scholarly journals Diffusion in systems crowded by active force-dipole molecules

Soft Matter ◽  
2017 ◽  
Vol 13 (20) ◽  
pp. 3741-3749 ◽  
Author(s):  
Matthew Dennison ◽  
Raymond Kapral ◽  
Holger Stark
Keyword(s):  
Active Force ◽  
Force Dipole

scholarly journals Twenty-one days of low-intensity eccentric training improve morphological characteristics and function of soleus muscles of mdx mice

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paulo S. Pedrazzani ◽  
Tatiana O. P. Araújo ◽  
Emilly Sigoli ◽  
Isabella R. da Silva ◽  
Daiane Leite da Roza ◽  
...  
Keyword(s):  
Soleus Muscle ◽  
Morphological Characteristics ◽  
Training Group ◽  
Mdx Mice ◽  
Eccentric Training ◽  
Active Force ◽  
Wild Type ◽  
Low Intensity ◽  
Sedentary Group ◽  
Group 3

AbstractDuchene muscular dystrophy (DMD) is caused by the absence of the protein dystrophin, which leads to muscle weakness, progressive degeneration, and eventually death due to respiratory failure. Low-intensity eccentric training (LIET) has been used as a rehabilitation method in skeletal muscles after disuse. Recently, LIET has also been used for rehabilitating dystrophic muscles, but its effects are still unclear. The purpose of this study was to investigate the effects of 21 days of LIET in dystrophic soleus muscle. Thirty-six male mdx mice were randomized into six groups (n = 6/each): mdx sedentary group; mdx training group-3 days; mdx training group-21 days; wild-type sedentary group; wild-type training group-3 days and wild-type training group-21 days. After the training sessions, animals were euthanized, and fragments of soleus muscles were removed for immunofluorescence and histological analyses, and measurements of active force and Ca2+ sensitivity of the contractile apparatus. Muscles of the mdx training group-21 days showed an improvement in morphological characteristics and an increase of active force when compared to the sedentary mdx group. The results show that LIET can improve the functionality of dystrophic soleus muscle in mice.

The origin of passive force enhancement in skeletal muscle

2008 ◽  
Vol 294 (1) ◽  
pp. C74-C78 ◽  
Author(s):  
V. Joumaa ◽  
D. E. Rassier ◽  
T. R. Leonard ◽  
W. Herzog
Keyword(s):  
Calcium Concentration ◽  
Force Production ◽  
Primary Source ◽  
Passive Force ◽  
Active Force ◽  
Force Enhancement ◽  
Bridge Formation ◽  
Calcium Dependent ◽  
Cross Bridge ◽  
High Calcium

The aim of the present study was to test whether titin is a calcium-dependent spring and whether it is the source of the passive force enhancement observed in muscle and single fiber preparations. We measured passive force enhancement in troponin C (TnC)-depleted myofibrils in which active force production was completely eliminated. The TnC-depleted construct allowed for the investigation of the effect of calcium concentration on passive force, without the confounding effects of actin-myosin cross-bridge formation and active force production. Passive forces in TnC-depleted myofibrils ( n = 6) were 35.0 ± 2.9 nN/ μm2 when stretched to an average sarcomere length of 3.4 μm in a solution with low calcium concentration (pCa 8.0). Passive forces in the same myofibrils increased by 25% to 30% when stretches were performed in a solution with high calcium concentration (pCa 3.5). Since it is well accepted that titin is the primary source for passive force in rabbit psoas myofibrils and since the increase in passive force in TnC-depleted myofibrils was abolished after trypsin treatment, our results suggest that increasing calcium concentration is associated with increased titin stiffness. However, this calcium-induced titin stiffness accounted for only ∼25% of the passive force enhancement observed in intact myofibrils. Therefore, ∼75% of the normally occurring passive force enhancement remains unexplained. The findings of the present study suggest that passive force enhancement is partly caused by a calcium-induced increase in titin stiffness but also requires cross-bridge formation and/or active force production for full manifestation.

scholarly journals Integrated active and semi-active control for seat suspension of a heavy duty vehicle

2017 ◽  
Vol 29 (1) ◽  
pp. 91-100 ◽  
Author(s):  
Donghong Ning ◽  
Shuaishuai Sun ◽  
Haiping Du ◽  
Weihua Li
Keyword(s):  
Resonance Frequency ◽  
Active Control ◽  
Integrated Control ◽  
Relative Displacement ◽  
Magnetorheological Damper ◽  
Active Force ◽  
Heavy Duty ◽  
Force Output ◽  
Seat Suspension ◽  
A Current

