Lever Force Research Articles

Effect of Ca2+ binding states of calmodulin on the conformational dynamics and force responses of myosin lever arm.

The mechanochemical coupling and biological function of myosin motors are regulated by Ca2+ concentrations. As one of the regulation pathways, Ca2+ binding induces a conformational change of the light chain calmodulin and its binding modes with a myosin lever arm, which can affect the stiffness of the lever arm and force transmission. However, the underlying molecular mechanism of the Ca2+ regulated stiffness change is not fully understood. Here, we study the effect of Ca2+ binding on the conformational dynamics and stiffness of the myosin VIIa lever arm bound with a calmodulin by performing molecular dynamics simulations and dynamic correlation network analysis. The results showed that the calmodulin bound lever arm at an apo state can sample three different conformations. In addition to the conformation observed in a crystal structure, a calmodulin bound lever arm at the apo condition can also adopt other two conformations featured by different extents of small-angle bending of the lever arm. However, large-angle bending is strongly prohibited. Such results suggest that the calmodulin bound lever arm without Ca2+ binding is plastic for small-angle deformation but shows high stiffness for large-angle deformation. In comparison, after the binding of Ca2+, although the calmodulin bound lever arm is locally more rigid, it can adopt largely deformed or even unfolded conformations, which may render the lever arm incompetent for force transmission. The conformational plasticity of the lever arm for small-angle deformation at the apo condition may be used as a force buffer to prevent the lever arm from unfolding during the power stroke action of the motor domain.

A Design Method for a Variable Combined Brake System for Motorcycles Applying the Adaptive Control Method

The variable combined brake system (VCBS) is a mechanism for motorcycles to simultaneously activate the front and rear brake systems by using one brake lever or pedal. The purpose is to reduce the risk of rollover accidents due to misuse of the front brake when panic braking. Due to its ability in a wide variation range of braking force distribution (BFD) ratios between the front and rear wheels, the VCBS can simultaneously achieve high braking effort and driving comfort performances, provided that the BFD ratio is designed appropriately. This paper aimed to develop the design method for the VCBS. A mathematical model of the VCBS mechanism is derived, and a parameter matching design method that applies adaptive control theory is proposed. A prototype of VCBS is designed and built based on the proposed method. The straight-line braking test results show that the motorcycle equipped with the VCBS prototype effectively obtained a high braking performance in deceleration. The obtained maximum deceleration is an average of 6.37 m/s2 (0.65 g) under an average handbrake lever force of 154.29 N. For front brake failure, maximum deceleration is obtained at an average of 3.38 m/s2 (0.34 g), which is higher than the homologation requirement of 2.9 m/s2.

Wrist movements induce torque and lever force in the scaphoid: an ex vivo study

PurposeWe hypothesised that intercarpal K-wire fixation of adjacent carpal bones would reduce torque and lever force within a fractured scaphoid bone.MethodsIn eight cadaver wrists, a scaphoid osteotomy was stabilised using a locking nail, which also functioned as a sensor to measure isometric torque and lever forces between the fragments. The wrist was moved through 80% of full range of motion (ROM) to generate torque and force within the scaphoid. Testing was performed with and without loading of the wrist and K-wire stabilisation of the adjacent carpal bones.ResultsAverage torque and lever force values were 49.6 ± 25.1 Nmm and 3.5 ± 0.9 N during extension and 41 ± 26.7 Nmm and 8.1 ± 2.8 N during flexion. Torque and lever force did not depend on scaphoid size, individual wrist ROM, or deviations of the sensor versus the anatomic axis. K-wire fixation did not produce significant changes in average torque and lever force values except with wrist radial abduction (P = 0.0485). Other than wrist extension, torque direction was not predictable.ConclusionIn unstable scaphoid fractures, we suggest securing rotational stability with selected implants for functional postoperative care. Wrist ROM within 20% extension and radial abduction to 50% flexion limit torque and lever force exacerbation between scaphoid fragments.

Critical Assessment of Single-Use Ureteroscopes in an In Vivo Porcine Model.

