Micromechanical contact stiffness devices and application for calibrating contact resonance atomic force microscopy

Science.gov (United States)

Rosenberger, Matthew R.; Chen, Sihan; Prater, Craig B.; King, William P.

2017-01-01

This paper reports the design, fabrication, and characterization of micromechanical devices that can present an engineered contact stiffness to an atomic force microscope (AFM) cantilever tip. These devices allow the contact stiffness between the AFM tip and a substrate to be easily and accurately measured, and can be used to calibrate the cantilever for subsequent mechanical property measurements. The contact stiffness devices are rigid copper disks of diameters 2-18 μm integrated onto a soft silicone substrate. Analytical modeling and finite element simulations predict the elastic response of the devices. Measurements of tip-sample interactions during quasi-static force measurements compare well with modeling simulation, confirming the expected elastic response of the devices, which are shown to have contact stiffness 32-156 N m-1. To demonstrate one application, we use the disk sample to calibrate three resonant modes of a U-shaped AFM cantilever actuated via Lorentz force, at approximately 220, 450, and 1200 kHz. We then use the calibrated cantilever to determine the contact stiffness and elastic modulus of three polymer samples at these modes. The overall approach allows cantilever calibration without prior knowledge of the cantilever geometry or its resonance modes, and could be broadly applied to both static and dynamic measurements that require AFM calibration against a known contact stiffness.

A contact-force regulated photoplethysmography (PPG) platform

Science.gov (United States)

Sim, Jai Kyoung; Ahn, Bongyoung; Doh, Il

2018-04-01

A photoplethysmography (PPG) platform integrated with a miniaturized force-regulator is proposed in this study. Because a thermo-pneumatic type regulator maintains a consistent contact-force between the PPG probe and the measuring site, a consistent and stable PPG signal can be obtained. We designed and fabricated a watch-type PPG platform with an overall size of 35 mm × 19 mm. In the PPG measurement on the radial artery wrist while posture of the wrist is changed to extension, neutral, or flexion, regulation of the contact-force provides consistent PPG measurements for which the variations in the PPG amplitude (PPGA) was 7.2 %. The proposed PPG platform can be applied to biosignal measurements in various fields such as PPG-based ANS monitoring to estimate nociception, sleep apnea syndrome, and psychological stress.

A contact-force regulated photoplethysmography (PPG platform

Directory of Open Access Journals (Sweden)

Jai Kyoung Sim

2018-04-01

Full Text Available A photoplethysmography (PPG platform integrated with a miniaturized force-regulator is proposed in this study. Because a thermo-pneumatic type regulator maintains a consistent contact-force between the PPG probe and the measuring site, a consistent and stable PPG signal can be obtained. We designed and fabricated a watch-type PPG platform with an overall size of 35 mm × 19 mm. In the PPG measurement on the radial artery wrist while posture of the wrist is changed to extension, neutral, or flexion, regulation of the contact-force provides consistent PPG measurements for which the variations in the PPG amplitude (PPGA was 7.2 %. The proposed PPG platform can be applied to biosignal measurements in various fields such as PPG-based ANS monitoring to estimate nociception, sleep apnea syndrome, and psychological stress.

Effect of contact stiffness on wedge calibration of lateral force in atomic force microscopy

International Nuclear Information System (INIS)

Wang Fei; Zhao Xuezeng

2007-01-01

Quantitative friction measurement of nanomaterials in atomic force microscope requires accurate calibration method for lateral force. The effect of contact stiffness on lateral force calibration of atomic force microscope is discussed in detail and an improved calibration method is presented. The calibration factor derived from the original method increased with the applied normal load, which indicates that separate calibration should be required for every given applied normal load to keep the accuracy of friction measurement. We improve the original method by introducing the contact factor, which is derived from the contact stiffness between the tip and the sample, to the calculation of calibration factors. The improved method makes the calculation of calibration factors under different applied normal loads possible without repeating the calibration procedure. Comparative experiments on a silicon wafer have been done by both the two methods to validate the method in this article

Quantitative Study of Nanoscale Contact and Pre-Contact Mechanics Using Force Modulation

National Research Council Canada - National Science Library

Syed Asif, S. A; Wahl, K. J; Colton, R. J

1999-01-01

.... However cantilever instability, conventional force detection and displacement sensing make contact area measurement difficult, hence the measured mechanical properties are usually only qualitative...

Active Control of Contact Force for a Pantograph-Catenary System

Directory of Open Access Journals (Sweden)

Jiqiang Wang

2016-01-01

Full Text Available The performance of the high speed trains depends critically on the quality of the contact in the pantograph-catenary interaction. Maintaining a constant contact force needs taking special measures and one of the methods is to utilize active control to optimize the contact force. A number of active control methods have been proposed in the past decade. However, the primary objective of these methods has been to reduce the variation of the contact force in the pantograph-catenary system, ignoring the effects of locomotive vibrations on pantograph-catenary dynamics. Motivated by the problems in active control of vibration in large scale structures, the author has developed a geometric framework specifically targeting the remote vibration suppression problem based only on local control action. It is the intention of the paper to demonstrate its potential in the active control of the pantograph-catenary interaction, aiming to minimize the variation of the contact force while simultaneously suppressing the vibration disturbance from the train. A numerical study is provided through the application to a simplified pantograph-catenary model.

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force

Energy Technology Data Exchange (ETDEWEB)

Ren, Juan; Zou, Qingze, E-mail: qzzou@rci.rutgers.edu [Department of Mechanical and Aerospace Engineering, Rutgers University, 98 Brett Rd, Piscataway, New Jersey 08854 (United States)

2014-07-15

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality.

High-speed adaptive contact-mode atomic force microscopy imaging with near-minimum-force

International Nuclear Information System (INIS)

Ren, Juan; Zou, Qingze

2014-01-01

In this paper, an adaptive contact-mode imaging approach is proposed to replace the traditional contact-mode imaging by addressing the major concerns in both the speed and the force exerted to the sample. The speed of the traditional contact-mode imaging is largely limited by the need to maintain precision tracking of the sample topography over the entire imaged sample surface, while large image distortion and excessive probe-sample interaction force occur during high-speed imaging. In this work, first, the image distortion caused by the topography tracking error is accounted for in the topography quantification. Second, the quantified sample topography is utilized in a gradient-based optimization method to adjust the cantilever deflection set-point for each scanline closely around the minimal level needed for maintaining stable probe-sample contact, and a data-driven iterative feedforward control that utilizes a prediction of the next-line topography is integrated to the topography feeedback loop to enhance the sample topography tracking. The proposed approach is demonstrated and evaluated through imaging a calibration sample of square pitches at both high speeds (e.g., scan rate of 75 Hz and 130 Hz) and large sizes (e.g., scan size of 30 μm and 80 μm). The experimental results show that compared to the traditional constant-force contact-mode imaging, the imaging speed can be increased by over 30 folds (with the scanning speed at 13 mm/s), and the probe-sample interaction force can be reduced by more than 15% while maintaining the same image quality

Diminution of contact angle hysteresis under the influence of an oscillating force.

Science.gov (United States)

Manor, Ofer

2014-06-17

We suggest a simple quantitative model for the diminution of contact angle hysteresis under the influence of an oscillatory force invoked by thermal fluctuations, substrate vibrations, acoustic waves, or oscillating electric fields. Employing force balance rather than the usual description of contact angle hysteresis in terms of Gibbs energy, we highlight that a wetting system, such as a sessile drop or a bubble adhered to a solid substrate, appears at long times to be partially or fully independent of contact angle hysteresis and thus independent of static friction forces, as a result of contact line pinning. We verify this theory by studying several well-known experimental observations such as the approach of an arbitrary contact angle toward the Young contact angle and the apparent decrease (or increase) in an advancing (or a receding) contact angle under the influence of an external oscillating force.

Surface contact potential patches and Casimir force measurements

International Nuclear Information System (INIS)

Kim, W. J.; Sushkov, A. O.; Lamoreaux, S. K.; Dalvit, D. A. R.

2010-01-01

We present calculations of contact potential surface patch effects that simplify previous treatments. It is shown that, because of the linearity of Laplace's equation, the presence of patch potentials does not affect an electrostatic calibration of a two-plate Casimir measurement apparatus. Using models that include long-range variations in the contact potential across the plate surfaces, a number of experimental observations can be reproduced and explained. For these models, numerical calculations show that if a voltage is applied between the plates which minimizes the force, a residual electrostatic force persists, and that the minimizing potential varies with distance. The residual force can be described by a fit to a simple two-parameter function involving the minimizing potential and its variation with distance. We show the origin of this residual force by use of a simple parallel capacitor model. Finally, the implications of a residual force that varies in a manner different from 1/d on the accuracy of previous Casimir measurements is discussed.

Contact force and mechanical loss of multistage cable under tension and bending

Science.gov (United States)

Ru, Yanyun; Yong, Huadong; Zhou, Youhe

2016-10-01

A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.

Shear forces in the contact patch of a braked-racing tyre

Science.gov (United States)

Gruber, Patrick; Sharp, Robin S.

2012-12-01

This article identifies tyre modelling features that are fundamental to the accurate simulation of the shear forces in the contact patch of a steady-rolling, slipping and cambered racing tyre. The features investigated include contact patch shape, contact pressure distribution, carcass flexibility, rolling radius (RR) variations and friction coefficient. Using a previously described physical tyre model of modular nature, validated for static conditions, the influence of each feature on the shear forces generated is examined under different running conditions, including normal loads of 1500, 3000 and 4500 N, camber angles of 0° and-3°, and longitudinal slip ratios from 0 to-20%. Special attention is paid to heavy braking, in which context the aligning moment is of great interest in terms of its connection with the limit-handling feel. The results of the simulations reveal that true representations of the contact patch shape, carcass flexibility and lateral RR variation are essential for an accurate prediction of the distribution and the magnitude of the shear forces generated at the tread-road interface of the cambered tyre. Independent of the camber angle, the contact pressure distribution primarily influences the shear force distribution and the slip characteristics around the peak longitudinal force. At low brake-slip ratios, the friction coefficient affects the shear forces in terms of their distribution, while, at medium to high-slip ratios, the force magnitude is significantly affected. On the one hand, these findings help in the creation of efficient yet accurate tyre models. On the other hand, the research results allow improved understanding of how individual tyre components affect the generation of shear forces in the contact patch of a rolling and slipping tyre.

Bacterial Adhesion Forces to Ag-Impregnated Contact Lens Cases and Transmission to Contact Lenses

NARCIS (Netherlands)

Qu, Wenwen; Busscher, Henk J.; van der Mei, Henny C.; Hooymans, Johanna M. M.

Purpose: To measure adhesion forces of Pseudomonas aeruginosa, Staphylococcus aureus, and Serratia marcescens to a rigid contact lens (CL), standard polypropylene, and Ag-impregnated lens cases using atomic force microscopy and determine bacterial transmission from lens case to CL. Methods: Adhesion

Intermittent contact atomic force microscopy in electrochemical environment

Energy Technology Data Exchange (ETDEWEB)

Haering, P; Koetz, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland); Siegenthaler, H [Bern Univ., Bern (Switzerland)

1997-06-01

In situ measurements with Atomic Force Microscopy may cause surface modifications due to the tip-surface interactions. As an alternative and less destructive method, Intermittent Contact Atomic Force Microscopy (ICAFM) has been tested in an electrolytic environment. In the ICAFM mode the tip is not constantly in contact with the surface under investigation but is tapping onto the surface with a certain frequency. A commercial Park Scientific Instruments Microscopy has been modified to enable in situ experiment with ICAFM. It was possible to image iridium oxide films with ICAFM in the electrolytic environment without any noticeable surface modifications. (author) 3 figs., 4 refs.

Medial knee joint contact force in the intact limb during walking in recently ambulatory service members with unilateral limb loss: a cross-sectional study

Directory of Open Access Journals (Sweden)

Ross H. Miller

2017-02-01

Full Text Available Background Individuals with unilateral lower limb amputation have a high risk of developing knee osteoarthritis (OA in their intact limb as they age. This risk may be related to joint loading experienced earlier in life. We hypothesized that loading during walking would be greater in the intact limb of young US military service members with limb loss than in controls with no limb loss. Methods Cross-sectional instrumented gait analysis at self-selected walking speeds with a limb loss group (N = 10, age 27 ± 5 years, 170 ± 36 days since last surgery including five service members with transtibial limb loss and five with transfemoral limb loss, all walking independently with their first prosthesis for approximately two months. Controls (N = 10, age 30 ± 4 years were service members with no overt demographical risk factors for knee OA. 3D inverse dynamics modeling was performed to calculate joint moments and medial knee joint contact forces (JCF were calculated using a reduction-based musculoskeletal modeling method and expressed relative to body weight (BW. Results Peak JCF and maximum JCF loading rate were significantly greater in limb loss (184% BW, 2,469% BW/s vs. controls (157% BW, 1,985% BW/s, with large effect sizes. Results were robust to probabilistic perturbations to the knee model parameters. Discussion Assuming these data are reflective of joint loading experienced in daily life, they support a “mechanical overloading” hypothesis for the risk of developing knee OA in the intact limb of limb loss subjects. Examination of the evolution of gait mechanics, joint loading, and joint health over time, as well as interventions to reduce load or strengthen the ability of the joint to withstand loads, is warranted.

The effect of adhesion on the contact radius in atomic force microscopy indentation

International Nuclear Information System (INIS)

Sirghi, L; Rossi, F

2009-01-01

The effect of adhesion on nanoscale indentation experiments makes the interpretation of force-displacement curves acquired in these experiments very difficult. The indentation force results from the addition of adhesive and elastic forces at the indenter-sample contact. The evolution of the two forces during the indentation is determined by the variation of the indenter-sample contact radius. In the present work the variation of contact radius during atomic force microscopy (AFM) indentation of elastic and adhesive samples with conical indenters (AFM tips) is indirectly determined by measurements of the contact dynamic stiffness. For weak sample deformations, the contact radius is determined mainly by the adhesion force and indenter apex radius. For strong sample deformations, the contact radius increases linearly with the increase of the indenter displacement, the slope of this linear dependence being in agreement with Sneddon's theory of indentation (Sneddon 1965 Int. J. Eng. Sci. 3 47). Based on these results, a theoretical expression of indentation force dependence on displacement is found. This expression allows for determination of the thermodynamic work of adhesion at the indenter-sample interface and the sample elasticity modulus.

Increased medial foot loading during drop jump in subjects with patellofemoral pain

DEFF Research Database (Denmark)

Rathleff, Michael S; Richter, Camilla; Brushøj, Christoffer

2014-01-01

PURPOSE: To compare medial-to-lateral plantar forces during drop jump and single leg squat in individuals with and without patellofemoral pain. METHODS: This cross-sectional study compared 23 young adults with patellofemoral pain to 20 age- and sex-matched controls without knee pain. The plantar...... pressure distribution was collected during drop jump and single leg squat using pressure-sensitive Pedar insoles, inserted into a standard flat shoe. The primary outcome was the medial-to-lateral force, quantified as the peak force under the medial forefoot as the percentage of force under the total...... forefoot during drop jump. Secondary outcomes included peak medial-to-lateral force during single leg squat and mean forces during drop jump and single leg squat. RESULTS: The primary outcome showed that individuals with patellofemoral pain had a 22 % higher medial-to-lateral peak force during drop jump...

modelingthe effect the effect of contact and seepage forces

African Journals Online (AJOL)

eobe

This research work has investigated the contribution of contact force and seepage force to the ... e equilibrium model has deduced an expression for the safe hydraulic head during well ...... Plastic deformation of soils simulation using DEM,.

Design and testing of an innovative measurement device for tyre-road contact forces

Science.gov (United States)

Cheli, F.; Braghin, F.; Brusarosco, M.; Mancosu, F.; Sabbioni, E.

2011-08-01

The measurement of tyre-road contact forces is the first step towards the development of new control systems for improving vehicle safety and performances. Tyre-road contact forces measurement systems are very expensive and significantly modify the unsprung masses of the vehicle as well as the rotational inertia of the tyres. Thus, vehicle dynamics results are significantly affected. As a consequence, the measured contact forces do not correspond to the contact forces under real working conditions. A new low-cost tyre-road contact forces measurement system is proposed in this paper that can be applied to passenger cars. Its working principle is based on the measurement of three deformations of the wheel rim through strain gauges. The tyre-rim assembly is thus turned into a sensor for tyre-road contact forces. The influence of the strain gauges position onto the measurement results has been assessed through finite element simulations and experimental tests. It has been proven that, for a large variety of rims, the strain gauge position that leads to high signal-to-noise ratios is almost the same. A dynamic calibration procedure has been developed in order to allow the reconstruction of contact force and torque components once per wheel turn. The capability of the developed device to correctly estimate tyre-road contact forces has been assessed, in a first stage, through indoor laboratory experimental test on an MTS Flat-Trac ® testing machine. Results show that the implemented measuring system allows to reconstruct contact forces once per wheel turn with a precision that is comparable to that of existing high-cost measurement systems. Subsequently, outdoor tests with a vehicle having all four wheels equipped with the developed measuring device have also been performed. Reliability of the measurements provided by the developed sensor has been assessed by comparing the global measured longitudinal/lateral forces and the product of the measured longitudinal

Learning to push and learning to move: The adaptive control of contact forces

Directory of Open Access Journals (Sweden)

Maura eCasadio

2015-11-01

Full Text Available To be successful at manipulating objects one needs to apply simultaneously well controlled movements and contact forces. We present a computational theory of how the brain may successfully generate a vast spectrum of interactive behaviors by combining two independent processes. One process is competent to control movements in free space and the other is competent to control contact forces against rigid constraints. Free space and rigid constraints are singularities at the boundaries of a continuum of mechanical impedance. Within this continuum, forces and motions occur in compatible pairs connected by the equations of Newtonian dynamics. The force applied to an object determines its motion. Conversely, inverse dynamics determine a unique force trajectory from a movement trajectory. In this perspective, we describe motor learning as a process leading to the discovery of compatible force/motion pairs. The learned compatible pairs constitute a local representation of the environment's mechanics. Experiments on force field adaptation have already provided us with evidence that the brain is able to predict and compensate the forces encountered when one is attempting to generate a motion. Here, we tested the theory in the dual case, i.e. when one attempts at applying a desired contact force against a simulated rigid surface. If the surface becomes unexpectedly compliant, the contact point moves as a function of the applied force and this causes the applied force to deviate from its desired value. We found that, through repeated attempts at generating the desired contact force, subjects discovered the unique compatible hand motion. When, after learning, the rigid contact was unexpectedly restored, subjects displayed after effects of learning, consistent with the concurrent operation of a motion control system and a force control system. Together, theory and experiment support a new and broader view of modularity in the coordinated control of forces and

Improving the contact resistance at low force using gold coated carbon nanotube surfaces

Science.gov (United States)

McBride, J. W.; Yunus, E. M.; Spearing, S. M.

2010-04-01

Investigations to determine the electrical contact performance under repeated cycles at low force conditions for carbon-nanotube (CNT) coated surfaces were performed. The surfaces under investigation consisted of multi-walled CNT synthesized on a silicon substrate and coated with a gold film. These planar surfaces were mounted on the tip of a PZT actuator and contacted with a plated Au hemispherical probe. The dynamic applied force used was 1 mN. The contact resistance (Rc) of these surfaces was investigated with the applied force and with repeated loading cycles performed for stability testing. The surfaces were compared with a reference Au-Au contact under the same experimental conditions. This initial study shows the potential for the application of gold coated CNT surfaces as an interface in low force electrical contact applications.

Kinematic analysis of a televised medial ankle sprain

Directory of Open Access Journals (Sweden)

Francesca E. Wade

2018-04-01

Full Text Available Ankle sprains are one of the most prevalent athletic injuries. Prior work has investigated lateral ankle sprains, but research on generally more severe medial sprains is lacking. This case report performs a kinematic analysis using novel motion analysis methods on a non-contact medial ankle sprain. Peak eversion (50° occurred 0.2 seconds following ground contact, maximum velocity of 426°/s, while peak dorsiflexion (64° occurred with a greater maximum velocity (573°/s. The combination of dorsiflexion at ground contact and rapid eversion is associated with a non-contact eversion sprain. This study provides a quantitative analysis of the eversion ankle sprain injury mechanism. Keywords: Athletic injury, Biomechanics, Ankle injury, Kinematics

Applied force and elongation in the medial rectus in esotropic patients with and without movement restriction.

Science.gov (United States)

Krieger, Fernanda; Cvintal, Tadeu; Bicas, Harley

2004-12-01

To study the different ways of expressing the force-elongation relationship in medial rectus muscles in esotropia with and without muscular restriction. Twenty-nine passive force-elongation curves were obtained without restriction (group I, n = 13) and with restriction (group II, n = 10) by means of a manual pachymeter and a digital dynamometer. In group I, the mean age was 14 years and 7 days and the mean esotropia was 53.88(Delta) while in group II the mean age was 35 years and 5 days and the mean esotropia was 60.5(Delta). Comparisons of structural muscular parameters between groups I and II were made for length (38.69 +/- 0.75 vs. 32.48 +/- 1.84 mm, p elongation relationship, whether normalized or not, followed an exponential curve. The constant c, which represents force when the elongation is zero, remained the same in all curves. In contrast, the constant b, which represents the slope of the curve, showed a significant difference between the two groups only for the curves of force-absolute elongation and tension-absolute elongation. The results imply that the constant b is better for characterizing the difference between the behavior of the medial rectus in esotropia with and without restriction. In addition, the elongation normalization showed that the contractile component is similar between the two groups and, therefore, the classical way of analysis, which does not employ normalization, is appropriate to correlate muscle properties with clinical findings.

Investigation of index finger triggering force using a cadaver experiment: Effects of trigger grip span, contact location, and internal tendon force.

Science.gov (United States)

Chang, Joonho; Freivalds, Andris; Sharkey, Neil A; Kong, Yong-Ku; Mike Kim, H; Sung, Kiseok; Kim, Dae-Min; Jung, Kihyo

2017-11-01

A cadaver study was conducted to investigate the effects of triggering conditions (trigger grip span, contact location, and internal tendon force) on index finger triggering force and the force efficiency of involved tendons. Eight right human cadaveric hands were employed, and a motion simulator was built to secure and control the specimens. Index finger triggering forces were investigated as a function of different internal tendon forces (flexor digitorum profundus + flexor digitorum superficialis = 40, 70, and 100 N), trigger grip spans (40, 50, and 60 mm), and contact locations between the index finger and a trigger. Triggering forces significantly increased when internal tendon forces increased from 40 to 100 N. Also, trigger grip spans and contact locations had significant effects on triggering forces; maximum triggering forces were found at a 50 mm span and the most proximal contact location. The results revealed that only 10-30% of internal tendon forces were converted to their external triggering forces. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dual-joint modeling for estimation of total knee replacement contact forces during locomotion.

Science.gov (United States)

Hast, Michael W; Piazza, Stephen J

2013-02-01

Model-based estimation of in vivo contact forces arising between components of a total knee replacement is challenging because such forces depend upon accurate modeling of muscles, tendons, ligaments, contact, and multibody dynamics. Here we describe an approach to solving this problem with results that are tested by comparison to knee loads measured in vivo for a single subject and made available through the Grand Challenge Competition to Predict in vivo Tibiofemoral Loads. The approach makes use of a "dual-joint" paradigm in which the knee joint is alternately represented by (1) a ball-joint knee for inverse dynamic computation of required muscle controls and (2) a 12 degree-of-freedom (DOF) knee with elastic foundation contact at the tibiofemoral and patellofemoral articulations for forward dynamic integration. Measured external forces and kinematics were applied as a feedback controller and static optimization attempted to track measured knee flexion angles and electromyographic (EMG) activity. The resulting simulations showed excellent tracking of knee flexion (average RMS error of 2.53 deg) and EMG (muscle activations within ±10% envelopes of normalized measured EMG signals). Simulated tibiofemoral contact forces agreed qualitatively with measured contact forces, but their RMS errors were approximately 25% of the peak measured values. These results demonstrate the potential of a dual-joint modeling approach to predict joint contact forces from kinesiological data measured in the motion laboratory. It is anticipated that errors in the estimation of contact force will be reduced as more accurate subject-specific models of muscles and other soft tissues are developed.

Meniscus and viscous forces during normal separation of liquid-mediated contacts

International Nuclear Information System (INIS)

Cai Shaobiao; Bhushan, Bharat

2007-01-01

Menisci form between two solid surfaces with the presence of an ultra-thin liquid film. Meniscus and viscous forces contribute to an adhesive force when two surfaces are separated. The adhesive force can be very large and can result in high friction, stiction and possibly high wear. The situation may become more pronounced when the contacting surfaces are ultra-smooth and the normal load is small, as is common for micro-/nanodevices. In this study, equations for meniscus and viscous forces during separation of two flat surfaces, and a sphere and a flat surface, are developed, and the corresponding adhesive forces contributed by these two types of forces are examined. The geometric meniscus curvatures and break point are theoretically determined, and the role of meniscus and viscous forces is evaluated during separation. The influence of separation distance, liquid thickness, meniscus area, separation time, liquid properties and contact angles are analyzed. Critical meniscus areas at which transition in the dominance of meniscus to viscous forces occurs for different given conditions, i.e. various initial liquid thicknesses, contact angles and designated separation time, are identified. The analysis provides a fundamental understanding of the physics of separation process, and insights into the relationships between meniscus and viscous forces. It is also valuable for the design of the interface for various devices

Contact wire positions and contact forces. Measurements at high-speed lines in China; Fahrdrahtlage und Kontaktkraefte. Messungen an Hochgeschwindigkeitsstrecken in China

Energy Technology Data Exchange (ETDEWEB)

Heland, Joerg; Rick, Frank; Sarnes, Bernhard [DB Systemtechnik GmbH, Muenchen (Germany); Puschmann, Rainer [Siemens AG, Erlangen (Germany). Infrastructure and Cities

2012-07-15

The reliable energy transmission from overhead contact line to pantograph of traction units without interruption decides on the successful operation of high-speed railway lines. Measurements of contact wire position and contact forces are suited to assess interaction of overhead contact line and pantograph. Chinese Railways actually implement the biggest electrification program for high-speed lines worldwide. For these projects contact wire position and contact forces are monitored by procedures developed in Germany. The experience confirms that keeping the contact wire position within the specified limits lead to a superior energy transmission up to 350 km/h. (orig.)

