IAF, FIR bandpass filters of theta, alpha1, alpha2, beta1, and beta2 bands were constructed to perform bandpass filtering on the EEG signals of all subjects in the two groups. Next, the Hilbert transform was applied to the filtered narrowband signals to obtain the two groups of analytical signals of each subject in a specific frequency band. Finally, 10% of the data at both ends of the analytic signals were removed. Based on the results obtained, the WPLI value between the two groups of EEG signals and the two groups of different channels was calculated using the following formula :xy(t) represents the cross-spectrum of EEG signals x(t) and y(t), ℑ(•) represents the imaginary part, and (•) represents the average value for a given period of time. The value of WPLI ranges from 0 to 1. The higher the value of WPLI, the higher the coupling degree of oscillatory neural activity.The SAfter preprocessing, the EEG data format of each group was 30 × 1,000 × 30 × 14, representing 30 channels, 1,000 data sampling points, 30 trials, and 14 subjects in each group. Next, the WPLI between all possible EEG channels was calculated, and 30 × 30 matrices of the coupling values of the subjects were obtained in each time window and frequency band. Therefore, the data format of each group of functional coupling matrix was 30 × 30 × 5 × 3 × 14, representing 30 × 30 WPLI connection matrix, 5 analyzed frequency bands, three-time windows, and 14 subjects. In addition, to study the connection values of each channel, we obtained the average connection strength of different channels obtained by averaging the row/column direction of the two groups of WPLI coupling matrices .To study the changes in the neural mechanism of professional archers before firing, the concept of event-related functional coupling change rate based on WPLI (ErWPLI) was used to describe the changes in functional coupling strength of the two archer groups. The calculation formula is as follows:WPLI is the functional coupling strength based on WPLI in a certain time band and R(f) represents the functional coupling strength of each frequency band at the baseline. In this article, the average WPLI connection strength of the two archer groups in −4 to −3 s before the shooting was considered the baseline, and the change rate of the functional coupling strength of the two archer groups in different frequency bands in three-time windows was calculated. The above-described calculation was performed using the MATLAB R2014a platform.Where In this experiment, the brain network research method based on graph theory was used to analyze the topological characteristics of the brain network of the WPLI connection matrix of the elite and expert groups. The analysis procedure is to transform the functional connection matrix obtained by the WPLI into the adjacency weight matrix, and then using the method of graph theory, different regions of the brain are regarded as nodes, and the connections are regarded as edges, so as to extract all kinds of topological characteristics of the brain networks of each subject in each group at each analysis frequency band .The experiment does not set the threshold, and the coupling values between all nodes are retained to form the functional weight brain network. The subsequent brain network topology analysis is also carried out on the basis of the brain network.In the experiment, the topological characteristics of global and local brain networks are used to analyze. Among the global topological characteristics, we selected the average clustering coefficient, characteristic path length, and analysis efficiency for analysis. The ratio of the clustering coefficient for the characteristic path length represents the small-world characteristic of the network. For local topological characteristics, the eigenvector centrality, average shortest path length, and local efficiency were selected. Please refer to p < 0.05) and not all results in the functional coupling change rate exhibit normal distribution. Because not all characteristics follow a normal distribution, we uniformly adopted the nonparametric test to analyze the samples. Then, the Wilcoxon signed-rank test, one of the nonparametric tests, was used to test whether the differences between the two sets of corresponding values were significant  to evaluate the EEG characteristics of the two groups, and it was found that all characteristics except the functional coupling change rate do not follow a normal distribution (nificant . We set p < 0.05). Therefore, Spearman rank correlation analysis was selected for correlation analysis, and the correlation coefficient (r) was calculated. Similarly, we also used FDR to correct the p-values in results obtained by the Spearman rank test. The statistical analysis part was also performed using the statistical test toolbox of the MATLAB R2014a platform, American MathWorks company.In addition, in this study, we assumed that the functional coupling strength, change rate, and network topology characteristics of the two archer groups are closely correlated with the average performance of 30 shots. To test this hypothesis, a cross-subject statistical test was used to analyze the correlation between EEG characteristics and archery performance of each subject. The K–S test was conducted on the average score of each archery athlete in the two groups after 30 shots, and it was found that the average score did not follow a normal distribution (p < 0.05); further, Wilcoxon signed-rank test found no significant difference in IAF between the two groups (p > 0.05). According to the archery performance indicators, as shown in p > 0.05), and the Wilcoxon signed-rank test result of p < 0.01 was used, which indicated that the average score of the elite group was significantly higher than that of the expert group.Before examining the functional coupling and topological characteristics of EEG, we first studied the differences in archery behavior indicators with respect to IAF between the two archer groups. We conducted the K–S test on the IAF of each subject in the two groups and found that IAF did not follow a normal distribution  and three windows (Win1 to Win3) was analyzed in the elite and expert groups. The most suitable frequency band and time window were determined by comparing the significant differences in connection strength between the two groups. As shown in p < 0.05); the thickness of the connection between nodes indicates the degree of significance; the higher the degree of significance, the thicker the connection line, and vice versa. Below the figure is the relationship between the thickness of the connection and the p-value of significance. No connection between nodes indicates no significant difference between the two archer groups’ connections. Furthermore, red indicates that the connection of elite archers is stronger than that of expert archers, and blue indicates the opposite. However, as per the statistical results, no blue connection appears in the figure. The results showed that the elite group has higher connection strength in beta1 and beta2 bands than the expert group. In the beta1 band, the difference in functional coupling among nodes Fp1–CP5, Fp2–C4, CP2–C4, C3–O1, and Cz–P7 was the most significant. Beta2 band showed more significantly different connections (p < 0.01), which were mainly concentrated in the prefrontal, central, left temporal, and frontal regions, and the most significant differences are found in nodes (p < 0.01), such as nodes Fpz, Fp1, Fp2, Fz, F3, FC1, FC2, FC5, T7, Cz, CP5, CP6, and Pz.As shown in p < 0.05), left central , left parietal (P8: p < 0.05), right central (C4: p < 0.05), and the right temporal regions. In contrast, in the beta2 band, the differences in average connection strength were mainly concentrated in the prefrontal (Fpz and Fp2: p < 0.05), left frontal (F3: p < 0.05), left central (CP1 and CP5: p < 0.05), and left temporal regions.p < 0.05), left frontal (F3: p < 0.05), central frontal (Fz: p < 0.05), central (Cz: p < 0.05), left central , right central , central parietal (Pz: p < 0.05), left parietal (P7: p < 0.05), parieto-occipital (POz: p < 0.05), and left occipital (O1: p < 0.05) regions.By determining the locations of the brain regions with significant differences in different average frequency bands between the two archer groups, we could further analyze the differences in functional coupling characteristics as a whole. p < 0.01). In contrast, the difference in the beta2 band was statistically significant in the prefrontal (Fpz: p < 0.05), left and right frontal (F7 and F8: p < 0.05), central, central parietal, and left parietal (P7: p < 0.05) regions.SD of the global topological characteristics of the brain network in the beta1 and beta2 bands in the Win3 window of the elite and expert groups, and the results of the different tests of the two groups of global topologies. As shown in the figure, in the analyzed frequency bands, the average clustering coefficient and global efficiency of the elite and expert groups showed that the eigenvalue of the beta1 frequency band was greater than that of the beta2 frequency band, and the eigenvalue of the elite group was greater than that of the expert group. In contrast, the characteristic path length shows the opposite result. Thus, the global topological characteristics of the two groups showed significant differences in each analyzed frequency band.p < 0.05), right central , right temporal, left parietal, and left occipital regions; further, a significant difference in beta2 frequency band in the right central region (CP2 and CP6: p < 0.05) and left parietal (P7: p < 0.05) regions was noted. According to the different results in the average beta frequency band, the local efficiency of the two groups was significant (p < 0.05) in most regions of the whole brain except F7, FC2, P8, and O2 nodes. Among them, the nodes F3, FC1, C3, CP1, CP5, CP2, and P7 all showed the most significant differences (p < 0.01).In the difference test of local topological characteristics, we only found a significant difference in local efficiency, with no significant difference in eigenvector centrality and average shortest path length. Therefore, in this article, the results of these two parameters are not demonstrated in any figure. As shown in p < 0.05) in the left central, left parietal, and left temporal regions of the beta1 band and the prefrontal, central, and right temporal regions of the beta2 band. Connections of F3-P4, FC5-Oz, and Cz-CP6 in the beta1 band showed a significant positive correlation in the elite group (p < 0.01), with the connections between prefrontal and occipital regions (Fpz-O1 and Fp1-OZ) in the beta2 band showing the most significant correlation (p < 0.01).p < 0.05), and the changes in the WPLI coupling of the expert group were more closely correlated to archery performance. The changes in WPLI coupling of the elite group in the beta1 band and those of the expert group in the beta2 band showed extremely less correlation with archery performance as the shooting time approaches.According to the results of the correlation test between the topological characteristics of brain network and archery performance of the two archer groups in the Win3 window, we only found a significant correlation with archery performance in the local topological characteristics of the eigenvector centrality and average shortest path length. In