Mechanical Tension Research Articles

Functional Comparison between Endogenous and Synthetic Notch Systems.

The Notch pathway converts receptor–ligand interactions at the cell surface into a transcriptional response in the receiver cell. In recent years, synthetic Notch systems (synNotch) that respond to different inputs and transduce different transcriptional responses have been engineered. One class of synNotch systems uses antibody–antigen interactions at the cell surface to induce the proteolytic cleavage cascade of the endogenous Notch autoregulatory core and the consequent release of a synNotch intracellular domain (ICD), converting surface antigen detection into a cellular response. While the activation of endogenous Notch requires ubiquitylation and subsequent endocytosis of the ligand ICD, these synNotch systems do not seem to have such a requirement because the synNotch ligands completely lack an ICD. This observation raises questions about existing models for the synNotch activation mechanism. Here, we test how different structural and biochemical factors affect the dependence of endogenous and synthetic Notch activation on ligand ICD. We compare the behavior of antibody–antigen synNotch (aa-synNotch) to that of endogenous Notch, and to a synNotch system that uses rapamycin induced dimerization of FK506 binding protein (FKBP) and FKBP rapamycin binding (FRB) domaindimerization domains (ff-synNotch), which still requires a ligand ICD. We found that differences in receptor–ligand affinity, in the identity of the transmembrane domain, or in the presence or absence of extracellular epidermal growth factor repeats cannot explain the differences in ligand ICD requirement that distinguishes aa-synNotch from endogenous Notch or ff-synNotch. We also found that unlike endogenous Notch and ff-synNotch, the aa-synNotch system does not exhibit trans-endocytosis of the receptor extracellular domain into the sender cell. These findings suggest that the aa-synNotch systems bypass the ligand ICD requirement because antigen–antibody pairs are able to promote other adhesive cell–cell interactions that provide the mechanical tension needed for ligand activation.

Epoxy Compositions with Reduced Flammability Based on DER-354 Resin and a Curing Agent Containing Aminophosphazenes Synthesized in Bulk Isophoronediamine.

A method for the synthesis of an amine-containing epoxy resin curing agent by dissolving hexakis-[(4-formyl)phenoxy]cyclotriphosphazene in an excess of isophoronediamine was developed. The curing agent was characterized via NMR and IR spectroscopy and MALDI-TOF mass spectrometry, and its rheological characteristics were studied. Compositions based on DER-354 epoxy resin and the synthesized curing agent with different amounts of phosphazene content were obtained. The rheological characteristics of these compositions were studied, followed by their curing. An improvement in several thermal (DSC), mechanical (compression, tension, and adhesion), and physicochemical (water absorption and water solubility) characteristics, as well as the fire resistance of the obtained materials modified with phosphazene, was observed, compared with unmodified samples. In particular, there was an improvement in adhesive characteristics and fire resistance. Thus, compositions based on a curing agent containing a 30% modifier were shown to fulfill the V-1 fire resistance category. The developed compositions can be processed by contact molding, winding, and resin transfer molding (RTM), and the resulting material is suitable for use in aircraft, automotive products, design applications, and home repairs.

Optimization on Material Removal Rate and Surface Roughness of Stainless Steel 304 Wire Cut EDM by Response Surface Methodology

In this work, wire cut electrical discharge machining (WEDM) is used for the material removing processes; it is utilized for machining conductive parts where it is required to produce complicated shapes, new profiles, new geometry, new product development, and high-accuracy components. This machining process is best suitable for high-end applications such as aerospace, automations, automobile, and medical devices. At present, most of the industrial sectors choose the WEDM process because it is used to develop products in a very short development cycle and at a better economic rate. In this paper, the selected complex geometry of the metal sample was eroded away from the wire during the WEDM process, which eliminates mechanical tensions during machining. The effect of different WEDM operation variables set as wire speed, wire tension, discharge current, dielectric flow rate, and pulse on and off time on the parameter, stainless steel 304 material removing rate (MRR) using RSM, has been studied. The MRR will be maximized if the optimum sets of operational variations are used and also achieve a superior surface finish.

Polycystin-2 mediates mechanical tension-induced osteogenic differentiation of human adipose-derived stem cells by activating transcriptional co-activator with PDZ-binding motif.