Methods A female pig was placed under general anesthesia and positioned supine, and retrograde access to the renal collecting system was obtained. The LithoVue (Boston Scientific) and Uscope (Pusen Medical) were evaluated by three experienced surgeons, and each surgeon started with a new scope. The following parameters were compared between each ureteroscope: time for navigation to upper and lower pole calyces with and without implements (1.9 F basket, 200 μm laser fiber, and 365 μm laser fiber for upper only) in the working channel and subjective evaluations of maneuverability, irrigant flow through the scope, lever force, ergonomics, and scope optics. Results Navigation to the lower pole calyx was significantly faster with LithoVue compared to Uscope when the working channel was empty (24.3 vs. 49.4 seconds, p < 0.01) and with a 200 μm fiber (63.6 vs. 94.4 seconds, p=0.04), but not with the 1.9 F basket. Navigation to the upper pole calyx was similar for all categories except faster with LithoVue containing the 365 μm fiber (67.1 vs. 99.7 seconds, p=0.02). Subjective assessments of scope maneuverability to upper and lower pole calyces when the scope was empty and with implements favored LithoVue in all categories, as did assessments of irrigant flow, illumination, image quality, and field of view. Both scopes had similar scores of lever force and ergonomics. Conclusions In an in vivo porcine model, the type of single-use ureteroscope employed affected the navigation times and subjective assessments of maneuverability and visualization. In all cases, LithoVue provided either equivalent or superior metrics than Uscope. Further clinical studies are necessary to determine the implications of these findings.

차량 도어 래치의 작동력 계산을 위한 수식 유도 : 파트 2-OS/IS래버, 전체 작동력 분석

차량 도어 래치의 작동력 계산을 위한 수식 유도 : 파트 2-OS/IS래버, 전체 작동력 분석

Variation in an Extreme Weapon: Horn Performance Differences across Rhinoceros Beetle (Trypoxylus dichotomus) Populations.

Japanese rhinoceros beetle (Trypoxylus dichotomus) males have exaggerated head horns that they use as weapons in combat over reproductive opportunities. In these contests, there is an advantage to having a longer horn, and there seems to be little cost to horn exaggeration. However, populations vary in the amount of horn exaggeration across this widespread species. Here, we examine four populations and quantify scaling and functional morphology of the horn. We then measure force production by the horn system in a combat-relevant movement. We find that not only does horn length vary among populations, but allometry of lever mechanics and force production varies in a complex way. For instance, some beetle populations make relatively long horns, but exert relatively low forces. Other populations make shorter horns and produce higher forces during fights. We suggest that this performance variation could be associated with differences in the intensity or type of sexual selection across the species.

Microstructure of injection moulding machine mould clamping mechanism: design and motion simulation

With the advent of intelligence, more and more machines and devices involve the creation of complex structures. In the intelligent manufacturing industries, moldings including injection molding, blow molding, compression molding and others play critical roles in manufacturing the highly precise parts required for building intelligent machines (such as computers, cell phones, robots, etc.). The performance of the clamping mechanism directly affects the quality of the microstructure of injection products. The design of injection molding mold clamping mechanism is based on the microstructure characteristics of the trip of toggle lever mechanism ratio, speed ratio, and force amplification ratio. These are used to study the main performance parameters, such as analysis, as well as for the establishment of the physical model of the clamping mechanism. The model is based on the microstructure of injection of hyperbolic elbow clamping mechanism kinematics simulation. Simulation results and the theoretical calculation contrast analysis shows that the maximum dynamic template speed is 215.34 mm/s. The dynamic templates and crosshead speed ratio is 2.15, therefore the design of injection molding mold clamping mechanism for microstructure provides favorable technical support. The method described here is important to build complicated molds required to build highly precise parts to build intelligent machineries.

Training experiments with Bombus terrestris and Apis mellifera on artificial ‘Salvia’ flowers

Many bee flowers demand physical force from their pollinators. An example is Salvia with lever-like anthers restricting access to nectar. Though the needed force is generally low, it is largely unknown how far even low forces affect flower preference and foraging behaviour of bees. In the present paper, we introduce a method to measure the response of bees to a force mechanism. We explain the construction of artificial flowers mimicking the lever mechanism of a Salvia flower and the procedure to train honeybees and bumblebees to the models. We document the behaviour of the bees on models without barriers and on those with low forces aiming at the same time to determine the bees’ sensibility for discriminating amongst slightly different flower constructions. Artificial flowers with and without movable levers are constructed to test the effect of a present or absent lever under standardised conditions. Both model types offer sugar syrup (37%) of the same volume. The lever force is 2.8–3.8mN corresponding to the average force in bee-pollinated Salvia species. Choice experiments, five minutes each, are conducted with single bumblebees (lab, n=40) and honeybees (outdoors, n=40). The animal's behaviour and visitation frequency, handling time and flight time between two flower visits are recorded and statistically evaluated. Both bee species can learn to handle the complex artificial flowers. They significantly prefer the model without any barrier indicating that they are able to discriminate amongst models without and with low force demands. The results clearly illustrate that the artificial flowers are suitable for experiments. Continuative choice experiments with reciprocal models of nectar concentration and force will provide a deeper insight into the cost-benefit ratio by bees.