contrast, none of the global topological characteristics showed a significant correlation with archery performance.As shown in The main aim of this study was to explore the changes in neural activity in cortical areas involved in archery preparation with different skill levels, as well as the physiological implications of these differences in highly trained athletes. Therefore, we performed a detailed analysis and comparison of the brain network characteristics of the two archer groups in accordance with the specific physiological features of different frequency bands and brain regions in the following paragraph.First, the EEG frequency band and time window most suitable for analyzing archery preparation were determined. Previous studies on the optimal timing for analysis during firing have suggested that EEG characteristics become more prominent as the shooting time approaches . By compThe characteristics of brain networks in different frequency bands reflect different physiological aspects of the brain. Previous studies have suggested that theta rhythm usually occurs during sleepiness and negative emotions ; alpha1 Functional coupling characteristics reflect the level of consciousness, the ability of the brain to integrate information, and the development of cognitive functions by studying the information interaction between two different cortical regions. By comparing the average WPLI connection strength of the two archer groups in the three-time windows of According to the analysis of connection differences in the frequency band, the electrodes with the most significant connection differences in the beta1 band were mainly distributed in the prefrontal, the left and right central, the left parietal, and the right temporal regions. Conversely, the differences in the beta2 band are concentrated in the prefrontal, left frontal, and left temporal regions. By comparing the functions of each brain area and the corresponding physiological features of the beta1 and beta2 bands, we believe that the experimental results are likely to reflect that the two archer groups have good spatial awareness, and elite archers were better at target recognition and concentration when aiming. Furthermore, the differences were speculated to be related to the psychological state of the archers in the experiment. Although several studies have revealed the physiological features corresponding to different brain regions from the perspective of power changes, the functional connectivity among different brain regions in EEG cannot be equal to power changes, i.e., it cannot represent the synchronous activity of numerous neurons in the brain region but only indicates the phase-locking relationship among neural activities of different brain regions . TherefoExcellent psychological quality is the prerequisite for archers to achieve excellent archery performance. Increased energy in the beta band leads to brain arousal, which promotes the brain’s processing of motor information . The resIn terms of the coupling change rate of functional connection, by analyzing the connection and node differences in the connection strength of the two groups compared with the baseline, we found that the ErWPLI of the elite group was higher in the Win3 window and the difference in functional coupling changes in the beta1 band was the most significant in the central and right temporal regions. Conversely, significant differences in the beta2 band are found in the prefrontal, left and right frontal, central, central parietal, and left parietal regions. It is commonly believed that beta1 rhythm plays a role in integrating sensorimotor information  and is aTo better understand the operation process of the brain network and analyze network complexity from the perspective of functional integration, we adopted the graph theory method to analyze WPLI-based brain network differences between the elite and expert groups. In graph theory, characteristic path length and average clustering coefficient are two measures to indicate functional integration and separation of the functional brain network, respectively . Global According to the results of the analysis of local characteristics of the brain network, there were significant differences in more nodes of the frequency band of which local efficiency was analyzed between the two archer groups, and the characteristic values of elite archers were stronger than those of expert archers. Local efficiency measures the degree of local information clustering and information exchange efficiency, indicating that the local neural connection of elite archers was more intensive and efficient than that of expert archers. Regarding the aiming stage of archery, In this experiment, we found that the difference in the local efficiency of the left brain was more obvious, with more nodes with extremely significant differences. For this result, we believe that it might be due to the right brain being more closely correlated with shooting performance . The resTo sum up, the process of archery aiming was fine activity coordinated by multiple types of brain networks. Compared with top archers, even highly skilled archers with the same long-term training also had a large number of significant differences, and a top striker global and local information processing ability of the brain is stronger. However, it should be emphasized that the results of this experiment in the average shortest path length and the eigenvector centrality only indicate that the differences in these characteristics between the two archer groups are insignificant, rather than being unimportant to the archery process. They are the commonalities in the brain activities of the two archer groups, and they are jointly involved in the neural activities related to archery tasks.Based on a study of the differences in EEG characteristics of professional archers, the correlation between the two archer groups and their archery performance was further analyzed. The neural adaptivity hypothesis indicates that high-level athletes had better adaptability and could complete good skill execution under different conditions, but the correlation between brain neural activity and performance was not high . MoreoveAccording to the correlation between the ErWPLI and archery performance, the neural activity of the elite archers in the beta1 band and the expert archers in the beta2 band showed less and less correlation with the advent of the shooting moment. This can also be explained by the neural adaptivity hypothesis, which indicates that both groups of subjects have strong brain regulation ability and mental state before shooting. In addition, from the point of view of the number of relevant connections in In the study of the topological characteristics of the brain network of the two archer groups, only the correlation between the eigenvector centrality and average shortest path length was statistically significant. Because there was no significant difference in these topological characteristics in the experimental results, it is suggested that these significantly correlated brain regions jointly play an essential role when professional archers aim to shoot. The eigenvector centrality reflects the importance of nodes , which iThis was a data-driven study, and the experiment did not preset regions of interest; therefore, this study has a certain scientific and comprehensive value. While exploring the differences, we also found the commonalities and proved the experimental results from physiological and psychological perspectives. Although the analysis has allowed us to understand the differences between elite and expert archers and the characteristics of archery-correlated brain networks, there are still some limitations in this study. First, owing to the limited number of top athletes, although the experiment included a considerable number of subjects, the data of these subjects are still less. This may result in the lack of independence of research objects, making it difficult for us to explain the characteristic values and their differences and draw limited conclusions. For example, in this experiment, no scientific and reasonable explanation has been obtained for the simultaneous occurrence of a significant positive and negative correlation in the functional coupling and the coupling change rate correlated with archery performance. Second, in the part of analysis and discussion, various conclusions of shooting research are cited, which may lead to inaccurate analysis and argument. To investigate the underlying reason, although the process of shooting and archery is similar, the relationship between brain activity and archery behavior process is extremely complex. The shooting process is different from archery; it can employ lying, kneeling, and standing postures, and the subjects in the shooting experiment are mostly experts and novices; the skill of shooters in the expert group did not reach the level of the top athletes in this study. Therefore, we cannot simply extend the physiological significance of rifle shooting to the related areas of brain activity during archery. Finally, although the functional coupling method of WPLI was employed in this study to address the common source problem to some extent, the obtained brain network matrix is not directional; therefore, the method cannot measure the causal relationship between the EEG signals of two brain regions (or electrodes). The next step would be to explore the development direction of EEG characteristics used by athletes at different levels in task-specific states using an effective connection to describe the causal relationship between events to establish a weighted brain network.From the perspective of functional brain networks, this study analyzed and compared brain network characteristics between 14 elite and 14 expert archers in the archery preparation stage and the correlation with archery performance. The results showed significant differences between the two groups in beta1 and beta2 bands within the Win3 window. The functional coupling, as well as local and overall information integration efficiency of elite archers, was stronger than that of expert archers in this band; however, it has less correlation with archery performance. This study showed that the information interaction between the specific functional cortex of elite archers was closer, which can more efficiently improve the level of brain arousal and cognitive processing, and speculated that these characteristics make the brain more neurologically adaptable to focus on the control of movement details. These results verify the hypothesis, which can provide a new physiological basis for professional athletes to further improve their skills, as well as a valuable reference for future exploration of neural activities in fine sports related to archery.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.The studies involving human participants were reviewed and approved by the Ethics Committee of the Capital Institute of Physical Education. The patients/participants provided their written informed consent to participate in this study.FG and AG collected the experimental data and wrote the original manuscript. YQ analyzed the experiments results. AB and JW designed the experiments and revised the manuscript. CJ and YF provided an important advice and help on key content of the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.