Human adipose-derived stem cells (hASCs) have multi-directional differentiation potential including osteogenic differentiation. Mechanical stimulation is thought to be a key regulator of bone remodeling and has been proved to promote osteogenic differentiation of mesenchymal stem cells. However, the mechanism how mechanical tension-induced osteogenesis of hASCs still remains poor understood. Polycystin-2 (PC2), a member of the transient receptor potential polycystic (TRPP) family, is involved in cilia-mediated mechanical transduction. To understand the role of PC2 in osteogenic differentiation under mechanical stimuli in hASCs, PKD2 gene was stably silenced by using lentivirus-mediated shRNA technology. The results showed that mechanical tension sufficiently enhanced osteogenic differentiation but hardly affected proliferation of hASCs. Silencing PKD2 gene caused hASCs to lose the ability of sensing mechanical stimuli and subsequently promoting osteogenesis. PC2 knock-out also reduced the cilia population frequency and cilia length in hASCs. TAZ (transcriptional coactivator with PDZ-binding motif, also known as Wwtr1) could mediate the genes regulation and biological functions of mechanotransduction signal pathway. Here, mechanical tension also enhanced TAZ nuclear translocation of hASCs. PC2 knock-out blocked tension-induced upregulation of nuclear TAZ and suppress tension-induced osteogenesis. TAZ could directly interact with Runx2, and inhibiting TAZ could suppress tension-induced upregulation of Runx2 expression. In summary, our findings demonstrated that PC2 mediate mechanical tension-induced osteogenic differentiation of hASCs by activating TAZ.

Analysis of ceRNA networks during mechanical tension-induced osteogenic differentiation of periodontal ligament stem cells.

The molecular mechanisms underlying osteogenic differentiation of periodontal ligament stem cells (PDLSCs) under mechanical tension remain unclear. This study aimed to identify a potential long non-coding ribonucleic acids (lncRNAs)/circular RNAs (circRNAs)-microRNAs (miRNAs)-messenger RNAs (mRNAs) network in mechanical tension-induced osteogenic differentiation of PDLSCs. PDLSCs were isolated from the healthy human periodontal ligament, identified, cultured, and exposed to tensile force. The expression of osteogenic markers was examined, and whole transcriptome sequencing was performed to identify the expression patterns of lncRNA, circRNA, miRNAs, and mRNAs. Enrichment analyses were also performed. Candidate targets of differentially expressed non-coding RNAs (ncRNAs) were predicted, and potential competitive endogenous RNA (ceRNA) networks were constructed by Cytoscape. We found that the osteogenic differentiation of PDLSCs was significantly enhanced under dynamic tension (magnitude: 12%, frequency: 0.7Hz). Overall, 344 lncRNAs, 57 miRNAs, 41 circRNAs, and 70mRNAs were differentially expressed in the tension group and the control group. Functional enrichment analysis showed that differentially expressed mRNAs were mainly enriched in osteogenesis-related and mechanical stress-related biological processes and signal transduction pathways (e.g., tumor necrosis factor [TNF] and Hippo signaling pathways). The lncRNA/circRNA-miRNA-mRNA networks were depicted, and potential key ceRNA networks were identified. Our findings may help to further explore the underlying regulatory mechanism of osteogenic differentiation of PDLSCs under mechanical tensile stress.

Load Dynamics, Recovery and Adaptation for Better Sporting Events

International result-oriented performance in sports requires systematic scientific training. A proper pedagogical approach is required for systematic loading of the athletes in order to record-breaking performance. The performance of an athlete largely depends upon a progressive training load for a relatively long period of time. The degree of mechanical tension, subcellular damage, and metabolic stress can all play a role in exercise-induced muscle adaptations. The process of adaptation largely depended upon the ratio of load and recovery stimulus. Thus the load dynamics and proper adaptation is reflected in the achievement of an athlete. The present research review-based article discussed systematically the procedure of training load, importance of recovery, and adaptation of load.

