Threshold Force Research Articles

The phosphodiester dissociative hydrolysis of a DNA model promoted by metal dications.

Phosphodiester bonds, which form the backbone of DNA, are highly stable in the absence of catalysts. This stability is crucial for maintaining the integrity of genetic information. However, when exposed to catalytic agents, these bonds become susceptible to cleavage. In this study, we investigated the role of different metal dications (Ca2⁺, Mg2⁺, Zn2⁺, Mn2⁺, and Cu2⁺) in promoting the hydrolysis of phosphodiester bonds. A minimal DNA model was constructed using two pyrimidine nucleobases (cytosine and thymine), two deoxyribose units, one phosphate group, and one metallic dication coordinated by six water molecules. The results highlight that Cu2⁺ is the most efficient in lowering the energy barrier for bond cleavage, with an energy barrier of 183kJ/mol, compared to higher barriers for metals like Zn2⁺ (202kJ/mol), Mn2⁺ (202kJ/mol), Mg2⁺ (210kJ/mol), and Ca2⁺ (223kJ/mol). Understanding the interaction between these metal ions and phosphodiester bonds offers insight into DNA stability and organic data storage systems. DFT calculations were employed using Gaussian 16 software, applying the B3LYP hybrid functional with def2-SVP basis sets and GD3BJ dispersion corrections. Full geometry optimizations were performed for the initial and transition states, followed by identifying energy barriers associated with phosphodiester bond cleavage. The optimization criteria included maximum force, root-mean-square force, displacement, and energy convergence thresholds.

Bidirectional Allostery Mechanism in Catch-Bond Formation of CD44 Mediated Cell Adhesion.

Catch-bonds, whereby noncovalent ligand-receptor interactions are counterintuitively reinforced by tensile forces, play a major role in cell adhesion under mechanical stress. A basic prerequisite for catch-bond formation, as implicated in classic catch-bond models, is that force-induced remodeling of the ligand binding interface occurs prior to bond rupture. However, what strategy receptor proteins utilize to meet such specific kinetic control remains elusive. Here we report a bidirectional allostery mechanism of catch-bond formation based on theoretical and molecular dynamics simulation studies. Binding of ligand allosterically reduces the threshold force for unlocking of otherwise stably folded force-sensing element (i.e., forward allostery), so that a much smaller tensile force can trigger the conformational switching of receptor protein to high binding-strength state via backward allosteric coupling before bond rupture. Such bidirectional allostery fulfills the specific kinetic control required by catch-bond formation and is likely to be commonly utilized in cell adhesion. The essential thermodynamic and kinetic features of receptor proteins essential for catch-bond formation were identified.

Shear-driven stability of a rigid particle in yield stress fluids

The stability of a rigid particle in yield stress fluids, comprised of soft particle glasses (SPGs), is investigated in shear flow under an applied external force, such as weight, using particle dynamics simulations. Results provide the critical force threshold, in terms of the dynamic yield stress and the flow strength, required to initiate sedimentation of the rigid particle over a wide range of shear rates and volume fractions. The streamlines of the SPGs show local disturbances when the rigid particle settles. The form of these disturbances is consistent with the microdynamics and microstructure response of the neighboring soft particles of the sedimenting rigid particle. Sedimenting particle induces non-affine displacement to the suspensions at low shear rates and high applied forces, while these dynamical events are localized and suppressed at high shear rates. Stability diagrams, which provide the conditions of the sedimentation of the rigid particle, are presented in terms of the applied force and the shear rate. These individual stability diagrams at each volume fraction map onto a universal stability diagram when the external force is scaled by the dynamic yield stress and shear rate with a ratio of the solvent viscosity to the low-frequency modulus of the SPGs.

Does static friction information predict the onset of sliding for soft material?

Friction behavior between soft and hard materials has long been a question of great interest in the fields of artificial joints, human skin contact, robotic grippers, and others. In this study, we presented a combination of theoretical and experimental analyses to investigate the friction behavior of soft materials. Using some geometric and stick–slip features in the early stage of static friction, the friction property of the interface between a soft material and a hard material is determined. Moreover, the onset of slip, the threshold force at which a friction interface begins to slide, is also predicted by a theoretical model. The predictive ability of this model may provide insights for improving interaction property recognition, as well as for developing fine tactile feedback and dexterous operation of robotic grasping.