A complex of structure-sensitive methods of morphology analysis was applied to study film materials obtained from blends of poly(3-hydroxybutyrate) (PHB) and chitosan (CHT) by pouring from a solution, and nonwoven fibrous materials obtained by the method of electrospinning (ES). It was found that with the addition of CHT to PHB, a heterophase system with a nonequilibrium stressed structure at the interface was formed. This system, if undergone accelerated oxidation and hydrolysis, contributed to the intensification of the growth of microorganisms. On the other hand, the antimicrobial properties of CHT led to inhibition of the biodegradation process. Nonwoven nanofiber materials, since having a large specific surface area of contact with an aggressive agent, demonstrated an increased ability to be thermo-oxidative and for biological degradation in comparison with film materials. Nowadays, much attention in world science is devoted to the creation of a new class of functional biodegradable highly porous materials based on ultrathin and nanoscale fibrous fibrillar structures with a wide variety of specific characteristics: physical, mechanical, sorption, and diffusion properties ,2,3. SucWith the employment of traditional technologies, such as extrusion of polymer melts and solutions, spinneret drawing, etc., technological difficulties arise in obtaining fibers with a diameter of less than 1 µm . Namely Earlier, on the example of PHB and a number of its compositions with other polymers ,12,13, tFor the effective regulation of operational properties, combined (composite or mixed) materials based on PHB and other biopolymers, various organic and inorganic dispersed and fibrous fillers are currently available. Such composites, due to their heterophase and high heterogeneity, create, for example, a multiform dynamic of transport of low-molecular substances, due to the cooperation of the processes of structure formation  and the kinetics of biodegradation of one of the components ,18.The most promising system from this view is a blend of PHB and CHT . As was The structural organization and resistance to aggressive media of ultra-fibrous materials based on PHB and ultra-low concentrations of CHT (0.05–0.3 wt%) have been already analyzed . The effHence, we would like to study in detail the structural organization and processes of thermo-oxidative and biodegradation of composite film and nonwoven fiber materials based on PHB with a high (40–70 wt%) content of CHT.ν) of 4.6 × 105 g·mol−1, with a degree of crystallinity around 59%, and CHT in the form of a fine powder with an average particle size of 1 ÷ 5 µm  with the Mν of 4.4 × 105 g·mol–1 and the degree of deacetylation of 82.3% were employed.PHB (16F series) was obtained by microbiological synthesis by Biomer  with a viscosity-average molecular mass . The calculation of the compatibility of these solvents with PHB was carried out on the basis of a comparison of the solubility parameters by three different methods . The average solubility parameter for PHB was 9.23, for chloroform 10.2, for DMF 12.5. Based on the data obtained, the solvent chloroform was selected as the most suitable in terms of solubility and toxicity.−1 [To obtain the fibers, forming solutions of PHB in chloroform were prepared. The concentration of PHB in the solution was 7 wt%. The content of CHT in the forming solution was 40, 50, and 60 wt%, relative to the mass of PHB. Forming solutions of PHB with CHT were prepared at a temperature of 60 °C using an automatic high-speed agitator and an ultrasonic bath. The fibers were obtained by ES using a single-capillary laboratory setup with a capillary diameter of 0.1 mm, voltage of 12 kV, distance between the electrodes of 18 cm, and electrical conductivity of 10 µScm−1 .7 Pa. The resulting film was crushed and dissolved in chloroform. CHT powder was added to the solution with vigorous stirring using a high-speed mechanical stirrer at 1000 rpm, Disperser IKA T18 digital ULTRA TURRAX , until a homogeneous suspension was obtained. Then, the suspension was subjected to exposure by simultaneous action of stirring at 500 rpm, 50 °C, 40 kHz for 30 min on an overhead stirrer LABTEH OS-20LT  in ultrasonic bath Vilitek VBS-10DS . The resulting suspension was poured into Petri dishes, covered with a lid, and conditioned at room temperature until the films were completely dry.In a comparison, samples of PHB/CHT were prepared in the form of films in several steps. First, PHB film was compressed from granules on the glass surface at a temperature of (180 ± 5) °C and a pressure of 10The morphology of fibrous materials was studied by scanning electron microscopy (SEM) on Hitachi TM-1000 scanning electron microscope . Changes in the microstructure of the samples before, during, and after the biological degradation was recorded with an Axio Imager Z2m optical microscope  in transmitted (TL) and reflected (RL) light at magnifications of 50, 200, and 500×.The study of thermophysical characteristics  was carried out with a differential scanning calorimeter (DSC) DSC 214 Polyma  according to ISO 11357-3:2018. The heating of the samples was carried out in the temperature range of 25–180 °C at a scanning speed of 10 °C/min. The weight of the sample was 10 ± 0.1 mg. The temperature scale and enthalpy of melting were calibrated against an indium standard sample.−1. The analysis was carried out by attenuated total reflection (ATR) using a diamond crystal.The analysis of the chemical composition was carried out according to the manufacturer’s recommendation on the Bruker Lumos IR Fourier microscope  at the temperature of (24 ± 2) °C in the range of wave numbers 400–4000 cm2 (Sturm method) according to ISO 14855-1:2012. To obtain an inoculum, compost was prepared according to Russian Standard GOST 9.060-75: equal proportions of sand, garden soil, and horse manure were mixed and conditioned for 60 days. Then, 860 g of prepared compost was mixed with 2 L of double-distilled water and filtered through a sieve with a mesh size of 0.5 mm. Subsequently, to purify the inoculum, the liquid part was subjected to separation in a laboratory centrifuge Hettich EBA 200  for 5 min at 1500 rpm, after which the liquid fraction was taken. Thereafter, the resulting suspension was passed through filter paper three times. The resulting soil concentrate was diluted with double distilled water to a volume of 9 L. The volume of round-bottomed test flasks was 500 mL. Six test flasks with inoculum without samples were bubbled with CO2-free air for 72 h before the start of the biodegradation experiment. The viability of bacteria in the soil concentrate (inoculum) was analyzed using a Polar 3 ToupCam 5.1 MP optical microscope  at 400 × magnification. In the process of biodegradation of materials by the microbiota of the inoculum, carbon dioxide was released. A 0.0125 M Ba (OH)2 solution was used as an absorbent. The amount of evolved carbon dioxide was estimated by titration with 0.05 M HCl solution and was calculated by the formula: CO2 (mg) = 1.1 × V(HCl), where V(HCl) is the amount of hydrochloric acid used for titration (ml). For alkalimetric testing, a set for automatic titration Titrion  was used. With a known initial content of total organic carbon in the samples, the biodegradation index was calculated. The analysis of the accumulation of carbon dioxide was carried out with an interval of 2–4 days. The biodegradation test was carried out for 60 days, the number of test flasks was 6: flasks 1, 2, 3, and 4 containing samples of the test materials and 500 mL of inoculum, as well as flasks 4 and 5 containing only inoculum (zero control).The study of biological degradation was carried out under the action of soil microorganisms for the release of COThe kinetics of oxidation of the samples was investigated by determining the amount of absorbed oxygen by the manometric method using a special manometric device . The anaw/w)%).At the first stage of our work, we studied the features of the morphology and kinetics of biodegradation of fibrous and film materials based on PHB/CHT blends. All film and fibrous samples in each group, regardless of the PHB/CHT ratio, showed approximately the same patterns of morphology formation. Therefore, to consider the comparative kinetics of biodegradation, we selected two samples of film and fibrous materials without CHT and with a CHT weight % of 40–50  means PHB/CHT  and PHB/CHT (film) (50/50) have similar absorption peaks in the entire wavelength range corresponding to pure PHB. For example, in the near-surface layers of the composite material with the equal content of components, PHB is predominantly located.