Mechanical Tension Research Articles

Experimental study and analysis of RC beams shear strengthened with FRP/SMA composites

In practice, the prestressing is difficult to apply to achieve shear reinforcement of reinforced concrete (RC) beams due to the limited operating space used for installing mechanical tensioning equipment. So, how to efficiently introduce prestressing into RC beams is a practical problem. In this study, the authors utilized the recovery effect of shape memory alloys (SMA) wires to successfully introduce prestressing into RC beams and externally bonded with fiber reinforced polymer (FRP) sheets, forming a FRP/SMA composite shear reinforcement technology. After that, shear behavior of RC beams strengthened with FRP/SMA composites was investigated by a series of experiments. In order to further illustrate the effect of FRP/SMA composite shear reinforcement on RC beams, other reinforcement materials, such as SMA wires and FRP sheets, have also been separately applied in shear reinforcement experiments. Moreover, carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) are respectively applied to prepare FRP/SMA composites. For beams strengthened with FRP/SMA composites, the prestressing generated by the recovery effect of SMA wires can effectively suppress the formation of diagonal cracks in RC beams. The ultimate load and the corresponding displacement of strengthened beams significantly increased due to the constraint effect of FRP on the propagation of shear cracks. The shear capacity of CFRP/SMA composites strengthening beams was higher than that of BFRP/SMA composites strengthening beams, as CFRP/SMA composites better limited the propagation of cracks. Based on the test results, an analytical model has been proposed to predict the shear capacity of strengthened beams, and its effectiveness has been confirmed through comparison with experimental results.

MIR-107/HMGB1/FGF-2 axis responds to excessive mechanical stretch to promote rapid repair of vascular endothelial cells

The increase of vascular wall tension can lead to endothelial injury during hypertension, but its potential mechanism remains to be studied. Our results of previous study showed that HUVECs could induce changes in HMGB1/RAGE to resist abnormal mechanical environments in pathological mechanical stretching. In this study, we applied two different kinds of mechanical tension to endothelial cells using the in vitro mechanical loading system FlexCell-5000T and focused on exploring the expression of miR-107 related pathways in HUVECs with excessive mechanical tension. The results showed that miR-107 negatively regulated the expression of the HMGB1/RAGE axis under excessive mechanical tension. Excessive mechanical stretching reduced the expression of miR-107 in HUVECs, and increased the expression of the HMGB1/RAGE axis. When miR-107 analog was transfected into HUVECs with lipo3000 reagent, the overexpression of miR-107 slowed down the increase of the HMGB1/RAGE axis caused by excessive mechanical stretching. At the same time, the overexpression of miR-107 inhibited the proliferation and migration of HUVECs to a certain extent. On the contrary, when miR-107 was silent, the proliferation and migration of HUVECs showed an upward trend. In addition, the study also showed that under excessive mechanical tension, miR-107 could regulate the expression of FGF-2 by HMGB1. In conclusion, these findings suggest that pathological mechanical stretching promote resistance to abnormal mechanical stimulation on HUVECs through miR-107/HMGB1/RAGE/FGF-2 pathway, thus promote vascular repair after endothelial injury. The suggest that miR-107 is a potential therapeutic target for hypertension.

Cardiovascular Functions of Ena/VASP Proteins: Past, Present and Beyond.

Actin binding proteins are of crucial importance for the spatiotemporal regulation of actin cytoskeletal dynamics, thereby mediating a tremendous range of cellular processes. Since their initial discovery more than 30 years ago, the enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) family has evolved as one of the most fascinating and versatile family of actin regulating proteins. The proteins directly enhance actin filament assembly, but they also organize higher order actin networks and link kinase signaling pathways to actin filament assembly. Thereby, Ena/VASP proteins regulate dynamic cellular processes ranging from membrane protrusions and trafficking, and cell-cell and cell-matrix adhesions, to the generation of mechanical tension and contractile force. Important insights have been gained into the physiological functions of Ena/VASP proteins in platelets, leukocytes, endothelial cells, smooth muscle cells and cardiomyocytes. In this review, we summarize the unique and redundant functions of Ena/VASP proteins in cardiovascular cells and discuss the underlying molecular mechanisms.

