scholarly journals Designed anchoring geometries determine lifetimes of biotin–streptavidin bonds under constant load and enable ultra-stable coupling

Nanoscale ◽  
2020 ◽  
Vol 12 (41) ◽  
pp. 21131-21137
Author(s):  
Sophia Gruber ◽  
Achim Löf ◽  
Steffen M. Sedlak ◽  
Martin Benoit ◽  
Hermann E. Gaub ◽  
...  
Keyword(s):  
Constant Load ◽  
Magnetic Tweezers ◽  
Constant Force

We engineer streptavidin to control the anchoring geometry and increase the lifetime of the biotin bond under constant force in magnetic tweezers 100-fold.

scholarly journals Force determination in lateral magnetic tweezers combined with TIRF microscopy

Nanoscale ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 4579-4590 ◽  
Author(s):  
J. Madariaga-Marcos ◽  
S. Hormeño ◽  
C. L. Pastrana ◽  
G. L. M. Fisher ◽  
M. S. Dillingham ◽  
...  
Keyword(s):  
Dna Binding ◽  
Magnetic Tweezers ◽  
Constant Force ◽  
Dna Molecules ◽  
Tirf Microscopy

We have designed and calibrated a magnetic tweezers module to laterally stretch DNA molecules at a constant force, which can be incorporated into conventional magnetic tweezers. We demonstrate the combination of lateral magnetic tweezers with TIRF microscopy by characterizing DNA binding by ParB.

scholarly journals Determination of thermodynamics and kinetics of RNA reactions by force

2006 ◽  
Vol 39 (4) ◽  
pp. 325-360 ◽  
Author(s):  
Ignacio Tinoco ◽  
Pan T. X. Li ◽  
Carlos Bustamante
Keyword(s):  
Free Energy ◽  
Single Molecule ◽  
Rate Constants ◽  
Magnetic Tweezers ◽  
Constant Force ◽  
Thermodynamics And Kinetics ◽  
Wide Range ◽  
Kinetic Mechanisms ◽  
Kinetics Of ◽  
Force Drop

1. Introduction 3262. Instrumentation 3282.1 Instruments to study mechanical properties of RNA 3282.1.1 AFM 3282.1.2 Magnetic tweezers 3282.1.3 Optical tweezers 3302.2 Optical trap instrumentation 3302.3 Calibrations 3322.3.1 Calibration of trap stiffness 3322.3.2 Calibration of force 3332.3.3 Calibration of distance 3342.4 Types of experiments 3342.4.1 Force-ramp 3342.4.2 Force-clamp or constant-force experiments 3352.4.3 Extension-clamp or constant extension experiments 3352.4.4 Force-jump, Force-drop 3362.4.5 Passive mode 3363. Thermodynamics 3363.1 Reversibility 3363.2 Gibbs free energy 3373.2.1 Stretching free energy 3383.2.1.1 Rigid molecules 3383.2.1.2 Compliant or flexible molecules 3393.2.2 Free energy of a reversible unfolding transition 3393.2.3 Free energy of unfolding at zero force 3403.2.4 Free energy of an irreversible unfolding transition 3403.2.4.1 Jarzynski's method 3413.2.4.2 Crooks fluctuation theorem 3434. Kinetics 3454.1 Measuring rate constants 3454.1.1 Hopping 3454.1.2 Force-jump, Force-drop 3474.1.3 Force-ramp 3484.1.4 Instrumental effects 3504.2 Kinetic mechanisms 3514.2.1 Free-energy landscapes 3514.2.2 Kinetics of unfolding 3535. Relating force-measured data to other measurements 3545.1 Thermodynamics 3545.2 Kinetics 3576. Acknowledgements 3577. References 358Single-molecule methods have made it possible to apply force to an individual RNA molecule. Two beads are attached to the RNA; one is on a micropipette, the other is in a laser trap. The force on the RNA and the distance between the beads are measured. Force can change the equilibrium and the rate of any reaction in which the product has a different extension from the reactant. This review describes use of laser tweezers to measure thermodynamics and kinetics of unfolding/refolding RNA. For a reversible reaction the work directly provides the free energy; for irreversible reactions the free energy is obtained from the distribution of work values. The rate constants for the folding and unfolding reactions can be measured by several methods. The effect of pulling rate on the distribution of force-unfolding values leads to rate constants for unfolding. Hopping of the RNA between folded and unfolded states at constant force provides both unfolding and folding rates. Force-jumps and force-drops, similar to the temperature jump method, provide direct measurement of reaction rates over a wide range of forces. The advantages of applying force and using single-molecule methods are discussed. These methods, for example, allow reactions to be studied in non-denaturing solvents at physiological temperatures; they also simplify analysis of kinetic mechanisms because only one intermediate at a time is present. Unfolding of RNA in biological cells by helicases, or ribosomes, has similarities to unfolding by force.