In this article, an integrated active and semi-active seat suspension for heavy duty vehicles is proposed, and its prototype is built; an integrated control algorithm applied measurable variables (suspension relative displacement and seat acceleration) is designed for the proposed seat prototype. In this seat prototype, an active actuator with low maximum force output (70 N), which is insufficient for an active seat suspension to control the resonance vibration, is applied together with a rotary magnetorheological damper. The magnetorheological damper can suppress the high vibration energy in resonance frequency, and then a small active force can further improve the seat suspension performance greatly. The suspension’s dynamic property is tested with a MTS system, and its model is identified based on the testing data. A modified on–off controller is applied for the rotary magnetorheological damper. A [Formula: see text] controller with the compensation of a disturbance observer is used for the active actuator. Considering the energy saving, the control strategy is designed as that only when the magnetorheological damper is in the off state (0 A current), the active actuator will have active force output, or the active actuator is off. Both simulation and experiment are implemented to verify the proposed seat suspension and controller. In the sinusoidal excitations experiment, the acceleration transmissibility of integrated control seat has lowest value in resonance frequency and frequencies above the resonance, when compared with power on (0.7 A current), power off (0 A current) and semi-active control seat. In the random vibration experiment, the root mean square acceleration of integrated control seat suspension has 47.7%, 33.1% and 26.5% reductions when compared with above-mentioned three kinds of seat suspension. The power spectral density comparison indicates that the integrated seat suspension will have good performance in practical application. The integrated active and semi-active seat suspension can fill energy consumption gap between active and semi-active control seat suspension.

A Sensor Used to Detect the Thigh Human-Machine Coupling Force in Lower Limb Rehabilitation Robot

2013 ◽  
Vol 310 ◽  
pp. 444-447 ◽  
Author(s):  
Yue Wen Li ◽  
Lin Yong Shen
Keyword(s):  
Lower Limb ◽  
Rehabilitation Robot ◽  
Active Force ◽  
Actual Usage ◽  
Coupling Force ◽  
Active Rehabilitation ◽  
Limb Rehabilitation ◽  
Relationship Of ◽  
The Relationship ◽  
Lower Limb Rehabilitation

The acquisition of the patients’ active force is the key process to realize the active rehabilitation function of lower limb rehabilitation robot. This paper analyzes the relationship of human-machine coupling force and patients’ active force, based on what put forward a proposal to acquire the active force .A sensor is designed to detect the human-machine coupling force and a stress analysis is carried on based on the actual usage of the sensor. The scheme of the stress foil arrangement and bridge circuit design are discussed in the paper. And a FEA is also carried out to analyze the strain situation of the elastomer.

scholarly journals Reports of the length dependence of fatigue are greatly exaggerated

2006 ◽  
Vol 101 (1) ◽  
pp. 23-29 ◽  
Author(s):  
M. B. MacNaughton ◽  
B. R. MacIntosh
Keyword(s):  
Muscle Length ◽  
Repetitive Stimulation ◽  
Double Pulse ◽  
Medial Gastrocnemius ◽  
Passive Force ◽  
Active Force ◽  
Rightward Shift ◽  
Length Dependence ◽  
Force Depression ◽  
In Series

Relative force depression associated with muscle fatigue is reported to be greater when assessed at short vs. long muscle lengths. This appears to be due to a rightward shift in the force-length relationship. This rightward shift may be caused by stretch of in-series structures, making sarcomere lengths shorter at any given muscle length. Submaximal force-length relationships (twitch, double pulse, 50 Hz) were evaluated before and after repetitive contractions (50 Hz, 300 ms, 1/s) in an in situ preparation of the rat medial gastrocnemius muscle. In some experiments, fascicle lengths were measured with sonomicrometry. Before repetitive stimulation, fascicle lengths were 11.3 ± 0.8, 12.8 ± 0.9, and 14.4 ± 1.2 mm at lengths corresponding to −3.6, 0, and 3.6 mm where 0 is a reference length that corresponds with maximal active force for double-pulse stimulation. After repetitive stimulation, there was no change in fascicle lengths; these lengths were 11.4 ± 0.8, 12.6 ± 0.9, and 14.2 ± 1.2 mm. The length dependence of fatigue was, therefore, not due to a stretch of in-series structures. Interestingly, the rightward shift that was evident when active force was calculated in the traditional way (subtraction of the passive force measured before contraction) was not seen when active force was calculated by subtracting the passive force that was associated with the fascicle length reached at the peak of the contraction. This calculation is based on the assumption that passive force decreases as the fascicles shorten during a fixed-end contraction. This alternative calculation revealed similar postfatigue absolute active force depression at all lengths. In relative terms, a length dependence of fatigue was still evident, but this was greatly diminished compared with that observed when active force was calculated with the traditional method.