The dual-band emissions, multicolor continuous mechanochromisms, and application based on a single luminogen

Currently, the high contrast and multicolor continuous mechanochromic materials still face a great challenge. Here, a novel D-π-A type luminogen named as CzIPCN, was successfully constructed. By solvent diffusion method, crystals YC, BT, RE, and RA were obtained, not only covering a large-span emission from blue to red, but also showing scare dual band emission. Interesting, the blue BT and yellow YC have similar intermolecular π-π stacking interactions and significantly different emission maxima, while two emission maxima of the RE and RA appear at the similar frequency but with different intensity ratios. More interesting, emission maxima of BT present tiny shifts before/after grinding, but RE and RA show very low mechanical force thresholds in mechanochromism, and yield significant color contrasts and wavelength shifts (＞100 nm). Under both light&hard crushing and grinding, YC presents multicolor continuous mechanochromism. Additionally, CzIPCN not only shows pH-dependent fluorescence emission but also white light emission in a DCM-TFA mixture. Finally, high-level anti-counterfeiting patterns controlled by different mechanical forces were successfully constructed. It is worth mentioning that this is the first report on multiple anti-counterfeiting patterns using a single luminogen.

Temporomandibular Joint Pain Measurement by Bite Force and Von Frey Filament Assays in Mice.

Temporomandibular joint (TMJ) pain and osteoarthritis (OA) are common and debilitating disorders that impair patients' quality of life. The mechanisms driving diseases-related pain are poorly understood, and current treatments fail to provide effective and long-term therapeutic effects. Additionally, pain assessment in research, particularly orofacial pain, poses several challenges that complicate studies in both clinical and basic science settings. Therefore, we have established an inflammatory TMJ pain mouse model via intra-articular injection of CFA (Complete Freund's Adjuvant) and evaluated pain behaviors by bite force measurement and the von Frey filament test. Mice with CFA injection exhibited orofacial pain behaviors compared to PBS injection, including reduced bite force and head withdrawal threshold in the von Frey filament test. These methods are relatively easy to execute to have reproducible results and can be potentially extended to pain studies for other disease models related to TMJ disorders. Together, bite force, and the von Frey filament tests are reliable in measuring orofacial pain, as demonstrated in CFA injection-induced painful TMJOA mouse models.

Enhancing dynamic stability of HTS maglev systems with preloading method

High temperature superconducting (HTS) bulks have strong flux pinning capabilities and are widely used in various fields. Their self-stabilizing characteristics also provide new ideas for ultra-high-speed rail transit. For HTS maglev systems, operational stability, curve negotiation and safety when subjected to external forces are very important. Due to the hysteresis effect of superconducting bulks, they do not always return to their initial positions after deviating from the levitated position in an alternative external magnetic field. In some cases, the levitation system can be destroyed. Studies have shown that preloading can enhance quasi-static levitation performance. Therefore, this paper conducts a detailed analysis of the quasi-static levitation and guidance forces of HTS bulks above a Halbach permanent magnet guideway (PMG) under conditions with and without preloading. Additionally, the dynamic responses of the HTS bulks under lateral or vertical pulsed excitations are studied, with a particular focus on the final equilibrium position offset after disturbance. The results indicate that preloading can suppress the attenuation of the levitation force, enhance the guidance performance, and raise stiffness in both lateral and vertical directions. It also effectively suppresses position deviation from disturbance and increases the maximum excitation force threshold for system instability. This study provides practical insights for HTS maglev applications.