The Tumor Suppressor DAB2IP Is Regulated by Cell Contact and Contributes to YAP/TAZ Inhibition in Confluent Cells.

External and internal mechanical forces modulate cell morphology, movement, proliferation and metabolism, and represent crucial inputs for tissue homeostasis. The transcriptional regulators YAP and TAZ are important effectors of mechanical signaling and are frequently activated in solid tumors, correlating with metastasis, chemoresistance, and shorter patient survival. YAP/TAZ activity is controlled by various pathways that sense cell shape, polarity, contacts, and mechanical tension. In tumors, aberrant YAP/TAZ activation may result from cancer-related alterations of such regulatory networks. The tumor suppressor DAB2IP is a Ras-GAP and scaffold protein that negatively modulates multiple oncogenic pathways and is frequently downregulated or inactivated in solid tumors. Here, we provide evidence that DAB2IP expression is sustained by cell confluency. We also find that DAB2IP depletion in confluent cells alters their morphology, reducing cell packing while increasing cell stiffness. Finally, we find that DAB2IP depletion in confluent cells favors YAP/TAZ nuclear localization and transcriptional activity, while its ectopic expression in subconfluent cells increases YAP/TAZ retention in the cytoplasm. Together, these data suggest that DAB2IP may function as a sensor of cell interactions, contributing to dampening cellular responses to oncogenic inputs in confluent cells and that DAB2IP loss-of-function would facilitate YAP/TAZ activation in intact epithelia, accelerating oncogenic transformation.

Comparison of main engine tension indicators tow-pusher when working in towing and pushing modes

Maintaining the operability of vessels that have worked out a significant resource since their construction will allow you to get additional profit. The paper presents a comparative analysis of the operational parameters of the main engine of a pusher tug operating in the modes of pushing and towing barge trains. The studies were carried out in a computational and theoretical way. The main attention is paid to the analysis of the parameters of the main engine, which determine its mechanical and thermal tension. In accordance with this, the areas of permissible operating conditions for pushing and towing barge trains are predicted. The weighting of the screw characteristics of the towing mode in comparison with the pushing mode requires additional restrictions on the power and speed of the main engine. The comparison of criteria and parameters at the characteristic points of the diesel cycle for the considered modes is carried out. Justification is given for individual parameters of the diesel cycle, which can be used as determining when assigning restrictive characteristics for thermal tension.

Defining Integrin Tension Required for Chemotaxis of Metastatic Breast Cancer Cells in Confinement.

Cancer metastasis is affected by chemical factors and physical cues. From cell adhesion to migration, mechanical tension applied to integrin expresses on the cell membrane and physical confinement significantly regulates cancer cell behaviors. Despite the physical interplay between integrins in cells and ligands in the tumor microenvironment, quantitative analysis of integrin tension during cancer cell migration in microconfined spaces remains elusive owing to the limited experimental tools. Herein, a platform termed microconfinement tension gauge tether to monitor spatial integrin tension with single-molecule precision by analyzing the epithelial-growth-factor-induced chemotaxis of metastatic human breast cancer cells in microfluidic channels is developed. The results reveal that the metastatic cancer cells exert the strongest integrin tension in the range of 54-100pN at the leading edges of cells during chemokinetic migration on a planar surface, while the cells exert the strongest integrin tension exceeding 100pN at the cell rear when entering microconfinement. Further analysis demonstrates that cells undergo mesenchymal migration under high integrin tension and less confinement, which is converted to amoeboid migration under low integrin tension or high confinement. In summary, the results identify a basic mechanism underlying the mechanical interactions between integrin tension and microenvironment that determines cancer invasion and metastasis.

Catch Bond-Mediated Adhesion Drives Staphylococcus aureus Host Cell Invasion.

Various viruses and pathogenic bacteria interact with annexin A2 to invade mammalian cells. Here, we show that Staphylococcus aureus engages in extremely strong catch bonds for host cell invasion. By means of single-molecule atomic force microscopy, we find that bacterial surface-located clumping factors bind annexin A2 with extraordinary strength, indicating that these bonds are extremely resilient to mechanical tension. By determining the lifetimes of the complexes under increasing mechanical stress, we demonstrate that the adhesins form catch bonds with their ligand that are capable to sustain forces of 1500-1700 pN. The force-dependent adhesion mechanism identified here provides a molecular framework to explain how S. aureus pathogens tightly attach to host cells during invasion and shows promise for the design of new therapeutics against intracellular S. aureus.