Abstract P2010: Cardiomyocyte Knockout Of Sorbs2 Rewires Cytoskeleton And Causes Dilated Cardiomyopathy

Sorbs2 is a cardiomyocyte-enriched, cytoskeletal adaptor protein and there is growing interest in understanding its roles in cardiac biology and disease. While Sorbs2 global knockout mice display lethal cardiomyopathy with severe arrhythmias, the underlying mechanisms remain unclear, and if this results from intrinsic loss of Sorbs2 in cardiomyocytes (CM) is unknown, as Sorbs2 is also well-expressed in the nervous system and vasculature. Thus, the potential relevance of Sorbs2 in human cardiomyopathy is underexplored. We aim to characterize the effects and potential mechanisms of CM-specific deletion of Sorbs2 on cardiac structure and function in mice, and to further examine Sorbs2 dysregulation in failing hearts and explore potential links between Sorbs2 genetic variations and human cardiovascular disease phenotypes. We report that heart Sorbs2 expression is consistently upregulated in humans with ischemic and idiopathic cardiomyopathies, and in animal models of heart failure (HF). We generated mice with CM-specific loss of Sorbs2 (Sorbs2-cKO) and found early atrial and ventricular conduction anomalies, despite unaltered expression of primary action potential ion channels and gap junction proteins. At mid-life, Sorbs2-cKO mice exhibit impaired cardiac contractility with cardiomyofibers failing to maintain adequate mechanical tension. These mice develop progressive diastolic and systolic dysfunction, enlarged cardiac chambers, and die with congestive HF at ~1 year of age. Comprehensive survey of potential underlying mechanisms show that Sorbs2-cKO hearts have defective microtubule polymerization and compensatory upregulation of desmin, vinculin, and tubulins. Finally, consistent with our mouse observations, we identified suggestive links between Sorbs2 genetic variants and human cardiac phenotypes, including conduction abnormalities, atrial enlargement, and dilated cardiomyopathy. In conclusion, our studies show that Sorbs2 is essential for maintaining cytoskeletal structural integrity in CM, likely through strengthening the interactions between microtubules and other structural proteins at crosslink sites, and highlights its potential clinical relevance to cardiomyopathy.

Tension-driven multi-scale self-organisation in human iPSC-derived muscle fibers.

Human muscle is a hierarchically organised tissue with its contractile cells called myofibers packed into large myofiber bundles. Each myofiber contains periodic myofibrils built by hundreds of contractile sarcomeres that generate large mechanical forces. To better understand the mechanisms that coordinate human muscle morphogenesis from tissue to molecular scales, we adopted a simple in vitro system using induced pluripotent stem cell-derived human myogenic precursors. When grown on an unrestricted two-dimensional substrate, developing myofibers spontaneously align and self-organise into higher-order myofiber bundles, which grow and consolidate to stable sizes. Following a transcriptional boost of sarcomeric components, myofibrils assemble into chains of periodic sarcomeres that emerge across the entire myofiber. More efficient myofiber bundling accelerates the speed of sarcomerogenesis suggesting that tension generated by bundling promotes sarcomerogenesis. We tested this hypothesis by directly probing tension and found that tension build-up precedes sarcomere assembly and increases within each assembling myofibril. Furthermore, we found that myofiber ends stably attach to other myofibers using integrin-based attachments and thus myofiber bundling coincides with stable myofiber bundle attachment in vitro. A failure in stable myofiber attachment results in a collapse of the myofibrils. Overall, our results strongly suggest that mechanical tension across sarcomeric components as well as between differentiating myofibers is key to coordinate the multi-scale self-organisation of muscle morphogenesis.

Effects of chemical and autoclave sterilization treatments on medical personal protective equipment made of nonwoven polypropylene fibers for recycling