Based on Mechanical Clamping Device Lever Force Amplifier by Linear Motor

This paper describes a new innovation design idea of mechanical clamping device based on lever force amplifier by linear motor. Based on the idea, design a series of mechanical clamping devices featuring clear logic idea. The corresponding formulas and graphic examples of output force are given of. The lever-toggle force amplifier is aimed to meet the needs of larger output force. Transform the shape of the lever to meet the processing requirements of different sizes of work-pieces.

Mechanical modelling of micro-scale abrasion in superfinish belt grinding

In synchronized transmission, the shift lever force and corresponding shiftability are the most important design considerations. The present paper introduces an engineering attempt to rigorously model a synchronizing functional surface (cone surface of idler gear) according to its finish specifications. The virtual input surface is generated by an original fractal function, which reproduces the surface “signature” due to the wheel grinding process. To model the subsequent superfinishing operation by belt finishing process, which uses a soft-coated belt as a tool, an algorithm simulating the abrasive polishing conditions is especially developed and applied to rework the initial fractal surface. The basic idea of this model is that the higher the height of a peak of the profile, the lower its probability of resistance during an abrasion cycle. The belt finishing process is hence modeled by five parameters: two parameters that characterize the initial surface (fractal dimension and range amplitude) and three parameters describing the abrasion polishing process (probability of resistance, wear volume and the number of abrasion cycles). In order to ascertain that the component will be manufactured to the required specifications, the model's parameters have to be determined. For this goal, a functional model with an optimization scheme is created. This simulation provides the morphology of the initial surface and how to cope with the superfinishing process to obtain the functionality of the surface. An elevated initial roughness is required from which slow erosion is proceeded to erode peaks and conserve some valleys of the initial profile (lubricant tanks). Finally, it is shown that automotive designers impose morphological specifications obtained by the belt grinding process to prevent scuffing of the motor parts.

Mastication force analysis on the fulcrum point of first class lever on lower jaw distal free end denture

The problem in first-class free end lever (distal extension base) Removable Partial Denture (RPD) is the lever force on the retention point that may harm the abutment tooth which has been discussed many times, but the amount of force on the fulcrum point (rest) on the abutment tooth has never discussed yet. The objective of this paper is to analyze the amount of force on the fulcrum point in the first class lever of lower free end denture on the two dimension static models. The analysis result reveals that the force on the fulcrum point is bigger than the mastication force on the free end saddle, or the force on the fulcrum point is equal to the sum of the force of the saddle and the force on the retention point. The force on the fulcrum point may cause trauma to the periodontal tissue of the abutment tooth. To decrease the amount of force on the fulcrum point is by mastication force limitation, decreasing the distance between the mastication point and the fulcrum point; and increasing the distance between retention point and fulcrum point. For clinical application, there are many biological variables to be considered.

Quantitation of ligament laxity in anterior shoulder instability: an experimental cadaver model.

Three groups of cadaver specimens were studied. In group 1 (20 shoulders) glenohumeral ligaments were detached from the humerus until a permanent dislocation of the humeral head occurred in abduction plus external rotation. On the dislocated joint the ligament was reconstructed using a fascia lata lengthening plasty. After the plasty had been completed, the shoulder was reduced and instability checked in the same position. Then the capsule (including the plasty) was harvested and measured. In group 2 (20 shoulders), after the plasty had been completed in the same conditions as above, the capsule was progressively reduced by 2 mm steps until the instability disappeared. Then the capsule (including the plasty) was harvested and measured. In group 3 (12 shoulders), measurements of the head and of the capsule were done. To dislocate the shoulder the section of the three glenohumeral ligaments was required. Lengthening of the capsule in group 1 was 240-250%. In all cases shortening of the capsule led to the stabilization of the shoulder. After stabilization of the shoulder was reached a residual lengthening of 175-185% was recorded. In 3 out of 4 shoulders the amount of capsule shortening required to return to a stable shoulder was between 16 and 18 mm. This experiment did not reproduce the Bankart lesion; therefore it only concerns atraumatic instability. The main limitation of this model is the low lever force that may be used to dislocate the shoulder; consequently the elasticity of the glenohumeral ligament was not taken in account. The experimental values were likely over-estimated. Nevertheless the present results provide useful information for building an experimental model of atraumatic instability of the shoulder.