The dynamics of red blood cells traversing slits of mechanical heart valves under high shear

Hemolysis, including subclinical hemolysis, is a potentially severe complications of mechanical heart valves (MHVs), which leads to shortened red blood cell (RBC) lifespan and hemolytic anemia. Serious hemolysis is usually associated with structural deterioration and regurgitation. However, the shear stress in MHVs’ narrow leakage slits is much lower than the shear stress threshold causing hemolysis and the mechanisms in this context remain largely unclear. This study investigated the hemolysis mechanism of RBCs in cell-size slits under high shear rates by establishing in vitro microfluidic devices and a coarse-grained molecular dynamics (CGMD) model, considering both fluid and structural effects simultaneously. Microfluidic experiments and computational simulation revealed six distinct dynamic states of RBC traversal through MHVs' microscale slits under various shear rates and slit sizes. It elucidated that RBC dynamic states were influenced by not only by fluid forces but significantly by the compressive force of slit walls. The variation of the potential energy of the cell membrane indicated its stretching, deformation, and rupture during traversal, corresponding to the six dynamic states. The maximum forces exerted on membrane by water particles and slit walls directly determined membrane rupture, serving as a critical determinant. This analysis helps in understanding the contribution of the slit walls to membrane rupture and identifying the threshold force that leads to membrane rupture. The hemolysis mechanism of traversing microscale slits is revealed to effectively explain the occurrences of hemolysis and subclinical hemolysis.

Sequential three-way decision with automatic threshold learning for credit risk prediction

Machine learning algorithms treat credit risk prediction as a binary classification problem. However, two-way decisions with a single threshold force to make either a default or non-default decision may be inappropriate. To reduce the risk of decision errors, this study introduces three-way decisions and proposes a sequential three-way decision model with automatic threshold learning to evaluate credit risk. Initially, the model uses the loan amount and interest to determine the decision loss of the three-way decision, assigning distinct decision thresholds to different samples. Subsequently, the model employs decision cost and information gain to formulate an objective for threshold optimisation. Finally, the model continuously optimises the classification process by using the outcomes of certain decisions as supplementary information. In addition, to validate our model, we conduct comparative experiments with various methods on a real credit dataset from a Chinese bank. The results indicate that the model not only enhances classification performance across several metrics but also assists financial institutions in reducing decision error costs.

Mechanistically Different Mechanochromophores Enable Calibration and Validation of Molecular Forces in Glassy Polymers and Elastomeric Networks.

Sterically distorted donor-acceptor π-systems, termed DA springs, can be progressively planarized under mechanical load causing a bathochromic shift of the photoluminescence (PL) spectrum. By combining theory and experiment, we here use a simple linear force calibration for two different conformational mechanochromophores to determine molecular forces in polymers from the mechanochromic shift in PL wavelength during multiple uniaxial tensile tests. Two systems are used, i) a highly entangled linear glassy polyphenylene and ii) a covalent elastomeric polydimethylsiloxane network. The mean forces estimated by this method are validated using known threshold forces for the mechanochemical ring-opening reactions of two different spiropyran force probes. The agreement between both approaches underlines that these DA springs provide the unique opportunity for the online monitoring of local molecular forces present in diverse polymer matrices.

Measuring Integrin Force Loading Rates Using a Two-Step DNA Tension Sensor.

Cells apply forces to extracellular matrix (ECM) ligands through transmembrane integrin receptors: an interaction which is intimately involved in cell motility, wound healing, cancer invasion and metastasis. These small (piconewton) integrin-ECM forces have been studied by molecular tension fluorescence microscopy (MTFM), which utilizes a force-induced conformational change of a probe to detect mechanical events. MTFM has revealed the force magnitude for integrin receptors in a variety of cell models including primary cells. However, force dynamics and specifically the force loading rate (LR) have important implications in receptor signaling and adhesion formation and remain poorly characterized. Here, we develop an LR probe composed of an engineered DNA structure that undergoes two mechanical transitions at distinct force thresholds: a low force threshold at 4.7 pN (hairpin unfolding) and a high force threshold at 47 pN (duplex shearing). These transitions yield distinct fluorescence signatures observed through single-molecule fluorescence microscopy in live cells. Automated analysis of tens of thousands of events from eight cells showed that the bond lifetime of integrins that engage their ligands and transmit a force >4.7 pN decays exponentially with a τ of 45.6 s. A subset of these events mature in magnitude to >47 pN with a median loading rate of 1.1 pN s-1 and primarily localize at the periphery of the cell-substrate junction. The LR probe design is modular and can be adapted to measure force ramp rates for a broad range of mechanoreceptors and cell models, thus aiding in the study of molecular mechanotransduction in living systems.