Evaluation of recovery in lip closing pressure and occlusal force and contact area after orthognathic surgery.

Science.gov (United States)

Ueki, Koichiro; Moroi, Akinori; Sotobori, Megumi; Ishihara, Yuri; Marukawa, Kohei; Iguchi, Ran; Kosaka, Akihiko; Ikawa, Hiroumi; Nakazawa, Ryuichi; Higuchi, Masatoshi

2014-10-01

The purpose of this study was to evaluate the relationship between lip closing force, occlusal contact area and occlusal force after orthognathic surgery in skeletal Class III patients. The subjects consisted of 54 patients (28 female and 26 male) diagnosed with mandibular prognathism who underwent sagittal split ramus osteotomy with and without Le Fort I osteotomy. Maximum and minimum lip closing forces, occlusal contact area and occlusal force were measured pre-operatively, 6 months and 1 year post-operative. Maximum and minimum lip closing forces, occlusal contact area and occlusal force increased with time after surgery, however a significant increase was not found in the occlusal contact area in women. In increased ratio (6 months/pre-operative and 1 year/pre-operative), the maximum lip closing force was significantly correlated with the occlusal contact area (P contact area and lip closing force, and an increase ratio in maximum lip closing force was associated with an increased ratio in occlusal contact area. Copyright © 2014 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.

iCub Whole-body Control through Force Regulation on Rigid Noncoplanar Contacts

Directory of Open Access Journals (Sweden)

Francesco eNori

2015-03-01

Full Text Available This paper details the implementation on the humanoid robot iCub of state-of-the-art algorithms for whole-body control. We regulate the forces between the robot and its surrounding environment to stabilize a desired robot posture. We assume that the forces and torques are exerted on rigid contacts. The validity of this assumption is guaranteed by constraining the contact forces and torques, e.g. the contact forces must belong to the associated friction cones. The implementation of this control strategy requires to estimate the external forces acting on the robot, and the internal joint torques. We then detail algorithms to obtain these estimations when using a robot with an iCub-like sensor set, i.e. distributed six-axis force-torque sensors and whole-body tactile sensors. A general theory for identifying the robot inertial parameters is also presented. From an actuation standpoint, we show how to implement a joint torque control in the case of DC brushless motors. In addition, the coupling mechanism of the iCub torso is investigated. The soundness of the entire control architecture is validated in a real scenario involving the robot iCub balancing and making contacts at both arms.

Automated setpoint adjustment for biological contact mode atomic force microscopy imaging

International Nuclear Information System (INIS)

Casuso, Ignacio; Scheuring, Simon

2010-01-01

Contact mode atomic force microscopy (AFM) is the most frequently used AFM imaging mode in biology. It is about 5-10 times faster than oscillating mode imaging (in conventional AFM setups), and provides topographs of biological samples with sub-molecular resolution and at a high signal-to-noise ratio. Unfortunately, contact mode imaging is sensitive to the applied force and intrinsic force drift: inappropriate force applied by the AFM tip damages the soft biological samples. We present a methodology that automatically searches for and maintains high resolution imaging forces. We found that the vertical and lateral vibrations of the probe during scanning are valuable signals for the characterization of the actual applied force by the tip. This allows automated adjustment and correction of the setpoint force during an experiment. A system that permanently performs this methodology steered the AFM towards high resolution imaging forces and imaged purple membrane at molecular resolution and live cells at high signal-to-noise ratio for hours without an operator.

Quantitative assessment of contact and non-contact lateral force calibration methods for atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Tran Khac, Bien Cuong; Chung, Koo-Hyun, E-mail: khchung@ulsan.ac.kr

2016-02-15

Atomic Force Microscopy (AFM) has been widely used for measuring friction force at the nano-scale. However, one of the key challenges faced by AFM researchers is to calibrate an AFM system to interpret a lateral force signal as a quantifiable force. In this study, five rectangular cantilevers were used to quantitatively compare three different lateral force calibration methods to demonstrate the legitimacy and to establish confidence in the quantitative integrity of the proposed methods. The Flat-Wedge method is based on a variation of the lateral output on a surface with flat and changing slopes, the Multi-Load Pivot method is based on taking pivot measurements at several locations along the cantilever length, and the Lateral AFM Thermal-Sader method is based on determining the optical lever sensitivity from the thermal noise spectrum of the first torsional mode with a known torsional spring constant from the Sader method. The results of the calibration using the Flat-Wedge and Multi-Load Pivot methods were found to be consistent within experimental uncertainties, and the experimental uncertainties of the two methods were found to be less than 15%. However, the lateral force sensitivity determined by the Lateral AFM Thermal-Sader method was found to be 8–29% smaller than those obtained from the other two methods. This discrepancy decreased to 3–19% when the torsional mode correction factor for an ideal cantilever was used, which suggests that the torsional mode correction should be taken into account to establish confidence in Lateral AFM Thermal-Sader method. - Highlights: • Quantitative assessment of three lateral force calibration methods for AFM. • Advantages and disadvantages of three different lateral force calibration method. • Implementation of Multi-Load Pivot method as non-contact calibration technique. • The torsional mode correction for Lateral AFM Thermal-Sader method.

Quantitative assessment of contact and non-contact lateral force calibration methods for atomic force microscopy

International Nuclear Information System (INIS)

Tran Khac, Bien Cuong; Chung, Koo-Hyun

2016-01-01

Atomic Force Microscopy (AFM) has been widely used for measuring friction force at the nano-scale. However, one of the key challenges faced by AFM researchers is to calibrate an AFM system to interpret a lateral force signal as a quantifiable force. In this study, five rectangular cantilevers were used to quantitatively compare three different lateral force calibration methods to demonstrate the legitimacy and to establish confidence in the quantitative integrity of the proposed methods. The Flat-Wedge method is based on a variation of the lateral output on a surface with flat and changing slopes, the Multi-Load Pivot method is based on taking pivot measurements at several locations along the cantilever length, and the Lateral AFM Thermal-Sader method is based on determining the optical lever sensitivity from the thermal noise spectrum of the first torsional mode with a known torsional spring constant from the Sader method. The results of the calibration using the Flat-Wedge and Multi-Load Pivot methods were found to be consistent within experimental uncertainties, and the experimental uncertainties of the two methods were found to be less than 15%. However, the lateral force sensitivity determined by the Lateral AFM Thermal-Sader method was found to be 8–29% smaller than those obtained from the other two methods. This discrepancy decreased to 3–19% when the torsional mode correction factor for an ideal cantilever was used, which suggests that the torsional mode correction should be taken into account to establish confidence in Lateral AFM Thermal-Sader method. - Highlights: • Quantitative assessment of three lateral force calibration methods for AFM. • Advantages and disadvantages of three different lateral force calibration method. • Implementation of Multi-Load Pivot method as non-contact calibration technique. • The torsional mode correction for Lateral AFM Thermal-Sader method.

The influence of rail surface irregularities on contact forces and local stresses

Science.gov (United States)

Andersson, Robin; Torstensson, Peter T.; Kabo, Elena; Larsson, Fredrik

2015-01-01

The effect of initial rail surface irregularities on promoting further surface degradation is investigated. The study concerns rolling contact fatigue formation, in particular in the form of the so-called squats. The impact of surface irregularities in the form of dimples is quantified by peak magnitudes of dynamic contact stresses and contact forces. To this end simulations of two-dimensional (later extended to three-dimensional) vertical dynamic vehicle-track interaction are employed. The most influencing parameters are identified. It is shown that even very shallow dimples might have a large impact on local contact stresses. Peak magnitudes of contact forces and stresses due to the influence of rail dimples are shown to exceed those due to rail corrugation.

Experimental study of tyre/road contact forces in rolling conditions for noise prediction

Science.gov (United States)

Cesbron, Julien; Anfosso-Lédée, Fabienne; Duhamel, Denis; Ping Yin, Hai; Le Houédec, Donatien

2009-02-01

This paper deals with the experimental study of dynamical tyre/road contact for noise prediction. In situ measurements of contact forces and close proximity noise levels were carried out for a slick tyre rolling on six different road surfaces between 30 and 50 km/h. Additional texture profiles of the tested surfaces were taken on the wheel track. Normal contact stresses were measured at a sampling frequency of 10752 Hz using a line of pressure sensitive cells placed both along and perpendicular to the rolling direction. The contact areas obtained during rolling were smaller than in static conditions. This is mainly explained by the dynamical properties of tyre compounds, like the viscoelastic behaviour of the rubber. Additionally the root-mean-square of the resultant contact forces at various speeds was in the same order for a given road surface, while their spectra were quite different. This is certainly due to a spectral influence of bending waves propagating in the tyre during rolling, especially when the wavelength is small in comparison with the size of the contact patch. Finally, the levels of contact forces and close proximity noise measured at 30 km/h were correlated. Additional correlations with texture levels were performed. The results show that the macro-texture generates contact forces linearly around 800 Hz and consequently noise levels between 500 and 1000 Hz via the vibrations transmitted to the tyre.

Comparison of Tibiofemoral Contact Mechanics After Various Transtibial and All-Inside Fixation Techniques for Medial Meniscus Posterior Root Radial Tears in a Porcine Model.

Science.gov (United States)

Chung, Kyu Sung; Choi, Choong Hyeok; Bae, Tae Soo; Ha, Jeong Ku; Jun, Dal Jae; Wang, Joon Ho; Kim, Jin Goo

2018-04-01

To compare tibiofemoral contact mechanics after fixation for medial meniscus posterior root radial tears (MMPRTs). Seven fresh knees from mature pigs were used. Each knee was tested under 5 conditions: normal knee, MMPRT, pullout fixation with simple sutures, fixation with modified Mason-Allen sutures, and all-inside fixation using Fastfix 360. The peak contact pressure and contact surface area were evaluated using a capacitive sensor positioned between the meniscus and tibial plateau, under a 1,000-N compression force, at different flexion angles (0°, 30°, 60°, and 90°). The peak contact pressure was significantly higher in MMPRTs than in normal knees (P = .018). Although the peak contact pressure decreased significantly after fixation at all flexion angles (P = .031), it never recovered to the values noted in the normal meniscus. No difference was observed among fixation groups (P = .054). The contact surface area was significantly lower in MMPRTs than in the normal meniscus (P = .018) and increased significantly after fixation at all flexion angles (P = .018) but did not recover to within normal limits. For all flexion angles except 60°, the contact surface area was significantly higher for fixation with Mason-Allen sutures than for fixation with simple sutures or all-inside fixation (P = .027). At 90° of flexion, the contact surface area was significantly better for fixation with simple sutures than for all-inside fixation (P = .031). The peak contact pressure and contact surface area improved significantly after fixation, regardless of the fixation method, but did not recover to the levels noted in the normal meniscus after any type of fixation. Among the fixation methods evaluated in this time 0 study, fixation using modified Mason-Allen sutures provided a superior contact surface area compared with that noted after fixation using simple sutures or all-inside fixation, except at 60° of flexion. However, this study had insufficient power to

Molar volume and adsorption isotherm dependence of capillary forces in nanoasperity contacts.

Science.gov (United States)

Asay, David B; Kim, Seong H

2007-11-20

The magnitude of the capillary force at any given temperature and adsorbate partial pressure depends primarily on four factors: the surface tension of the adsorbate, its liquid molar volume, its isothermal behavior, and the contact geometry. At large contacting radii, the adsorbate surface tension and the contact geometry are dominating. This is the case of surface force apparatus measurements and atomic force microscopy (AFM) experiments with micrometer-size spheres. However, as the size of contacting asperities decreases to the nanoscale as in AFM experiments with sharp tips, the molar volume and isotherm of the adsorbate become very important to capillary formation as well as capillary adhesion. This effect is experimentally and theoretically explored with simple alcohol molecules (ethanol, 1-butanol, and 1-pentanol) which have comparable surface tensions but differing liquid molar volumes. Adsorption isotherms for these alcohols on silicon oxide are also reported.

Force Trends and Pulsatility for Catheter Contact Identification in Intracardiac Electrograms during Arrhythmia Ablation.

Science.gov (United States)

Rivas-Lalaleo, David; Muñoz-Romero, Sergio; Huerta, Mónica; Erazo-Rodas, Mayra; Sánchez-Muñoz, Juan José; Rojo-Álvarez, José Luis; García-Alberola, Arcadi

2018-05-02

The intracardiac electrical activation maps are commonly used as a guide in the ablation of cardiac arrhythmias. The use of catheters with force sensors has been proposed in order to know if the electrode is in contact with the tissue during the registration of intracardiac electrograms (EGM). Although threshold criteria on force signals are often used to determine the catheter contact, this may be a limited criterion due to the complexity of the heart dynamics and cardiac vorticity. The present paper is devoted to determining the criteria and force signal profiles that guarantee the contact of the electrode with the tissue. In this study, we analyzed 1391 force signals and their associated EGM recorded during 2 and 8 s, respectively, in 17 patients (82 ± 60 points per patient). We aimed to establish a contact pattern by first visually examining and classifying the signals, according to their likely-contact joint profile and following the suggestions from experts in the doubtful cases. First, we used Principal Component Analysis to scrutinize the force signal dynamics by analyzing the main eigen-directions, first globally and then grouped according to the certainty of their tissue-catheter contact. Second, we used two different linear classifiers (Fisher discriminant and support vector machines) to identify the most relevant components of the previous signal models. We obtained three main types of eigenvectors, namely, pulsatile relevant, non-pulsatile relevant, and irrelevant components. The classifiers reached a moderate to sufficient discrimination capacity (areas under the curve between 0.84 and 0.95 depending on the contact certainty and on the classifier), which allowed us to analyze the relevant properties in the force signals. We conclude that the catheter-tissue contact profiles in force recordings are complex and do not depend only on the signal intensity being above a threshold at a single time instant, but also on time pulsatility and trends. These

An in-fiber Bragg grating sensor for contact force and stress measurements in articular joints

International Nuclear Information System (INIS)

Dennison, Christopher R; Wild, Peter M; Wilson, David R; Gilbart, Michael K

2010-01-01

We present an in-fiber Bragg grating-based sensor (240 µm diameter) for contact force/stress measurements in articular joints. The contact force sensor and another Bragg grating-based pressure sensor (400 µm diameter) are used to conduct the first simultaneous measurements of contact force/stress and fluid pressure in intact cadaveric human hips. The contact force/stress sensor addresses limitations associated with stress-sensitive films, the current standard tools for contact measurements in joints, including cartilage modulus-dependent sensitivity of films and the necessity to remove biomechanically relevant anatomy to implant the films. Because stress-sensitive films require removal of anatomy, it has been impossible to validate the mechanical rationale underlying preventive or corrective surgeries, which repair these anatomies, by conducting simultaneous stress and pressure measurements in intact hips. Methods are presented to insert the Bragg grating-based sensors into the joint, while relevant anatomy is left largely intact. Sensor performance is predicted using numerical models and the predicted sensitivity is verified through experimental calibrations. Contact force/stress and pressure measurements in cadaveric joints exhibited repeatability. With further validation, the Bragg grating-based sensors could be used to study the currently unknown relationships between contact forces and pressures in both healthy and degenerated joints

Molecular dynamics study of the nanosized droplet spreading: The effect of the contact line forces on the kinetic energy dissipation

Energy Technology Data Exchange (ETDEWEB)

Yoon, Hong Min [Department of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Kondaraju, Sasidhar [Department of Mechanical Science, Indian Institute of Technology Bhubaneswar, Bhubaneswar, Odisha 751013 (India); Lee, Jung Shin [Department of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Suh, Youngho; Lee, Joonho H. [Samsung Electronics, Mechatronics R& D Center, Hwaseong-si, Gyeonggi-do 445-330 (Korea, Republic of); Lee, Joon Sang, E-mail: joonlee@yonsei.ac.kr [Department of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

2017-07-01

Highlights: • Contact line forces, including friction and spreading forces are directly calculated. • Overall trends of variations in contact line forces during droplet spreading process show characteristics of contact line forces. • Detail relations of contact line forces and atomic kinetics in the contact line provide a clear evidence of the possible energy dissipation mechanism in droplet spreading process. - Abstract: Recent studies have revealed that contact line forces play an important role in the droplet spreading process. Despite their significance, the physics related to them has been studied only indirectly and the effect of contact line forces is still being disputed. We performed a molecular dynamics simulation and mimicked the droplet spreading process at the nanoscale. Based on the results of the simulation, the contact line forces were directly calculated. We found that the forces acting on the bulk and the contact line region showed different trends. Distinct positive and negative forces, contact line spreading, and friction forces were observed near the contact line. We also observed a strong dependency of the atomic kinetics in the contact line region on the variations in the contact line forces. The atoms of the liquid in the contact line region lost their kinetic energy due to the contact line friction force and became partially immobile on the solid surface. The results of the current study will be useful for understanding the role of the contact line forces on the kinetic energy dissipation in the contact line region.

Molecular dynamics study of the nanosized droplet spreading: The effect of the contact line forces on the kinetic energy dissipation

International Nuclear Information System (INIS)

Yoon, Hong Min; Kondaraju, Sasidhar; Lee, Jung Shin; Suh, Youngho; Lee, Joonho H.; Lee, Joon Sang

2017-01-01

Highlights: • Contact line forces, including friction and spreading forces are directly calculated. • Overall trends of variations in contact line forces during droplet spreading process show characteristics of contact line forces. • Detail relations of contact line forces and atomic kinetics in the contact line provide a clear evidence of the possible energy dissipation mechanism in droplet spreading process. - Abstract: Recent studies have revealed that contact line forces play an important role in the droplet spreading process. Despite their significance, the physics related to them has been studied only indirectly and the effect of contact line forces is still being disputed. We performed a molecular dynamics simulation and mimicked the droplet spreading process at the nanoscale. Based on the results of the simulation, the contact line forces were directly calculated. We found that the forces acting on the bulk and the contact line region showed different trends. Distinct positive and negative forces, contact line spreading, and friction forces were observed near the contact line. We also observed a strong dependency of the atomic kinetics in the contact line region on the variations in the contact line forces. The atoms of the liquid in the contact line region lost their kinetic energy due to the contact line friction force and became partially immobile on the solid surface. The results of the current study will be useful for understanding the role of the contact line forces on the kinetic energy dissipation in the contact line region.

A Study on the Effect of the Contact Point and the Contact Force of a Glass Fiber under End-Face Polishing Process

Directory of Open Access Journals (Sweden)

Ying-Chien Tsai

2015-01-01

Full Text Available The offset between the center lines of the polished end-face and the fiber core has a significant effect on coupling efficiency. The initial contact point and the contact force are two of the most important parameters that induce the offset. This study proposes an image assistant method to find the initial contact point and a mathematical model to estimate the contact force when fabricating the double-variable-curvature end-face of single mode glass fiber. The repeatability of finding the initial contact point via the vision assistant program is 0.3 μm. Based on the assumption of a large deflection, a mathematical model is developed to study the relationship between the contact force and the displacement of the lapping film. In order to verify the feasibility of the mathematical model, experiments, as well as DEFORM simulations, are carried out. The results show that the contact forces are alomst linearly proportional to the feed amounts of the lapping film and the errors are less than 9%. By using the method developed in this study, the offset between the grinding end-face and the center line of the fiber core is within 0.15 to 0.35 μm.

Development of method for experimental determination of wheel–rail contact forces and contact point position by using instrumented wheelset

International Nuclear Information System (INIS)

Bižić, Milan B; Petrović, Dragan Z; Tomić, Miloš C; Djinović, Zoran V

2017-01-01

This paper presents the development of a unique method for experimental determination of wheel–rail contact forces and contact point position by using the instrumented wheelset (IWS). Solutions of key problems in the development of IWS are proposed, such as the determination of optimal locations, layout, number and way of connecting strain gauges as well as the development of an inverse identification algorithm (IIA). The base for the solution of these problems is the wheel model and results of FEM calculations, while IIA is based on the method of blind source separation using independent component analysis. In the first phase, the developed method was tested on a wheel model and a high accuracy was obtained (deviations of parameters obtained with IIA and really applied parameters in the model are less than 2%). In the second phase, experimental tests on the real object or IWS were carried out. The signal-to-noise ratio was identified as the main influential parameter on the measurement accuracy. Тhе obtained results have shown that the developed method enables measurement of vertical and lateral wheel–rail contact forces Q and Y and their ratio Y / Q with estimated errors of less than 10%, while the estimated measurement error of contact point position is less than 15%. At flange contact and higher values of ratio Y / Q or Y force, the measurement errors are reduced, which is extremely important for the reliability and quality of experimental tests of safety against derailment of railway vehicles according to the standards UIC 518 and EN 14363. The obtained results have shown that the proposed method can be successfully applied in solving the problem of high accuracy measurement of wheel–rail contact forces and contact point position using IWS. (paper)

Changes in contact area characteristics of the ankle after a cartilage biopsy at the postero-medial rim of the talar dome.

Science.gov (United States)

Matricali, G A; Bartels, W; Labey, L; Dereymaeker, G Ph E; Luyten, F P; Vander Sloten, J

2009-11-01

Study the changes in local and generalized biomechanical characteristics of the ankle joint, associated with a well defined cartilage biopsy at the postero-medial rim of the talar dome, to evaluate its safety. Ten cadaver ankles were (sub-) physiologically loaded pre- and post-biopsy; in neutral position, 10 degrees of plantar-flexion (PF) and 10 degrees of dorsi-flexion (DF). Fuji film was used as transducer. Qualitatively, the coverage of the biopsy by the tibial plafond, and changes in the shape of the footprint were analyzed. Quantitatively, the pressure profile plot, normalized-tibio-talar contact area and the centroid position of pressure were examined. Results were reported as a mean for all specimens, and as individual values for every single specimen as well. Mean results did not show significant changes, but those of some single specimens did. The majority of those changes were in PF. Some occurred in N, and besides two exceptions none occurred in DF. Two specimens did not show any change. One specimen showed an isolated quantitative change. Seven specimens showed both qualitative and quantitative changes. However, all changes were of low-magnitude and contact stresses did not show any rebound effect. Although biopsies at the postero-medial rim of the talar dome did not induce on average significant changes in quantitative contact characteristics, few specimens did show some alterations. Currently, the investigated biopsy site seems safe, but long term follow-up studies in patients are needed for confirmation.

Experimental quantification of contact forces with impact, friction and uncertainty analysis

DEFF Research Database (Denmark)

Lahriri, Said; Santos, Ilmar

2013-01-01

and whirl motions in rotor-stator contact investigations. Dry friction coefficient is therefore estimated using two different experimental setups: (a) standard pin-on-disk tests and (b) rotor impact test rig fully instrumented. The findings in both setups indicate that the dry friction coefficient for brass......During rotor-stator contact dry friction plays a significant role in terms of reversing the rotor precession. The frictional force causes an increase in the rotor's tangential velocity in the direction opposite to that of the angular velocity. This effect is crucial for defining ranges of dry whip......-aluminum configuration significantly varies in a range of 0.16-0.83. The rotor enters a full annular contact mode shortly after two impacts with a contact duration of approximately 0.004 s at each location. It is experimentally demonstrated that the friction force is not present when the rotor enters a full annular...

Muscle optimization techniques impact the magnitude of calculated hip joint contact forces

NARCIS (Netherlands)

Wesseling, M.; Derikx, L.C.; de Groote, F.; Bartels, W.; Meyer, C.; Verdonschot, Nicolaas Jacobus Joseph; Jonkers, I.

2015-01-01

In musculoskeletal modelling, several optimization techniques are used to calculate muscle forces, which strongly influence resultant hip contact forces (HCF). The goal of this study was to calculate muscle forces using four different optimization techniques, i.e., two different static optimization

Thigh muscle activity, knee motion, and impact force during side-step pivoting in agility-trained female basketball players.