The study for constant force characteristic of C-shaped superelastic SMA

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1253-1259
Author(s):  
Minghui Wang ◽  
Hongliu Yu
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Medical Device ◽  
Soft Tissues ◽  
Computational Simulation ◽  
Force Characteristic ◽  
Constant Force ◽  
Curve Shape ◽  
Artificial Sphincter ◽  
Round Bar

Clamping devices with constant force or pressure are desired in medical device, such as hemostatic forceps and the artificial sphincter, to prevent soft tissues from injures due to overloading. It is easily obtained by stretching an SMA wire. However, studies with SMA bending round bar have seldom been reported before. This paper studied constant force characteristic of C-shaped round bar with shape memory alloys. Optimization designs of the components were carried out with computational simulation. Numerical results show that the phenomenon of constant force strongly depends on contour curve shape and geometric dimensions of the C-shaped round bar of SMA component.

Fatigue of Unidirectional Cord-Rubber Composites

1999 ◽  
Vol 27 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Y. Liu ◽  
Z. Wan ◽  
Z. Tian ◽  
X. Du ◽  
J. Jiang ◽  
...  
Keyword(s):  
Damage Accumulation ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Testing System ◽  
Rubber Composites ◽  
Cycle Frequency ◽  
Periodic Loading ◽  
Fatigue Damage Accumulation ◽  
Rubber Composite

Abstract A fatigue testing system is established with which the real-time recording of stress, strain, temperature, and hysteresis loss of rubbers or cord-rubber composite specimens subjected to periodic loading or extension can be successfully carried out. Several problems are connected with the experimental study of the fatigue of rubber composites. In constant extension cycling, the specimen becomes relaxed because of the viscoelasticity of rubber composites, and the imposed tension-tension deformation becomes complex. In this method, the specimen is unlikely to fail unless the imposed extensions are very large. Constant load cycling can avoid the shortcomings of constant extension cycling. The specially designed clamps ensure that the specimen does not slip when the load retains a constant value. The Deformation and fatigue damage accumulation processes of rubber composites under periodic loading are also examined. Obviously, the effect of cycle frequency on the fatigue life of rubber composites can not be ignored because of the viscoelasticity of constituent materials. The increase of specimen surface temperature is relatively small in the case of 1 Hz, but the temperature can easily reach 100°C at the 8 Hz frequency. A method for evaluating the fatigue behavior of tires is proposed.

Exercise slightly above the maximal lactate steady state reduces self-efficacy and increases negative affect

2019 ◽  
Author(s):  
James Graeme Wrightson ◽  
Louis Passfield
Keyword(s):  
Steady State ◽  
Negative Affect ◽  
Power Output ◽  
Self Efficacy ◽  
Repeated Measures ◽  
Physiological State ◽  
Constant Load ◽  
Peak Power Output ◽  
Time To Exhaustion ◽  
Maximal Lactate Steady State

Objectives: To examine the effect of exercise at and slightly above the maximal lactate steady state (MLSS) on self-efficacy, affect and effort, and their associations with exercise tolerance.Design: Counterbalanced, repeated measures designMethod: Participants performed two 30‐minute constant‐load cycling exercise at a power output equal to that at MLSS and 10 W above MLSS, immediately followed by a time‐to‐exhaustion test at 80% of their peak power output. Self-efficacy, affect and effort were measured before and after 30 minutes of cycling at and above MLSS.Results: Negative affect and effort higher, and self-efficacy and time to exhaustion were reduced, following cycling at MLSS + 10 W compared to cycling at the MLSS. Following exercise at the MLSS self-efficacy, affect and effort were all associated with subsequent time-to exhaustion. However, following exercise at MLSS + 10 W, only affect was associated with time-to exhaustion. Conclusions: Self efficacy, affect and effort are profoundly affected by physiological state, highlighting the influence of somatic states on perceptions and emotions during exercise. The affective response to exercise appears to be associated with exercise tolerance, indicating that the emotional, as well as physiological, responses should be considered when prescribing exercise training.