Spatial-Time Inhomogeneity Due to the Portevin-Le Chatelier Effect Depending on Stiffness

This work is devoted to the study of the influence of the rigidity of the loading system on the kinetics of the initiation and propagation of the Portevin-Le Chatelier (PLC) strain bands due to the jerky flow in Al-Mg alloy. To estimate the influence of the loading system, the original loading attachment, which allows reducing the stiffness in a given range, was used. Registration of displacement and strain fields on the specimen surface was carried out with the Vic-3D non-contacting deformation measurement system based on the Digital Image Correlation (DIC) technique. The mechanical uniaxial tension tests were carried out using samples of Al-Mg alloy at the biaxial servo-hydraulic testing system Instron 8850. As a result of tensile tests, deformation diagrams were obtained for Al-Mg alloy samples tested at different values of stiffness of the loading system: 120 MN/m (nominal value), 50 MN/m, 18 MN/m, and 5 MN/m. All diagrams show discontinuous plastic deformations (the Portevin-Le Chatelier effect). It is noted that a decrease in the rigidity of the loading system leads to a change in the type of jerky flow. At constant parameters of the loading rate, temperature, and chemical composition of the material, the PLC effects of types A, B, and C are recorded in tests.

Differences in Effects of Length-Dependent Regulation of Force and Ca2+ Transient in the Myocardial Trabeculae of the Rat Right Atrium and Ventricle.

The comparative differences in the fundamental mechanisms of contractility regulation and calcium handling of atrial and ventricular myocardium remain poorly studied. An isometric force-length protocol was performed for the entire range of preloads in isolated rat right atrial (RA) and ventricular (RV) trabeculae with simultaneous measurements of force (Frank-Starling mechanism) and Ca2+ transients (CaT). Differences were found between length-dependent effects in RA and RV muscles: (a) the RA muscles were stiffer, faster, and presented with weaker active force than the RV muscles throughout the preload range; (b) the active/passive force-length relationships were almost linear for the RA and RV muscles; (c) the value of the relative length-dependent growth of passive/active mechanical tension did not differ between the RA and RV muscles; (d) the time-to-peak and amplitude of CaT did not differ between the RA and RV muscles; (e) the CaT decay phase was essentially monotonic and almost independent of preload in the RA muscles, but not in the RV muscles. Higher peak tension, prolonged isometric twitch, and CaT in the RV muscle may be the result of higher Ca2+ buffering by myofilaments. The molecular mechanisms that constitute the Frank-Starling mechanism are common in the rat RA and RV myocardium.

Acoustic and electromagnetic properties of a martensitic-aging ferro-nickel alloy with the addition of copper under mechanical tension

The paper presents the results of a study of the effect of mechanical longitudinal uniaxial stretching on the velocity of longitudinal and transverse waves in XM-12 steel samples. During the research, an acoustic mirror-shadow method was used on multiple reflections of the control using an electromagnetic acoustic transducer and a piezoelectric transducer based on a polyvinylidene fluoride film to excite and receive waves. The elastic modules of the studied samples and the coefficients of acoustoelasticity are calculated.

Robust microtubule dynamics facilitate low-tension kinetochore detachment in metaphase.

During mitosis, sister chromatids are stretched apart at their centromeres via their attachment to oppositely oriented kinetochore microtubules. This stretching generates inwardly directed tension across the separated sister centromeres. The cell leverages this tension signal to detect and then correct potential errors in chromosome segregation, via a mechanical tension signaling pathway that detaches improperly attached kinetochores from their microtubules. However, the sequence of events leading up to these detachment events remains unknown. In this study, we used microfluidics to sustain and observe low-tension budding yeast metaphase spindles over multiple hours, allowing us to elucidate the tension history prior to a detachment event. We found that, under conditions in which kinetochore phosphorylation weakens low-tension kinetochore-microtubule connections, the mechanical forces produced via the dynamic growth and shortening of microtubules is required to efficiently facilitate detachment events. Our findings underscore the critical role of robust kinetochore microtubule dynamics in ensuring the fidelity of chromosome segregation during mitosis.