Science.gov (United States)

Wilderman, Danielle R; Ross, Scott E; Padua, Darin A

2009-01-01

Improving neuromuscular control of hamstrings muscles might have implications for decreasing anterior cruciate ligament injuries in females. To examine the effects of a 6-week agility training program on quadriceps and hamstrings muscle activation, knee flexion angles, and peak vertical ground reaction force. Prospective, randomized clinical research trial. Sports medicine research laboratory. Thirty female intramural basketball players with no history of knee injury (age = 21.07 +/- 2.82 years, height = 171.27 +/- 4.66 cm, mass = 66.36 +/- 7.41 kg). Participants were assigned to an agility training group or a control group that did not participate in agility training. Participants in the agility training group trained 4 times per week for 6 weeks. We used surface electromyography to assess muscle activation for the rectus femoris, vastus medialis oblique, medial hamstrings, and lateral hamstrings for 50 milliseconds before initial ground contact and while the foot was in contact with the ground during a side-step pivot maneuver. Knee flexion angles (at initial ground contact, maximum knee flexion, knee flexion displacement) and peak vertical ground reaction force also were assessed during this maneuver. Participants in the training group increased medial hamstrings activation during ground contact after the 6-week agility training program. Both groups decreased their vastus medialis oblique muscle activation during ground contact. Knee flexion angles and peak vertical ground reaction force did not change for either group. Agility training improved medial hamstrings activity in female intramural basketball players during a side-step pivot maneuver. Agility training that improves hamstrings activity might have implications for reducing anterior cruciate ligament sprain injury associated with side-step pivots.

Apparent-contact-angle model at partial wetting and evaporation: impact of surface forces.

Science.gov (United States)

Janeček, V; Nikolayev, V S

2013-01-01

This theoretical and numerical study deals with evaporation of a fluid wedge in contact with its pure vapor. The model describes a regime where the continuous wetting film is absent and the actual line of the triple gas-liquid-solid contact appears. A constant temperature higher than the saturation temperature is imposed at the solid substrate. The fluid flow is solved in the lubrication approximation. The introduction of the surface forces in the case of the partial wetting is discussed. The apparent contact angle (the gas-liquid interface slope far from the contact line) is studied numerically as a function of the substrate superheating, contact line velocity, and parameters related to the solid-fluid interaction (Young and microscopic contact angles, Hamaker constant, etc.). The dependence of the apparent contact angle on the substrate temperature is in agreement with existing approaches. For water, the apparent contact angle may be 20° larger than the Young contact angle for 1 K superheating. The effect of the surface forces on the apparent contact angle is found to be weak.

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact.

Science.gov (United States)

Sylos-Labini, Francesca; d'Avella, Andrea; Lacquaniti, Francesco; Ivanenko, Yury

2018-01-01

Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free) arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating) arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries ("quadrupedal" arm-leg coordination) during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and coordinate steps during

Human-Human Interaction Forces and Interlimb Coordination During Side-by-Side Walking With Hand Contact

Directory of Open Access Journals (Sweden)

Francesca Sylos-Labini

2018-03-01

Full Text Available Handholding can naturally occur between two walkers. When people walk side-by-side, either with or without hand contact, they often synchronize their steps. However, despite the importance of haptic interaction in general and the natural use of hand contact between humans during walking, few studies have investigated forces arising from physical interactions. Eight pairs of adult subjects participated in this study. They walked on side-by-side treadmills at 4 km/h independently and with hand contact. Only hand contact-related sensory information was available for unintentional synchronization, while visual and auditory communication was obstructed. Subjects walked at their natural cadences or following a metronome. Limb kinematics, hand contact 3D interaction forces and EMG activity of 12 upper limb muscles were recorded. Overall, unintentional step frequency locking was observed during about 40% of time in 88% of pairs walking with hand contact. On average, the amplitude of contact arm oscillations decreased while the contralateral (free arm oscillated in the same way as during normal walking. Interestingly, EMG activity of the shoulder muscles of the contact arm did not decrease, and their synergistic pattern remained similar. The amplitude of interaction forces and of trunk oscillations was similar for synchronized and non-synchronized steps, though the synchronized steps were characterized by significantly more regular orientations of interaction forces. Our results further support the notion that gait synchronization during natural walking is common, and that it may occur through interaction forces. Conservation of the proximal muscle activity of the contact (not oscillating arm is consistent with neural coupling between cervical and lumbosacral pattern generation circuitries (“quadrupedal” arm-leg coordination during human gait. Overall, the findings suggest that individuals might integrate force interaction cues to communicate and

Uncertainties in forces extracted from non-contact atomic force microscopy measurements by fitting of long-range background forces

Directory of Open Access Journals (Sweden)

Adam Sweetman

2014-04-01

Full Text Available In principle, non-contact atomic force microscopy (NC-AFM now readily allows for the measurement of forces with sub-nanonewton precision on the atomic scale. In practice, however, the extraction of the often desired ‘short-range’ force from the experimental observable (frequency shift is often far from trivial. In most cases there is a significant contribution to the total tip–sample force due to non-site-specific van der Waals and electrostatic forces. Typically, the contribution from these forces must be removed before the results of the experiment can be successfully interpreted, often by comparison to density functional theory calculations. In this paper we compare the ‘on-minus-off’ method for extracting site-specific forces to a commonly used extrapolation method modelling the long-range forces using a simple power law. By examining the behaviour of the fitting method in the case of two radically different interaction potentials we show that significant uncertainties in the final extracted forces may result from use of the extrapolation method.

Medial epicondylitis in occupational settings: prevalence, incidence and associated risk factors

Science.gov (United States)

Descatha, Alexis; Leclerc, Annette; Chastang, Jean-François; Roquelaure, Yves

2003-01-01

As medial epicondylitis has not been studied alone, we investigated its links between personal and occupational factors in repetitive work, and its course. 1757 workers were examined by an occupational health physician in 1993–94. 598 of them were re-examined three years later. Prevalence was between 4 and 5%, with annual incidence estimated at 1.5%. Forceful work was a risk factor for medial epicondylitis (OR 1.95 CI [1.15–3.32]), but not exposure to repetitive work (OR 1.11, CI [0.59–2.10]). Workers with medial epicondylitis had a significantly higher prevalence of other work-related upper-limb musculoskeletal disorders (WRMD). Risk factors differed for medial and lateral epicondylitis. The prognosis for medial epicondylitis in this population was good with a three-year recovery rate at 81%. Medial epicondylitis was clearly associated with forceful work and other upper-limb WRMD, and its prognosis was good. PMID:14506342

Theoretical modelling, analysis and validation of the shaft motion and dynamic forces during rotor–stator contact

DEFF Research Database (Denmark)

Lahriri, Said; Santos, Ilmar

2013-01-01

and stator. Expressions for the restoring magnetic forces are derived using Biot Savart law for uniformed magnetised bar magnets and the contact forces are derived by use of a compliant contact force model. The theoretical mathematical model is verified with experimental results, and shows good agreements...

A General Contact Force Analysis of an Under-Actuated Finger in Robot Hand Grasping

Directory of Open Access Journals (Sweden)

Xuan Vinh Ha

2016-02-01

Full Text Available This paper develops a mathematical analysis of contact forces for the under-actuated finger in a general under-actuated robotic hand during grasping. The concept of under-actuation in robotic grasping with fewer actuators than degrees of freedom (DOF, through the use of springs and mechanical limits, allows the hand to adjust itself to an irregularly shaped object without complex control strategies and sensors. Here the main concern is the contact forces, which are important elements in grasping tasks, based on the proposed mathematical analysis of their distributions of the n-DOF under-actuated finger. The simulation results, along with the 3-DOF finger from the ADAMS model, show the effectiveness of the mathematical analysis method, while comparing them with the measured results. The system can find magnitudes of the contact forces at the contact positions between the phalanges and the object.

Effect of Complete Syndesmotic Disruption and Deltoid Injuries and Different Reduction Methods on Ankle Joint Contact Mechanics.

Science.gov (United States)

LaMothe, Jeremy; Baxter, Josh R; Gilbert, Susannah; Murphy, Conor I; Karnovsky, Sydney C; Drakos, Mark C

2017-06-01

Syndesmotic injuries can be associated with poor patient outcomes and posttraumatic ankle arthritis, particularly in the case of malreduction. However, ankle joint contact mechanics following a syndesmotic injury and reduction remains poorly understood. The purpose of this study was to characterize the effects of a syndesmotic injury and reduction techniques on ankle joint contact mechanics in a biomechanical model. Ten cadaveric whole lower leg specimens with undisturbed proximal tibiofibular joints were prepared and tested in this study. Contact area, contact force, and peak contact pressure were measured in the ankle joint during simulated standing in the intact, injured, and 3 reduction conditions: screw fixation with a clamp, screw fixation without a clamp (thumb technique), and a suture-button construct. Differences in these ankle contact parameters were detected between conditions using repeated-measures analysis of variance. Syndesmotic disruption decreased tibial plafond contact area and force. Syndesmotic reduction did not restore ankle loading mechanics to values measured in the intact condition. Reduction with the thumb technique was able to restore significantly more joint contact area and force than the reduction clamp or suture-button construct. Syndesmotic disruption decreased joint contact area and force. Although the thumb technique performed significantly better than the reduction clamp and suture-button construct, syndesmotic reduction did not restore contact mechanics to intact levels. Decreased contact area and force with disruption imply that other structures are likely receiving more loads (eg, medial and lateral gutters), which may have clinical implications such as the development of posttraumatic arthritis.

Fabrication of robot head module using contact resistance force sensor for human robot interaction and its evaluation

Energy Technology Data Exchange (ETDEWEB)

Kim, Dong Ki; Kim, Jong Ho [Korea Reserch Institute of Standards and Science, Daejeon (Korea, Republic of); Kwon, Hyun Joon [Univ. of Maryland, Maryland (United States); Kwon, Young Ha [Kyung Hee Univ., Gyunggi Do (Korea, Republic of)

2012-10-15

This paper presents a design of a robot head module with touch sensing algorithms that can simultaneously detect contact force and location. The module is constructed with a hemisphere and three sensor units that are fabricated using contact resistance force sensors. The surface part is designed with the hemisphere that measures 300 mm in diameter and 150 mm in height. Placed at the bottom of the robot head module are three sensor units fabricated using a simple screen printing technique. The contact force and the location of the model are evaluated through the calibration setup. The experiment showed that the calculated contact positions almost coincided with the applied load points as the contact location changed with a location error of about {+-}8.67 mm. The force responses of the module were evaluated at two points under loading and unloading conditions from 0 N to 5 N. The robot head module showed almost the same force responses at the two points.

Tactile Robotic Topographical Mapping Without Force or Contact Sensors

Science.gov (United States)

Burke, Kevin; Melko, Joseph; Krajewski, Joel; Cady, Ian

2008-01-01

A method of topographical mapping of a local solid surface within the range of motion of a robot arm is based on detection of contact between the surface and the end effector (the fixture or tool at the tip of the robot arm). The method was conceived to enable mapping of local terrain by an exploratory robot on a remote planet, without need to incorporate delicate contact switches, force sensors, a vision system, or other additional, costly hardware. The method could also be used on Earth for determining the size and shape of an unknown surface in the vicinity of a robot, perhaps in an unanticipated situation in which other means of mapping (e.g., stereoscopic imaging or laser scanning with triangulation) are not available. The method uses control software modified to utilize the inherent capability of the robotic control system to measure the joint positions, the rates of change of the joint positions, and the electrical current demanded by the robotic arm joint actuators. The system utilizes these coordinate data and the known robot-arm kinematics to compute the position and velocity of the end effector, move the end effector along a specified trajectory, place the end effector at a specified location, and measure the electrical currents in the joint actuators. Since the joint actuator current is approximately proportional to the actuator forces and torques, a sudden rise in joint current, combined with a slowing of the joint, is a possible indication of actuator stall and surface contact. Hence, even though the robotic arm is not equipped with contact sensors, it is possible to sense contact (albeit with reduced sensitivity) as the end effector becomes stalled against a surface that one seeks to measure.

An instrumented implant for in vivo measurement of contact forces and contact moments in the shoulder joint.

Science.gov (United States)

Westerhoff, P; Graichen, F; Bender, A; Rohlmann, A; Bergmann, G

2009-03-01

To improve implant design, fixation and preclinical testing, implant manufacturers depend on realistic data of loads acting on the shoulder joint. Furthermore, these data can help to optimize physiotherapeutic treatment and to advise patients in their everyday living conditions. Calculated shoulder joint loads vary extremely among different authors [Anglin C, Wyss UP, Pichora DR. Glenohumeral contact forces. Proc Inst Mech Eng [H] 2000;214:637-44]. Additionally the moments acting in the joint caused by friction or incongruent articular surfaces, for example, are not implemented in most models. An instrumented shoulder joint implant was developed to measure the contact forces and the contact moments acting in the glenohumeral joint. This article provides a detailed description of the implant, containing a nine-channel telemetry unit, six load sensors and an inductive power supply, all hermetically sealed inside the implant. The instrumented implant is based on a clinically proven BIOMET Biomodular shoulder replacement and was calibrated before implantation by using complex mathematical calculation routines in order to achieve an average measuring precision of approximately 2%.

Technique to measure contact angle of micro/nanodroplets using atomic force microscopy

International Nuclear Information System (INIS)

Jung, Yong Chae; Bhushan, Bharat

2008-01-01

Contact angle is the primary parameter that characterizes wetting; however, the measurement techniques have been limited to droplets with a diameter as low as about 50 μm. The authors developed an atomic force microscopy-based technique to measure the contact angle of micro- and nanodroplets deposited using a modified nanoscale dispensing tip. The obtained contact angle results were compared with those of a macrodroplet (2.1 mm diameter). It was found that the contact angle on various surfaces decreases with decreasing the droplet size

Sub-Angstrom oscillation amplitude non-contact atomic force microscopy for lateral force gradient measurement

International Nuclear Information System (INIS)

Atabak, Mehrdad; Unverdi, Ozhan; Ozer, H. Ozguer; Oral, Ahmet

2009-01-01

We report the first results from novel sub-Angstrom oscillation amplitude non-contact atomic force microscopy developed for lateral force gradient measurements. Quantitative lateral force gradients between a tungsten tip and Si(1 1 1)-(7 x 7) surface can be measured using this microscope. Simultaneous lateral force gradient and scanning tunnelling microscope images of single and multi atomic steps are obtained. In our measurement, tunnel current is used as feedback. The lateral stiffness contrast has been observed to be 2.5 N/m at single atomic step, in contrast to 13 N/m at multi atomic step on Si(1 1 1) surface. We also carried out a series of lateral stiffness-distance spectroscopy. We observed lateral stiffness-distance curves exhibit sharp increase in the stiffness as the sample is approached towards the surface. We usually observed positive stiffness and sometimes going into slightly negative region.

Investigation of force, contact area, and dwell time in finger-tapping tasks on membrane touch interface.

Science.gov (United States)

Liu, Na; Yu, Ruifeng

2018-06-01

This study aimed to determine the touch characteristics during tapping tasks on membrane touch interface and investigate the effects of posture and gender on touch characteristics variables. One hundred participants tapped digits displayed on a membrane touch interface on sitting and standing positions using all fingers of the dominant hand. Touch characteristics measures included average force, contact area, and dwell time. Across fingers and postures, males exerted larger force and contact area than females, but similar dwell time. Across genders and postures, thumb exerted the largest force and the force of the other four fingers showed no significant difference. The contact area of the thumb was the largest, whereas that of the little finger was the smallest; the dwell time of the thumb was the longest, whereas that of the middle finger was the shortest. Relationships among finger sizes, gender, posture and touch characteristics were proposed. The findings helped direct membrane touch interface design for digital and numerical control products from hardware and software perspectives. Practitioner Summary: This study measured force, contact area, and dwell time in tapping tasks on membrane touch interface and examined effects of gender and posture on force, contact area, and dwell time. The findings will direct membrane touch interface design for digital and numerical control products from hardware and software perspectives.

Bilateral neuromuscular and force differences during a plyometric task.

Science.gov (United States)

Ball, Nick B; Scurr, Joanna C

2009-08-01

The purpose of this article is to compare the bilateral neuromuscular and force contribution during a plyometric bounce drop jump task and to assess the affects of nonsimultaneous foot placement. Sixteen male participants performed bounce drop jumps from a height of 0.4 m. Mean peak electromyography activity of the soleus, medial, and lateral gastrocnemius of both legs was recorded from each phase of the drop jump and normalized to a reference dynamic muscle action. Resultant ground reaction force, ground contact time, and duration of the drop jumps were recorded from each leg. Multivariate analysis of variance was used to compare bilateral electromyographic activity, resultant peak ground reaction force, and contact duration. Pearson's correlations (r) ascertained relationships between normalized electromyographic activity and contact time. Significant differences were shown between left and right triceps surae normalized electromyography during precontact and contact40ms (p 0.01). Significant differences were found between normalized soleus electromyography and both gastrocnemii for both legs during precontact (p 0.01). Weak relationships were found between normalized electromyographic activity and nonsimultaneous foot contact (r < 0.2). This study showed differences between left and right triceps surae in neuromuscular strategies engaged in the early stages of a drop jump task. Differences in contact time initiation were present; however, they are not significant enough to cause neuromuscular differences in the plantar flexor muscles.

An accurate tangential force-displacement model for granular-flow simulations: Contacting spheres with plastic deformation, force-driven formulation

International Nuclear Information System (INIS)

Vu-Quoc, L.; Lesburg, L.; Zhang, X.

2004-01-01

An elasto-plastic frictional tangential force-displacement (TFD) model for spheres in contact for accurate and efficient granular-flow simulations is presented in this paper; the present TFD is consistent with the elasto-plastic normal force-displacement (NFD) model presented in [ASME Journal of Applied Mechanics 67 (2) (2000) 363; Proceedings of the Royal Society of London, Series A 455 (1991) (1999) 4013]. The proposed elasto-plastic frictional TFD model is accurate, and is validated against non-linear finite-element analyses involving plastic flows under both loading and unloading conditions. The novelty of the present TFD model lies in (i) the additive decomposition of the elasto-plastic contact area radius into an elastic part and a plastic part, (ii) the correction of the particles' radii at the contact point, and (iii) the correction of the particles' elastic moduli. The correction of the contact-area radius represents an effect of plastic deformation in colliding particles; the correction of the radius of curvature represents a permanent indentation after impact; the correction of the elastic moduli represents a softening of the material due to plastic flow. The construction of both the present elasto-plastic frictional TFD model and its consistent companion, the elasto-plastic NFD model, parallels the formalism of the continuum theory of elasto-plasticity. Both NFD and TFD models form a coherent set of force-displacement (FD) models not available hitherto for granular-flow simulations, and are consistent with the Hertz, Cattaneo, Mindlin, Deresiewicz contact mechanics theory. Together, these FD models will allow for efficient simulations of granular flows (or granular gases) involving a large number of particles

Knotless double-row SutureBridge rotator cuff repairs have improved self-reinforcement compared with double-row SutureBridge repairs with tied medial knots: a biomechanical study using an ovine model.

Science.gov (United States)

Smith, Geoffrey C S; Bouwmeester, Theresia M; Lam, Patrick H

2017-12-01

In double-row SutureBridge (Arthrex, Naples, FL, USA) rotator cuff repairs, increasing tendon load may generate progressively greater compression forces at the repair footprint (self-reinforcement). SutureBridge rotator cuff repairs using tied horizontal mattress sutures medially may limit this effect compared with a knotless construct. Rotator cuff repairs were performed in 9 pairs of ovine shoulders. One group underwent repair with a double-row SutureBridge construct with tied horizontal medial-row mattress sutures. The other group underwent repair in an identical fashion except that medial-row knots were not tied. Footprint contact pressure was measured at 0° and 20° of abduction under loads of 0 to 60 N. Pull-to-failure tests were then performed. In both repair constructs, each 10-N increase in rotator cuff tensile load led to a significant increase in footprint contact pressure (P row SutureBridge configuration, self-reinforcement is seen in repairs with and without medial-row knots. Self-reinforcement is greater with the knotless technique. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Comparison Of Medial Arch-Supporting Insoles And Heel Pads In The Treatment Of Plantar Fasciitis

Directory of Open Access Journals (Sweden)

Malkoc Melih

2015-03-01

Full Text Available Plantar fasciitis is a disorder caused by inflammation of the insertion point of the plantar fascia over the medial tubercle of the calcaneus. Foot orthotics are used to treat plantar fasciitis. Heel pads medialise the centre of force, whereas medial arch supporting insoles lateralise the force. We assessed the clinical results of the treatment of plantar fasciitis with silicone heel pads and medial arch-supported silicone insoles.

Direct-Current Forced Interruption and Breaking Performance of Spiral-Type Contacts in Aero Applications

Directory of Open Access Journals (Sweden)

Wenlei Huo

2017-05-01

Full Text Available This paper analyses the transient characteristics and breaking performance of direct-current (DC forced-interruption vacuum interrupters in 270 V power-supply systems. Three stages are identified in forced interruption: the DC-arcing stage, current-commutation stage, and voltage-recovery stage. During the current-commutation stage, the reverse peak-current coefficient k, which is a key design factor, is used to calculate the rate of current at zero-crossing (di/dt. MATLAB/Simulink simulation models are established to obtain the transient characteristics influenced by the forced-commutation branch parameters and the coefficient k. To study the breaking performance of spiral-type contacts, experiments are conducted for different contact materials and arcing times for currents less than 3.5 kA. During the DC-arcing stage, a locally intensive burning arc is observed in the CuW80 contact; however, it is not observed in the CuCr50 contact. On examining the re-ignition interruption results of the CuW80 contact, the intensive burning arc is found to be positioned within a possible re-ignition region. When the arcing time is longer than 1 ms, the intensive burning arc occurs and affects the breaking performance of the spiral-type contacts. If the DC-arcing stage is prolonged, the total arcing energy increases, which leads to a lower breaking capacity.

The influence of muscle pennation angle and cross-sectional area on contact forces in the ankle joint.

Science.gov (United States)

Sopher, Ran S; Amis, Andrew A; Davies, D Ceri; Jeffers, Jonathan Rt

2017-01-01

Data about a muscle's fibre pennation angle and physiological cross-sectional area are used in musculoskeletal modelling to estimate muscle forces, which are used to calculate joint contact forces. For the leg, muscle architecture data are derived from studies that measured pennation angle at the muscle surface, but not deep within it. Musculoskeletal models developed to estimate joint contact loads have usually been based on the mean values of pennation angle and physiological cross-sectional area. Therefore, the first aim of this study was to investigate differences between superficial and deep pennation angles within each muscle acting over the ankle and predict how differences may influence muscle forces calculated in musculoskeletal modelling. The second aim was to investigate how inter-subject variability in physiological cross-sectional area and pennation angle affects calculated ankle contact forces. Eight cadaveric legs were dissected to excise the muscles acting over the ankle. The mean surface and deep pennation angles, fibre length and physiological cross-sectional area were measured. Cluster analysis was applied to group the muscles according to their architectural characteristics. A previously validated OpenSim model was used to estimate ankle muscle forces and contact loads using architecture data from all eight limbs. The mean surface pennation angle for soleus was significantly greater (54%) than the mean deep pennation angle. Cluster analysis revealed three groups of muscles with similar architecture and function: deep plantarflexors and peroneals, superficial plantarflexors and dorsiflexors. Peak ankle contact force was predicted to occur before toe-off, with magnitude greater than five times bodyweight. Inter-specimen variability in contact force was smallest at peak force. These findings will help improve the development of experimental and computational musculoskeletal models by providing data to estimate force based on both surface and deep

Nonsmooth Newton method for Fischer function reformulation of contact force problems for interactive rigid body simulation

DEFF Research Database (Denmark)

Silcowitz, Morten; Niebe, Sarah Maria; Erleben, Kenny

2009-01-01

contact response. In this paper, we present a new approach to contact force determination. We reformulate the contact force problem as a nonlinear root search problem, using a Fischer function. We solve this problem using a generalized Newton method. Our new Fischer - Newton method shows improved...... qualities for specific configurations where the most widespread alternative, the Projected Gauss-Seidel method, fails. Experiments show superior convergence properties of the exact Fischer - Newton method....

Some image artefacts in non-contact mode force microscopy

International Nuclear Information System (INIS)

Dinte, B.P.; Watson, G.S.; Dobson, J.F.; Myhra, S.

1996-01-01

Full text: Non-contact mode Atomic Force Microscopy (AFM), performed in air, of two-dimensional hexagonal close-packed (2DHCP) layers of 200 nm diameter polystyrene spheres yields images containing artefacts ('ghost spheres') at layer edges and vacancy sites. The origin of these artefacts is clearly not the simple convolution of the tip and sample geometries, but must be the interaction between them. A computer program was written to simulate the experimental contours, assuming that the only force between the tip and the sample is the van der Waals (dispersion) force, and that the contours traced by the AFM tip are those of constant force derivative. The energy was calculated by integrating R -6 over the volumes of the tip and the sample, with a (constant) arbitrary scaling factor. The experimental contours were reproduced by the simulations, except for the 'ghost' artefacts. The assumption that there is only a dispersion force is thus incorrect. The experiments were performed in air, so that all surfaces were coated by a layer of adsorbed moisture. It is proposed that meniscus forces may be the origin of the artefacts

Indentation analysis of nano-particle using nano-contact mechanics models during nano-manipulation based on atomic force microscopy

International Nuclear Information System (INIS)

Daeinabi, Khadijeh; Korayem, Moharam Habibnejad

2011-01-01

Atomic force microscopy is applied to measure intermolecular forces and mechanical properties of materials, nano-particle manipulation, surface scanning and imaging with atomic accuracy in the nano-world. During nano-manipulation process, contact forces cause indentation in contact area between nano-particle and tip/substrate which is considerable at nano-scale and affects the nano-manipulation process. Several nano-contact mechanics models such as Hertz, Derjaguin–Muller–Toporov (DMT), Johnson–Kendall–Roberts–Sperling (JKRS), Burnham–Colton–Pollock (BCP), Maugis–Dugdale (MD), Carpick–Ogletree–Salmeron (COS), Pietrement–Troyon (PT), and Sun et al. have been applied as the continuum mechanics approaches at nano-scale. In this article, indentation depth and contact radius between tip and substrate with nano-particle for both spherical and conical tip shape during nano-manipulation process are analyzed and compared by applying theoretical, semiempirical, and empirical nano-contact mechanics models. The effects of adhesion force, as the main contrast point in different nano-contact mechanics models, on nano-manipulation analysis is investigated for different contact radius, and the critical point is discussed for mentioned models.