−1. In this case, the intensity of the absorption peak with a maximum at 1720 cm−1, characteristic of PHB and corresponding to stretching vibrations of carbonyl groups (C=O), significantly decreased [After 60 days of biodegradation in the soil inoculum, changes in the chemical composition were observed both in materials based on pure PHB and in composites based on PHB and CHT. Moreover, composite nonwoven materials were characterized by greater changes than film samples. When comparing the IR spectra of PHB (film) of the original and subjected to biodegradation, a significant increase in absorption bands was found in the regions of 3100–3600, 1580–1700, 1490–1580, and 950–1150 cmecreased .–1 indicates the accumulation of hydroxyl groups (–OH) and amide groups (–NH2) in the near-surface layers of the material [–1 correspond to bending vibrations of amide groups (–NH2) in primary amides [−1. This band corresponds to vibrations of C-O-C bonds and is characteristic of carbohydrates [The appearance of a diffuse absorption peak in the region of 3100–3600 cmy amides . There whydrates .Changes in the microstructure of the samples were examined by optical microscopy. The original PHB sample (nonwoven) c is charThe original film sample of PHB/CHT (50/50) e differsThe original nonwoven sample PHB/CHT (60/40) g is charUnder real conditions of biodegradation of products, the processes of hydrolysis and oxidation proceed simultaneously. In our experiment with the Sturm method, the samples were incubated in an aqueous inoculum, which led to the predominant contact of materials with water and a relatively small amount of oxygen dissolved in water. In this case, the processes of hydrolytic degradation of polymers predominantly took place. Therefore, in the second part of our study, we will separately consider the processes of oxidative degradation of PHB/CHT samples. For acceleration, the oxidation process was carried out at 140 °C in an oxygen atmosphere. This is the maximum possible temperature at which no noticeable changes in the chemical composition and supramolecular structure occurred in the samples.The kinetic curves of oxidation of mixed fibers containing 40–50 wt% of CHT are intermediate between pure PHB and CHT, but are relatively close to the kinetic curve of the latter. It should be noted that CHT is oxidized better than PHB. This is due to the better oxygen permeability. Such closeness of the oxidation curves of blends to CHT is explained by the fact that, in the range of CHT content of 40–50 wt%, phase inversion occurs in the mixed fibers and both components form a continuous network. It should also be noted that the analysis of the IR spectra (ATR) of blended fibers with a CHT content of 40–50 wt%, presented above, exhibited the presence of only the PHB phase in the surface layers. It is known that crystallization does not occur in the surface layers of films and fibers ,39. In tWith an increase in the content of CHT in blends to 60–70 wt%, the structure of the fibers changes. The PHB phase becomes dispersed and acts as a binder for CHT particles during the formation of a nonwoven fibrous material. The kinetic curves of oxidation of these materials are significantly higher than of PHB and CHT themselves.When heated, pure CHT is characterized by an endothermic peak at 50–100 °C, which is related to the process of moisture evaporation. In this case, CHT is thermostable up to 250 °C . TherefoFrom the data presented in At the same time, it should be noted that the change in the melting temperatures of the PHB phase in the mixed fibers changes insignificantly (3–4 °C), which indicates the invariability of the average crystallite size. According to The interaction of PHB and CHT is contingent on forming hydrogen bonds. According to the available published data, the interaction of PHB and CT was proved through the formation of hydrogen bonds between the ester groups of PHB and the mobile protons of the amino and hydroxyl groups of CHT . These iThe biodegradability of PHB-based materials is an important parameter. One of the objectives of this work was to study the kinetics of biodegradation of PHB/CHT materials under the influence of soil microorganisms and to reveal the effect of CHT on the biodegradation of PHB. It is well known that PHB is capable of hydrolysis ,44, whilThere are several publications devoted to the degradation of PHB composites with other polymers in model media. As a rule, water or aqueous solutions of acids and alkalines are used as media. For example, the kinetics of degradation of fibrous scaffolds based on PHB with additions of CHT and bioglass were studied in the work . The fibIn this work, the study of biological degradation was carried out under the action of soil microorganisms for the release of carbon dioxide. The amount of emitted carbon dioxide, measured using the Sturm method, is the most reliable criterion for the biodegradation of organic molecules. The results of this study showed that PHB-based fibrous material was characterized by the highest biodegradability (biodegradation rate was 45.8% after 60 days). Pure chitosan has slow biodegradation compared to PHB, about 12% for 30 days . The add–1 attributed to amide groups and a significant increase in the absorption band at 1041 cm−1 (C-O-C bonds in carbohydrates) is likely related to the increased number of chitin molecules contained in fungal cell walls [After the biodegradation process under the action of soil microbiota, significant changes in chemical composition and microstructure were observed. The emerging absorption peaks at 1530 and 1635 cmll walls . This fa−1 for the blends PHB/CHT and a decrease in the intensity for the pure PHB after biodegradation test indicate the destruction of PHB followed by forming microdefects and integrity damage. According to optical microscopy analysis, the materials based on pure PHB were characterized by biodeterioration throughout the samples. The film and fibrous materials based on the blends PHB/CHT had numerous sites of biodeterioration.The complete disappearance of the peak at 1720 cmThe reports also revealed the effect of CHT on the ability of PHB to oxidative destruction. Some publications confirmed that during the mild oxidation of CHT, hydroxyl groups (C3 and C6 sites) are oxidized to carbonyl ones without the noticeable effect of the polymer backbone structure. The number of amino groups may also decrease . HoweverIn this case, the supramolecular structure of PHB/CHT blends plays an important role in the process of oxygen sorption. As shown earlier , the amoThis work analyzes the patterns of structure formation of film and fibrous biocomposites based on blends of natural polymers—poly(3-hydroxybutyrate) and chitosan. Chitosan having antimicrobial activity due to its cationic residue is an efficient additive for biomedical materials based on fully biodegradable PHB. Since chitosan possesses hydroxy and amino groups, PHB can be chemically bonded with it by blending. The use of a complex of such structure-sensitive methods like FTIR spectroscopy, DSC, and SEM made it possible to establish that PHB and CHT interact with each other due to the presence of polar reactive ester (PHB) and amino groups (CHT). This affects the formation of the supramolecular structure of materials, which, in turn, becomes more or less reactive with oxygen or water in the course of natural degradation.The peculiarities of the composition and structure of composites had a significant effect on the oxidative destruction and biological degradation of fibrous and film materials based on blends of PHB and CHT. The lack of compatibility of the polymer components in the system is not a disadvantage. The availability of immiscible heterogeneous structures is generally higher than that of homogeneous continuous structures. Since heterogeneous structural elements are more actively attacked by water and other hydrolyzing agents , then, by regulating the degree of heterogeneity and sizes of structural elements, there is a potential opportunity to control the rate of hydrolytic decomposition of the polymer system.The obtained results show a high biodegradability of the materials based on PHB and CHT and allow predicting the complete degradation of the materials within seven months under biocompost conditions ). At the same time, elevated temperatures will accelerate the degradation of materials due to the occurrence of oxidative destruction. It was found that the introduction of high concentrations (over 60 wt%) of CHT into film and fibrous materials based on PHB significantly accelerates the processes of oxidative and hydrolytic destruction, but leads to a slight inhibition of the growth of micromycetes at the initial stage.In addition, the effect of the type of material  on the rate of biodegradation under the influence of soil microbiota was shown, which is due to the different accessibility for attack by microorganisms.Thus, the developed materials on the PHB/CHT basis have an increased ability for biodegradation and oxidative degradation, as well as have potential antibacterial properties due to the presence of CHT. These composite materials can be recommended for the creation of disposable biodegradable sorbents, medicine materials, and hygiene products.