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

2008 ◽  
Author(s):  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Gabriele Vassura ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanism ◽  
Structural Parameters ◽  
Dielectric Elastomer ◽  
Constant Force ◽  
Element Analysis ◽  
Body Model ◽  
Rigid Body Model ◽  
Supporting Frame

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

scholarly journals Finite-difference equations of quasistatic motion of the shallow concrete shells in nonlinear setting

2020 ◽  
Vol 7 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Bolat Duissenbekov ◽  
Abduhalyk Tokmuratov ◽  
Nurlan Zhangabay ◽  
Zhenis Orazbayev ◽  
Baisbay Yerimbetov ◽  
...  
Keyword(s):  
Finite Difference ◽  
Differential Equations ◽  
Difference Equations ◽  
Constant Load ◽  
Time Interval ◽  
Test Case ◽  
Algebraic Equations ◽  
Nonlinear Properties ◽  
Finite Difference Equations ◽  
Concrete Shells

AbstractThe study solves a system of finite difference equations for flexible shallow concrete shells while taking into account the nonlinear deformations. All stiffness properties of the shell are taken as variables, i.e., stiffness surface and through-thickness stiffness. Differential equations under consideration were evaluated in the form of algebraic equations with the finite element method. For a reinforced shell, a system of 98 equations on a 8×8 grid was established, which was next solved with the approximation method from the nonlinear plasticity theory. A test case involved computing a 1×1 shallow shell taking into account the nonlinear properties of concrete. With nonlinear equations for the concrete creep taken as constitutive, equations for the quasi-static shell motion under constant load were derived. The resultant equations were written in a differential form and the problem of solving these differential equations was then reduced to the solving of the Cauchy problem. The numerical solution to this problem allows describing the stress-strain state of the shell at each point of the shell grid within a specified time interval.

Effects of conform, non-conform, and hybrid conformity toward stress distribution at the glenoid implant and cement: A finite element study

2021 ◽  
pp. 039139882199939
Author(s):  
Abdul Hadi Abdul Wahab ◽  
Nor Aqilah Mohamad Azmi ◽  
Mohammed Rafiq Abdul Kadir ◽  
Amir Putra Md Saad
Keyword(s):  
Stress Distribution ◽  
Daily Living ◽  
3D Model ◽  
Promising Result ◽  
High Stress ◽  
Constant Load ◽  
Posterior Region ◽  
Implant Stability ◽  
Eccentric Load ◽  
Standing Up

Glenoid conformity is one of the important aspects that could contribute to implant stability. However, the optimal conformity is still being debated among the researchers. Therefore, this study aims to analyze the stress distribution of the implant and cement in three types of conformity (conform, non-conform, and hybrid) in three load conditions (central, anterior, and posterior). Glenoid implant and cement were reconstructed using Solidwork software and a 3D model of scapula bone was done using MIMICS software. Constant load, 750 N, was applied at the central, anterior, and posterior region of the glenoid implant which represents average load for daily living activities for elder people, including, walking with a stick and standing up from a chair. The results showed that, during center load, an implant with dual conformity (hybrid) showed the best (Max Stress—3.93 MPa) and well-distributed stress as compared to other conformity (Non-conform—7.21 MPa, Conform—9.38 MPa). While, during eccentric load (anterior and posterior), high stress was located at the anterior and posterior region with respect to the load applied. Cement stress for non-conform and hybrid implant recorded less than 5 MPa, which indicates it had a very low risk to have cement microcracks, whilst, conform implant was exposed to microcrack of the cement. In conclusion, hybrid conformity showed a promising result that could compromise between conform and non-conform implant. However, further enhancement is required for hybrid implants when dealing with eccentric load (anterior and posterior).

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