Vorticity dipoles and a theoretical model of a finite force at the moving contact line singularity

Science.gov (United States)

Zhang, Peter; Devoria, Adam; Mohseni, Kamran

2017-11-01

In the well known works of Moffatt (1964) and Huh & Scriven (1971), an infinite force was reported at the moving contact line (MCL) and attributed to a non-integrable stress along the fluid-solid boundary. In our recent investigation of the boundary driven wedge, a model of the MCL, we find that the classical solution theoretically predicts a finite force at the contact line if the forces applied by the two boundaries that make up the corner are taken into consideration. Mathematically, this force can be obtained by the complex contour integral of the holomorphic vorticity-pressure function given by G = μω + ip . Alternatively, this force can also be found using a carefully defined real integral that incorporates the two boundaries. Motivated by this discovery, we have found that the rate of change in circulation, viscous energy dissipation, and viscous energy flux is also finite per unit contact line length. The analysis presented demonstrates that despite a singular stress and a relatively simple geometry, the no-slip semi-infinite wedge is capable of capturing some physical quantities of interest. Furthermore, this result provides a foundation for other challenging topics such as dynamic contact angle.

Dynamic simulation of knee-joint loading during gait using force-feedback control and surrogate contact modelling.

Science.gov (United States)

Walter, Jonathan P; Pandy, Marcus G

2017-10-01

The aim of this study was to perform multi-body, muscle-driven, forward-dynamics simulations of human gait using a 6-degree-of-freedom (6-DOF) model of the knee in tandem with a surrogate model of articular contact and force control. A forward-dynamics simulation incorporating position, velocity and contact force-feedback control (FFC) was used to track full-body motion capture data recorded for multiple trials of level walking and stair descent performed by two individuals with instrumented knee implants. Tibiofemoral contact force errors for FFC were compared against those obtained from a standard computed muscle control algorithm (CMC) with a 6-DOF knee contact model (CMC6); CMC with a 1-DOF translating hinge-knee model (CMC1); and static optimization with a 1-DOF translating hinge-knee model (SO). Tibiofemoral joint loads predicted by FFC and CMC6 were comparable for level walking, however FFC produced more accurate results for stair descent. SO yielded reasonable predictions of joint contact loading for level walking but significant differences between model and experiment were observed for stair descent. CMC1 produced the least accurate predictions of tibiofemoral contact loads for both tasks. Our findings suggest that reliable estimates of knee-joint loading may be obtained by incorporating position, velocity and force-feedback control with a multi-DOF model of joint contact in a forward-dynamics simulation of gait. Copyright © 2017 IPEM. Published by Elsevier Ltd. All rights reserved.

On the non-proportionality between wheel/rail contact forces and speed during wheelset passage over specific welds

Science.gov (United States)

Correa, Nekane; Vadillo, Ernesto G.; Santamaria, Javier; Blanco-Lorenzo, Julio

2018-01-01

This study investigates the influence on the wheel-rail contact forces of the running speed and the shape and position of weld defects along the track. For this purpose, a vertical dynamic model in the space domain is used. The model is obtained from the transformation between the domains of frequency and space using a Rational Fraction Polynomials (RFP) method, which is modified with multiobjective genetic algorithms in order to improve the fitting of track receptance and to assist integration during simulations. This produces a precise model with short calculation times, which is essential to this study. The wheel-rail contact is modelled using a non-linear Hertz spring. The contact forces are studied for several types of characteristic welds. The way in which forces vary as a function of weld position and running speed is studied for each type of weld. This paper studies some of the factors that affect the maximum forces when the vehicle moves over a rail weld, such as weld geometry, parametric excitation and contact stiffness. It is found that the maximum force in the wheel-rail contact when the vehicle moves over a weld is not always proportional to the running speed. The paper explains why it is not proportional in specific welds.

Differential MS2 Interaction with Food Contact Surfaces Determined by Atomic Force Microscopy and Virus Recovery.

Science.gov (United States)

Shim, J; Stewart, D S; Nikolov, A D; Wasan, D T; Wang, R; Yan, R; Shieh, Y C

2017-12-15

Enteric viruses are recognized as major etiologies of U.S. foodborne infections. These viruses are easily transmitted via food contact surfaces. Understanding virus interactions with surfaces may facilitate the development of improved means for their removal, thus reducing transmission. Using MS2 coliphage as a virus surrogate, the strength of virus adhesion to common food processing and preparation surfaces of polyvinyl chloride (PVC) and glass was assessed by atomic force microscopy (AFM) and virus recovery assays. The interaction forces of MS2 with various surfaces were measured from adhesion peaks in force-distance curves registered using a spherical bead probe preconjugated with MS2 particles. MS2 in phosphate-buffered saline (PBS) demonstrated approximately 5 times less adhesion force to glass (0.54 nN) than to PVC (2.87 nN) ( P force for PVC (∼0 nN) and consistently increased virus recovery by 19%. With direct and indirect evidence of virus adhesion, this study illustrated a two-way assessment of virus adhesion for the initial evaluation of potential means to mitigate virus adhesion to food contact surfaces. IMPORTANCE The spread of foodborne viruses is likely associated with their adhesive nature. Virus attachment on food contact surfaces has been evaluated by quantitating virus recoveries from inoculated surfaces. This study aimed to evaluate the microenvironment in which nanometer-sized viruses interact with food contact surfaces and to compare the virus adhesion differences using AFM. The virus surrogate MS2 demonstrated less adhesion force to glass than to PVC via AFM, with the force-contributing factors including the intrinsic nature and the topography of the contact surfaces. This adhesion finding is consistent with the virus recoveries, which were determined indirectly. Greater numbers of viruses were recovered from glass than from PVC, after application at the same levels. The stronger MS2 adhesion onto PVC could be interrupted by incorporating a

Bacterial adhesion forces to Ag-impregnated contact lens cases and transmission to contact lenses.

Science.gov (United States)

Qu, Wenwen; Busscher, Henk J; van der Mei, Henny C; Hooymans, Johanna M M

2013-03-01

To measure adhesion forces of Pseudomonas aeruginosa, Staphylococcus aureus, and Serratia marcescens to a rigid contact lens (CL), standard polypropylene, and Ag-impregnated lens cases using atomic force microscopy and determine bacterial transmission from lens case to CL. Adhesion forces of bacterial strains to Ag-impregnated and polypropylene lens cases and a rigid CL were measured using atomic force microscopy. Adhesion forces were used to calculate Weibull distributions, from which transmission probabilities from lens case to CL were derived. Transmission probabilities were compared with actual transmission of viable bacteria from a lens case to the CL in 0.9% NaCl and in an antimicrobial lens care solution. Bacterial transmission probabilities from polypropylene lens cases based on force analysis coincided well for all strains with actual transmission in 0.9% NaCl. Bacterial adhesion forces on Ag-impregnated lens cases were much smaller than that on polypropylene and CLs, yielding a high probability of transmission. Comparison with actual bacterial transmission indicated bacterial killing due to Ag ions during colony-forming unit transmission from an Ag-impregnated lens case, especially for P. aeruginosa. Transmission of viable bacteria from Ag-impregnated lens cases could be further decreased by use of an antimicrobial lens care solution instead of 0.9% NaCl. Bacterial transmission probabilities are higher from Ag-impregnated lens cases than from polypropylene lens cases because of small adhesion forces, but this is compensated for by enhanced bacterial killing due to Ag impregnation, especially when in combination with an antimicrobial lens care solution. This calls for a balanced combination of antimicrobial lens care solutions and surface properties of a lens case and CL.

Quantitative analysis of tip-sample interaction in non-contact scanning force spectroscopy

International Nuclear Information System (INIS)

Palacios-Lidon, Elisa; Colchero, Jaime

2006-01-01

Quantitative characterization of tip-sample interaction in scanning force microscopy is fundamental for optimum image acquisition as well as data interpretation. In this work we discuss how to characterize the electrostatic and van der Waals contribution to tip-sample interaction in non-contact scanning force microscopy precisely. The spectroscopic technique presented is based on the simultaneous measurement of cantilever deflection, oscillation amplitude and frequency shift as a function of tip-sample voltage and tip-sample distance as well as on advanced data processing. Data are acquired at a fixed lateral position as interaction images, with the bias voltage as fast scan, and tip-sample distance as slow scan. Due to the quadratic dependence of the electrostatic interaction with tip-sample voltage the van der Waals force can be separated from the electrostatic force. Using appropriate data processing, the van der Waals interaction, the capacitance and the contact potential can be determined as a function of tip-sample distance. The measurement of resonance frequency shift yields very high signal to noise ratio and the absolute calibration of the measured quantities, while the acquisition of cantilever deflection allows the determination of the tip-sample distance

Calculation of force and time of contact formation at diffusion metal joining

Energy Technology Data Exchange (ETDEWEB)

Sukhanov, V E [Tsentral' nyj Nauchno-Issledovatel' skij Inst. Chernoj Metallurgii, Moscow (USSR); Grushevskij, A V [Moskovskij Stankoinstrumental' nyj Inst., Moscow (USSR); Surovtsev, A P

1989-03-01

An analytical model of contact for mation at diffusion joining is suggested. It is based on the introduction of a rough surface with roughnesses in the form of absolutely rigid spherical segnunts into a smooth laminar body. Mathematical expressions, permitting to calculate maximum welding force (pressure) providing close contact of the surfaces welded and time for contact formation between rough surfaces joined, are obtained. Divergence of calculational and experimental data does not exceed 20%. It is confirmed that the most intensive formation of joining occurs in the initial period of welding -the stage of formation of a physical contact, when deformation processes proceed in tensively. Finite formation of a strength joint occurs at the stage of diffusion interaction.

Nonlinear vibration of rectangular atomic force microscope cantilevers by considering the Hertzian contact theory

Energy Technology Data Exchange (ETDEWEB)

Sadeghi, A., E-mail: a_sadeghi@srbiau.ac.ir [Islamic Azad Univ., Dept. of Mechanical and Aerospace Engineering, Science and Research Branch, Tehran (Iran, Islamic Republic of); Zohoor, H. [Sharif Univ. of Technology, Center of Excellence in Design, Robotics and Automation, Tehran (Iran, Islamic Republic of); The Academy of Sciences if I.R. Iran (Iran, Islamic Republic of)

2010-05-15

The nonlinear flexural vibration for a rectangular atomic force microscope cantilever is investigated by using Timoshenko beam theory. In this paper, the normal and tangential tip-sample interaction forces are found from a Hertzian contact model and the effects of the contact position, normal and lateral contact stiffness, tip height, thickness of the beam, and the angle between the cantilever and the sample surface on the nonlinear frequency to linear frequency ratio are studied. The differential quadrature method is employed to solve the nonlinear differential equations of motion. The results show that softening behavior is seen for most cases and by increasing the normal contact stiffness, the frequency ratio increases for the first mode, but for the second mode, the situation is reversed. The nonlinear-frequency to linear-frequency ratio increases by increasing the Timoshenko beam parameter, but decreases by increasing the contact position for constant amplitude for the first and second modes. For the first mode, the frequency ratio decreases by increasing both of the lateral contact stiffness and the tip height, but increases by increasing the angle α between the cantilever and sample surface. (author)

Normal and friction stabilization techniques for interactive rigid body constraint-based contact force computations

DEFF Research Database (Denmark)

Silcowitz-Hansen, Morten; Abel, Sarah Maria Niebe; Erleben, Kenny

2010-01-01

We present a novel, yet simple, method for stabilization of normal forces. A normal stabilization term, carefully designed from hypotheses about interactive usability, is added to the contact force problem. Further, we propose friction stabilization as a completely new stabilization paradigm...

Importance of catheter contact force during irrigated radiofrequency ablation: evaluation in a porcine ex vivo model using a force-sensing catheter.

Science.gov (United States)

Thiagalingam, Aravinda; D'Avila, Andre; Foley, Lori; Guerrero, J Luis; Lambert, Hendrik; Leo, Giovanni; Ruskin, Jeremy N; Reddy, Vivek Y

2010-07-01

Ablation electrode-tissue contact has been shown to be an important determinant of lesion size and safety during nonirrigated ablation but little data are available during irrigated ablation. We aimed to determine the importance of contact force during irrigated-tip ablation. Freshly excised hearts from 11 male pigs were perfused and superfused using fresh, heparinized, oxygenated swine blood in an ex vivo model. One-minute ablations were placed using one of 3 different power control strategies (impedance control-15 Omega target impedance drop, and 20 W or 30 W fixed power) and 3 different contact forces (2 g, 20 g, and 60 g) to give a grid of 9 ablation groups. The force sensing catheter (Tacticath, Endosense SA) was irrigated at 17 mL/min for all of the ablations. Of a total 101 ablations, no thrombus formation was noted but popping was seen in 17 lesions. The lesion depth and incidence of pops was 5.0 +/- 1.3 mm /0%, 5.0 +/- 1.6 mm /10% and 6.7 +/- 2.5 mm /45% for the 15 Omega, 20 W, and 30 W groups (P force: 9.7 +/- 9.9 Omega, 22.3 +/- 11.0 Omega, and 41.7 +/- 22.1 Omega, respectively, for the 2 g, 20 g, and 60 g groups (Pearson's r = 0.65, P force has an important impact on both ablation lesion size and the incidence of pops.

Incorporating contact angles in the surface tension force with the ACES interface curvature scheme

Science.gov (United States)

Owkes, Mark

2017-11-01

In simulations of gas-liquid flows interacting with solid boundaries, the contact line dynamics effect the interface motion and flow field through the surface tension force. The surface tension force is directly proportional to the interface curvature and the problem of accurately imposing a contact angle must be incorporated into the interface curvature calculation. Many commonly used algorithms to compute interface curvatures (e.g., height function method) require extrapolating the interface, with defined contact angle, into the solid to allow for the calculation of a curvature near a wall. Extrapolating can be an ill-posed problem, especially in three-dimensions or when multiple contact lines are near each other. We have developed an accurate methodology to compute interface curvatures that allows for contact angles to be easily incorporated while avoiding extrapolation and the associated challenges. The method, known as Adjustable Curvature Evaluation Scale (ACES), leverages a least squares fit of a polynomial to points computed on the volume-of-fluid (VOF) representation of the gas-liquid interface. The method is tested by simulating canonical test cases and then applied to simulate the injection and motion of water droplets in a channel (relevant to PEM fuel cells).

Contact forces between a particle and a wet wall at both quasi-static and dynamic state

Directory of Open Access Journals (Sweden)

Zhang Huang

2017-01-01

Full Text Available The contact regime of particle-wall is investigated by the atomic force microscope (AFM and theoretical models. First, AFM is used to measure the cohesive force between a micron-sized grain and a glass plate at quasi-static state under various humidity. It is found out that the cohesive force starts to grow slowly and suddenly increase rapidly beyond a critical Relative Humidity (RH. Second, mathematical models of contacting forces are presented to depict the dynamic process that a particle impacts on a wet wall. Then the energy loss of a falling grain is calculated in comparison with the models and the experimental data from the previous references. The simulation results show that the force models presented here are adaptive for both low and high viscosity fluid films with different thickness.

Chewing side, bite force symmetry, and occlusal contact area of subjects with different facial vertical patterns

Directory of Open Access Journals (Sweden)

Simone Guimarães Farias Gomes

2011-10-01

Full Text Available Craniofacial dimensions influence oral functions; however, it is not known whether they are associated with function asymmetry. The objective of this study was to evaluate chewing side preference and lateral asymmetry of occlusal contact area and bite force of individuals with different craniofacial patterns. Seventy-eight dentate subjects were divided into 3 groups according to the VERT index as follows: (1 mesofacial, (2 brachyfacial and (3 dolichofacial. Chewing side preference was evaluated using jaw tracking equipment, occlusal contact area was measured by silicon registration of posterior teeth, and bite force was measured unilaterally on molar regions using 2.25 mm-thick sensors. Statistical analysis was performed using ANOVA on Ranks, Student's t-test, and Mann-Whitney tests at a 5% significance level. Mesofacial, brachyfacial, and dolichofacial subjects presented more occlusal contact area on the left side. Only dolichofacial subjects showed lateral asymmetry for bite force, presenting higher force on the left side. No statistically significant differences were found for chewing side preference among all groups. Within the limitations of this study, it can be concluded that craniofacial dimensions play a role in asymmetry of bite force. ClinicalTrials.gov ID: NCT01286363.

Imaging contrast and tip-sample interaction of non-contact amplitude modulation atomic force microscopy with Q -control

International Nuclear Information System (INIS)

Shi, Shuai; Guo, Dan; Luo, Jianbin

2017-01-01

Active quality factor ( Q ) exhibits many promising properties in dynamic atomic force microscopy. Energy dissipation and image contrasts are investigated in the non-contact amplitude modulation atomic force microscopy (AM-AFM) with an active Q -control circuit in the ambient air environment. Dissipated power and virial were calculated to compare the highly nonlinear interaction of tip-sample and image contrasts with different Q gain values. Greater free amplitudes and lower effective Q values show better contrasts for the same setpoint ratio. Active quality factor also can be employed to change tip-sample interaction force in non-contact regime. It is meaningful that non-destructive and better contrast images can be realized in non-contact AM-AFM by applying an active Q -control to the dynamic system. (paper)

In vivo cartilage contact deformation in the healthy human tibiofemoral joint.

Science.gov (United States)

Bingham, J T; Papannagari, R; Van de Velde, S K; Gross, C; Gill, T J; Felson, D T; Rubash, H E; Li, G

2008-11-01

In vivo cartilage contact deformation is instrumental for understanding human joint function and degeneration. This study measured the total deformation of contacting articular cartilage in the human tibiofemoral joint during in vivo weight-bearing flexion. Eleven healthy knees were magnetic resonance (MR) scanned and imaged with a dual fluoroscopic system while the subject performed a weight-bearing single-leg lunge. The tibia, femur and associated articulating cartilage were constructed from the MR images and combined with the dual fluoroscopic images to determine in vivo cartilage contact deformation from full extension to 120 degrees of flexion. In both compartments, minimum peak compartmental contact deformation occurred at 30 degrees of flexion (24 +/- 6% medial, 17 +/- 7% lateral) and maximum peak compartmental deformation occurred at 120 degrees of flexion (30 +/- 13% medial, 30 +/- 10% lateral) during the weight-bearing flexion from full extension to 120 degrees. Average medial contact areas and peak contact deformations were significantly greater than lateral compartment values (P In addition, cartilage thickness in regions of contact was on average 1.4- and 1.1-times thicker than the average thickness of the tibial and femoral cartilage surfaces, respectively (P line knowledge for investigating the effects of various knee injuries on joint contact biomechanics and the aetiology of cartilage degeneration.

Sensor Prototype to Evaluate the Contact Force in Measuring with Coordinate Measuring Arms

Directory of Open Access Journals (Sweden)

Eduardo Cuesta

2015-06-01

Full Text Available This paper describes the design, development and evaluation tests of an integrated force sensor prototype for portable Coordinate Measuring Arms (CMAs or AACMMs. The development is based on the use of strain gauges located on the surface of the CMAs’ hard probe. The strain gauges as well as their cables and connectors have been protected with a custom case, made by Additive Manufacturing techniques (Polyjet 3D. The same method has been selected to manufacture an ergonomic handle that includes trigger mechanics and the electronic components required for synchronizing the trigger signal when probing occurs. The paper also describes the monitoring software that reads the signals in real time, the calibration procedure of the prototype and the validation tests oriented towards increasing knowledge of the forces employed in manual probing. Several experiments read and record the force in real time comparing different ways of probing (discontinuous and continuous contact and measuring different types of geometric features, from single planes to exterior cylinders, cones, or spheres, through interior features. The probing force is separated into two components allowing the influence of these strategies in probe deformation to be known. The final goal of this research is to improve the probing technique, for example by using an operator training programme, allowing extra-force peaks and bad contacts to be minimized or just to avoid bad measurements.

Contact force sensing for ablation of persistent atrial fibrillation: A randomized, multicenter trial.

Science.gov (United States)

Conti, Sergio; Weerasooriya, Rukshen; Novak, Paul; Champagne, Jean; Lim, Hong Euy; Macle, Laurent; Khaykin, Yaariv; Pantano, Alfredo; Verma, Atul

2018-02-01

Impact of contact force sensing (CFS) on ablation of persistent atrial fibrillation (PeAF) is unknown. The purpose of the TOUCH AF (Therapeutic Outcomes Using Contact force Handling during Ablation of Persistent Atrial Fibrillation) randomized trial was to compare CFS-guided ablation to a CFS-blinded strategy. Patients (n = 128) undergoing first-time ablation for persistent AF were randomized to a CFS-guided vs CFS-blinded strategy. In the CFS-guided procedure, operators visualized real-time force data. In the blinded procedure, force data were hidden. Wide antral pulmonary vein isolation plus a roof line were performed. Patients were followed at 3, 6, 9, and 12 months with clinical visit, ECG, and 48-hour Holter monitoring. The primary endpoint was cumulative radiofrequency (RF) time for all procedures. Atrial arrhythmia >30 seconds after 3 months was a recurrence. PeAF was continuous for 26 weeks (interquartile range [IQR] 13-52), and left atrial size was 45 ± 5 mm. Force in the CFS-blinded and CFS-guided arms was 12 g [IQR 6-20] and 14 g [IQR 9-20] (P = .10), respectively. Total RF time did not differ between CFS-guided and CFS-blinded groups (49 ± 14 min vs 50 ± 20 min, respectively; P = .70). Single procedure freedom from atrial arrhythmia was 60% in the CFS-guided arm and 63% in the CFS-blinded arm off drugs. Lesions with gaps were associated with significantly less force (11.4 g [IQR 6-19] vs 13.2 g [IQR 8-20], respectively; P = .0007) and less force-time integral (174 gs [IQR 91-330] vs 210 gs [IQR 113-388], respectively; P force/force-time integral was associated with significantly more gaps. Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

Evaluation of a Surrogate Contact Model in Force-Dependent Kinematic Simulations of Total Knee Replacement

NARCIS (Netherlands)

Marra, M.A.; Andersen, M.S.; Damsgaard, M.; Koopman, B.; Janssen, D.W.; Verdonschot, N.J.

2017-01-01

Knowing the forces in the human body is of great clinical interest and musculoskeletal (MS) models are the most commonly used tool to estimate them in vivo. Unfortunately, the process of computing muscle, joint contact, and ligament forces simultaneously is computationally highly demanding. The goal

Evaluation of a surrogate contact model in force-dependent kinematic simulations of total knee replacement

NARCIS (Netherlands)

Marra, Marco Antonio; Andersen, Michael S.; Damsgaard, Michael; Koopman, Bart F.J.M.; Janssen, Dennis; Verdonschot, Nico

2017-01-01

Knowing the forces in the human body is of great clinical interest and musculoskeletal (MS) models are the most commonly used tool to estimate them in vivo. Unfortunately, the process of computing muscle, joint contact, and ligament forces simultaneously is computationally highly demanding. The goal

Elastic-properties measurement at high temperatures through contact resonance atomic force microscopy

DEFF Research Database (Denmark)

Marinello, Francesco; Pezzuolo, Andrea; Carmignato, Simone

2015-01-01

fast direct and non-destructive measurement of Young's modulus and related surface parameters.In this work an instrument set up for Contact Resonance Atomic Force Microscopy is proposed, where the sample with is coupled to a heating stage and a piezoelectric transducer directly vibrate the cantilever...

Calculation of locomotive traction force in transient rolling contact

Directory of Open Access Journals (Sweden)

Voltr P.

2017-06-01

Full Text Available To represent thewheel-rail contact in numerical simulations of rail vehicles, simplified models (Fastsim, Pola´ch etc. are usually employed. These models are designed for steady rolling only, which is perfectly suitable in many cases. However, it is shown to be limiting for simulations at very low vehicle speeds, and therefore it does not actually allow simulation of vehicle running at arbitrarily variable speed. The simplified model of transient rolling, which involves calculation of the stress distribution in the discretised contact area, overcomes this disadvantage but might be unnecessarily complex for more simple simulations. In this paper, an approximative creep force computation method for transient rolling is presented. Its purpose is not to study the transient phenomena themselves but provide a simple and readily available way to prevent incorrect results of the numerical simulation when the vehicle speed approaches zero. The proper function of the proposed method is demonstrated by a simulation of start-up and interrupted sliding of a four-axle locomotive.

Mechanical properties of cellulose nanomaterials studied by contact resonance atomic force microscopy

Science.gov (United States)

Ryan Wagner; Robert J. Moon; Arvind Raman

2016-01-01

Quantification of the mechanical properties of cellulose nanomaterials is key to the development of new cellulose nanomaterial based products. Using contact resonance atomic force microscopy we measured and mapped the transverse elastic modulus of three types of cellulosic nanoparticles: tunicate cellulose nanocrystals, wood cellulose nanocrystals, and wood cellulose...