scholarly journals Stretch and quick release of rat cardiac trabeculae accelerates Ca2+ waves and triggered propagated contractions

2001 ◽  
Vol 281 (5) ◽  
pp. H2133-H2142 ◽  
Author(s):  
Yuji Wakayama ◽  
Masahito Miura ◽  
Yoshinao Sugai ◽  
Yutaka Kagaya ◽  
Jun Watanabe ◽  
...  
Keyword(s):  
Strain Gauge ◽  
Sarcomere Length ◽  
Muscle Length ◽  
Laser Diffraction ◽  
Active Force ◽  
Quick Release ◽  
Rat Hearts ◽  
Initiation And Propagation ◽  
Intracellular Ca ◽  
Ventricular Trabeculae

Rapid shortening of active cardiac muscle [quick release (QR)] dissociates Ca2+ from myofilaments. We studied, using muscle stretches and QR, whether Ca2+ dissociation affects triggered propagated contractions (TPCs) and Ca2+waves. The intracellular Ca2+ concentration was measured by a SIT camera in right ventricular trabeculae dissected from rat hearts loaded with fura 2 salt, force was measured by a silicon strain gauge, and sarcomere length was measured by laser diffraction while a servomotor controlled muscle length. TPCs ( n = 27) were induced at 28°C by stimulus trains (7.5 s at 2.65 ± 0.13 Hz) at an extracellular Ca2+ concentration ([Ca2+]o) = 2.0 mM or with 10 μM Gd3+ at [Ca2+]o = 5.2 ± 0.73 mM. QR during twitch relaxation after a 10% stretch for 100–200 ms reduced both the time between the last stimulus and the peak TPC (PeakTPC) and the time between the last stimulus and peak Ca2+ wave (PeakCW) and increased PeakTPC and PeakCW ( n= 13) as well as the propagation velocity ( V prop; n = 8). Active force during stretch also increased V prop( r = 0.84, n = 12, P < 0.01), but Gd3+ had no effect ( n = 5). These results suggest that Ca2+ dissociation by QR during relaxation accelerates the initiation and propagation of Ca2+ waves.

scholarly journals Knowledge-Based Trajectory Error Pattern Method Applied to an Active Force Control Scheme

1970 ◽  
Vol 3 (1) ◽  
Author(s):  
Endra Pitowarno, Musa Mailah, Hishamuddin Jamaluddin
Keyword(s):  
Force Control ◽  
Error Pattern ◽  
Robot Arm ◽  
Active Force ◽  
Trajectory Error ◽  
Track Error ◽  
Knowledge Based ◽  
Inertia Matrix ◽  
Active Force Control ◽  
Control Scheme

The active force control (AFC) method is known as a robust control scheme that dramatically enhances the performance of a robot arm particularly in compensating the disturbance effects. The main task of the AFC method is to estimate the inertia matrix in the feedback loop to provide the correct (motor) torque required to cancel out these disturbances. Several intelligent control schemes have already been introduced to enhance the estimation methods of acquiring the inertia matrix such as those using neural network, iterative learning and fuzzy logic. In this paper, we propose an alternative scheme called Knowledge-Based Trajectory Error Pattern Method (KBTEPM) to suppress the trajectory track error of the AFC scheme. The knowledge is developed from the trajectory track error characteristic based on the previous experimental results of the crude approximation method. It produces a unique, new and desirable error pattern when a trajectory command is forced. An experimental study was performed using simulation work on the AFC scheme with KBTEPM applied to a two-planar manipulator in which a set of rule-based algorithm is derived. A number of previous AFC schemes are also reviewed as benchmark. The simulation results show that the AFC-KBTEPM scheme successfully reduces the trajectory track error significantly even in the presence of the introduced disturbances.Key Words:  Active force control, estimated inertia matrix, robot arm, trajectory error pattern, knowledge-based.

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