Medical personal protective equipment (PPE) made from nonwoven thermoplastic fibers has been intensively used, resulting in a large amount of biohazardous waste. Sterilization is indispensable before recycling medical waste. The aim of this work is to evaluate the effects of the decontamination treatments and help properly recycle the PPE materials. The study investigated the effects of three disinfection treatments (NaClO, H2O2, and autoclave) on chemical composition, molecular weight, thermal properties, crystallinity, crystallization kinetics, and mechanical tension of three types of PPE (Gown #1, Gown #2, and Wrap) made of isotactic polypropylene fibers. The chemical compositions of the materials were not evidently affected by any of the treatments. However, the Mw of the polymers decreased about 2–7% after the treatments, although the changes were not statistically significant. The treatments barely affected the melting and crystallization temperatures and the maximum force at break, but they tended to elevate the thermal degradation temperatures. Although the treatments did not notably influence the crystallinities, crystallization rates and crystal growths were altered based on the Avrami model regression. Since the detected changes would not significantly affect polymer processing, the treated materials were suitable for recycling. Meanwhile, evident differences in the three types of raw materials were recorded. Their initial properties fluctuated notably, and they often behaved differently during the treatments, which could affect recycling operation. Recyclers should test and sort the raw materials to assure product quality. The results in this study provide fundamental data for recycling medical PPE to reduce its environmental footprint. Supplementary InformationThe online version contains supplementary material available at 10.1007/s10965-022-03217-w.

The normal force evolution of the substrate during the withdrawal process

AbstractThe evolution of normal force on the smooth plate immersed in Newtonian and yield stress fluids was investigated during the dip coating. The influences of withdrawal velocity, liquid rheological property, and plate roughness were elaborated. For all fluids, the variation of force versus the withdrawing height was divided into four stages. Importantly, the control forces for coating in each stage were determined, which are in turn viscous force‐capillary, viscous force‐gravity, capillary‐viscous force, and gravity. The critical value of normal force controlled from capillary to viscous effect during drainage was adopted to calculate the surface tension. The possibility of measuring the surface tension was verified under the negligible interference of viscous effect and film instability through a detailed analysis on the evolution of force in a series of tests. Accordingly, the applicable conditions with the low withdrawal speed, high viscosity, and rough surface were finally achieved. This work can provide a theoretical basis for the film‐formation mechanism and surface tension measurement in dip coating.

Subtransmission overhead lines mechanical monitoring for fast detection of damaging events

Different harmful events affecting high voltage overhead lines (OHLs) cause changes in the mechanical tension (tensile strength) of conductors. A mechanical monitoring of OHLs, therefore, can provide useful additional information (compared with the information provided by the widely used SCADA systems) about the power system state. The tension measurements combined with a few environmental measurements (air temperature, wind speed) can be used for an automatic (fast) detection of different events and for their approximate location along an OHL, reducing the impact of these events. Referring to 132–150 kV sub-transmission OHLs, this paper proposes some original algorithms, based on the mechanical monitoring of OHLs, for the automatic detection of the following events: conductor breaking, fall of trees on the conductors, ice/snow sleeve accretion on the conductors, strands breaking and galloping. The proposed algorithms require a limited number of sensors placed along the OHLs for measurements of the conductor tension and weather-related quantities.

759 Mechanical tension mobilizes Lgr6+ epidermal stem cells to drive skin growth

Uniquely among mammalian organs, skin is capable of dramatic size change in adults, yet the mechanisms underlying this striking capacity are unclear. Here, we utilize a system of controlled tissue expansion in mice to uncover cellular and molecular determinants of tension-induced skin growth. Through machine learning-guided three-dimensional tissue reconstruction, we capture morphometric changes in growing skin. We find that most growth is driven by the proliferation of the epidermis in response to mechanical tension, with more limited changes in dermal and subdermal compartments.

Stimuli-Responsive Electrochemical Energy Storage Devices.

Electrochemical energy storage (EES) devices have been swiftly developed in recent years. Stimuli-responsive EES devices that respond to different external stimuli are considered the most advanced EES devices. The stimuli-responsive EES devices enhanced the performance and applications of the EES devices. The capability of the EES devices to respond to the various external stimuli due to produced advanced EES devices that distinguished the best performance and interactions in different situations. The stimuli-responsive EES devices have responsive behavior to different external stimuli including chemical compounds, electricity, photons, mechanical tensions, and temperature. All of these advanced responsiveness behaviors have originated from the functionality and specific structure of the EES devices. The multi-responsive EES devices have been recognized as the next generation of stimuli-responsive EES devices. There are two main steps in developing stimuli-responsive EES devices in the future. The first step is the combination of the economical, environmental, electrochemical, and multi-responsiveness priorities in an EES device. The second step is obtaining some advanced properties such as biocompatibility, flexibility, stretchability, transparency, and wearability in novel stimuli-responsive EES devices. Future studies on stimuli-responsive EES devices will be allocated to merging these significant two steps to improve the performance of the stimuli-responsive EES devices to challenge complicated situations.