Acoustic and Electromagnetic Properties of Maraging Iron–Chromium–Nickel Alloy with Addition of Copper in Mechanical Tension

Acoustic and Electromagnetic Properties of Maraging Iron–Chromium–Nickel Alloy with Addition of Copper in Mechanical Tension

Differential gene expression and protein-protein interaction networks of human periodontal ligament stromal cells under mechanical tension

Orthodontic treatment is based on complex strategies and takes up to years until a desired therapeutic outcome is accomplished, implying long periods of high costs and discomfort for the patient. Choosing the optimal settings for force intensities in the initial phase of orthodontic tooth movement is the key to successful orthodontic treatment. It is known that orthodontic tooth movement is mainly mediated by tensile and compressive forces that are communicated to the alveolar bone via the periodontal ligament. While the revelation of the complex molecular network was already approached by transcriptomic analysis of compressed periodontal ligament cells, the entity of molecular key players activated by tensile forces remains elusive. Therefore, the aim of this study was to assess the effect of mechanical tensile forces on the gene expression profile of human primary periodontal ligament stromal cells, mimicking the initial phase of orthodontic tooth movement. A transcriptomic analysis of tension-treated and untreated periodontal ligament stromal cells yielded 543 upregulated and 793 downregulated differentially expressed genes. Finally, six highly significant genes were found in the transcriptome that are related to biological processes with relevance to orthodontic tooth movement, including apelin, fibroblast growth factor receptor 2, noggin, sulfatase 1, secreted frizzled-related protein 4 and stanniocalcin 1. Additionally, differences of gene expression profiles between individual cell donors showed a high effect size. Closer understanding of the roles of the identified candidates in the initial phase of orthodontic tooth movement could help to clarify the underlying mechanisms, which will be essential for the development of personalized treatment strategies in orthodontics.

Composites Based on Cotton Microfibers Impregnated with Magnetic Liquid for Magneto-Tactile Sensors.

In this paper, we report the preparation of two new composite materials based on cotton fibers and magnetic liquid consisting of magnetite nanoparticles and light mineral oil. Using the composites and two simple textolite plates plated with copper foil assembled with self-adhesive tape, electrical devices are manufactured. By using an original experimental setup, we measured the electrical capacitance and the loss tangent in a medium-frequency electric field superimposed on a magnetic field. We found that in the presence of the magnetic field, the electrical capacity and the electrical resistance of the device change significantly with the increase of the magnetic field, then, the electrical device is suitable to be used as a magnetic sensor. Furthermore, the electrical response functions of the sensor, for fixed values of the magnetic flux density, change linearly with the increase in the value of the mechanical deformation stress, which gives it a tactile function. When applying mechanical stresses of fixed values, by increasing the value of the magnetic flux density, the capacitive and resistive functions of the electrical device change significantly. So, by using the external magnetic field, the sensitivity of the magneto-tactile sensor increases, therefore the electrical response of this device can be amplified in the case of low values of mechanical tension. This makes the new composites promising candidates for the fabrication of magneto-tactile sensors.

Why do human ears get longer with age? Auricular stretching by facial adiposity: A hypothesis

Historically, in old Chinese writings, long human ears were associated with wealth and increased survival. Over the last three decades, several studies have demonstrated that ear length increases as we age. Despite various hypotheses, there is no clear understanding of the mechanism or the purpose of such an interesting phenomenon. The author is proposing, herein that ear elongation occurs secondary to chronic mechanical tension on the auricle by the facial fat accumulation (facial adiposity), particularly in the area anterior to the ear. Facial adiposity occurs not only during aging but also with postmenopausal transition, as well as medical conditions associated with central obesity. Further research is needed to test the proposed hypothesis.