In this paper iron tailing sand (TS) are used as aggerate to develop ultra high-performance concrete (UHPC). The mix proportion of UHPC is designed and TS were added by 25%, 50%, 75% and 100%  to replace natural river sand. Firstly, the influence of TS on the slurry behavior was carried out. The experimental result indicates that with the continuously increasing content of TS, the workability of slurry decreases, while the air content increases. Considering the workability, the optimal replacing dosage of TS should be less than 50%. Then, tests for the hardened specimens were taken. The compressive behavior and micro-porosity deteriorate with increasing content of TS, and the compressive strength had a positive linear relationship with the workability, which indicated that the decline the compressive behavior is mainly due to the loss of flowability. Finally, autogenous shrinkages of UHPC with different TS dosage were also tested. At the same time, the micro-structure of specimens was discussed, which was deteriorate with the increasing dosage of TS. Therefore, comprehensively considering the compressive behavior, micro-structure and shrinkage behavior, as much as 50% of the aggregate could be replaced by TS when developing UHPC. Ultra-high-performance concrete (UHPC) is a new type of cement-based material with high mechanical properties  . ConsideAlthough exhibiting outstanding performance, heave consumption of fine aggregate in UHPC greatly increase the cost and limit the application range. Hence, some researchers have been exploring ways to use other aggregate to reduce the raw material costs in UHPC production. Natural river sand, which exhibits mechanical properties similar to those of expensive silica sands, is widely used aggregate in UHPC . HoweverIron ore tailing (IT), which is one of the main industrial solid wastes in China, is generated with the beneficiation process of iron ore. The wide use of steel has led to an increase in the deposition of IT. According to the statistics, more than 10 billion tons of TS are discharged every year worldwide, of which storage encroaches upon large landfills ,20,21. TUsing tailings sand as a replacement of river sand or silicon sand in the preparation of UHPC has been reported in previous studies, where the particle size of tailing sand is much finer than that of river sand or silicon sand, and mainly play a role of pore-filling effect ,30,31. HIn this study, P.II 52.5 ordinary Portland cement meeting Chinese Standard TB175-2007 and silica fume were utilized as the binary cementitious materials. The chemical compositions and particle size distributions of materials are shown in Natural river sand (RS) and iron tailing sand (TS) with the particle sizes of 0.15–0.3 mm were utilized as aggregate to prepare UHPC. TS used in this work were obtained from Benxi City, Liaoning Province, China. Before the test, a sieving experiment was first conducted shown in . The che2/kg) and greater water absorption (12%) than that of RS .Scanning electron microscopic (SEM) was used to compare the surfaces and shapes between TS and RS; the images are shown in In order to characterize the difference of mechanical properties, a KC-3 particle strength tester is used to measure the particle strength of RS and TS, shown in the The mix design of all of the UHPC mixtures are shown in A JJ-5 mixer was used to prepare the mixture, of which the low speed and high speed were 140 ± 5 rpm and 285 ± 5 rpm, respectively. Before mixing, two aggregates were dried at 105 °C for 24 h and then cooled to room temperature. During the cooling process, the container surface was covered to avoid the moisture. The mixing procedure for all of the UHPC mixtures is shown in Workability is an important property of fresh UHPC which significantly influence its mechanical and other properties. After the mixing process, the workability of UHPC was tested firstly, the fresh mixture was poured into a steel cone lying on a flat plate. The cone was lifted vertically while ensuring that the mixture flowed freely. The diameters of the two vertical directions of the mixture were then measured, and the mean of the measurements was used as the workability of the UHPC mixture, as shown in mA is the air content of mixture, A0 is the readout of the instrument, and GA is the correction factor of aggregate.In order to discuss the influence of TS on the air bubble and pore structure of UHPC, an air content test was carried out using measurement instrument according to the literature . The airAfter mixing, all specimens were curing in a water tank with temperature of 60 ± 2 °C for 3 d. The compressive strength was tested and three specimens were carried out for each mixture of which the mean strength value was taken as the compressive strength of the mixture.A test was carried out to measure the effect of TS content on the autogenous shrinkage of UHPC. After mixing procedure, the slurry was poured into the mold with a size of 25 mm × 25 mm × 280 mm based on ASTM C490-17 , and twoA Micromeritics Mercury Porosimeter (AutoPore IV-9500) was used to measure the pore structure of the UHPC, and the test range of pore sizes was 3 nm to 360 μm. Before the test, the samples were soaked in acetone and dried for 4 h in vacuum at 80 ± 2 °C.Microstructural studies were conducted using an Ultra-plus SEM . Before the test, the sample was covered with gold film. Observations were conducted using a wide range of magnifications from 12× to 1M×.On the contrast, the air content increase with dosage of TS, as shown in (a) the lower workability with the increasing TS dosage will improve the entrapped air and the internal porosity of slurry , and fin(b) the different shape between two aggregate also influenced dramatically the packing model of UHPC. Ostrowski et al. discussed the morphology of aggregate on the properties of HPC (high-performance concrete), of which the result is similar to that of this study ,47. ElliAutogenous shrinkage is a critical factor that affects the mechanical properties and durability of other cement-based materials. Compared with other cement-based concrete, UHPC exhibits greater early autogenous shrinkage due to the low w/b ratio and the substantial amount of binder, which may cause a high internal stress and lead to the generation of microcrack significantly ,50,51. FIt is worth noting that, compared with the reference T0, the greatest autogenous shrinkage increasing of UHPC is 7.96% of T100, which means that the negative effect of TS on the autogenous shrinkage of UHPC is limited.A micrograph of UHPC is shown in In this paper, a green-designed UHPC is prepared using iron tailing sand as aggregate. With the rapid development of construction industry and highway transportation industry, the demand for UHPC is also increasing, which means that more and more fine aggregate is required. As a typical solid waste, iron tailing has high potential application value. As a type of aggregate used in UHPC production, it can not only produce economic benefits as a product, but also effectively reduce the exploitation of natural sand and solve the environmental pollution caused by the stacking of iron tailings at the same time.This study addresses the properties of a new UHPC incorporating iron ore tailings. Based on the experimental results, the following conclusions are drawn:(1) With increasing TS content of UHPC, the workability decreases, while the air content increases correspondingly. This result is mainly attributed to the higher water absorption and larger shear resistance of TS than RS during the mixing process.