A comparison of hamstring muscle activity during different screening tests for non-contact ACL injury.

Science.gov (United States)

Husted, Rasmus S; Bencke, Jesper; Andersen, Lars L; Myklebust, Grethe; Kallemose, Thomas; Lauridsen, Hanne B; Hölmich, Per; Aagaard, Per; Zebis, Mette K

2016-06-01

Reduced ability to activate the medial hamstring muscles during a sports-specific sidecutting movement has been found to be a potential risk factor for non-contact ACL injury. However, whether a reduced ability to activate the medial hamstring muscle is a general neuromuscular phenomenon and thereby observable independently of the type of clinical screening tests used is not known. This cross sectional study investigated the rank correlation of knee joint neuromuscular activity between three different ACL injury risk screening tests. Sixty-two adolescent female elite football and handball players (16.7±1.3years) participated in the study. Using surface electromyography (EMG) assessment, the neuromuscular activity of medial hamstring muscle (semitendinosus, ST), lateral hamstring muscle (biceps femoris, BF) and quadriceps muscle (vastus lateralis, VL) were monitored during three standardized screening tests - i.e. one-legged horizontal hop (OLH), drop vertical jump (DJ) and sidecutting (SC). Neuromuscular pre-activity was measured in the time interval 10ms prior to initial contact on a force plate. For neuromuscular hamstring muscle pre-activity, correlation analysis (Spearman correlation coefficient) showed low-to-moderate correlations between SC and 1) DJ (rs=0.34-0.36, Phamstring pre-activity share some common variance during the examined tests. However, a lack of strong correlation suggests that we cannot generalize one risk factor during one test to another test. The present data demonstrate that one-legged horizontal hop and drop vertical jump testing that are commonly used in the clinical setting does not resemble the specific neuromuscular activity patterns known to exist during sidecutting, a well known high risk movement for non-contact ACL injury. Copyright © 2016 Elsevier B.V. All rights reserved.

Adaptation of manipulation skills in physical contact with the environment to reference force profiles

DEFF Research Database (Denmark)

Abu-Dakka, Fares J.; Nemec, Bojan; Jørgensen, Jimmy A.

2015-01-01

We propose a new methodology for learning and adaption of manipulation skills that involve physical contact with the environment. Pure position control is unsuitable for such tasks because even small errors in the desired trajectory can cause significant deviations from the desired forces...... and torques. The proposed algorithm takes a reference Cartesian trajectory and force/torque profile as input and adapts the movement so that the resulting forces and torques match the reference profiles. The learning algorithm is based on dynamic movement primitives and quaternion representation...

Changes of contact pressure and area in patellofemoral joint after different meniscectomies.

Science.gov (United States)

Bai, Bo; Shun, Hui; Yin, Zhi Xun; Liao, Zhuang-Wen; Chen, Ni

2012-05-01

We investigated the contact pressure and area of the patellofemoral joint both before and after different meniscectomies to provide a biomechanical basis for selecting meniscectomy and its clinical application for meniscus injuries. Six fresh cadaveric knees were used in the study. Using Staubli robots and an ultra-low-min-type pressure-sensitive tablet, changes in contact area and stress in the patellofemoral joint were measured at various flexion angles following different parts and degrees of meniscectomy. The patellofemoral contact area enlarged with the increase of knee flexion angle. From the values obtained from contact areas and average contact pressure of the patellofemoral joint, we found no significant difference between partial meniscectomy and intact knees, but a significant difference was found between total meniscectomy and intact knees. The contact area after lateral meniscectomy was statistically less than that of intact knees. The mean patellofemoral contact pressure after lateral meniscectomy was larger than in intact knees at each angle of flexion. No significant difference in contact area was observed between intact knees and medial meniscectomy. The average patellofemoral contact pressure after medial meniscectomy was larger than in intact knees from 0° ~ 30° of knee flexion, and no significant differences were found between intact knees and medial meniscectomy while knee bending from 60° to 90°. Different meniscectomies result in high contact pressure or disordered distribution of contact pressure, which may be the cause of postoperative patellofemoral degenerative arthrosis.

Surgical outcome in headache due to mucosal contact

International Nuclear Information System (INIS)

Goto, Fumiyuki; Yabe, Haruna; Ogawa, Kaoru

2010-01-01

Headaches is classified as primary and secondary, with secondary originating in head and neck conditions, the most important etiology being acute sinusitis. Headache due to mucosal contact, rarely encountered by otorhinolaryngologists, is an important secondary headache, whose criteria are defined by the International Classification of Headache Disorders to include intermittent pain localized in the periorbital and medial canthal or temporozygomatic regions, evidence that pain is attributable to mucosal contact and the presence of mucosal contact in the absence of acute rhinosinusitis, obtained using clinical examinations, nasal endoscopy, and/or computed tomography (CT). After mucosal contact is surgically corrected pain usually disappears permanently within 7 days. We reviewed mucosal contact headaches in 63 subjects undergoing nasal or paranasal surgery from April 2007 to March 2008. Of those 7 were diagnosed with headaches due to contact points in nasal mucosa, ranging from canthal to the temporozygomatic. The most common contact, between the middle turbinate and nasal septum, was seen in 6 of the 7. Surgery eliminated symptoms in 4 and ameliorated them in 3 indicating effective headache management. Subjects with severe headaches or localized periorbital and medial canthal pain regions, mucosal contact involvement is ruled out when CT allows no lesions. When mucosal contact headache is suspected, however surgery should be considered as a last resort. (author)

An in vitro analysis of medial structures and a medial soft tissue reconstruction in a constrained condylar total knee arthroplasty.

Science.gov (United States)

Athwal, Kiron K; El Daou, Hadi; Inderhaug, Eivind; Manning, William; Davies, Andrew J; Deehan, David J; Amis, Andrew A

2017-08-01

The aim of this study was to quantify the medial soft tissue contributions to stability following constrained condylar (CC) total knee arthroplasty (TKA) and determine whether a medial reconstruction could restore stability to a soft tissue-deficient, CC-TKA knee. Eight cadaveric knees were mounted in a robotic system and tested at 0°, 30°, 60°, and 90° of flexion with ±50 N anterior-posterior force, ±8 Nm varus-valgus, and ±5 Nm internal-external torque. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were transected and their relative contributions to stabilising the applied loads were quantified. After complete medial soft tissue transection, a reconstruction using a semitendinosus tendon graft was performed, and the effect on kinematic behaviour under equivocal conditions was measured. In the CC-TKA knee, the sMCL was the major medial restraint in anterior drawer, internal-external, and valgus rotation. No significant differences were found between the rotational laxities of the reconstructed knee to the pre-deficient state for the arc of motion examined. The relative contribution of the reconstruction was higher in valgus rotation at 60° than the sMCL; otherwise, the contribution of the reconstruction was similar to that of the sMCL. There is contention whether a CC-TKA can function with medial deficiency or more constraint is required. This work has shown that a CC-TKA may not provide enough stability with an absent sMCL. However, in such cases, combining the CC-TKA with a medial soft tissue reconstruction may be considered as an alternative to a hinged implant.

Magnitude and Spatial Distribution of Impact Intensity Under the Foot Relates to Initial Foot Contact Pattern.

Science.gov (United States)

Breine, Bastiaan; Malcolm, Philippe; Segers, Veerle; Gerlo, Joeri; Derie, Rud; Pataky, Todd; Frederick, Edward C; De Clercq, Dirk

2017-12-01

In running, foot contact patterns (rear-, mid-, or forefoot contact) influence impact intensity and initial ankle and foot kinematics. The aim of the study was to compare impact intensity and its spatial distribution under the foot between different foot contact patterns. Forty-nine subjects ran at 3.2 m·s -1 over a level runway while ground reaction forces (GRF) and shoe-surface pressures were recorded and foot contact pattern was determined. A 4-zone footmask (forefoot, midfoot, medial and lateral rearfoot) assessed the spatial distribution of the vertical GRF under the foot. We calculated peak vertical instantaneous loading rate of the GRF (VILR) per foot zone as the impact intensity measure. Midfoot contact patterns were shown to have the lowest, and atypical rearfoot contact patterns the highest impact intensities, respectively. The greatest local impact intensity was mainly situated under the rear- and midfoot for the typical rearfoot contact patterns, under the midfoot for the atypical rearfoot contact patterns, and under the mid- and forefoot for the midfoot contact patterns. These findings indicate that different foot contact patterns could benefit from cushioning in different shoe zones.

Ipsilateral Medial and Lateral Discoid Meniscus with Medial Meniscus Tear

OpenAIRE

Shimozaki, Kengo; Nakase, Junsuke; Ohashi, Yoshinori; Numata, Hitoaki; Oshima, Takeshi; Takata, Yasushi; Tsuchiya, Hiroyuki

2016-01-01

Introduction: Discoid meniscus is a well-documented knee pathology, and there are many cases of medial or lateral discoid meniscus reported in the literature. However, ipsilateral concurrent medial and lateral discoid meniscus is very rare, and only a few cases have been reported. Herein, we report a case of concurrent medial and lateral discoid meniscus. Case Report: A 27-year-old Japanese man complained of pain on medial joint space in his right knee that was diagnosed as a complete medial ...

Kinematics of partial and total ruptures of the medial collateral ligament of the elbow

DEFF Research Database (Denmark)

Eygendaal, D; Olsen, Bo Sanderhoff; Jensen, Steen Lund

2000-01-01

In this study the kinematics of partial and total ruptures of the medial collateral ligament of the elbow are investigated. After selective transection of the medial collateral ligament of 8 osteoligamentous intact elbow preparations was performed, 3-dimensional measurements of angular displacement......, increase in medial joint opening, and translation of the radial head were examined during application of relevant stress. Increase in joint opening was significant only after complete transection of the anterior part of the medial collateral ligament was performed. The joint opening was detected during...... valgus and internal rotatory stress only. After partial transection of the anterior bundle of the medial collateral ligament was performed, there was an elbow laxity to valgus and internal rotatory force, which became significant after transection of 100% of the anterior bundle of the medial collateral...

Atraumatic medial collateral ligament oedema in medial compartment knee osteoarthritis

International Nuclear Information System (INIS)

Bergin, D.; Keogh, C.; O'Connell, M.; Zoga, A.; Rowe, D.; Shah, B.; Eustace, S.

2002-01-01

Objective: To describe and determine the prevalence of atraumatic medial collateral oedema identified in patients with medial compartment osteoarthritis. Design and patients: Sixty patients, 30 patients with medial compartment knee osteoarthritis (Kellgren and Lawrence grade 2 to 4) and 30 age-matched patients with atraumatic knee pain without osteoarthritis, referred for MR imaging over a 2 year period were included in the study. In each case, severity of osteoarthritis was recorded on radiographs and correlated with the presence or absence of medial collateral ligament oedema at MR imaging. Results: Medial collateral oedema was identified in 27 of the 30 patients with osteoarthritis, of whom 14 had grade 1 oedema and 13 had grade 2 oedema compared with the presence of medial collateral ligament oedema (grade 1) in only two of the 30 control patients without osteoarthritis (P<<0.0001). Conclusion: Medial collateral oedema is common in patients with osteoarthritis in the absence of trauma. When identified, medial collateral ligament oedema should be considered to be a feature of osteoarthritis and should not be incorrectly attributed to an acute traumatic injury. (orig.)

Forced Vibrations of a Two-Layer Orthotropic Shell with an Incomplete Contact Between Layers

Science.gov (United States)

Ghulghazaryan, L. G.; Khachatryan, L. V.

2018-01-01

Forced vibrations of a two-layer orthotropic shell, with incomplete contact conditions between layers, when the upper face of the shell is free and the lower one is subjected to a dynamic action are considered. By an asymptotic method, the solution of the corresponding dynamic equations and correlations of a 3D problem of elasticity theory is obtained. The amplitudes of forced vibrations are determined, and resonance conditions are established.

Detection of stiff nanoparticles within cellular structures by contact resonance atomic force microscopy subsurface nanomechanical imaging.

Science.gov (United States)

Reggente, Melania; Passeri, Daniele; Angeloni, Livia; Scaramuzzo, Francesca Anna; Barteri, Mario; De Angelis, Francesca; Persiconi, Irene; De Stefano, Maria Egle; Rossi, Marco

2017-05-04

Detecting stiff nanoparticles buried in soft biological matrices by atomic force microscopy (AFM) based techniques represents a new frontier in the field of scanning probe microscopies, originally developed as surface characterization methods. Here we report the detection of stiff (magnetic) nanoparticles (NPs) internalized in cells by using contact resonance AFM (CR-AFM) employed as a potentially non-destructive subsurface characterization tool. Magnetite (Fe 3 O 4 ) NPs were internalized in microglial cells from cerebral cortices of mouse embryos of 18 days by phagocytosis. Nanomechanical imaging of cells was performed by detecting the contact resonance frequencies (CRFs) of an AFM cantilever held in contact with the sample. Agglomerates of NPs internalized in cells were visualized on the basis of the local increase in the contact stiffness with respect to the surrounding biological matrix. A second AFM-based technique for nanomechanical imaging, i.e., HarmoniX™, as well as magnetic force microscopy and light microscopy were used to confirm the CR-AFM results. Thus, CR-AFM was demonstrated as a promising technique for subsurface imaging of nanomaterials in biological samples.

Dynamically adjustable foot-ground contact model to estimate ground reaction force during walking and running.

Science.gov (United States)

Jung, Yihwan; Jung, Moonki; Ryu, Jiseon; Yoon, Sukhoon; Park, Sang-Kyoon; Koo, Seungbum

2016-03-01

Human dynamic models have been used to estimate joint kinetics during various activities. Kinetics estimation is in demand in sports and clinical applications where data on external forces, such as the ground reaction force (GRF), are not available. The purpose of this study was to estimate the GRF during gait by utilizing distance- and velocity-dependent force models between the foot and ground in an inverse-dynamics-based optimization. Ten males were tested as they walked at four different speeds on a force plate-embedded treadmill system. The full-GRF model whose foot-ground reaction elements were dynamically adjusted according to vertical displacement and anterior-posterior speed between the foot and ground was implemented in a full-body skeletal model. The model estimated the vertical and shear forces of the GRF from body kinematics. The shear-GRF model with dynamically adjustable shear reaction elements according to the input vertical force was also implemented in the foot of a full-body skeletal model. Shear forces of the GRF were estimated from body kinematics, vertical GRF, and center of pressure. The estimated full GRF had the lowest root mean square (RMS) errors at the slow walking speed (1.0m/s) with 4.2, 1.3, and 5.7% BW for anterior-posterior, medial-lateral, and vertical forces, respectively. The estimated shear forces were not significantly different between the full-GRF and shear-GRF models, but the RMS errors of the estimated knee joint kinetics were significantly lower for the shear-GRF model. Providing COP and vertical GRF with sensors, such as an insole-type pressure mat, can help estimate shear forces of the GRF and increase accuracy for estimation of joint kinetics. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of typical faults over the dynamic behavior of pantograph-catenary contact force in electric rail transport

Science.gov (United States)

Rusu-Anghel, S.; Ene, A.

2017-05-01

The quality of electric energy capture and also the equipment operational safety depend essentially of the technical state of the contact line (CL). The present method for determining the technical state of CL based on advance programming is no longer efficient, due to the faults which can occur into the not programmed areas. Therefore, they cannot be remediated. It is expected another management method for the repairing and maintenance of CL based on its real state which must be very well known. In this paper a new method for determining the faults in CL is described. It is based on the analysis of the variation of pantograph-CL contact force in dynamical regime. Using mathematical modelling and also experimental tests, it was established that each type of fault is able to generate ‘signatures’ into the contact force diagram. The identification of these signatures can be accomplished by an informatics system which will provide the fault location, its type and also in the future, the probable evolution of the CL technical state. The measuring of the contact force is realized in optical manner using a railway inspection trolley which has appropriate equipment. The analysis of the desired parameters can be accomplished in real time by a data acquisition system, based on dedicated software.

Multi-segment foot kinematics and ground reaction forces during gait of individuals with plantar fasciitis.

Science.gov (United States)

Chang, Ryan; Rodrigues, Pedro A; Van Emmerik, Richard E A; Hamill, Joseph

2014-08-22

Clinically, plantar fasciitis (PF) is believed to be a result and/or prolonged by overpronation and excessive loading, but there is little biomechanical data to support this assertion. The purpose of this study was to determine the differences between healthy individuals and those with PF in (1) rearfoot motion, (2) medial forefoot motion, (3) first metatarsal phalangeal joint (FMPJ) motion, and (4) ground reaction forces (GRF). We recruited healthy (n=22) and chronic PF individuals (n=22, symptomatic over three months) of similar age, height, weight, and foot shape (p>0.05). Retro-reflective skin markers were fixed according to a multi-segment foot and shank model. Ground reaction forces and three dimensional kinematics of the shank, rearfoot, medial forefoot, and hallux segment were captured as individuals walked at 1.35 ms(-1). Despite similarities in foot anthropometrics, when compared to healthy individuals, individuals with PF exhibited significantly (pfoot kinematics and kinetics. Consistent with the theoretical injury mechanisms of PF, we found these individuals to have greater total rearfoot eversion and peak FMPJ dorsiflexion, which may put undue loads on the plantar fascia. Meanwhile, increased medial forefoot plantar flexion at initial contact and decreased propulsive GRF are suggestive of compensatory responses, perhaps to manage pain. Copyright © 2014 Elsevier Ltd. All rights reserved.

Optimization of Contact Force and Pull-in Voltage for Series based MEMS Switch

Directory of Open Access Journals (Sweden)

Abhijeet KSHIRSAGAR

2010-04-01

Full Text Available Cantilever based metal-to-metal contact type MEMS series switch has many applications namely in RF MEMS, Power MEMS etc. A typical MEMS switch consists of a cantilever as actuating element to make the contact between the two metal terminals of the switch. The cantilever is pulled down by applying a pull-in voltage to the control electrode that is located below the middle portion of the cantilever while only the tip portion of the cantilever makes contact between the two terminals. Detailed analysis of bending of the cantilever for different pull-in voltages reveals some interesting facts. At low pull-in voltage the cantilever tip barely touches the two terminals, thus resulting in very less contact area. To increase contact area a very high pull-in voltage is applied, but it lifts the tip from the free end due to concave curving of the cantilever in the middle region of the cantilever where the electrode is located. Again it results in less contact area. Furthermore, the high pull-in voltage produces large stress at the base of the cantilever close to the anchor. Therefore, an optimum, pull-in voltage must exist at which the concave curving is eliminated and contact area is maximum. In this paper authors report the finding of optimum contact force and pull-in voltage.

A pairwise residue contact area-based mean force potential for discrimination of native protein structure

Directory of Open Access Journals (Sweden)

Pezeshk Hamid

2010-01-01

Full Text Available Abstract Background Considering energy function to detect a correct protein fold from incorrect ones is very important for protein structure prediction and protein folding. Knowledge-based mean force potentials are certainly the most popular type of interaction function for protein threading. They are derived from statistical analyses of interacting groups in experimentally determined protein structures. These potentials are developed at the atom or the amino acid level. Based on orientation dependent contact area, a new type of knowledge-based mean force potential has been developed. Results We developed a new approach to calculate a knowledge-based potential of mean-force, using pairwise residue contact area. To test the performance of our approach, we performed it on several decoy sets to measure its ability to discriminate native structure from decoys. This potential has been able to distinguish native structures from the decoys in the most cases. Further, the calculated Z-scores were quite high for all protein datasets. Conclusions This knowledge-based potential of mean force can be used in protein structure prediction, fold recognition, comparative modelling and molecular recognition. The program is available at http://www.bioinf.cs.ipm.ac.ir/softwares/surfield

Medial tibial “spackling” to lessen chronic medial tibial soft tissue irritation

Directory of Open Access Journals (Sweden)

J. Ryan Martin, MD

2016-09-01

Full Text Available We describe a unique, utilitarian reconstructive treatment option known as tibial “spackling” for chronic, localized medial joint line pain corresponding with progressive radiographic peripheral medial tibial bone loss beneath a well-fixed revision total knee arthroplasty tibial baseplate. It is believed that this localized pain is due to chronic irritation of the medial capsule and collateral ligament from the prominent medial edge of the tibial component. In the setting of failed nonoperative treatment, our experience with utilizing bone cement to reconstruct the medial tibial bone defect and create a smooth medial tibial surface has been successful in eliminating chronic medial soft tissue irritation.

Medial patellofemoral ligament: Research progress in anatomy and injury imaging

International Nuclear Information System (INIS)

Zheng Lei; Zhao Bin

2013-01-01

The medial patellofemoral ligament (MPFL) is considered as the most important soft tissue restraint providing medial stability of the patellofemoral joint. During patellar dislocation, the MPFL is subjected to severe stretching forces, resulting in injuries of the ligament in the most patients. With the development of medical imaging technology, a variety of non-invasive diagnostic imaging methods have been becoming important means in diagnosis of MPFL injury. In this paper, MPFL anatomy, the applications of medical imaging technology in diagnosis of MPFL injury and the distributions of MPFL injury site were reviewed. (authors)

Development of a Subject-Specific Foot-Ground Contact Model for Walking.

Science.gov (United States)

Jackson, Jennifer N; Hass, Chris J; Fregly, Benjamin J

2016-09-01

Computational walking simulations could facilitate the development of improved treatments for clinical conditions affecting walking ability. Since an effective treatment is likely to change a patient's foot-ground contact pattern and timing, such simulations should ideally utilize deformable foot-ground contact models tailored to the patient's foot anatomy and footwear. However, no study has reported a deformable modeling approach that can reproduce all six ground reaction quantities (expressed as three reaction force components, two center of pressure (CoP) coordinates, and a free reaction moment) for an individual subject during walking. This study proposes such an approach for use in predictive optimizations of walking. To minimize complexity, we modeled each foot as two rigid segments-a hindfoot (HF) segment and a forefoot (FF) segment-connected by a pin joint representing the toes flexion-extension axis. Ground reaction forces (GRFs) and moments acting on each segment were generated by a grid of linear springs with nonlinear damping and Coulomb friction spread across the bottom of each segment. The stiffness and damping of each spring and common friction parameter values for all springs were calibrated for both feet simultaneously via a novel three-stage optimization process that used motion capture and ground reaction data collected from a single walking trial. The sequential three-stage process involved matching (1) the vertical force component, (2) all three force components, and finally (3) all six ground reaction quantities. The calibrated model was tested using four additional walking trials excluded from calibration. With only small changes in input kinematics, the calibrated model reproduced all six ground reaction quantities closely (root mean square (RMS) errors less than 13 N for all three forces, 25 mm for anterior-posterior (AP) CoP, 8 mm for medial-lateral (ML) CoP, and 2 N·m for the free moment) for both feet in all walking trials. The

Benefit of cup medialization in total hip arthroplasty is associated with femoral anatomy.

Science.gov (United States)

Terrier, Alexandre; Levrero Florencio, Francesc; Rüdiger, Hannes A

2014-10-01

other preoperative parameters in this series. The benefit of cup medialization is variable and depends on the individual anatomy. Cup medialization with compensatory increase of the femoral offset may be particularly effective in patients with less femoral antetorsion. However, cup medialization must be balanced against its tradeoffs, including the additional loss of medial acetabular bone stock, and eventual proprioceptive implications of the nonanatomic center of rotation and perhaps joint reaction forces. Clinical studies should better determine the relevance of small changes of moment arms on function and joint reaction forces.

Complex Medial Meniscus Tears Are Associated With a Biconcave Medial Tibial Plateau.

Science.gov (United States)

Barber, F Alan; Getelman, Mark H; Berry, Kathy L

2017-04-01

To determine whether an association exists between a biconcave medial tibial plateau and complex medial meniscus tears. A consecutive series of stable knees undergoing arthroscopy were evaluated retrospectively with the use of preoperative magnetic resonance imaging (MRI), radiographs, and arthroscopy documented by intraoperative videos. Investigators independently performed blinded reviews of the MRI or videos. Based on the arthroscopy findings, medial tibial plateaus were classified as either biconcave or not biconcave. A transverse coronal plane ridge, separating the front of the tibial plateau from the back near the inner margin of the posterior body of the medial meniscus, was defined as biconcave. The medial plateau slope was calculated with MRI sagittal views. General demographic information, body mass index, and arthroscopically confirmed knee pathology were recorded. A total of 179 consecutive knees were studied from July 2014 through August 2015; 49 (27.2%) biconcave medial tibial plateaus and 130 (72.8%) controls were identified at arthroscopy. Complex medial meniscus tears were found in 103. Patients with a biconcave medial tibial plateau were found to have more complex medial meniscus tears (69.4%) than those without a biconcavity (53.1%) (P = .049) despite having lower body mass index (P = .020). No difference in medial tibial plateau slope was observed for biconcavities involving both cartilage and bone, bone only, or an indeterminate group (P = .47). Biconcave medial tibial plateaus were present in 27.4% of a consecutive series of patients undergoing knee arthroscopy. A biconcave medial tibial plateau was more frequently associated with a complex medial meniscus tear. Level III, case-control study. Copyright © 2016 Arthroscopy Association of North America. All rights reserved.