Identification of force chains in wet coal dust layer and the effect of porosity on three-body contact stiffness

Aiming at the three-body contact problem of mechanical rough surface containing wet coal dust interface, the three-body contact model of rough surface containing wet coal dust interface is constructed by comprehensively considering the contact deformation of rough surface and contact characteristics of wet coal dust, and based on the crushing theory. By analysing the contact force, load-bearing particle size and adjacent contact angle thresholds of the wet coal dust layer, the force chain identification criterion is formulated. Finally, quantitative calculations of the force chain characteristics are performed to reveal the effect of different initial porosities on the three-body contact stiffness, which is verified experimentally. The results of the study show that the average contact force of the wet coal dust layer can be used as the force chain contact force threshold, the average particle size can be used as the force chain particle size threshold, and the force chain angle threshold is determined by the particle coordination number. As the initial porosity decreases, the number, length and stiffness of force chains in the wet coal dust layer increase significantly, and the stiffness reaches a maximum value of 2.007 × 108 pa/m at the moment of downward pressure to stabilisation, while the trend of force chain bending varies in the opposite direction, and its minimum bending degree decreases to 20°. The maximum relative error between the simulation and experimental results of three-body contact stiffness is 9.64%, which proves the accuracy of the force chain identification criterion and the quantitative calculation of three-body contact stiffness by force chain.

Design and fabrication of a multi-purpose four arm electrothermal microgripper; a novel approach to control maximum gripping force limit

The development of microgrippers requires accurate control of force and position for the grasping mechanisms in micromanipulation. This controllability ensures the safe transfer of sensitive micro-objects, such as living cells. The design of microgrippers is often limited by the dimensions and adaptability of the micro-objects being manipulated. Therefore, microgrippers should be customized for each micro-object. Additionally, complex sensor mechanisms are required to control the gripping force. This study introduces a novel design of a four-arm MEMS electrothermal microgripper intended for versatile micromanipulation purposes. The microgripper design procedure is compatible with a list of constraints, including biological and microfabrication constraints. The jaw form is designed to manipulate micro-objects with a wide range of dimensions (1 to 360 μm). Furthermore, a novel approach is presented here to control the force threshold of gripping without a sensor during manipulation. The proposed solution involves using structure stiffening to control the force and prevent damage to micro-objects. GA and analytical models (transient behaviour of structure) are used to satisfy the long list of constraints. The device is fabricated through UV-LIGA, utilizing nickel and copper as the structural and sacrificial layer. The experimental and simulation results demonstrate that the microgripper can achieve a 60 μm jaw displacement at a voltage of 0.329V. The gripping arms can provide a force of 15 to 450 μN for the handling of micro-objects. The maximum gripper temperature of 98 °C makes it suitable for biological applications. The innovative form and systematic design of the microgripper enable its adaptability for various applications.

Study of an auxiliary trimming device for cracked carrots

AbstractCracked carrots account for a large proportion of defective carrots, which are usually discarded or used as feed, resulting in resource waste and economic benefit loss. Cracked carrots can be used as raw materials for further processed carrot products after being trimmed. So, an auxiliary device was developed combining PLC (Programmable Logic Controller) and machine vision to achieve clamping and crack defect localization for intelligent trimming of crack defect. The carrot was orientated based on the area method, rotated by flexible jaws and a rotating cylinder to make the carrot head and tail aligned. The clamping device could non‐destructively clamp carrot in axial and radial direction with a force threshold of 10 and 22 N respectively, and rotate carrot to make the crack defect upwards. The results showed that the recognition accuracy of carrot head and tail orientation was 98%, the average deviation of carrot centroid clamping position was less than 9 mm at a speed of 300 mm/s, the rotational positioning time was less than 3 s and the number of adjustments were no more than 2 at a motor speed of 180 rpm, which could meet the subsequent trimming requirements.Practical applicationsTrimming the cracked area of carrots can reduce bacterial growth and decay, which is beneficial for subsequent processing and reduces resource waste. This article designs a carrot auxiliary trimming device, which uses image processing technology to recognize the orientation of the head and tail of carrots and the cracked area, and uses automated equipment to achieve stable clamping of carrots and make the cracked area face the trimming tool. This study is beneficial for the refined management of agricultural products.