(2) The compressive strengths of UHPC decrease with the enhancing content of TS, but still reaches 120 MPa with 50% TS content, which is tightly related to the workability of slurry. Therefore, to ensure the workability and mechanical behavior of UHPC, the TS content of should be 50% or less;(3) The addition of TS has a certain adverse effect on the internal pore structure of UHPC. The angular shape of TS leads to the loose contact between particles, resulting in the increase of internal porosity, and affects the fresh and mechanical behavior.(4) The autogenous shrinkage of UHPC increases with the addition of TS but is still under 10%. The main reasons are the higher water absorption and finer equivalent particle size of TS. Future research will focus on how to reduce the autogenous shrinkage of UHPC and improve its properties.


The selective laser melting (SLM) forming process of 24CrNiMo alloy steel was optimized by orthogonal experiment. The density and microstructure of the sample were analyzed, and the optimized process parameters were as follows: laser power 300 W, scanning speed 530 mm/s. The 24CrNiMo alloy steel samples were prepared with optimized parameters. The relationship between residual stress and thermal fatigue and the effect of stress-relieving annealing (SR) on residual stress were analyzed. The density of the sample was found to increase at first and then to decrease with the increase of laser power and then to decrease with the increase of scanning speed. Increasing the laser power and scanning speed widened and deepened the weld. Under the optimized process window, the formability of 24CrNiMo alloy steel samples was improved significantly. The residual stress distribution was tensile stress, which had a negative effect on the thermal fatigue properties of the sample. After SR, the residual stress changed to compressive stress, which had a positive effect on the thermal fatigue properties of the samples. Compared with the deposited state, the thermal fatigue cracks were significantly shortened after SR, which was able to further promote the improvement of thermal fatigue performance. The gradient residual stress test showed that the gradient residual stress in the edge region and the central region of the deposited sample had the same trend, and decreased gradually from the surface layer to the base layer. The 24CrNiMo low alloys, as a branch of Cr-Ni alloys, have been widely applied in the braking systems of the high-speed trains ,2,3 due Selective laser melting (SLM) technology has the characteristic of a high degree of flexibility ,9. Compa3. The chemical composition and mechanical properties of 30CrNiMo steel and 24CrNiMo alloy steel are shown in The powder material in this paper was 24CrNiMo alloy steel, and the powder morphology is shown in According to the selection requirements of density and microstructure as optimal process parameters, two orthogonal experiments were designed. The first parameter of orthogonal experiment combination was: laser power 150~450 W, scanning speed 400~1200 mm/s. The second parameter of orthogonal experiment combination was: laser power 300~360 W, scanning speed 470~630 mm/s. After the first experiment, the second orthogonal test was carried out to find the optimal combination of process parameters. The primary and preferred test parameters are shown in 3. The maximum power of the fiber laser was 500 W, and the wavelength was 1070 nm. The other process parameters were as follows: the scanning distance was 0.11 mm, the fixed layer thickness was 50 μm, the substrate was preheated at 50 °C, and the scanning strategy was to rotate 67°. After the sample was formed, the sample was heat treated by SR, and the samples were kept at 600 °C for 2 h and cooled in the furnace. The densification test, microstructure characterization and hardness test samples were 10 × 10 × 5 mm3. After ultrasonic cleaning, the sample density was measured by a DX-100E  automatic electronic densitometer. The hardness of the sample was measured by an FM-700  microhardness tester, and the load was 200 g. The microstructure was observed by a LeicaDMi8A  optical microscope. A self-made thermal fatigue testing machine was used in the thermal fatigue test. The schematic diagram of the thermal equipment and the size of the sample are shown in In this paper, the 3D printing equipment used an EP-M250 metal printer , and the forming size could reach 262 × 262 × 350 mmIt can also be seen in In the first orthogonal test, the samples under different laser processes showed defects such as spheroidization, pores and cracks, as shown in 0.2. Compared with the test results of other groups, the surface of the SLM formed sample under this process parameter was smooth and well formed, the microstructure was basically free of defects, such as pores, and the density was higher under this process parameter. Therefore, the optimized process parameters obtained in the experiment were reasonable.Under the optimized process parameters, 24CrNiMo alloy steel samples were prepared by SLM technology. The surface morphology and low-power optical microstructure of the samples are shown in As shown in The test results of residual stress on the surface of samples in different states are shown in The residual stress on the surface of the deposited sample was tensile stress, with a peak value of (453 MPa)~(583 MPa), which was about 50% of the yield strength of the material. After SR, the residual stress of the sample became compressive stress, and the peak value was concentrated in (−11 MPa)~−22 MPa). The residual stress on the deposited surface was caused by the excessive temperature gradient. During the forming of the SLM, the cladding layer experienced a sharp increase and decrease in temperature within a short period of time, resulting in the temperature near the molten pool being much higher than others area, so a large temperature gradient was formed. In the subsequent cooling and solidification stage, the larger temperature gradient restricted the shrinkage and deformation of the cladding layer in the surrounding colder area, resulting in inconsistency of volume shrinkage and expansion, mutual restriction and large residual stress. It has been reported in literature that large tensile stress will lead to premature fatigue failure of parts ,22,23. T MPa. TheIn this paper, 24CrNiMo alloy steel was formed by SLM, the residual stress distribution of deposited and SR specimens was analyzed and the relationship between residual stress and thermal fatigue was studied. The following conclusions were obtained.(1)0.2.Through the process optimization, the optimized parameters were obtained as follows: laser power P = 300 W, scanning speed V = 550 mm/s, scanning spacing d = 0.11 mm, fixed layer thickness h = 50 μm. Under the optimized parameters, the alloy steel samples were prepared with SLM, with a density of 99.8% and a hardness of 365–388 HV(2)With the increase of laser power, the density of deposited samples increased at first and then decreased, and decreased with the increase of scanning speed. At a low laser power, there were spherical particles in the overlap zone of the molten channel, then the enrichment of oxides or inclusions was easily formed during the solidification of the molten pool and cracks were finally formed under the action of stress.(3)The residual stress of the deposited sample was relatively large, which was about 50% of the yield strength of the material. The residual stress distribution of the SR sample showed that the residual stress was relatively stable and compressive, which improved the thermal fatigue performance. The gradient residual stress of the deposited sample decreased gradually from the surface layer to the base layer, which was mainly due to the stress caused by the relaxed thermal cycle deposition in front of the deposition layer. After SR, the performance and service life of the brake disc was effectively improved.