YAP1 controls degeneration of human cartilage chondrocytes in response to mechanical tension

Disc herniation is a kind of disease caused by degenerative discs, which is common in the elderly, bringing substantial financial burden to families and society. Mechanical tension has a vital effect on the maintenance of cartilage function, however, the molecular mechanism by which mechanical tension causes degenerative discs to remain unclear. This study was the first to reveal Yes-associated protein 1(YAP1) is a key regulator in mechanical tension-mediated degenerative discs. Activation of YAP1 may be a valuable strategy to delays the degeneration of human cartilage chondrocytes. We found that YAP1 expression was significantly decreased in degenerative human endplate cartilage and tissue with the strength and time of mechanical stimulation, but the cell cycle distribution was significantly changed under the 10% cyclic mechanical tension(CMT). Besides, the degeneration of endplate cartilage can be delayed by activating the expression level of YAP1 in vitro and it has also been verified in the cartilage endplate tissue in vitro. Furthermore, We found that YAP1 and TEAD1 overexpression increased the activity of the ACAN or COL2A1 promoter to enhance the transcriptional activity of human chondrocyte collagen. The CMT activates the classic Hippo signaling pathway of YAP1, and piezo1 may regulate YAP1 expression through the Hippo signaling pathway. In conclusion, these results suggest the novel mechanism of YAP contributes to delaying the degeneration of endplate cartilage and targeting YAP in combination with Piezo1 is a potential therapeutic approach for the treatment of endplate cartilage degeneration.

Self-construction of actin networks through phase separation–induced abLIM1 condensates

The abLIM1 is a nonerythroid actin-binding protein critical for stable plasma membrane-cortex interactions under mechanical tension. Its depletion by RNA interference results in sparse, poorly interconnected cortical actin networks and severe blebbing of migrating cells. Its isoforms, abLIM-L, abLIM-M, and abLIM-S, contain, respectively four, three, and no LIM domains, followed by a C terminus entirely homologous to erythroid cortex protein dematin. How abLIM1 functions, however, remains unclear. Here we show that abLIM1 is a liquid-liquid phase separation (LLPS)-dependent self-organizer of actin networks. Phase-separated condensates of abLIM-S-mimicking ΔLIM or the major isoform abLIM-M nucleated, flew along, and cross-linked together actin filaments (F-actin) to produce unique aster-like radial arrays and interconnected webs of F-actin bundles. Interestingly, ΔLIM condensates facilitated actin nucleation and network formation even in the absence of Mg2+. Our results suggest that abLIM1 functions as an LLPS-dependent actin nucleator and cross-linker and provide insights into how LLPS-induced condensates could self-construct intracellular architectures of high connectivity and plasticity.

Chromatin sequesters pioneer transcription factor Sox2 from exerting force on DNA

Biomolecular condensation constitutes an emerging mechanism for transcriptional regulation. Recent studies suggest that the co-condensation between transcription factors (TFs) and DNA can generate mechanical forces driving genome rearrangements. However, the reported forces generated by protein-DNA co-condensation are typically below one piconewton (pN), questioning its physiological significance. Moreover, the force-generating capacity of these condensates in the chromatin context remains unknown. Here, we show that Sox2, a nucleosome-binding pioneer TF, forms co-condensates with DNA and generates forces up to 7 pN, exerting considerable mechanical tension on DNA strands. We find that the disordered domains of Sox2 are required for maximum force generation but not for condensate formation. Furthermore, we show that nucleosomes dramatically attenuate the mechanical stress exerted by Sox2 by sequestering it from coalescing on bare DNA. Our findings reveal that TF-mediated DNA condensation can exert significant mechanical stress on the genome which can nonetheless be attenuated by the chromatin architecture.