Influence of a waveform on the bit–rock impact response considering reflected waves in a drill rod

Percussive drilling is considered an efficient approach for penetrating hard formations. Understanding the responses and mechanical properties of rocks while being impacted and crushed by rock drills is essential for further improving their penetration efficiencies. This paper examines the consecutive impacts between the drill bit and rock, which are induced by the waves reflected in the drill rod after an initial hammer impact. Firstly, the loading and unloading principle for consecutive impacts is proposed. Based on this principle and one-dimensional (1-D) longitudinal wave propagation, a 1-D bit-rock interaction dynamics model is subsequently established. This model considers switches between the states of impact and separation, to instantly predict rock responses. Selecting marble as a representative material, the findings from the 1-D theoretical model and three-dimensional (3-D) Finite Element Method (FEM) simulations indicate that the number of repeated crushing impacts, which substantially contribute to the final penetration displacement, increases as the wavelength or the baseline level of fc (dimensionless crushing threshold force) in a rock decreases. fc is related to the loading rate, and its baseline level diminishes with decreasing impact energy (waveform amplitude). Due to the increases in fc and loading stiffness for short waves, the overall increasing trend of the final penetration displacement with decreasing wavelength weakens. A suitably-short wave with a high dimensionless exponential growth rate r or a long wave with approximately a unit of r can lead to a relatively-high final penetration displacement. In addition, we find that the dynamic loading and unloading stiffness and crushing threshold force have specific relationships with the penetration displacement and rock loading rate.

Design and Test of Discrete Element-Based Separation Roller Potato–Soil Separation Device

To address the problems of low bright rates and high rates of potato injuries, a left and right-hand rotation combination of potato–soil separation devices was developed. Its overall structure and working principle were introduced. A Texture Analyzer and pressure sensor were used to measure the force threshold of different varieties of potatoes. A discrete element model of separation rollers and potatoes was established. The collision characteristics of potatoes were analyzed using the device inclination angle, rotational speed, and the center distance of the separation rollers as test factors. A field trial was carried out to optimize the best combination of factors by taking the rate of injured potatoes, bright potatoes, and skin-breaking rate as the test indexes. The force threshold for skin-breaking injury in potatoes was found to be 190–195 N. When the inclination angle of the device was 6°, the rotation speed of the separation roller was 100 r/min, and the distance between the centers of the separation rollers was 79 mm. The rate of injury was 1.25%, the rate of bright potatoes was 99.01%, and the rate of skin-breaking was 1.58%. When the inclination angle of the device was 8°, the rotational speed of the separating roller was 80 r/min, and the center distance of the separating roller was 79 mm, the rate of injured potato was 1.43%, the rate of bright potato was 98.64%, and the rate of broken skin was 1.77%. This paper offers an optimized reference for the effectual removal of sticky soil.

Development and Initial Evaluation of a Cost-Effective Force Sensor for Ureteroscopic Application.

Purpose: Retrograde intrarenal surgery is the gold-standard treatment for most kidney stones. During ureteroscopy, ureteral access sheath insertion at forces greater than 8.0 Newtons (N) risks high-grade ureteral injury. To monitor force, our institution utilizes a unique, Bluetooth-equipped device (i.e., the University of California-Irvine Force Sensor). Given the unique nature of the force sensor, we sought to develop an inexpensive and accessible force sensor based on Boyle's law and the specific amount of force required to compress an occluded 1.0 mL syringe. Materials and Methods: We evaluated three brands of 1.0 mL syringes. After setting the plunger at 1.0 mL, the syringe was occluded, and the syringe plunger was compressed. The syringe volume was recorded when the applied force on the plunger reached 4.0 N, 6.0 N, and 8.0 N. Multiple trials were performed to assess reliability and reproducibility. A method for applying this clinically was also developed. Results: The precise force thresholds identified for a 1.0 mL Luer-Lok™ Syringe (Becton Dickinson, Franklin Lakes, NJ) were 0.30 mL for 4.00 N, 0.20 mL for 6.00 N, and 0.15 mL for 8.00 N. The 1.0 mL Tuberculin Syringe and 1.0 mL Luer Slip Syringe were less precise, but compression from 1.0 to 0.40 mL, 0.25 mL, and 0.20 mL corresponded to force sensor readings that did not exceed 4.00 N, 6.00 N, and 8.00 N, respectively. Conclusions: Based on volume changes, 4.00 N, 6.00 N, and 8.00 N of force can be reliably and reproducibly achieved using an occluded 1.0 mL syringe.