DNA tension assays reveal that force-dependent integrin activation regulates neurite outgrowth in primary cortical neurons

Biomechanical inputs are ubiquitously present in biological systems and are known to regulate various cell functions. In particular, neural cell development is sensitive to mechanical regulation, as these cells reside in one of the softest microenvironments in the body. To fully characterize and comprehend how mechanical force modulates early neuronal processes, we prepared substrates functionalized with DNA probes displaying integrin ligands, including cRGD and laminin, to quantify integrin-mediated molecular tension during neurite initiation in primary cortical neurons. Our live-cell imaging analysis reveals that integrin-mediated tension force is highly dynamic and distributed across the cell body, with the overall tension signal gradually increasing during neurite outgrowth. Notably, we detected a consistent level of mechanical force (amplitude = 4.7–12 piconewtons, pN) for cell integrin-ligand interactions. Further quantifications reveal that neurons exhibit faster cell spreading and neurite outgrowth upon interacting with ligands functionalized with 4.7 pN relative to 12 pN probes. These findings indicate that the magnitude of integrin-mediated mechanical feedback regulates neuronal activity during early neuritogenesis. Additionally, we observed that mechanical tension is correlated with calcium signaling, since inhibiting calcium influx substantially reduced mechanical tension. Thus, our findings support that the magnitude of integrin-mediated mechanical feedback regulates neuronal activity during early neuritogenesis and that mechanical force is an essential element complementing well-known biochemical regulatory mechanisms orchestrating the integrin activation machinery and controlled neurite outgrowth in cortical neurons.

Effect of Mechanical Tension on the Long-Chain Noncoding RNA Expression Profile of Human Skin Regeneration.

This study investigates the potential gene regulation of long-chain noncoding RNAs (lncRNAs) during skin regeneration by analyzing the changes in the lncRNA expression profile during skin regeneration under mechanical tension. Through the effect of mechanical tension on human skin tissue, the authors observed that after the accelerated differentiation and proliferation of skin epidermal cells, the lncRNA expression profile was compared with that of normal epidermal cells, and differential expression of lncRNA in skin tissue was found. Fifty-three lncRNAs were differentially expressed between the experimental and control groups, and compared with the control group, 22 lncRNAs were upregulated and 31 lncRNAs were downregulated in the experimental group. In addition, through the annotation of the functions of gene ontology and kyoto encyclopedia of genes and genomes, it was further clarified that the main signaling pathway of lncRNAs in the process of skin tissue expansion is involved in the regulation of skin tissue regeneration, and the regulatory network of lncRNAs and microRNAs was established. The results of this study will provide a theoretical basis for the mechanism of lncRNA regulation of skin regeneration, and changes in the lncRNA expression profile can also provide clues for the study of the biological regulation mechanism of skin regeneration.

Development and characteristics of multifunctional ultra-lightweight engineered cementitious composites incorporating cenospheres and PE fibre

Ultra-lightweight, high ductility, high strength, and multi-functionality are recent development trends in concrete. This study proposed a design concept of multifunctional ultra-lightweight engineered cementitious composites (ULW-ECCs) without functional fillers using fly ash cenosphere (FAC) and polyethylene (PE) fibre, which has heat insulation, self-sensing, and self-healing functions. The mechanical (tension, compression, flexure) and corresponding self-sensing properties under monotonic and cyclic loading, self-healing, thermal conductivity, and thermal effusivity properties were examined. The ULW-ECCs were developed based on the maximum packing density of the matrix, which showed high pseudo-strain-hardening indices and had an apparent density of 1055–1333 (Oven-dry density: 946–1261) kg/m3, compressive strength of 36–58 MPa, and a tensile strain capacity of 4%–8% under standard curing condition. With the use of FAC with a highly stiff shell, the ULW-ECCs show high strength and high thermal insulation properties. ULW-ECCs incorporating FAC show excellent self-sensing properties without any conductive fillers under compression, bending and tension. The electromechanical behaviour was consistent and repeatable during cyclic and monotonic loading processes, and a microstructure model was used to explain the self-sensing mechanism. The cement paste in the matrix can form a 3D-like honeycomb structure because a large number of FACs evenly divide the cement paste, which shows sensitive self-sensing ability. Additionally, the multiple micro-cracks of ULW-ECCs show excellent self-healing properties. Optical microscope and SEM analyses of ULW-ECC were used to explain the results. The developed multifunctional ULW-ECCs without functional fillers would be a promising material for sustainable development.

1053 Mechanical tension influences the immunocompetency of ex vivo skin tissue

1053 Mechanical tension influences the immunocompetency of ex vivo skin tissue

375 Mechanical tension promotes maintenance of ex vivo skin viability and integrity

375 Mechanical tension promotes maintenance of ex vivo skin viability and integrity