(Digital Presentation) Adsorption Characteristics of SiO2/Si, Nanocomposites of Multiwalled Carbon Nanotubes and Polyamide, Polyvinyl Chloride, Polyethylene, Porous Polystyrene

Kyiv national university, Kyiv-01601, Ukraineonanko@i.ua : In this work nondestructive method, which is allow to determine from internal friction difference ΔQ-1/Q-1 0 of elastic vibrations structure defects density Nd and the depth of broken layer hb, is offered for SiO2/Si wafer-plates. Outcomes of the evaluation of dynamic characteristics interstitial atoms, vacancy and O-complexes can be applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si wafer-plates. Introduction The leading factor of the elastic anisotropy forming is a crystallography orientation and the orientation of grains on the form with the orientation of miсrocracks, pores [1]. Acoustic emission (AE) allow to receive the additional information about the process of miсrocracks [2]. A non-destructive method for the technological control of the structure defects by measuring internal friction (IF) and elastic modulus E after laser radiation was developed. Experimental procedure The study of influence of structure defects on damping of vibrations in Si/SiO2 plates by the diameter of D = 100÷60 mm and by the thickness of hSiO2 ≈ 600 nm, hSi ≈ 470 000 nm, allows to estimate the degree of perfection of crystalline structure. Brief thermal influence is created by the powerful impulsive nanosecond neodymium laser resulted to local surface tissue fusion. After stopping of the laser radiation action of fusion solidification begun exactly from the surface, but the crater underbody is extended (molten) and created the additional squeezing mechanical tension σi, that „pull” the central part of crater surface in depth with the liquid crater fusion.The pressure dynamics Рi(t) is following: at the beginning of destruction Рi grows quickly, and on the completion of impulse action diminishes instantly on the value of the light pressure created by the laser. Then the diminishing pressure Рi becomes slower, for nanosecond times of laser influence the appearance of acoustic emission (AE) review is important in time range τ ≈ 0.2 nanosec [3,4]. Results and discussion Effects of AE after nanosecond neodymium and ruby laser irradiation in fluid SiO2 are investigated. The fusion depth as the result of relaxation of photothermal elastic strains Ϭi at the large time ∂T/∂t = (55±100).109 K/sec and spatial ∂T/∂x = (1±2).104 K/sm temperature gradients on the SiO2 surface was appraised Δh ≈ 10000 nm. The quantity of reflections N = τ/t ≈ 0.2 nsec/0.02 nsec = 10, approximately 10 times forward-back in specimen. There was a small value of IF background in SiO2 Qo -1 ≈ 2.10-6 to T ≈ 385 K. AE method was measured the group longitudinal wave velocity in fluid SiO2 by water solution of NaCl with the concentration ρ ≈ 38.125 g/l there was v║ = l/τ » 0.03032 m/10.7 mcsec » 2830 m/sec; shear wave velocity v┴ » 2300 m/sec. Oscilloscopegramma of impulses with transversal polarization, which are reflected in SiO2/Si wafer-plate is represented in Figure 1. Figure 1. Oscilloscopegramma of impulses with transversal polarization, which are reflected in SiO2/Si wafer-plate.Taking into account the value of density ρ ≈ 2.63.103 kg/m3, shear modulus G = ρ.v┴ 2 » 13.91 GPa and elastic modulus E = ρ.v║ 2 » 21.06 GPa were determined. Conclusions The value of internal friction background Q-1 0 after temperature, mechanical treatments describes the changes of the elastic stress σi fields in SiO2/Si wafer-plate after laser radiation.After laser radiation outcomes of the evaluation of dynamic characteristics interstitial atoms Sij, vacancy V and O-complexes can be applied for account of a condition of an annealing with the purpose of deriving specific structural defects in SiO2/Si. Acknowledgements This work has been supported by Ministry of Education and Science of Ukraine: Grant of the Ministry of Education and Science of Ukraine for perspective development of a scientific direction "Mathematical sciences and natural sciences" at Taras Shevchenko National University of Kyiv.

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

Highly Ordered Supramolecular Assembled Networks Tailored by Bioinspired H-Bonding Confinement for Recyclable Ion-Transport Materials

Tensioning device increases coracoid bone block healing rates in arthroscopic Latarjet procedure with suture-button fixation.