Modulation of synchrony between single motor units during precision grip tasks in humans

During precision grip, coherence between motor cortex and hand muscle EMG oscillatory activity in the 15-30 Hz range covaries with the compliance of the manipulated object. The current study investigated whether short-term synchrony and coherence between discharges of single motor units (SMUs) in the first dorsal interosseous (1DI) muscle were similarly modulated by object compliance during precision grip. Eight subjects used index finger and thumb to grip two levers that were under robotic control. Guided by visual feedback of the lever force levels, subjects held the levers against a steady force of 1.3 N for 8 s; they then linearly increased the force to 1.6 N over a 2 s period and held for a further 8 s before linearly decreasing the force back to the 1.3 N level over another 2 s period. Subjects performed the task at two different levels of compliance, each with identical grip force levels. Both surface EMG and SMU activity were recorded from the 1DI muscle. Short-term synchrony between the discharges of pairs of SMUs was assessed in the time domain by cross-correlation and in the frequency domain by coherence analysis. Coherence was seen in two frequency ranges: 6-12 Hz and 15-30 Hz. The compliance of the gripped object had a significant effect on both short-term synchronisation and coherence in the 15-30 Hz range between SMUs; both were greater for the more compliant condition. There was no change in the 6-12 Hz coherence.

EFFECT OF PROGRESSIVE RESISTANCE TRAINING ON SINGLE MYOFIBER CALCIUM SENSITIVITY IN OLDER WOMEN

The purpose of this investigation was to determine the effects of a 12-week progressive resistance-training program (PRT) on single myofiber calcium sensitivity in six older women (73 ± 2 yr.). Muscle biopsies of the vastus lateralis were obtained pre-and-post PRT. Single muscle fibers were dissected and mounted between a lever arm and force transducer in an experimental chamber. The experimental sequence for each fiber was the determination of maximal isometric tension (Po) at pCa 4.5 (pCa = −log[Ca2+]), and then subsequent submaximal activations of the fiber at nine Ca2+ concentrations (pCa 6.8 to 4.7). MHC I and IIa fiber diameter increased 16% (p < 0.05) and 2% pre-to-post PRT, respectively. Peak isometric tension in MHC I and IIa fibers increased 34% (p < 0.05) and 18% as a result of the training. The mean MHC I Ca2+ activation threshold increased from 6.83 ± 0.02 to 6.91 ± 0.01 (p < 0.05) as did the mean half-maximal activation 5.51 ± 0.02 to 5.71 ± 0.03 (p < 0.05) with PRT. The slope of the Hill plot above (n1) half-maximal activation for MHC I did not change significantly with the PRT (1.80 ± 0.04 to 1.86 ± 0.08). However, the slope of the Hill plot below (n2) half-maximal activation for MHC I demonstrated an increase (p < 0.05) with training (1.70 ± 0.11 to 2.43 ± 0.09). There were no differences with MHC IIa fibers with PRT for any of the Ca2+ variables measured. In conclusion, the results of this investigation indicate that myofibril ca2+ sensitivity and activation properties are altered in MHC I, but not MHC IIa fibers with PRT in older women. The alterations in the MHC I Ca2+ properties appear to have a significant effect on the mechanisms involved with skeletal muscle adaptability in older women following PRT. Supported by NIH AG154876

Human Cortical Muscle Coherence Is Directly Related to Specific Motor Parameters

Cortical oscillations have been the target of many recent investigations, because it has been proposed that they could function to solve the "binding" problem. In the motor cortex, oscillatory activity has been reported at a variety of frequencies between approximately 4 and approximately 60 Hz. Previous research has shown that 15-30 Hz oscillatory activity in the primary motor cortex is coherent or phase locked to activity in contralateral hand and forearm muscles during isometric contractions. However, the function of this oscillatory activity remains unclear. Is it simply an epiphenomenon or is it related to specific motor parameters? In this study, we investigated task-dependent modulation in coherence between motor cortex and hand muscles during precision grip tasks. Twelve right-handed subjects used index finger and thumb to grip two levers that were under robotic control. Each lever was fitted with a sensitive force gauge. Subjects received visual feedback of lever force levels and were instructed to keep them within target boxes throughout each trial. Surface EMGs were recorded from four hand and forearm muscles, and magnetoencephalography (MEG) was recorded using a 306 channel neuromagnetometer. All subjects showed significant levels of coherence (0.086-0.599) between MEG and muscle in the 15-30 Hz range. Coherence was significantly smaller when the task was performed under an isometric condition (levers fixed) compared with a compliant condition in which subjects moved the levers against a spring-like load. Furthermore, there was a positive, significant relationship between the level of coherence and the degree of lever compliance. These results argue in favor of coherence between cortex and muscle being related to specific parameters of hand motor function.