Diabetes mellitus as a systemic metabolic disease is one of the most serious threats to global health in this century. Diabetic cardiomyopathy is increasingly recognized as one of the most important complications of the disease, which is associated with impaired cell energy metabolism and damage to mitochondria in cardiomyocytes. Therefore, targeting mitochondrial dysfunction by pharmacological agents can be used as a therapeutic strategy in diabetic heart disease. The aim of the work was to study the effect of the mitochondria-targeted agent alisporivir on the development of mitochondrial dysfunction in the heart of mice with experimental diabetes mellitus. Alisporivir has been recently identified as a non-immunosuppressive analogue of cyclosporin A, a selective inhibitor of cyclophilin D and the mitochondrial permeability transition pore opening, with a potential in a wide range of therapeutic indications. Our results indicated that alisporivir alleviates diabetes-induced abnormalities in the ultrastructure and functions of mitochondria in cardiomyocytes and increases the rate of glucose utilization in diabetic mice. The data suggest that alisporivir acts as a mitochondria-targeted metabolic reprogramming agent and attenuates oxidative damage to the heart tissue of diabetic mice.Pink1 and Parkin in the heart tissue of alisporivir-treated diabetic mice were elevated, suggesting the stimulation of mitophagy. In parallel, alisporivir decreased the level of mtDNA in the heart tissue. These findings suggest that targeting the MPT pore opening by alisporivir alleviates the development of mitochondrial dysfunction in the diabetic heart. The cardioprotective effect of the drug in diabetes can be mediated by the induction of mitophagy and the inhibition of lipid peroxidation in the organelles.Diabetes mellitus is a systemic metabolic disorder associated with mitochondrial dysfunction, with the mitochondrial permeability transition (MPT) pore opening being considered as one of its possible mechanisms. The effect of alisporivir, a non-immunosuppressive cyclosporin derivative and a selective inhibitor of the MPT pore opening, on the ultrastructure and functions of the heart mitochondria of mice with diabetes mellitus induced by a high-fat diet combined with streptozotocin injections was studied. The treatment of diabetic animals with alisporivir (2.5 mg/kg ip for 20 days) increased the rate of glucose clearance during the glucose tolerance test. The blood glucose level and the indicator of heart rate in alisporivir-treated diabetic mice tended to restore. An electron microscopy analysis showed that alisporivir prevented mitochondrial swelling and ultrastructural alterations in cardiomyocytes of diabetic mice. Alisporivir canceled the diabetes-induced increases in the susceptibility of heart mitochondria to the MPT pore opening and the level of lipid peroxidation products, but it did not affect the decline in mitochondrial oxidative phosphorylation capacity. The mRNA expression levels of  Diabetes mellitus (DM) as a metabolic disease is one of the most serious threats to human health throughout the world. It is based on hyperglycemia and insufficient insulin secretion or malfunction. These metabolic disturbances lead to damage to many organs and tissues of the organism. One of the most common complications of diabetes mellitus is cardiomyopathy ,2,3. Dia2+ homeostasis [2+ handling. Indeed, the development of diabetes mellitus was marked by a decrease in the rate of Ca2+ uptake by cardiac mitochondria due to the reduction of MCU, a channel subunit of the mitochondrial Ca2+ uniporter complex [Diabetic cardiomyopathy is known to be closely associated with impaired mitochondrial function, dysregulation of mitophagy and mitochondrial biogenesis, pathological changes in the dynamics of the organelles, as well as oxidative stress ,6. It iseostasis . Therefo complex ,10,11,12 complex ,8.The MPT pore is a calcium-activated multiprotein channel that permeates both the inner and outer mitochondrial membranes. The opening of the MPT pore makes the inner mitochondrial membrane permeable to compounds with molecular weights up to 1.5 kDa, causing ion imbalance, mitochondrial depolarization, and swelling of the organelles. Subsequently, these processes can result in a decline in the cell’s energy supply, mitochondrial and cellular destruction ,13. It sAs mentioned above, diabetic cardiomyopathy is accompanied by a decrease in mitochondrial resistance to the MPT pore induction ,10,18,19Alisporivir (Ali) is a non-immunosuppressive analogue of cyclosporin A, inhibiting MPT pore assembly through interaction with cyclophilin D ,24. The n = 9); (2) control + alisporivir (CTR + Ali) (n = 9); (3) mice with diabetes mellitus (DM) (n = 9); and (4) mice with DM treated with alisporivir (DM + Ali) (n = 9). DM was induced in animal groups 3 and 4 by high-fat diet feeding  for 28 days. Thereafter, mice received intraperitoneal (ip) injections of streptozotocin (STZ) (30 mg/kg) for five consecutive days during high-fat diet feeding [v/v%). The control animals received solvent alone. Successful development of diabetes mellitus was assessed by the intraperitoneal glucose tolerance test (IPGTT). Before testing, mice were fasted for 16 h (IPGTT) with free access to water. The blood glucose level was recorded using a One Touch Select Plus glucometer . The triglyceride level was estimated using a Multicare-in biochemistry analyzer .Male mice of the C57BL/6NCrl line weighing 23–26 g were used in this work. Mice were randomly divided into four groups: (1) non-treated control (CTR)  using an ExtractRNA kit . The real-time PCR was performed on a DTLite5 amplifier  . A PrimeT method .ND4 gene of the mitochondrial genome and the Gapdh gene of the nuclear one were used for this assay (Nd4 DNA/Gapdh DNA). Gene-specific primers are shown in Total DNA (nuclear and mtDNA) was isolated from 10 mg of the left ventricle myocardium of mice using a DNA-Extran 2 kit  . The mtD2 consumption by mitochondrial samples was estimated using Oxygraph-2k  [2PO4, 2.5 mM potassium malate, 2.5 mM potassium glutamate, and 10 mM HEPES–KOH (pH 7.4). Ca2+ transport by mitochondria was estimated with an arsenazo III indicator at 675–685 nm using a plate reader Tecan Spark 10M  [2PO4, 2.5 mM malate, 2.5 mM glutamate, 10 μM EGTA, 50 μM arsenazo III, and 10 mM HEPES-KOH (pH 7.4.). Intensity of lipid peroxidation in mitochondrial membranes was assessed by quantification of thiobarbituric acid-reactive substances (TBARS) represented by malondialdehyde and some other minor aldehyde species [Mitochondria were isolated from heart tissue by differential centrifugation . Final sAustria) . The reazerland) . The rea species .For electrocardiograms examinations, the animals were immobilized using combined anesthesia . A mousen = 4–9). Differences between the groups were calculated using the GraphPad Prism 7.0 software and one-way analysis of variance (ANOVA) followed by the Tukey multiple comparison post hoc test.The data were presented as mean ± SEM . Standardized animal feeds  were purchased from Envigo . RNA extraction and quantitative real-time PCR reagents were from Evrogen . DNA extraction reagents were from Sintol . All other reagents were purchased from Invitrogen or Sigma-Aldrich .The development of diabetes mellitus is known to be accompanied by a change in the cardiac phenotype. As shown in our work, the induction of diabetes causes a decrease in the heart weight relative to the weight of this organ in control animals . This chAlisporivir is a specific inhibitor of the mitochondrial pore . This pr2+ retention capacity of the heart mitochondria of mice in four experimental groups. It can be seen that the