Versatile 3D-printed LPFG: Characterization, challenges and insights

This manuscript studies a method to create Long Period Fiber Gratings in optical fibers using a cost-effective 3D-printed device equipped with interchangeable masks, allowing fast reconfiguration and non-permanent modifications. We investigate diverse configurations by analyzing their transmission spectra in the range from 1520 nm to 1570 nm, and measure the dip wavelength (λDip) evolution with the force applied to the device. A force-dependent blue-shift is observed, and the refractive index modulation is estimated up to 2.84×10−3 and 2.39×10−3 for the two examined gratings masks. Analysis of the λDip and the figure of merit suggest a threshold force beyond which the spectral characteristics tendency reverse. This is likely linked to the different elasticity between the optical fiber and the mask material and the way they deform. Although the method imposes certain limitations in bandwidth, it can produce LPFGs with good applicability in scenarios such as low Technology Readiness Level or swiftly deployable cost-efficient systems for optical filtering or sensing. Considering sensing applications, we present a simple model for real-time computing of displacement, strain, or pressure through spectrum monitoring. The model aligns with the observed experimental results, underlining its practicality for potential applications.

Does the current testing standard of chest protectors warrant the devices’ protection for PTW riders in collisions?

Non-inflatable chest protector is a passive safety device to protect powered two-wheeler (PTW) riders from thorax injuries. Before being put on the market, the protectors should be qualified for the European standard tests EN1621-3:2018 which remains uncertain regarding the impact energy level, force evaluation thresholds, and impact configurations. This study aims to ascertain whether the standard EN1621-3:2018 ensures adequate chest protection for PTW riders. Thus, three generic protectors were created to qualify for standard tests and then evaluated against rider chest impact scenarios by finite element modelling. Bar-to-rider and rider-to-bar virtual impacts were simulated with a range of impact energy 50 ∼ 1563 J. In virtual standard tests, protector 1 had the lowest impact force, followed by protectors 2 and 3. In chest impact analysis, the rider with or without protector was rarely found injured under the testing standard energy level (50 J). The chest impact force was below the standard force threshold of 24 kN under all impact energy levels. Protector 3 had a generally better protection performance in terms of chest deflection than protectors 1 and 2, which were not consistent with the standard testing results. The rider chest responses in bar-to-rider impacts differed significantly from the responses in bar-to-rider impacts. Therefore, future testing standard might introduce more appropriate impact energy, force thresholds and accident-relevant impact configurations to ensure the device’s effectiveness in providing protection during PTW crashes. This study furnishes valuable insights into enhancing the design and evaluation methodologies of protective gear, thus directly contributing to the advancement of PTW rider safety.

Assessment of a continuous passive motion assistive device in dogs following stifle surgery

Canine rehabilitation optimizes recovery and the quality of life in dogs with musculoskeletal conditions or after surgery. Achieving proper range of motion (ROM) is vital post-stifle surgery, often accomplished through manual therapy and active exercises. We investigated the mechanical performance of a continuous passive motion (CPM) device for dogs and its potential use in canine rehabilitation therapy.In the ethical review process, our research was accepted to be evaluated in a sample of four dogs that had undergone left stifle surgery. Each dog underwent four sessions with the device at three different speeds. Results showed the device replicated extension angles close to goniometer measurements used in manual therapy. Flexion was also achieved, but not to the same extent. A force threshold stopped the device, avoiding discomfort in dogs with restricted ROM. Dog-specific factors like body position, opposition to movement, limb size, stage of recovery, haircoat, and discomfort, appeared to influence device operation. Mechanical improvements to allow for enhanced flexion are recommended in future CPM device designs, including a resistance threshold that could be adjusted for individual dogs and stages of healing. This study serves as a foundation for future advancements in canine rehabilitation systems. A canine CPM device may provide an affordable option to improve ROM. This could be beneficial for dog owners, who may not be comfortable with manual therapy, to assist with home rehabilitation exercises.