Contact stiffness and damping of liquid films in dynamic atomic force microscope

International Nuclear Information System (INIS)

Xu, Rong-Guang; Leng, Yongsheng

2016-01-01

The mechanical properties and dissipation behaviors of nanometers confined liquid films have been long-standing interests in surface force measurements. The correlation between the contact stiffness and damping of the nanoconfined film is still not well understood. We establish a novel computational framework through molecular dynamics (MD) simulation for the first time to study small-amplitude dynamic atomic force microscopy (dynamic AFM) in a simple nonpolar liquid. Through introducing a tip driven dynamics to mimic the mechanical oscillations of the dynamic AFM tip-cantilever assembly, we find that the contact stiffness and damping of the confined film exhibit distinct oscillations within 6-7 monolayer distances, and they are generally out-of-phase. For the solid-like film with integer monolayer thickness, further compression of the film before layering transition leads to higher stiffness and lower damping, while much lower stiffness and higher damping occur at non-integer monolayer distances. These two alternating mechanisms dominate the mechanical properties and dissipation behaviors of simple liquid films under cyclic elastic compression and inelastic squeeze-out. Our MD simulations provide a direct picture of correlations between the structural property, mechanical stiffness, and dissipation behavior of the nanoconfined film.

Design and fabrication of robotic gripper for grasping in minimizing contact force

Science.gov (United States)

Heidari, Hamidreza; Pouria, Milad Jafary; Sharifi, Shahriar; Karami, Mahmoudreza

2018-03-01

This paper presents a new method to improve the kinematics of robot gripper for grasping in unstructured environments, such as space operations. The robot gripper is inspired from the human hand and kept the hand design close to the structure of human fingers to provide successful grasping capabilities. The main goal is to improve kinematic structure of gripper to increase the grasping capability of large objects, decrease the contact forces and makes a successful grasp of various objects in unstructured environments. This research will describe the development of a self-adaptive and reconfigurable robotic hand for space operations through mechanical compliance which is versatile, robust and easy to control. Our model contains two fingers, two-link and three-link, with combining a kinematic model of thumb index. Moreover, some experimental tests are performed to examine the effectiveness of the hand-made in real, unstructured tasks. The results represent that the successful grasp range is improved about 30% and the contact forces is reduced approximately 10% for a wide range of target object size. According to the obtained results, the proposed approach provides an accommodative kinematic model which makes the better grasping capability by fingers geometries for a robot gripper.

Contact stiffness and damping of liquid films in dynamic atomic force microscope

Energy Technology Data Exchange (ETDEWEB)

Xu, Rong-Guang; Leng, Yongsheng, E-mail: leng@gwu.edu [Department of Mechanical and Aerospace Engineering, The George Washington University, Washington, DC 20052 (United States)

2016-04-21

The mechanical properties and dissipation behaviors of nanometers confined liquid films have been long-standing interests in surface force measurements. The correlation between the contact stiffness and damping of the nanoconfined film is still not well understood. We establish a novel computational framework through molecular dynamics (MD) simulation for the first time to study small-amplitude dynamic atomic force microscopy (dynamic AFM) in a simple nonpolar liquid. Through introducing a tip driven dynamics to mimic the mechanical oscillations of the dynamic AFM tip-cantilever assembly, we find that the contact stiffness and damping of the confined film exhibit distinct oscillations within 6-7 monolayer distances, and they are generally out-of-phase. For the solid-like film with integer monolayer thickness, further compression of the film before layering transition leads to higher stiffness and lower damping, while much lower stiffness and higher damping occur at non-integer monolayer distances. These two alternating mechanisms dominate the mechanical properties and dissipation behaviors of simple liquid films under cyclic elastic compression and inelastic squeeze-out. Our MD simulations provide a direct picture of correlations between the structural property, mechanical stiffness, and dissipation behavior of the nanoconfined film.

Elastic moduli of faceted aluminum nitride nanotubes measured by contact resonance atomic force microscopy

International Nuclear Information System (INIS)

Stan, G; Cook, R F; Ciobanu, C V; Thayer, T P; Wang, G T; Creighton, J R; Purushotham, K P; Bendersky, L A

2009-01-01

A new methodology for determining the radial elastic modulus of a one-dimensional nanostructure laid on a substrate has been developed. The methodology consists of the combination of contact resonance atomic force microscopy (AFM) with finite element analysis, and we illustrate it for the case of faceted AlN nanotubes with triangular cross-sections. By making precision measurements of the resonance frequencies of the AFM cantilever-probe first in air and then in contact with the AlN nanotubes, we determine the contact stiffness at different locations on the nanotubes, i.e. on edges, inner surfaces, and outer facets. From the contact stiffness we have extracted the indentation modulus and found that this modulus depends strongly on the apex angle of the nanotube, varying from 250 to 400 GPa for indentation on the edges of the nanotubes investigated.

The effect of medial arch support over the plantar pressure and triceps surae muscle strength after prolonged standing

Directory of Open Access Journals (Sweden)

Hindun Saadah

2015-11-01

Full Text Available Background: The activity with prolonged standing position is one of the causes of abnormalities in the lower leg and foot. The aim of this study is to discover the effect of medial arch support over the distribution of plantar pressure when standing and walking.Methods: This was an experimental study with pre- and post-design the strength of triceps surae muscle after prolonged standing, was also evaluated in an experimental study with pre- and post-design. Variables of plantar pressure measurement are the contact area and pressure peak were measured by using the Mat-scan tool. The measurement of the triceps surae muscle strength was done with a hand-held dynamometer, before and after using the medial arch support. Measurement was performed before and after working with prolonged standing position which took place about seven hours using the medial arch support inserted in the shoes. Data was analyzed using paired T-test.Results: There was a significant difference of peak pressure between standing (p = 0.041 and walking (p = 0.001. Whereas the contact area showed a significant decrease in the width of the contact area when standing (104.12 ± 12.42 vs 99.08 ± 10.21 p = 0.023. Whereas, the triceps surae muscle strength pre- and post-standing prolonged did not indicate a significant difference.Conclusion: There was decrease in peak pressure when standing and walking and decrease in contact area when standing on plantar after used of the medial arch support after prolonged standing.

Transosseous-equivalent rotator cuff repair: a systematic review on the biomechanical importance of tying the medial row.

Science.gov (United States)

Mall, Nathan A; Lee, Andrew S; Chahal, Jaskarndip; Van Thiel, Geoffrey S; Romeo, Anthony A; Verma, Nikhil N; Cole, Brian J

2013-02-01

Double-row and transosseous-equivalent repair techniques have shown greater strength and improved healing than single-row techniques. The purpose of this study was to determine whether tying of the medial-row sutures provides added stability during biomechanical testing of a transosseous-equivalent rotator cuff repair. We performed a systematic review of studies directly comparing biomechanical differences. Five studies met the inclusion and exclusion criteria. Of the 5 studies, 4 showed improved biomechanical properties with tying the medial-row anchors before bringing the sutures laterally to the lateral-row anchors, whereas the remaining study showed no difference in contact pressure, mean failure load, or gap formation with a standard suture bridge with knots tied at the medial row compared with knotless repairs. The results of this systematic review and quantitative synthesis indicate that the biomechanical factors ultimate load, stiffness, gap formation, and contact area are significantly improved when medial knots are tied as part of a transosseous-equivalent suture bridge construct compared with knotless constructs. Further studies comparing the clinical healing rates and functional outcomes between medial knotted and knotless repair techniques are needed. This review indicates that biomechanical factors are improved when the medial row of a transosseous-equivalent rotator cuff is tied compared with a knotless repair. However, this has not been definitively proven to translate to improved healing rates clinically. Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

PREFACE: Non-contact AFM Non-contact AFM

Science.gov (United States)

Giessibl, Franz J.; Morita, Seizo

2012-02-01

This special issue is focussed on high resolution non-contact atomic force microscopy (AFM). Non-contact atomic force microscopy was established approximately 15 years ago as a tool to image conducting and insulating surfaces with atomic resolution. Since 1998, an annual international conference has taken place, and although the proceedings of these conferences are a useful source of information, several key developments warrant devoting a special issue to this subject. In the theoretic field, the possibility of supplementing established techniques such as scanning tunneling microscopy (STM) and Kelvin probe microscopy with atomically resolved force micrsoscopy poses many challenges in the calculation of contrast and contrast reversal. The surface science of insulators, self-assembled monolayers and adsorbates on insulators is a fruitful field for the application of non-contact AFM: several articles in this issue are devoted to these subjects. Atomic imaging and manipulation have been pioneered using STM, but because AFM allows the measurement of forces, AFM has had a profound impact in this field as well. Three-dimensional force spectroscopy has allowed many important insights into surface science. In this issue a combined 3D tunneling and force microscopy is introduced. Non-contact AFM typically uses frequency modulation to measure force gradients and was initially used mainly in a vacuum. As can be seen in this issue, frequency modulation is now also used in ambient conditions, allowing better spatial and force resolution. We thank all of the contributors for their time and efforts in making this special issue possible. We are also very grateful to the staff of IOP Publishing for handling the administrative aspects and for steering the refereeing process. Non-contact AFM contents Relation between the chemical force and the tunnelling current in atomic point contacts: a simple model Pavel Jelínek, Martin Ondrácek and Fernando Flores Theoretical simulation of

Numerical Analysis of Masticatory Forces on a Lower First Molar considering the Contact between Dental Tissues

Directory of Open Access Journals (Sweden)

Rosa Alicia Hernández-Vázquez

2018-01-01

Full Text Available The aim of the present work is to identify the reactions of the dental organs to the different forces that occur during chewing and the transcendence of the union and contact maintained by the dental tissues. The study used a lower first molar biomodel with a real morphology and morphometry and consisting of the three dental tissues (enamel, dentin, and pulp each with its mechanical properties. In it, two simulations were carried out, as would the process of chewing a food. One of the simulations considers the contact between the enamel and the dentin, and the other does not take it into account. The results obtained differ significantly between the simulations that consider contact and those that do not, establishing the importance of taking this contact into account. In this way, the theories that establish horizontal and lateral occlusion forces are present during the functional chewing process which are viable to be correct. The case studies carried out present not only the reasons for the failure of enamel but also the failure of the restoration materials used. This reflection will allow the development of more adequate materials, mechanical design of prostheses, implants, and treatment.

Effects of counteracting external valgus moment on lateral tibial cartilage contact conditions and tibial rotation.

Science.gov (United States)

Shriram, Duraisamy; Parween, Rizuwana; Lee, Yee Han Dave; Subburaj, Karupppasamy

2017-07-01

Knee osteoarthritis that prevalently occurs at the medial compartment is a progressive chronic disorder affecting the articular cartilage of the knee joint, and lead to loss of joint functionality. Valgus braces have been used as a treatment procedure to unload the medial compartment for patients with medial osteoarthritis. Valgus braces through the application of counteracting external valgus moment shift the load from medial compartment towards the lateral compartment. Previous biomechanical studies focused only on the changes in varus moments before and after wearing the brace. The objective of this study was to investigate the influence of opposing external valgus moment applied by knee braces on the lateral tibial cartilage contact conditions using a 3D finite element model of the knee joint. Finite element simulations were performed on the knee joint model without and with the application of opposing valgus moment to mimic the unbraced and braced conditions. Lateral tibial cartilage contact pressures and contact area, and tibial rotation (varus-valgus and internal-external) were estimated for the complete walking gait cycle. The opposing valgus moment increased the maximum contact pressure and contact area on the lateral tibial cartilage compared to the normal gait moment. A peak contact pressure of 8.2 MPa and maximum cartilage loaded area of 28% (loaded cartilage nodes) on the lateral cartilage with the application of external valgus moment were induced at 50% of the gait cycle. The results show that the use of opposing valgus moment may significantly increase the maximum contact pressures and contact area on the lateral tibial cartilage and increases the risk of articular cartilage damage on the lateral compartment.

Atomic force microscopy and scanning electron microscopy analysis of daily disposable limbal ring contact lenses.

Science.gov (United States)

Lorenz, Kathrine Osborn; Kakkassery, Joseph; Boree, Danielle; Pinto, David

2014-09-01

Limbal ring (also known as 'circle') contact lenses are becoming increasingly popular, especially in Asian markets because of their eye-enhancing effects. The pigment particles that give the eye-enhancing effects of these lenses can be found on the front or back surface of the contact lens or 'enclosed' within the lens matrix. The purpose of this research was to evaluate the pigment location and surface roughness of seven types of 'circle' contact lenses. Scanning electron microscopic (SEM) analysis was performed using a variable pressure Hitachi S3400N instrument to discern the placement of lens pigments. Atomic force microscopy (Dimension Icon AFM from Bruker Nano) was used to determine the surface roughness of the pigmented regions of the contact lenses. Atomic force microscopic analysis was performed in fluid phase under contact mode using a Sharp Nitride Lever probe (SNL-10) with a spring constant of 0.06 N/m. Root mean square (RMS) roughness values were analysed using a generalised linear mixed model with a log-normal distribution. Least square means and their corresponding 95% confidence intervals were estimated for each brand, location and pigment combination. SEM cross-sectional images at 500× and 2,000× magnification showed pigment on the surface of six of the seven lens types tested. The mean depth of pigment for 1-DAY ACUVUE DEFINE (1DAD) lenses was 8.1 μm below the surface of the lens, while the remaining lens types tested had pigment particles on the front or back surface. Results of the atomic force microscopic analysis indicated that 1DAD lenses had significantly lower root mean square roughness values in the pigmented area of the lens than the other lens types tested. SEM and AFM analysis revealed pigment on the surface of the lens for all types tested with the exception of 1DAD. Further research is required to determine if the difference in pigment location influences on-eye performance. © 2014 The Authors. Clinical and Experimental

Investigation of the influence of vertical force on the contact between truck tyre and road using finite element analyses

Science.gov (United States)

Moisescu, Alexandra-Raluca; Anghelache, Gabriel

2017-10-01

In the modern context of automobile integration with the emerging technologies of the interconnected society, the interaction between tyre and road is an element of major importance for automobile safety systems such as the intelligent tyres, as well as for passenger comfort, fuel economy, environmental protection, infrastructure and vehicle durability. The tyre-road contact generates the distribution of forces exerted on each unit area in the contact patch, therefore the distribution of contact stresses on three orthogonal directions. The numerical investigation of stresses distribution in the contact patch requires the development of finite element models capable of accurately describing the interaction between tyre and rolling surface. The complex finite element model developed for the 11R22.5 truck tyre has been used for investigating the influence of vertical force on the distributions of contact stresses. In addition to these contributions, the paper presents aspects related to the simulation of truck tyre radial stiffness. The influence of tyre rolling has not been taken into consideration, as the purpose of the current research is the investigation of tyre-road contact in stationary conditions.

Pace-capture-guided ablation after contact-force-guided pulmonary vein isolation: results of the randomized controlled DRAGON trial.

Science.gov (United States)

Masuda, Masaharu; Fujita, Masashi; Iida, Osamu; Okamoto, Shin; Ishihara, Takayuki; Nanto, Kiyonori; Kanda, Takashi; Sunaga, Akihiro; Tsujimura, Takuya; Matsuda, Yasuhiro; Ohashi, Takuya; Uematsu, Masaaki

2017-11-17

Before the discovery of contact-force guidance, eliminating pacing capture along the pulmonary vein (PV) isolation line had been reported to improve PV isolation durability and rhythm outcomes. DRAGON (UMIN-CTR, UMIN000015332) aimed to elucidate the efficacy of pace-capture-guided ablation following contact-force-guided PV isolation ablation in paroxysmal atrial fibrillation (AF) patients. A total of 156 paroxysmal AF patients with AF-trigger ectopies from any of the four PVs induced by isoproterenol were randomly assigned to undergo pace-capture-guided ablation along a contact-force-guided isolation line around AF-trigger PVs (PC group, n = 76) or contact-force-guided PV isolation ablation alone (control group, n = 80). Follow-up of at least 1 year commenced with serial 24 h Holter and symptom-triggered ambulatory monitoring. There was no significant difference in acute PV reconnection rates during a 20 min waiting period after the last ablation or adenosine infusion testing between the PC and the control groups (per patient, 21% vs. 27%, P = 0.27; per AF-trigger PV, 5.9% vs. 7.3%, P = 0.70; and per non-AF-trigger PV, 7.1% vs. 7.4%, P = 0.92). Atrial tachyarrhythmia-free survival rates off antiarrhythmic drugs after the initial session were comparable at 19.3 ± 6.2 months between the two groups (82% vs. 80%, P = 0.80). Among 22 patients who required a second ablation procedure, there was no difference between the PC and the control groups in the PV reconnection rates at both previously AF-trigger (29% vs. 43%, P = 0.70) and non-AF-trigger PVs (18% vs. 19%, P = 0.88). Pace-capture-guided ablation performed after contact-force-guided PV isolation demonstrated no improvement in PV isolation durability or rhythm outcome. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2017. For permissions, please email: journals.permissions@oup.com.

Erosion by sliding wear in granular flows: Experiments with realistic contact forces

Science.gov (United States)

Stark, C. P.; Hung, C. Y.; Smith, B.; Li, L.; Grinspun, E.; Capart, H.

2015-12-01

Debris flow erosion is a powerful and sometimes dominant process in steep channels. Despite its importance, this phenomenon is relatively little studied in the lab. The large drum experiments of Hsu are a notable exception, in which almost-field-scale impact forces were generated at the head of a synthetic debris flow whose properties (grain size, proportion of fines, etc) were varied widely.A key challenge in these and similar experiments is to explore how erosion rate varies as a function of the scale of the flow (thereby varying inertial stresses, impact forces, etc). The geometrical limitations of most lab experiments, and their short run time, severely limit the scope of such explorations.We achieve this scale exploration in a set of drum erosion experiments by varying effective gravity across several orders of magnitude (1g, 10g, 100g) in a geotechnical centrifuge. By half-filling our 40cm-diameter drum with dry 2.3mm grains, placing a synthetic rock plate at the back and a glass plate at the front 3cm apart, and rotating the drum at 1-50rpm, we simulate wear in a channelized dry granular flow. In contrast to Hsu's experiments, we focus on sliding wear erosion at the flow boundary rather than impact/frictional wear at the flow head. By varying effective gravity from 1g-100g we can tune the pressure exerted by the grains at the boundary without having to change the scale of our apparatus. Using a recently developed depth-averaged, kinetic-energy closure theory for granular flow, we can simultaneously tune the drum rotation rate such that the flow dynamics remain invariant. We can thereby explore how changing the scale of a granular flow, and thus the contact forces of grains on the boundary, controls the rate of rock erosion. Using a small apparatus we can simulate the erosion generated by debris flows several meters deep involving grains up to 10cm in diameter.Our results suggest that sliding wear is the main erosion process, and are consistent with Archard

Attenuated Increase in Maximal Force of Rat Medial Gastrocnemius Muscle after Concurrent Peak Power and Endurance Training

Directory of Open Access Journals (Sweden)

Regula Furrer

2013-01-01

Full Text Available Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM is composed of high and low oxidative compartments which are recruited task specifically, we hypothesised that the adaptive responses to peak power training were unaffected by additional endurance training. Thirty rats were subjected to either no training (control, peak power training (PT, or both peak power and endurance training (PET, which was performed on a treadmill 5 days per week for 6 weeks. Maximal running velocity increased 13.5% throughout the training and was similar in both training groups. Only after PT, GM maximal force was 10% higher than that of the control group. In the low oxidative compartment, mRNA levels of myostatin and MuRF-1 were higher after PT as compared to those of control and PET groups, respectively. Phospho-S6 ribosomal protein levels remained unchanged, suggesting that the elevated myostatin levels after PT did not inhibit mTOR signalling. In conclusion, even by using task-specific recruitment of the compartmentalized rat GM, additional endurance training interfered with the adaptive response of peak power training and attenuated the increase in maximal force after power training.

Altered Tibiofemoral Joint Contact Mechanics and Kinematics in Patients with Knee Osteoarthritis and Episodic Complaints of Joint Instability

Science.gov (United States)

Farrokhi, Shawn; Voycheck, Carrie A.; Klatt, Brian A.; Gustafson, Jonathan A.; Tashman, Scott; Fitzgerald, G. Kelley

2014-01-01

Background To evaluate knee joint contact mechanics and kinematics during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. Methods Forty-three subjects, 11 with medial compartment knee osteoarthritis and self-reported instability (unstable), 7 with medial compartment knee osteoarthritis but no reports of instability (stable), and 25 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a downhill gait task on a treadmill. Findings The medial compartment contact point excursions were longer in the unstable group compared to the stable (p=0.046) and the control groups (p=0.016). The peak medial compartment contact point velocity was also greater for the unstable group compared to the stable (p=0.047) and control groups (p=0.022). Additionally, the unstable group demonstrated a coupled movement pattern of knee extension and external rotation after heel contact which was different than the coupled motion of knee flexion and internal rotation demonstrated by stable and control groups. Interpretation Our findings suggest that knee joint contact mechanics and kinematics are altered during the loading response phase of downhill gait in knee osteoarthritis patients with self-reported instability. The observed longer medial compartment contact point excursions and higher velocities represent objective signs of mechanical instability that may place the arthritic knee joint at increased risk for disease progression. Further research is indicated to explore the clinical relevance of altered contact mechanics and kinematics during other common daily activities and to assess the efficacy of rehabilitation programs to improve altered joint biomechanics in knee osteoarthritis patients with self-reported instability. PMID:24856791

Two-year follow-up of changes in bite force and occlusal contact area after intraoral vertical ramus osteotomy with and without Le Fort I osteotomy.

Science.gov (United States)

Choi, Y J; Lim, H; Chung, C J; Park, K H; Kim, K H

2014-06-01

This study was performed to examine the longitudinal changes in bite force and occlusal contact area after mandibular setback surgery via intraoral vertical ramus osteotomy (IVRO). Patients with mandibular prognathism who underwent IVRO (surgical group: 39 men and 39 women) were compared with subjects with class I skeletal and dental relationships (control group; 32 men and 35 women). The surgical group was divided into two subgroups: 1-jaw surgery (n = 30) and 2-jaw surgery (n = 48). Bite force and contact area were measured in maximum intercuspation with the Dental Prescale System before treatment, within 1 month before surgery, and at 1, 3, 6, 9, 12, and 24 months postsurgery. A linear mixed model was used to investigate the time-dependent changes and associated factors. Bite force and contact area decreased during presurgical orthodontic treatment, were minimal at 1 month postsurgery, and increased gradually thereafter. The 1-jaw and 2-jaw subgroups showed no significant differences in bite force. The time-dependent changes in bite force were significantly different according to the contact area (P contact area gradually increase throughout the postsurgical evaluation period. Increasing the occlusal contact area may be essential for improving bite force after surgery. Copyright © 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

Patellofemoral Pressure Changes After Static and Dynamic Medial Patellofemoral Ligament Reconstructions.

Science.gov (United States)

Rood, Akkie; Hannink, Gerjon; Lenting, Anke; Groenen, Karlijn; Koëter, Sander; Verdonschot, Nico; van Kampen, Albert

2015-10-01

Reconstructing the medial patellofemoral ligament (MPFL) has become a key procedure for stabilizing the patella. Different techniques to reconstruct the MPFL have been described: static techniques in which the graft is fixed rigidly to the bone or dynamic techniques with soft tissue fixation. Static MPFL reconstruction is most commonly used. However, dynamic reconstruction deforms more easily and presumably functions more like the native MPFL. The aim of the study was to evaluate the effect of the different MPFL fixation techniques on patellofemoral pressures compared with the native situation. The hypothesis was that dynamic reconstruction would result in patellofemoral pressures closer to those generated in an intact knee. Controlled laboratory study. Seven fresh-frozen knee specimens were tested in an in vitro knee joint loading apparatus. Tekscan pressure-sensitive films fixed to the retropatellar cartilage measured mean patellofemoral and peak pressures, contact area, and location of the center of force (COF) at fixed flexion angles from 0° to 110°. Four different conditions were tested: intact, dynamic, partial dynamic, and static MPFL reconstruction. Data were analyzed using linear mixed models. Static MPFL reconstruction resulted in higher peak and mean pressures from 60° to 110° of flexion (P .05). The COF in the static reconstruction group moved more medially on the patella from 50° to 110° of flexion compared with the other conditions. The contact area showed no significant differences between the test conditions. After static MPFL reconstruction, the patellofemoral pressures in flexion angles from 60° to 110° were 3 to 5 times higher than those in the intact situation. The pressures after dynamic MPFL reconstruction were similar as compared with those in the intact situation, and therefore, dynamic MPFL reconstruction could be a safer option than static reconstruction for stabilizing the patella. This study showed that static MPFL reconstruction

Contact angles in thin liquid films III. Interaction forces in Newton black soap films

NARCIS (Netherlands)

Feijter, J.A. de; Vrij, A.

The interaction parameters of Newton black soap films stabilized by NaDS, as derived from contact angle experiments, have been interpretated in terms of the structure and the interaction forces in the films. From the film thickness and the difference between the surface excess of the salt in the

Did Failure Occur Because of Medial Column Instability That Was Not Recognized, or Did It Develop After Surgery?