cardiac mitochondria of diabetic mice have a higher susceptibility to the pore induction  than the mitochondria of mice in the control group. Alisporivir administration to diabetic animals resulted in a significant increase in Ca2+ retention capacity.At the same time, alisporivir, as a specific MPT pore blocker, significantly increased the resistance of diabetic mitochondria to its opening. Alisporivir treatment of diabetic animals also led to a decrease in the production of TBA-reactive substances  by mitochondria to the values of control animals . This inWe also determined the level of mitochondrial DNA in the left ventricular tissue, indirectly reflecting the number of mitochondria . One canPpargc1a, Pink1, and Parkin genes encoding the proteins responsible for the processes of mitochondrial biogenesis (PGC1α) and mitophagy (Pink1 and Parkin). We noted a downward trend in the Ppargc1a level in the CTR + Ali, DM, and DM + Ali groups  relative to the CTR group. In the DM group, there is a significant increase in the expression of the Parkin gene, but at the same time, a trend towards a decrease in the expression of the Pink1 gene. The DM + Ali group showed a significant increase in the expression of the Pink1 and Parkin genes. This allows us to say that this group observes the induction of mitophagy.The data obtained indicate that both the development of diabetes mellitus and the administration of alisporivir may lead to a decrease in the number of mitochondria in cardiomyocytes. This may be based on a change in the processes of mitochondrial biogenesis and mitophagy. In this work, we have determined the effect of alisporivir (non-immunosuppressive inhibitor of the MPT pore) on structural and functional changes in cardiac mitochondria in high-fat/streptozotocin-induced diabetes mellitus.There are quite contradictory studies on the role of the MPT pore in the development of diabetes mellitus. Indeed, a number of studies have shown that MPT pore inhibitors reduce the risk of heart attack in diabetic animals ,21. HoweOn the one hand, administration of alisporivir to diabetic animals (2.5 mg/kg/day) did not lead to a significant decrease in the level of glucose (fed state), triglycerides, and malondialdehyde in blood plasma, although we noted a tendency towards their recovery to control values. The same tendency to recovery was observed in the structural and functional characteristics of the heart—weight and heart rate. At the same time, one should note that during the glucose tolerance test, the administration of alisporivir showed an increase in the glucose clearance rate in diabetic animals. Previously, it was shown that knockout of cyclophilin D led to a similar effect in animals, which was associated with an increase in the rate of glucose uptake by skeletal muscle cells of mice .2+ capacity in comparison with the mitochondria of diabetic animals. This suggests that alisporivir treatment of diabetic animals prevents MPT pore opening. In addition, alisporivir prevented the development of oxidative stress. In particular, the level of malondialdehyde in the mitochondria of DM + Ali mice significantly decreased in comparison with the level of the DM group and reached control values. Previously, other inhibitors of MPT pore opening have shown similar protective effects against the development of oxidative stress in the diabetic heart [2+ homeostasis and cardiac activity. At the same time, the administration of alisporivir did not reveal a reliable restoration of the respiration process and oxidative phosphorylation of mitochondria. The respiration rate of cardiac mitochondria in state 3, as well as the respiratory control parameter of alisporivir-treated DM mice, did not significantly differ from these parameters in the DM group and were significantly lower than in the CTR group.At the same time, we noted that administration of alisporivir to diabetic animals partially prevented the DM-induced ultrastructural and functional alterations in heart mitochondria. Indeed, alisporivir normalized the structure of the heart mitochondria in mice. Administration of alisporivir to diabetic animals led to a decrease in vacuolization of organelles and restoration of the regular structure of the cristae. Moreover, we found that cardiac mitochondria of the DM + Ali group showed a significant increase in Caic heart . PossiblAn important result of this work are changes in the level of mitochondrial DNA, as well as in the expression of genes responsible for mitochondrial biogenesis and mitophagy. According to the obtained and published data, the development of diabetes mellitus is associated with a reduction in the level of mitochondrial DNA. At the same time, the administration of alisporivir did not lead to the normalization of this parameter, and moreover, caused a further decrease in the level of mtDNA in the heart of diabetic animals. In addition, alisporivir reduced the amount of mtDNA in the heart cells of control animals. This suggests that alisporivir treatment reduces the number of mitochondria in heart cells. Additionally, if in the case of diabetes mellitus, a decrease in the number of damaged mitochondria may be a positive factor, then in healthy animals the similar effect of alisporivir is rather negative.Ppargc1a gene encoding PGC-1α responsible for mitochondrial biogenesis. However, we observed a downward trend in the expression level of this gene in three experimental groups  relative to the CTR group. One could speculate that such a decrease has an effect on a decrease in the number of mitochondria in the heart cells of these groups of animals. At the same time, the DM + Ali group showed a significant increase in the expression of Pink1 and Parkin genes encoding the proteins responsible for the mitophagy. Thus, one could assume that the administration of alisporivir to diabetic animals leads to the activation of mitophagy and the removal of damaged mitochondria from the heart cells of diabetic animals.Reduction of mtDNA and, as a consequence, the number of mitochondria in a cell can occur as a result of suppression of biogenesis or induction of mitophagy. For example, it was previously shown that cyclosporin A, whose molecule only slightly differs from alisporivir, suppresses mitochondrial biogenesis in HepG2 cell culture . In thisPink1 and Parkin genes, encoding proteins responsible for mitophagy. Thus, alisporivir can reduce the number of damaged mitochondria in the diabetic heart. However, a decrease in the number of mitochondria in healthy animals may indicate negative effects of this compound. All this suggests that the use of this drug should be undertaken with care, bearing in mind multiple effects of alisporivir, a proper evaluation of which would require multivariate analysis.The data obtained in this work allow us to draw the following conclusions. First, alisporivir at the concentration used (2.5 mg/kg/day) is not antidiabetic. At the same time, the tendency to restore a number of parameters (the level of glucose (fed state), malondialdehyde and plasma triglycerides, heart rate), as well as the fact that Ali-treated DM animals showed a significant increase in the rate of glucose clearance in the blood, allows us to hope that more high concentrations of this compound may have beneficial effects against the development of diabetic cardiomyopathy. Secondly, alisporivir partially restores the ultrastructure and functions of the heart mitochondria in diabetic animals. At the same time, the administration of alisporivir results in a decrease of the amount of mitochondrial DNA in both diabetic and control animals. In parallel with this, diabetic animals treated with alisporivir showed a significant increase in the expression of the