Three-dimensional beam tracking for optical lever detection in atomic force microscopy

For the requirement to move a probe with respect to a large specimen like a silicon wafer, a three-dimensional beam tracking for optical lever force detection in atomic force microscopy has been developed. This beam tracking is not an approximate solution but an ideal solution in three-dimensional scanning. A set of tracking mirrors that are attached at the middle of a tube scanner steers a laser beam to a probe and to a detector during scanning. Tracking errors achieved were 2 and 7 nm in horizontal and vertical direction scans over 50 μm scanning. A simple theoretical error estimate revealed that less than 2 nm error is obtainable with moderate mirror mounting accuracy. To reduce the thickness of the scanner for coaxial optical microscope observation, the tube scanner was arranged sideways, resulting in 12 mm scanner thickness. A twist probe, pointed in the vertical direction to enter its tip into a narrow trench, was used for the probe. This system could obtain a semiconductor trench image successfully.

Fixed-ratio schedules increase generalized self-control: Preference for large rewards despite high effort or punishment.

Three experiments investigated the effects of fixed-ratio reinforcement on generalized self-control involving high effort and punishment. In Experiment 1, rats received food in a runway for the completion of each round trip (continuous-reinforcement group) or every fifth round trip (fixedratio group). Control rats received food at the same temporal intervals as these groups but without any instrumental requirement. When all rats were next given a series of choices between a large food reward requiring high lever force versus a small reward requiring low lever force, the fixed-ratio rats showed the greatest self-control. In Experiments 2 and 3, rats were rewarded on a continuous or fixed-ratio schedule followed by choice between a large food reward accompanied by intermittent shock versus a small or absent food reward without shock. The fixed-ratio rats again showed the greatest self-control. Self-control refers to an individual's decision to undergo the increased costs that may be necessary to achieve the larger of alternative goals. In the natural environment, self-control may involve a required long delay of reinforcement (Mischel, 1974), high effort (Eisenberger, Mitchell, & Masterson, 1985; Mischel, 1974), or punishment (Dollard & Miller, 1950). Most research on self-control involves delay, the choice between the early receipt of a small reinforcer versus the deferred delivery of a large reinforcer (Ainslie, 1974, 1975; Logue, 1988; Navarick & Fantino, 1976; Rachlin, 1974, 1976; Rachfin & Green, 1972). A variety of findings suggest that self-control involving delay is hindered by the precipitous decrease of the value of reinforcers with initial delay, there being a slower decline with further delay (Aiuslie, 1974; Ainslie & Herrnstein, 1981; Green, Fisher, Perlow, & Sherman, 1981; Green & Snyderman, 1980; Navarick & Fantino, 1976; Rachlin & Green, 1972). Research using pigeons, rats, and children indicates that the effects of reinforcement delay depend on experience, with the repeated receipt of long delays acting to increase subsequent self-control in both familiar and novel contexts (Eisenberger & Adornetto, 1986; Eisenberger & Masterson, 1986; Eisenberger, Masterson, & Lowman, 1982; Logue & Mazur, 1981; Logue, Rodriguez, Pena-Correal, & Mauro, 1984; Mazur & Logne, 1978). The present research investigates the possibility that experience with rewarded high effort might produce similar generalized effects on self-control involving required effort and punishment. Adding a response requirement to delay was found to lessen pigeons choice of a delayed large reward (Grossbard & Mazur, 1986), indicating that required high effort may reduce selfcontrol. Research on the generalized effects of rewarded high effort suggests that effort training might increase self-control involving effort. Various findings suggest that required high effort with one or more behaviors raises the effort subse

Manual compression device for fluoroscopy.

A device for manual compression and palpation during supine fluoroscopy has been designed. It enables effective use of the physiologic grasping and lever force potentials of the hand and wrist. The device permits optimal fluoroscopic palpation and compression techniques and prevents direct exposure to the lead-gloved hand.