Science.gov (United States)

Kadakia, Anish R; Kelikian, Armen S; Barbosa, Mauricio; Patel, Milap S

2017-09-01

Medial column instability is a primary deforming force in the setting of pes planovalgus deformity. Consideration for medial column stabilization only after correction of the hindfoot deformity may result in creating a rigid hindfoot, compromising clinical outcomes. Careful analysis of the lateral radiograph to determine whether the deformity is secondary to the medial column or true peritalar subluxation may allow superior outcomes. Iatrogenic creation of an excessively rigid medial column may lead to significant instability of the remaining joints in the short term and arthrosis in the long term. Medial column arthrodesis should be used selectively to correct gross instability. Copyright © 2017 Elsevier Inc. All rights reserved.

Computer Simulations of Contact Forces for Airbags with Different Folding Patterns During Deployment Phase

Directory of Open Access Journals (Sweden)

King H. Yang

1995-01-01

Full Text Available An explicit finite element method was used to study the neck load and the contact force between an occupant and an airbag during an out-of-position frontal automobile crash. Two different folding patterns and two different mounting angles of the airbag were simulated. For the four cases simulated, the occupant’s neck axial force ranged from 156 to 376% of the data obtained from in-position sled tests using the Hybrid III dummy. The neck shear force ranged from 87 to 229% and the neck flexion moment ranged from 68 to 127% of in-position experimental results. In both 300 mounting angle simulations, the neck axial forces were higher than that of the two simulations with 00 mounting angles, but the trend for the neck shear force was the opposite. Although the kinematics of the model appear reasonable, the numbers generated by the model must be reviewed with great caution because the model has not been fully validated.

Analysis of contact stiffness in ultrasound atomic force microscopy: three-dimensional time-dependent ultrasound modeling

International Nuclear Information System (INIS)

Piras, Daniele; Sadeghian, Hamed

2017-01-01

Ultrasound atomic force microscopy (US-AFM) has been used for subsurface imaging of nanostructures. The contact stiffness variations have been suggested as the origin of the image contrast. Therefore, to analyze the image contrast, the local changes in the contact stiffness due to the presence of subsurface features should be calculated. So far, only static simulations have been conducted to analyze the local changes in the contact stiffness and, consequently, the contrast in US-AFM. Such a static approach does not fully represent the real US-AFM experiment, where an ultrasound wave is launched either into the sample or at the tip, which modulates the contact stiffness. This is a time-dependent nonlinear dynamic problem rather than a static and stationary one. This paper presents dynamic 3D ultrasound analysis of contact stiffness in US-AFM (in contrast to static analysis) to realistically predict the changes in contact stiffness and thus the changes in the subsurface image contrast. The modulation frequency also influences the contact stiffness variations and, thus, the image contrast. The three-dimensional time-dependent ultrasound analysis will greatly aid in the contrast optimization of subsurface nano imaging with US-AFM. (paper)

Outside-In Deep Medial Collateral Ligament Release During Arthroscopic Medial Meniscus Surgery.

Science.gov (United States)

Todor, Adrian; Caterev, Sergiu; Nistor, Dan Viorel

2016-08-01

Arthroscopic partial medial meniscectomy is a very common orthopaedic procedure performed for symptomatic, irreparable meniscus tears. It is usually associated with a very good outcome and minimal complications. In some patients with tight medial compartment, the posterior horn of the medial meniscus can be difficult to visualize, and access in this area with instruments may be challenging. To increase the opening of the medial compartment, after valgus-extension stress position of the knee, different techniques of deep medial collateral ligament release have been described. The outside-in pie-crusting technique shown in this technical note has documented effectiveness and good outcomes with minimal or no morbidity.

Medial Canthoplasty Combined with Conjunctivodacryocystorhinostomy for the Treatment of Delayed Medial Telecanthal Deformity

Directory of Open Access Journals (Sweden)

Hua Sun

2017-01-01

Conclusions: Medial canthoplasty combined with CDCR is an effective surgical method for treatment of patients with medial telecanthal deformity and lacrimal drainage system obstruction. The study indicates that medial canthoplasty combined with CDCR surgery rebuilds normal appearance of eyelid and contour of the medial canthus and successfully repairs the function of the lacrimal drainage system.

Characterization of polyethersulfone-polyimide hollow fiber membranes by atomic force microscopy and contact angle goniometery

NARCIS (Netherlands)

Khulbe, K.C.; Feng, C.; Matsuura, T.; Kapantaidakis, G.; Wessling, Matthias; Koops, G.H.

2003-01-01

Asymmetric blend polyethersulfone-polyimide (PES-PI) hollow fiber membranes prepared at different air gap and used for gas separation are characterized by atomic force microscopy (inside and out side surfaces) and by measuring the contact angle of out side surface. The outer surface was entirely

Injerto libre braquial medial Free medial arm graft

Directory of Open Access Journals (Sweden)

P. Martos Díaz

2007-12-01

Full Text Available Introducción. Entre las reconstrucciones de defectos titulares de cabeza y cuello, el injerto libre microvascularizado braquial medial no ha adquirido mucha popularidad debido a las variaciones anatómicas que se reflejan en la vascularización de éste. Nuestro objetivo es realizar una descripción de la anatomía y técnica quirúrgica, así como una revisión de la literatura describiendo las ventajas y desventajas de este tipo de injerto. Material y método. Presentamos el caso de una paciente con carcinoma epidermoide de mucosa yugal izquierda con afectación ganglionar ipsilateral. Se procedió a su resección con márgenes más disección cervical funcional. La reconstrucción del defecto se llevó a cabo mediante un injerto libre microvascularizado braquial medial de brazo izquierdo. Discusión. Pensamos que el injerto libre braquial medial de brazo se trata de una opción más segura a la hora de la reconstrucción de defectos cervicofaciales, aportando una serie de ventajas entre las que destacan: no sacrificio de una arteria terminal, cierre primario de la zona donante, mínimo defecto estético, y poseer una piel fina, elástica y sin vello.Introduction. Free medial microvascularized arm grafts have not become very popular for the reconstruction of head and neck defects due to anatomic variations in their vascularization. Our objective was to describe the anatomy and surgical technique and to review the literature on the advantages and disadvantages of free medial arm grafts. Material and methods. We report the case of a patient with squamous cell carcinoma of the left jugal mucosa with same-side lymph node involvement. The tumor was resected with margins and a functional cervical dissection was performed. The defect was reconstructed using a free medial microvascularized graft from the left arm. Discussion. We believe that free medial arm grafts are a safer option for the reconstruction of cervicofacial defects and that they offer

Robust Load Cell Cell for Discrete Contact Force Measurements of Sampling Systems and/or Instruments, Phase I

Data.gov (United States)

National Aeronautics and Space Administration — Bear Engineering proposes to develop a simple, robust, extreme environment compatible, mechanical load cell to enable the control of contact forces for placement of...

The Role of Medial Frontal Cortex in Action Anticipation in Professional Badminton Players.

Science.gov (United States)

Xu, Huan; Wang, Pin; Ye, Zhuo'er; Di, Xin; Xu, Guiping; Mo, Lei; Lin, Huiyan; Rao, Hengyi; Jin, Hua

2016-01-01

Some studies show that the medial frontal cortex is associated with more skilled action anticipation, while similar findings are not observed in some other studies, possibly due to the stimuli employed and the participants used as the control group. In addition, no studies have investigated whether there is any functional connectivity between the medial frontal cortex and other brain regions in more skilled action anticipation. Therefore, the present study aimed to re-investigate how the medial frontal cortex is involved in more skilled action anticipation by circumventing the limitations of previous research and to investigate that the medial frontal cortex functionally connected with other brain regions involved in action processing in more skilled action anticipation. To this end, professional badminton players and novices were asked to anticipate the landing position of the shuttlecock while watching badminton match videos or to judge the gender of the players in the matches. The video clips ended right at the point that the shuttlecock and the racket came into contact to reduce the effect of information about the trajectory of the shuttlecock. Novices who lacked training and watching experience were recruited for the control group to reduce the effect of sport-related experience on the medial frontal cortex. Blood oxygenation level-dependent activation was assessed by means of functional magnetic resonance imaging. Compared to novices, badminton players exhibited stronger activation in the left medial frontal cortex during action anticipation and greater functional connectivity between left medial frontal cortex and some other brain regions (e.g., right posterior cingulate cortex). Therefore, the present study supports the position that the medial frontal cortex plays a role in more skilled action anticipation and that there is a specific brain network for more skilled action anticipation that involves right posterior cingulate cortex, right fusiform gyrus

Dissipative and electrostatic force spectroscopy of indium arsenide quantum dots by non-contact atomic force microscopy

Science.gov (United States)

Stomp, Romain-Pierre

This thesis is devoted to the studies of self-assembled InAs quantum dots (QD) by low-temperature Atomic Force Microscopy (AFM) in frequency modulation mode. Several spectroscopic methods are developed to investigate single electron charging from a two-dimensional electron gas (2DEG) to an individual InAs QD. Furthermore, a new technique to measure the absolute tip-sample capacitance is also demonstrated. The main observables are the electrostatic force between the metal-coated AFM tip and sample as well as the sample-induced energy dissipation, and therefore no tunneling current has to be collected at the AFM tip. Measurements were performed by recording simultaneously the shift in the resonant frequency and the Q-factor degradation of the oscillating cantilever either as a function of tip-sample voltage or distance. The signature of single electron charging was detected as an abrupt change in the frequency shift as well as corresponding peaks in the dissipation. The main experimental features in the force agree well with the semi-classical theory of Coulomb blockade by considering the free energy of the system. The observed dissipation peaks can be understood as a back-action effect on the oscillating cantilever beam due to the fluctuation in time of electrons tunneling back and forth between the 2DEG and the QD. It was also possible to extract the absolute value of the tip-sample capacitance, as a consequence of the spectroscopic analysis of the electrostic force as a function of tip-sample distance for different values of the applied voltage. At the same time, the contact potential difference and the residual non-capacitive force could also be determined as a function of tip-sample distance.

Simulated non-contact atomic force microscopy for GaAs surfaces based on real-space pseudopotentials

International Nuclear Information System (INIS)

Kim, Minjung; Chelikowsky, James R.

2014-01-01

We simulate non-contact atomic force microscopy (AFM) with a GaAs(1 1 0) surface using a real-space ab initio pseudopotential method. While most ab initio simulations include an explicit model for the AFM tip, our method does not introduce the tip modeling step. This approach results in a considerable reduction of computational work, and also provides complete AFM images, which can be directly compared to experiment. By analyzing tip-surface interaction forces in both our results and previous ab initio simulations, we find that our method provides very similar force profile to the pure Si tip results. We conclude that our method works well for systems in which the tip is not chemically active.

Successful catheter ablation of ventricular premature complexes from the right atrial side of the atrioventricular septum with good contact force.

Science.gov (United States)

Arai, Marina; Fukamizu, Seiji; Kawamura, Iwanari; Miyazawa, Satoshi; Hojo, Rintaro; Sakurada, Harumizu; Hiraoka, Masayasu

2018-04-01

The acquisition of good contact force for radiofrequency catheter ablation of ventricular premature complexes (VPCs) originating from the basal septum of the left ventricle (LV) is often difficult. We describe a case of VPCs originating from the basal septum of the LV, which were successfully eliminated by applying radiofrequency at the right atrium (RA) side of the atrioventricular septum (AVS) without causing any significant impairment of atrioventricular conduction because the ablation catheter could obtain better contact force through the RA approach. Moreover, intracardiac echocardiography (ICE) and RA angiography effectively demonstrated the AVS.

Actuation of atomic force microscopy microcantilevers using contact acoustic nonlinearities

Energy Technology Data Exchange (ETDEWEB)

Torello, D.; Degertekin, F. Levent, E-mail: levent.degertekin@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2013-11-15

A new method of actuating atomic force microscopy (AFM) cantilevers is proposed in which a high frequency (>5 MHz) wave modulated by a lower frequency (∼300 kHz) wave passes through a contact acoustic nonlinearity at the contact interface between the actuator and the cantilever chip. The nonlinearity converts the high frequency, modulated signal to a low frequency drive signal suitable for actuation of tapping-mode AFM probes. The higher harmonic content of this signal is filtered out mechanically by the cantilever transfer function, providing for clean output. A custom probe holder was designed and constructed using rapid prototyping technologies and off-the-shelf components and was interfaced with an Asylum Research MFP-3D AFM, which was then used to evaluate the performance characteristics with respect to standard hardware and linear actuation techniques. Using a carrier frequency of 14.19 MHz, it was observed that the cantilever output was cleaner with this actuation technique and added no significant noise to the system. This setup, without any optimization, was determined to have an actuation bandwidth on the order of 10 MHz, suitable for high speed imaging applications. Using this method, an image was taken that demonstrates the viability of the technique and is compared favorably to images taken with a standard AFM setup.

Biomechanical Effects of Posterior Condylar Offset and Posterior Tibial Slope on Quadriceps Force and Joint Contact Forces in Posterior-Stabilized Total Knee Arthroplasty

Directory of Open Access Journals (Sweden)

Kyoung-Tak Kang

2017-01-01

Full Text Available This study aimed to determine the biomechanical effect of the posterior condylar offset (PCO and posterior tibial slope (PTS in posterior-stabilized (PS fixed-bearing total knee arthroplasty (TKA. We developed ±1, ±2, and ±3 mm PCO models in the posterior direction and −3°, 0°, 3°, and 6° PTS models using a previously validated FE model. The influence of changes in the PCO and PTS on the biomechanical effects under deep-knee-bend loading was investigated. The contact stress on the PE insert increased by 14% and decreased by 7% on average as the PCO increased and decreased, respectively, compared to the neutral position. In addition, the contact stress on post in PE insert increased by 18% on average as PTS increased from −3° to 6°. However, the contact stress on the patellar button decreased by 11% on average as PTS increased from −3° to 6° in all different PCO cases. The quadriceps force decreased by 14% as PTS increased from −3° to 6° in all PCO models. The same trend was found in patellar tendon force. Changes in PCO had adverse biomechanical effects whereas PTS increase had positive biomechanical effects. However, excessive PTS should be avoided to prevent knee instability and subsequent failure.

Detection of defects in formed sheet metal using medial axis transformation

Science.gov (United States)

Murmu, Naresh C.; Velgan, Roman

2003-05-01

In the metal forming processes, the sheet metals are often prone to various defects such as thinning, dents, wrinkles etc. In the present manufacturing environments with ever increasing demand of higher quality, detecting the defects of formed sheet metal using an effective and objective inspection system is the foremost norm to remain competitive in market. The defect detection using optical techniques aspire to satisfy its needs to be non-contact and fast. However, the main difficulties to achieve this goal remain essentially on the development of efficient evaluation technique and accurate interpretation of extracted data. The defect like thinning is detected by evaluating the deviations of the thickness in the formed sheet metal against its nominal value. The present evaluation procedure for determination of thickness applied on the measurements data is not without deficiency. To improve this procedure, a new evaluation approach based on medial axis transformation is proposed here. The formed sheet metals are digitized using fringe projection systems in different orientations, and afterwards registered into one coordinate frame. The medial axis transformation (MAT) is applied on the point clouds, generating the point clouds of MAT. This data is further processed and medial surface is determined. The thinning defect is detected by evaluating local wall thickness and other defects like wrinkles are determined using the shape recognition on the medial surface. The applied algorithm is simple, fast and robust.

The role of medial frontal gyrus in action anticipation in professional badminton players

Directory of Open Access Journals (Sweden)

Huan Xu

2016-11-01

Full Text Available Some studies show that the medial frontal cortex is associated with more skilled action anticipation, while similar findings are not observed in some other studies, possibly due to the stimuli employed and the participants used as the control group. In addition, no studies have investigated whether there is any functional connectivity between the medial frontal cortex and other brain regions in more skilled action anticipation. Therefore, the present study aimed to re-investigate how the medial frontal cortex is involved in more skilled action anticipation by circumventing the limitations of previous research and to investigate that the medial frontal cortex functionally connected with other brain regions involved in action processing in more skilled action anticipation. To this end, professional badminton players and novices were asked to anticipate the landing position of the shuttlecock while watching badminton match videos or to judge the gender of the players in the matches. The video clips ended right at the point that the shuttlecock and the racket came into contact to reduce the effect of information about the trajectory of the shuttlecock. Novices who lacked training and watching experience were recruited for the control group to reduce the effect of sport-related experience on the medial frontal cortex. Blood oxygenation level-dependent (BOLD activation was assessed by means of functional magnetic resonance imaging (fMRI. Compared to novices, badminton players exhibited stronger activation in the left medial frontal cortex during action anticipation and greater functional connectivity between left medial frontal cortex and some other brain regions (e.g., right posterior cingulate cortex. Therefore, the present study supports the position that the medial frontal cortex plays a role in more skilled action anticipation and that there is a specific brain network for more skilled action anticipation that involves right posterior cingulate

The Role of Medial Frontal Cortex in Action Anticipation in Professional Badminton Players

Science.gov (United States)

Xu, Huan; Wang, Pin; Ye, Zhuo’er; Di, Xin; Xu, Guiping; Mo, Lei; Lin, Huiyan; Rao, Hengyi; Jin, Hua

2016-01-01

Some studies show that the medial frontal cortex is associated with more skilled action anticipation, while similar findings are not observed in some other studies, possibly due to the stimuli employed and the participants used as the control group. In addition, no studies have investigated whether there is any functional connectivity between the medial frontal cortex and other brain regions in more skilled action anticipation. Therefore, the present study aimed to re-investigate how the medial frontal cortex is involved in more skilled action anticipation by circumventing the limitations of previous research and to investigate that the medial frontal cortex functionally connected with other brain regions involved in action processing in more skilled action anticipation. To this end, professional badminton players and novices were asked to anticipate the landing position of the shuttlecock while watching badminton match videos or to judge the gender of the players in the matches. The video clips ended right at the point that the shuttlecock and the racket came into contact to reduce the effect of information about the trajectory of the shuttlecock. Novices who lacked training and watching experience were recruited for the control group to reduce the effect of sport-related experience on the medial frontal cortex. Blood oxygenation level-dependent activation was assessed by means of functional magnetic resonance imaging. Compared to novices, badminton players exhibited stronger activation in the left medial frontal cortex during action anticipation and greater functional connectivity between left medial frontal cortex and some other brain regions (e.g., right posterior cingulate cortex). Therefore, the present study supports the position that the medial frontal cortex plays a role in more skilled action anticipation and that there is a specific brain network for more skilled action anticipation that involves right posterior cingulate cortex, right fusiform gyrus

Minimising the effect of nanoparticle deformation in intermittent contact amplitude modulation atomic force microscopy measurements

International Nuclear Information System (INIS)

Babic, Bakir; Lawn, Malcolm A.; Coleman, Victoria A.; Jämting, Åsa K.; Herrmann, Jan

2016-01-01

The results of systematic height measurements of polystyrene (PS) nanoparticles using intermittent contact amplitude modulation atomic force microscopy (IC-AM-AFM) are presented. The experimental findings demonstrate that PS nanoparticles deform during AFM imaging, as indicated by a reduction in the measured particle height. This deformation depends on the IC-AM-AFM imaging parameters, material composition, and dimensional properties of the nanoparticles. A model for nanoparticle deformation occurring during IC-AM-AFM imaging is developed as a function of the peak force which can be calculated for a particular set of experimental conditions. The undeformed nanoparticle height can be estimated from the model by extrapolation to zero peak force. A procedure is proposed to quantify and minimise nanoparticle deformation during IC-AM-AFM imaging, based on appropriate adjustments of the experimental control parameters.

Minimising the effect of nanoparticle deformation in intermittent contact amplitude modulation atomic force microscopy measurements

Energy Technology Data Exchange (ETDEWEB)

Babic, Bakir, E-mail: bakir.babic@measurement.gov.au; Lawn, Malcolm A.; Coleman, Victoria A.; Jämting, Åsa K.; Herrmann, Jan [National Measurement Institute, 36 Bradfield Road, West Lindfield, New South Wales 2070 (Australia)

2016-06-07

The results of systematic height measurements of polystyrene (PS) nanoparticles using intermittent contact amplitude modulation atomic force microscopy (IC-AM-AFM) are presented. The experimental findings demonstrate that PS nanoparticles deform during AFM imaging, as indicated by a reduction in the measured particle height. This deformation depends on the IC-AM-AFM imaging parameters, material composition, and dimensional properties of the nanoparticles. A model for nanoparticle deformation occurring during IC-AM-AFM imaging is developed as a function of the peak force which can be calculated for a particular set of experimental conditions. The undeformed nanoparticle height can be estimated from the model by extrapolation to zero peak force. A procedure is proposed to quantify and minimise nanoparticle deformation during IC-AM-AFM imaging, based on appropriate adjustments of the experimental control parameters.

Automatic quantification of tibio-femoral contact area and congruity

DEFF Research Database (Denmark)

Tummala, Sudhakar; Nielsen, Mads; Lillholm, Martin

2012-01-01

We present methods to quantify the medial tibio- femoral (MTF) joint contact area (CA) and congruity index (CI) from low-field magnetic resonance imaging (MRI). Firstly, based on the segmented MTF cartilage compartments, we computed the contact area using the Euclidian distance transformation....... The CA was defined as the area of the tibial superior surface and the femoral inferior surface that are less than a voxel width apart. Furthermore, the CI is computed point-by-point by assessing the first- and second-order general surface features over the contact area. Mathematically, it is the inverse...

Corrected direct force balance method for atomic force microscopy lateral force calibration

International Nuclear Information System (INIS)

Asay, David B.; Hsiao, Erik; Kim, Seong H.

2009-01-01

This paper reports corrections and improvements of the previously reported direct force balance method (DFBM) developed for lateral calibration of atomic force microscopy. The DFBM method employs the lateral force signal obtained during a force-distance measurement on a sloped surface and relates this signal to the applied load and the slope of the surface to determine the lateral calibration factor. In the original publication [Rev. Sci. Instrum. 77, 043903 (2006)], the tip-substrate contact was assumed to be pinned at the point of contact, i.e., no slip along the slope. In control experiments, the tip was found to slide along the slope during force-distance curve measurement. This paper presents the correct force balance for lateral force calibration.

Self-Sealed Bionic Long Microchannels with Thin Walls and Designable Nanoholes Prepared by Line-Contact Capillary-Force Assembly.

Science.gov (United States)

Lao, Zhao-Xin; Hu, Yan-Lei; Pan, Deng; Wang, Ren-Yan; Zhang, Chen-Chu; Ni, Jin-Cheng; Xu, Bing; Li, Jia-Wen; Wu, Dong; Chu, Jia-Ru

2017-06-01

Long microchannels with thin walls, small width, and nanoholes or irregular shaped microgaps, which are similar to capillaries or cancerous vessels, are urgently needed to simulate the physiological activities in human body. However, the fabrication of such channels remains challenging. Here, microchannels with designable holes are manufactured by combining laser printing with line-contact capillary-force assembly. Two microwalls are first printed by femtosecond laser direct-writing, and subsequently driven to collapse into a channel by the capillary force that arises in the evaporation of developer. The channel can remain stable in solvent due to the enhanced Van der Waals' force caused by the line-contact of microwalls. Microchannels with controllable nanoholes and almost arbitrary patterns can be fabricated without any bonding or multistep processes. As-prepared microchannels, with wall thicknesses less than 1 µm, widths less than 3 µm, lengths more than 1 mm, are comparable with human capillaries. In addition, the prepared channels also exhibit the ability to steer the flow of liquid without any external pump. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Air microjet system for non-contact force application and the actuation of micro-structures

International Nuclear Information System (INIS)

Khare, S M; Venkataraman, V

2016-01-01

We demonstrate a non-contact technique to apply calibrated and localized forces in the micro-Newton to milli-Newton range using an air microjet. An electromagnetically actuated diaphragm controlled by a signal generator is used to generate the air microjet. With a nozzle diameter of 150 μm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m s −1 were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 μN on a poly dimethyl siloxane (PDMS) micropillar (50 μm in diameter, 157 μm in height) and 415 μN on a PDMS membrane (3 mm in diameter, 28 μm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 μN on a flat surface with 8 V operating voltage. Out of the cleanroom fabrication and robust design make this system cost effective and durable. (technical note)

Air microjet system for non-contact force application and the actuation of micro-structures

Science.gov (United States)

Khare, S. M.; Venkataraman, V.

2016-01-01

We demonstrate a non-contact technique to apply calibrated and localized forces in the micro-Newton to milli-Newton range using an air microjet. An electromagnetically actuated diaphragm controlled by a signal generator is used to generate the air microjet. With a nozzle diameter of 150 μm, the microjet diameter was maintained to a maximum of 1 mm at a distance of 5 mm from the nozzle. The force generated by the microjet was measured using a commercial force sensor to determine the velocity profile of the jet. Axial flow velocities of up to 25 m s-1 were obtained at distances as long as 6 mm. The microjet exerted a force up to 1 μN on a poly dimethyl siloxane (PDMS) micropillar (50 μm in diameter, 157 μm in height) and 415 μN on a PDMS membrane (3 mm in diameter, 28 μm thick). We also demonstrate that from a distance of 6 mm our microjet can exert a peak pressure of 187 Pa with a total force of about 84 μN on a flat surface with 8 V operating voltage. Out of the cleanroom fabrication and robust design make this system cost effective and durable.

Design of a lightweight, cost effective thimble-like sensor for haptic applications based on contact force sensors.

Science.gov (United States)

Ferre, Manuel; Galiana, Ignacio; Aracil, Rafael

2011-01-01

This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i) force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii) the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation.