There is growing interest in using suture buttons for coracoid fixation to avoid the complications associated with screws during the Latarjet procedure. However, achieving bone block healing is critical for successful shoulder stabilization and return to sport. The purpose of this study was to assess and compare the healing rates and positioning of the coracoid bone block fixed with cortical suture buttons that were either manually tensioned (using a knot pusher) or mechanically tensioned (using a tensioning device) during arthroscopic Latarjet procedures. This prospective, nonrandomized, comparative study enrolled 69 consecutive patients (mean age, 27 years) who underwent an arthroscopic guided Latarjet procedure with suture-button fixation. Hand tensioning was performed in the first 34 shoulders, whereas the next 35 shoulders underwent mechanical tensioning. Twelve patients (17%) had a history of failed Bankart stabilization. The characteristics of the patients in each group in terms of age, sex, type of sport, bone loss, number of previous failed surgical procedures, smoking, and length of follow-up were comparable. Intraoperatively, the tensioning device was set at 100 N successively 3 times until complete immobilization of the bone block was confirmed, as assessed with a probe. The primary outcome measure was coracoid bone block union and position on computed tomography scan images at 6 months' follow-up. Secondary outcome measures included functional outcome scores, shoulder stability, return to sports, and complications at last follow-up. Overall, the rate of bone block healing was 74% (25 of 34 patients) in the hand-tensioning group and 94% (33 of 35 patients) in the mechanical tensioning group (P=.043). Smoking was an independent risk factor associated with nonunion (P<.001) in each group. Patient age, size of the preoperative glenoid bone defect (<20% or >20%), and a history of surgery were not found to have any influence. The tensioning modality did not affect the bone block position, which was subequatorial in 92% of the cases and flush with the glenoid rim in 92%. At a mean of 34 months of follow-up (range, 24-62 months), 96% of the patients (65 of 69) had a stable shoulder and 87% returned to sports. At final follow-up, no significant difference in clinical scores was noted between the groups; no neurologic or hardware complications were observed. Mechanical tensioning achieves significantly higher healing rates than hand tensioning during the arthroscopic Latarjet procedure with suture-button fixation. The use of a suture-tensioning device is a key step to the suture-button fixation technique during arthroscopic Latarjet procedures. By making the suture-button construct rigid, the tensioning device transforms the initially flexible suture into a "rigid fixation", similar to a bolt (or a rivet).

Peculiarities of the relationship between social intelligence and cardiorhythm variability parameters of first year students during cognitive load

It is known that the mechanisms of cardioregulation provided by the frontal cortex are also involved in the regulation of social interaction, the success of which is related to social intelligence (SI). At the same time, there are no data on the relationship between cardiohemodynamic indicators of students and the level of social intelligence, as well as insufficient data on the features of cardio-regulation at rest and under cognitive load in students with certain features of SI. In this regard, the purpose of this study was to investigate the variability of cardiorhythm variability in students and describe their relationship with the level of development of social intelligence and its components. Social intelligence was studied using the Guilford Social Intelligence test (E.S. Mikhailova (Aleshina)). Specific features of cardio-regulation were studied by the "OMEGA-M" hardware-software complex in two stages: at rest and when performing a cognitive task (while performing the test "counting in mind"). The results showed that the highest values of heart rate (108,7±12,9 bpm), as well as tension index (TI = 277,5±265,9 units) (according to Baevsky R.M.) are observed in the students, who also have the highest level of social intelligence. At the same time, students with a low level of social intelligence did not have the situation of cognitive strain causing strain of adaptive mechanisms (TI=69.8±70.5 c.u.). An analysis of the relationship between the parameters studied showed that the level of social intelligence is associated with integral measures of cardiorhythm (TI = 0.424, at a significance level of p≤0.05, Pearson correlation coefficient), and measures of spectral power density of cardiorhythm frequencies (VLF = -0.373, at a significance level of p≤0.05, Pearson correlation coefficient). The results obtained indicate that the low level of social intelligence, contributes to the tension of adaptive mechanisms, as students experience psycho-emotional stress associated with low levels of arbitrariness in situations relating to the ability to understand, accept and solve emerging situations in interpersonal interaction. At the same time it is revealed that in response to cognitive load depending on the level of social intelligence there is an activation of both parasympathetic and sympathetic type of response of cardiohemodynamic indicators, the most optimal of which is parasympathetic.