Design of a Lightweight, Cost Effective Thimble-Like Sensor for Haptic Applications Based on Contact Force Sensors

Directory of Open Access Journals (Sweden)

Ignacio Galiana

2011-12-01

Full Text Available This paper describes the design and calibration of a thimble that measures the forces applied by a user during manipulation of virtual and real objects. Haptic devices benefit from force measurement capabilities at their end-point. However, the heavy weight and cost of force sensors prevent their widespread incorporation in these applications. The design of a lightweight, user-adaptable, and cost-effective thimble with four contact force sensors is described in this paper. The sensors are calibrated before being placed in the thimble to provide normal and tangential forces. Normal forces are exerted directly by the fingertip and thus can be properly measured. Tangential forces are estimated by sensors strategically placed in the thimble sides. Two applications are provided in order to facilitate an evaluation of sensorized thimble performance. These applications focus on: (i force signal edge detection, which determines task segmentation of virtual object manipulation, and (ii the development of complex object manipulation models, wherein the mechanical features of a real object are obtained and these features are then reproduced for training by means of virtual object manipulation.

Assessment of the Medial Longitudinal Arch in children with Flexible Pes Planus by Plantar Pressure Mapping.

Science.gov (United States)

Elmoatasem, E M; Eid, M A

2016-12-01

Plantar Pressure mapping was introduced as a new modality for assessment of the height of the medial longitudinal arch of the foot. Therefore, the aim of this study is to correlate the plantar pressure mapping readings of arch index contact force ratio (AICFR) in children with flexible pes planus with radiographic measurements and static plantar footprints in order to determine the reliability of pressure mapping as a modality for the assessment and follow up of the flat foot deformity. Radiographic measurements, foot prints, and pressure mapping scans were recorded for each foot at initial presentation and at latest follow up in 28 children (56 feet) with flexible pes planus. A positive correlation of pressure mapping results was found with the talo-first metatarsal angle, the calcaneal pitch angle, as well as the footprint scans (P plantar pressure mapping is a reliable and effective tool in screening, diagnosis, and follow up of children with flexible pes planus.

The Influence of Articular Cartilage Thickness Reduction on Meniscus Biomechanics.

Science.gov (United States)

Łuczkiewicz, Piotr; Daszkiewicz, Karol; Chróścielewski, Jacek; Witkowski, Wojciech; Winklewski, Pawel J

2016-01-01

Evaluation of the biomechanical interaction between meniscus and cartilage in medial compartment knee osteoarthritis. The finite element method was used to simulate knee joint contact mechanics. Three knee models were created on the basis of knee geometry from the Open Knee project. We reduced the thickness of medial cartilages in the intact knee model by approximately 50% to obtain a medial knee osteoarthritis (OA) model. Two variants of medial knee OA model with congruent and incongruent contact surfaces were analysed to investigate the influence of congruency. A nonlinear static analysis for one compressive load case was performed. The focus of the study was the influence of cartilage degeneration on meniscal extrusion and the values of the contact forces and contact areas. In the model with incongruent contact surfaces, we observed maximal compressive stress on the tibial plateau. In this model, the value of medial meniscus external shift was 95.3% greater, while the contact area between the tibial cartilage and medial meniscus was 50% lower than in the congruent contact surfaces model. After the non-uniform reduction of cartilage thickness, the medial meniscus carried only 48.4% of load in the medial compartment in comparison to 71.2% in the healthy knee model. We have shown that the change in articular cartilage geometry may significantly reduce the role of meniscus in load transmission and the contact area between the meniscus and cartilage. Additionally, medial knee OA may increase the risk of meniscal extrusion in the medial compartment of the knee joint.

Footprint Contact Area and Interface Pressure Comparison Between the Knotless and Knot-Tying Transosseous-Equivalent Technique for Rotator Cuff Repair.

Science.gov (United States)

Kim, Sung-Jae; Kim, Sung-Hwan; Moon, Hyun-Soo; Chun, Yong-Min

2016-01-01

To quantify and compare the footprint contact area and interface pressure on the greater tuberosity between knotless and knot-tying transosseous-equivalent (TOE) repair using pressure-sensitive film. We used 11 pairs of fresh-frozen cadaveric shoulders (22 specimens), in which rotator cuff tears were created before repair. Each pair was randomized to either conventional medial knot-tying TOE repair (group A) or medial knotless TOE repair using the modified Mason-Allen technique (group B). Pressure-sensitive film was used to quantify the pressurized contact area and interface pressure between the greater tuberosity and supraspinatus tendon. The mean pressurized contact area was 33.2 ± 2.5 mm(2) for group A and 28.4 ± 2.4 mm(2) for group B. There was a significant difference between groups (P = .005). Although the overall contact configuration of both groups was similar and showed an M shape, group A showed a greater pressurized configuration around the medial row. The mean interface pressure was 0.20 ± 0.02 MPa for group A and 0.17 ± 0.02 MPa for group B. There was a significant difference between groups (P = .001). Contrary to our hypothesis, in this time-zero study, medial knotless TOE repair using a modified Mason-Allen suture produced a significantly inferior footprint contact area and interface pressure compared with conventional medial knot-tying TOE repair. Even though we found a statistically significant difference between the 2 repair methods, it is still unknown if this statistical difference seen in our study has any clinical and radiologic significance. Copyright © 2016 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Ground reaction forces and knee kinetics during single and repeated badminton lunges.

Science.gov (United States)

Lam, Wing Kai; Ding, Rui; Qu, Yi

2017-03-01

Repeated movement (RM) lunge that frequently executed in badminton might be used for footwear evaluation. This study examined the influence of single movement (SM) and RM lunges on the ground reaction forces (GRFs) and knee kinetics during the braking phase of a badminton lunge step. Thirteen male university badminton players performed left-forward lunges in both SM and RM sessions. Force platform and motion capturing system were used to measure GRFs and knee kinetics variables. Paired t-test was performed to determine any significant differences between SM and RM lunges regarding mean and coefficient of variation (CV) in each variable. The kinetics results indicated that compared to SM lunges, the RM lunges had shorter contact time and generated smaller maximum loading rate of impact force, peak knee anterior-posterior force, and peak knee sagittal moment but generated larger peak horizontal resultant forces (Ps < 0.05). Additionally, the RM lunges had lower CV for peak knee medial-lateral and vertical forces (Ps < 0.05). These results suggested that the RM testing protocols had a distinct loading response and adaptation pattern during lunge and that the RM protocol showed higher within-trial reliability, which may be beneficial for the knee joint loading evaluation under different interventions.

Frequency shift and hysteresis suppression in contact-mode AFM using contact stiffness modulation

Directory of Open Access Journals (Sweden)

Belhaq M.

2012-07-01

Full Text Available In this paper the frequency response shift and hysteresis suppression of contact-mode atomic force microscopy is investigated using parametric modulation of the contact stiffness. Based on the Hertzian contact theory, a lumped single degree of freedom oscillator is considered for modeling the cantilever dynamics contact-mode atomic force microscopy. We use the technique of direct partition of motion and the method of multiple scales to obtain, respectively, the slow dynamic and the corresponding slow flow of the system. As results, this study shows that the amplitude of the contact stiffness modulation has a significant effect on the frequency response. Specifically, increasing the amplitude of the stiffness modulation suppresses hysteresis, decreases the peak amplitude and produces shifts towards higher and lower frequencies.

Longitudinal analysis of tibiofemoral cartilage contact area and position in ACL reconstructed patients.

Science.gov (United States)

Chen, Ellison; Amano, Keiko; Pedoia, Valentina; Souza, Richard B; Ma, C Benjamin; Li, Xiaojuan

2018-04-18

Patients who have suffered ACL injury are more likely to develop early onset post-traumatic osteoarthritis despite reconstruction. The purpose of our study was to evaluate the longitudinal changes in the tibiofemoral cartilage contact area size and location after ACL injury and reconstruction. Thirty-one patients with isolated unilateral ACL injury were followed with T 2 weighted Fast Spin Echo, T 1ρ and T 2 MRI at baseline prior to reconstruction, and 6 months, 1 year, and 2 years after surgery. Areas were delineated in FSE images with an in-house Matlab program using a spline-based semi-automated segmentation algorithm. Tibiofemoral contact area and centroid position along the anterior-posterior axis were calculated along with T 1ρ and T 2 relaxation times on both the injured and non-injured knees. At baseline, the injured knees had significantly smaller and more posteriorly positioned contact areas on the medial tibial surface compared to corresponding healthy knees. These differences persisted 6 months after reconstruction. Moreover, subjects with more anterior medial centroid positions at 6 months had elevated T 1ρ and T 2 measures in the posterior medial tibial plateau at 1 year. Changes in contact area and centroid position after ACL injury and reconstruction may characterize some of the mechanical factors contributing to post-traumatic osteoarthritis. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

The relationship between chondromalacia patella, medial meniscal tear and medial periarticular bursitis in patients with osteoarthritis

Directory of Open Access Journals (Sweden)

Resorlu Mustafa

2017-11-01

Full Text Available This study investigated the presence of bursitis in the medial compartment of the knee (pes anserine, semimembranosus-tibial collateral ligament, and medial collateral ligament bursa in osteoarthritis, chondromalacia patella and medial meniscal tears.

Competitive swimmers with hypermobility have strength and fatigue deficits in shoulder medial rotation

DEFF Research Database (Denmark)

Liaghat, Behnam; Juul-Kristensen, Birgit; Frydendal, Thomas

2018-01-01

rotation (60°/s). Swimmers with GJHS showed significantly larger isokinetic fatigue at 180°/s (0.321 J/repetition; p = .010), and tendencies to lower levels of muscle activity in infraspinatus (20%, p = .066) and pectoralis major (34%, p = .092) at 60°/s during medial rotation. Young competitive swimmers...... rotations. Totally, 38 competitive swimmers (aged 13-17 years) participated, 19 were competitive swimmers with GJHS and 19 were age, sex and club matched swimmers without GJHS. Concentric isokinetic force in medial and lateral rotations were measured at 60°/s (5 repetitions) and 180°/s (10 repetitions...

Tibiofemoral loss of contact area but no changes in peak pressures after meniscectomy in a Lapine in vivo quadriceps force transfer model.

Science.gov (United States)

Leumann, Andre; Fortuna, Rafael; Leonard, Tim; Valderrabano, Victor; Herzog, Walter

2015-01-01

The menisci are thought to modulate load transfer and to absorb shocks in the knee joint. No study has experimentally measured the meniscal functions in the intact, in vivo joint loaded by physiologically relevant muscular contractions. Right knee joints of seven New Zealand white rabbits were loaded using isometric contractions of the quadriceps femoris muscles controlled by femoral nerve stimulation. Isometric knee extensor torques at the maximal and two submaximal force levels were performed at knee angles of 70°, 90°, 110°, and 130°. Patellofemoral and tibiofemoral contact areas and pressure distributions were measured using Fuji Presensor film inserted above and below the menisci and also with the menisci removed. Meniscectomy was associated with a decrease in tibiofemoral contact area ranging from 30 to 70% and a corresponding increase in average contact pressures. Contact areas measured below the menisci were consistently larger than those measured on top of the menisci. Contact areas in the patellofemoral joint (PFJ), and peak pressures in tibiofemoral and PFJs, were not affected by meniscectomy. Contact areas and peak pressures in all joints depended crucially on knee joint angle and quadriceps force: The more flexed the knee joint was, the larger were the contact areas and the higher were the peak pressures. In agreement with the literature, removal of the menisci was associated with significant decreases in tibiofemoral contact area and corresponding increases in average contact pressures, but surprisingly, peak pressures remained unaffected, indicating that the function of the menisci is to distribute loads across a greater contact area.

Contact-impact algorithms on parallel computers

International Nuclear Information System (INIS)

Zhong Zhihua; Nilsson, Larsgunnar

1994-01-01

Contact-impact algorithms on parallel computers are discussed within the context of explicit finite element analysis. The algorithms concerned include a contact searching algorithm and an algorithm for contact force calculations. The contact searching algorithm is based on the territory concept of the general HITA algorithm. However, no distinction is made between different contact bodies, or between different contact surfaces. All contact segments from contact boundaries are taken as a single set. Hierarchy territories and contact territories are expanded. A three-dimensional bucket sort algorithm is used to sort contact nodes. The defence node algorithm is used in the calculation of contact forces. Both the contact searching algorithm and the defence node algorithm are implemented on the connection machine CM-200. The performance of the algorithms is examined under different circumstances, and numerical results are presented. ((orig.))

Molecular dynamics simulation of subnanometric tool-workpiece contact on a force sensor-integrated fast tool servo for ultra-precision microcutting

International Nuclear Information System (INIS)

Cai, Yindi; Chen, Yuan-Liu; Shimizu, Yuki; Ito, So; Gao, Wei; Zhang, Liangchi

2016-01-01

Highlights: • Subnanometric contact between a diamond tool and a copper workpiece surface is investigated by MD simulation. • A multi-relaxation time technique is proposed to eliminate the influence of the atom vibrations. • The accuracy of the elastic-plastic transition contact depth estimation is improved by observing the residual defects. • The simulation results are beneficial for optimization of the next-generation microcutting instruments. - Abstract: This paper investigates the contact characteristics between a copper workpiece and a diamond tool in a force sensor-integrated fast tool servo (FS-FTS) for single point diamond microcutting and in-process measurement of ultra-precision surface forms of the workpiece. Molecular dynamics (MD) simulations are carried out to identify the subnanometric elastic-plastic transition contact depth, at which the plastic deformation in the workpiece is initiated. This critical depth can be used to optimize the FS-FTS as well as the cutting/measurement process. It is clarified that the vibrations of the copper atoms in the MD model have a great influence on the subnanometric MD simulation results. A multi-relaxation time method is then proposed to reduce the influence of the atom vibrations based on the fact that the dominant vibration component has a certain period determined by the size of the MD model. It is also identified that for a subnanometric contact depth, the position of the tool tip for the contact force to be zero during the retracting operation of the tool does not correspond to the final depth of the permanent contact impression on the workpiece surface. The accuracy for identification of the transition contact depth is then improved by observing the residual defects on the workpiece surface after the tool retracting.

Effect of implanted doses of N+-ions on the contact resistance of copper contacts

International Nuclear Information System (INIS)

Dubravec, B.; Kovac, P.; Lipka, F.; Padysak, M.

1997-01-01

The paper deals with the effect of implanted doses of N + ions on the contact resistance. Dependencies of the contact resistance versus contact force R c =f(F c ) and microhardness of implanted surfaces were measured for three implanted profiles. The influence of the aggressive environs on the contact resistance of implanted contact is given too

Accurate measurement of Atomic Force Microscope cantilever deflection excluding tip-surface contact with application to force calibration

Energy Technology Data Exchange (ETDEWEB)

Slattery, Ashley D.; Blanch, Adam J.; Quinton, Jamie S.; Gibson, Christopher T., E-mail: christopher.gibson@flinders.edu.au

2013-08-15

calibrate the cantilever spring constant using the thermal noise method, allowing complete force calibration to be accurately performed without tip-sample contact. - Highlights: • A technique for determining AFM cantilever sensitivity is developed and tested. • The error on the method is between 2–5% and does not require tip surface contact. • The method is simple to implement and can be applied to any type of cantilever. • The current method can be used to determine the spring constant of the cantilever.

Fragmented medial coronoid process

International Nuclear Information System (INIS)

Juhasz, Cs.; Juhasz, T.

1997-01-01

Fragmented medial coronoid process: (FCP) is often considered to be part of the osteochondrosis dissecans complex, but trauma and growth discrepancies between the radius and ulna are proposed as causes. There is little to clinically differentiate FCP, from osteochondrosis dissecans (OCD) of the elbow. Pain on, flexion-extension of the elbow and lateral rotation of the paw is a little more consistent in FCP. Radiographic examination of the elbow is important despite the, fact that radiographic signs of the FCP are often nonspecific. Excessive osteoarthrosis and superimposition of the radial head and coronoid process make identification of the FCP difficult. Craniocaudal, flexed mediolateral and 25 degree craniocaudal-lateromedial views are necessary for diagnosis. Osteophyte production is more dramatic with FCP than with OCD and suggests therefore the occurrence of OCP in many cases. Although the detached process may be seen on any view, the oblique projection offers the least obstructed view. Exposure of the joint is identical to that for OCD, that means a medial approach with osteotomy of the epicondyle. In most cases the process is loose enough to be readily apparent, but in some it is necessary to exert force on the process in order to find the cleavage plane. It is necessary to remove the osteophytes as well and to inspect and irrigate the joint carefully to remove cartilage fragments before closure. Confinement is advisable for 4 weeks before returning the dog to normal activity. The outlook for function is good if the FCP is removed before secondary degenerative joint disease is well established

Traumatic posterior root tear of the medial meniscus in patients with severe medial instability of the knee.

Science.gov (United States)

Ra, Ho Jong; Ha, Jeong Ku; Jang, Ho Su; Kim, Jin Goo

2015-10-01

To examine the incidence and diagnostic rate of traumatic medial meniscus posterior root tear associated with severe medial instability and to evaluate the effectiveness of pullout repair. From 2007 to 2011, 51 patients who underwent operation due to multiple ligament injuries including medial collateral ligament rupture were reviewed retrospectively. The International Knee Documentation Committee (IKDC) subjective and Lysholm score were evaluated pre- and postoperatively. Postoperative magnetic resonance imaging (MRI) was performed, and if indicated, a second-look arthroscopic examination was conducted. Fourteen out of 51 patients were associated with severe medial instability. Seven patients were diagnosed with traumatic medial meniscus posterior root tear and underwent arthroscopic pullout repair. Five of them were missed at initial diagnosis using MRI. In seven patients, the mean Lysholm and IKDC subjective scores improved from 74.6 ± 10.3 and 47.6 ± 7.3 to 93.0 ± 3.7 and 91.6 ± 2.6, respectively. All showed complete healing of meniscus root on follow-up MRI and second-look arthroscopy. Medial meniscus posterior root tear may occur in severe medial instability from trauma. It is a common mistake that surgeons may not notice on the diagnosis of those injuries using MRI. Therefore, a high index of suspicion is required for the diagnosis of medial meniscus posterior root tear in this type of injuries. The traumatic medial meniscus posterior root tear could be healed successfully using arthroscopic pullout repair technique. The possibility of the medial meniscus posterior root tear should be considered in severe medial instability and arthroscopic pullout repair can be an effective option for treatment. Case series with no comparison group, Level IV.

A Facile All-Solution-Processed Surface with High Water Contact Angle and High Water Adhesive Force.

Science.gov (United States)

Chen, Mei; Hu, Wei; Liang, Xiao; Zou, Cheng; Li, Fasheng; Zhang, Lanying; Chen, Feiwu; Yang, Huai

2017-07-12

A series of sticky superhydrophobicity surfaces with high water contact angle and high water adhesive force is facilely prepared via an all-solution-processed method based on polymerization-induced phase separation between liquid crystals (LCs) and epoxy resin, which produces layers of epoxy microspheres (EMSs) with nanofolds on the surface of a substrate. The morphologies and size distributions of EMSs are confirmed by scanning electron microscopy. Results reveal that the obtained EMS coated-surface exhibits high apparent contact angle of 152.0° and high water adhesive force up to 117.6 μN. By varying the composition of the sample or preparing conditions, the sizes of the produced EMSs can be artificially regulated and, thus, control the wetting properties and water adhesive behaviors. Also, the sticky superhydrophobic surface exhibits excellent chemical stability, as well as long-term durability. Water droplet transportation experiments further prove that the as-made surface can be effectively used as a mechanical hand for water transportation applications. Based on this, it is believed that the simple method proposed in this paper will pave a new way for producing a sticky superhydrophobic surface and obtain a wide range of use.

Arthroscopic partial medial meniscectomy

Directory of Open Access Journals (Sweden)

Dašić Žarko

2011-01-01

Full Text Available Background/Aim. Meniscal injuries are common in professional or recreational sports as well as in daily activities. If meniscal lesions lead to physical impairment they usually require surgical treatment. Arthroscopic treatment of meniscal injuries is one of the most often performed orthopedic operative procedures. Methods. The study analyzed the results of arthroscopic partial medial meniscectomy in 213 patients in a 24-month period, from 2006, to 2008. Results. In our series of arthroscopically treated medial meniscus tears we noted 78 (36.62% vertical complete bucket handle lesions, 19 (8.92% vertical incomplete lesions, 18 (8.45% longitudinal tears, 35 (16.43% oblique tears, 18 (8.45% complex degenerative lesions, 17 (7.98% radial lesions and 28 (13.14% horisontal lesions. Mean preoperative International Knee Documentation Committee (IKDC score was 49.81%, 1 month after the arthroscopic partial medial meniscectomy the mean IKDC score was 84.08%, and 6 months after mean IKDC score was 90.36%. Six months after the procedure 197 (92.49% of patients had good or excellent subjective postoperative clinical outcomes, while 14 (6.57% patients subjectively did not notice a significant improvement after the intervention, and 2 (0.93% patients had no subjective improvement after the partial medial meniscectomy at all. Conclusion. Arthroscopic partial medial meniscetomy is minimally invasive diagnostic and therapeutic procedure and in well selected cases is a method of choice for treatment of medial meniscus injuries when repair techniques are not a viable option. It has small rate of complications, low morbidity and fast rehabilitation.

Correlation of the SLAP lesion with lesions of the medial sheath of the biceps tendon and intra-articular subscapularis tendon

Directory of Open Access Journals (Sweden)

Bennett William

2009-01-01

Full Text Available Background: Superior labral anterior to posterior (SLAP lesions have been well described in the literature and are thought to be secondary to traction injuries to the biceps anchor and/or falls on the outstretched arm. The pulley has recently been described as a structure that aids in the prevention of biceps instability. The intra-articular subscapularis insertion (IASS has been noted to contribute to the robust nature of the medial sheath. The purpose of the study was to determine a potential correlation of SLAP lesions and pulley lesions with/without IASS lesions, (hereafter referred to as medial sheath as forces that can disrupt the biceps anchor and may also disrupt structures of the medial sheath or vice-versa. Materials and Methods: Three hundred and sixteen consecutive shoulder arthroscopies performed by one surgeon were reviewed retrospectively. Operative reports and arthroscopic pictures were carefully reviewed with particular attention paid to the labral and pulley pathology. Selection bias was noted as the author had never operated primarily for a Type 1 SLAP lesion. Following, however, and as such, the exclusion criteria, was a Type 1 SLAP. Results: There were a total of 30 SLAP lesions and a total of 126 medial sheath lesions. There were 13 patients who had both SLAP and medial sheath lesions. There were 17 patients who had a SLAP lesion without a medial sheath lesion. There were 96 medial sheath lesions without a SLAP. A comparison of rates between patients who had a medial sheath lesion with a SLAP and those who had a medial sheath lesion without a SLAP, for the 316 patients, and when tested with a Fisher exact test revealed that there was no statistical significance, P = 0.673. The prevalence of SLAP lesions in this population of 316 patients was 9.4%, Buford 1%, medial sheath lesions 39%, and SLAP and medial sheath lesions 4%. Interestingly, there were three Buford complexes, all associated with a SLAP and one Buford complex

Custom-Made Foot Orthoses Decrease Medial Foot Loading During Drop Jump in Individuals With Patellofemoral Pain

DEFF Research Database (Denmark)

Rathleff, Michael S; Richter, Camilla; Brushøj, Christoffer

2016-01-01

OBJECTIVE: To investigate the effect of foot orthoses on medial-to-lateral plantar forces during drop jump and single leg squat, and second, to explore the self-reported change in symptoms after 12 weeks of wearing the orthoses in individuals with patellofemoral pain (PFP). DESIGN: Cohort study...... with 12 weeks of follow-up. SETTING: Hospital setting. PARTICIPANTS: 23 adults with PFP. INTERVENTIONS: Custom-made foot orthoses. MAIN OUTCOME MEASURES: Foot loading (plantar pressure) was collected from the most painful side during drop jump and single leg squat using pressure sensitive Pedar insoles....... Primary outcome was the medial-to-lateral peak force under the forefoot during drop jump. The PFP syndrome severity score was used to measure self-reported improvement from baseline to follow-up. RESULTS: Orthoses were associated with a significant 2.9%-point (95% confidence intervals: 0.7-5.1) reduction...

Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

International Nuclear Information System (INIS)

Czaplewski, David A; Nordquist, Christopher D; Dyck, Christopher W; Patrizi, Gary A; Kraus, Garth M; Cowan, William D

2012-01-01

We present lifetime limitations and failure analysis of many packaged RF MEMS ohmic contacting switches with Au–Au, Au–Ir, and Au–Pt contact materials operating with 100 µN of contact force per contact in hermetically sealed glass wall packages. All metals were tested using the same switch design in a controlled environment to provide a comparison between the performance of the different materials and their corresponding failure mechanisms. The switch lifetimes of the different contact materials varied from several hundred cycles to 200 million cycles with different mechanisms causing failures for different contact materials. Switches with Au–Au contacts failed due to adhesion when thoroughly cleaned while switches with dissimilar metal contacts (Au–Ir and Au–Pt) operated without adhesion failures but failed due to carbon accumulation on the contacts even in a clean, packaged environment as a result of the catalytic behavior of the contact materials. Switch lifetimes correlated inversely with catalytic behavior of the contact metals. The data suggests the path to increase switch lifetime is to use favorable catalytic materials as contacts, design switches with higher contact forces to break through any residual contamination, and use cleaner, probably smaller, packages. (paper)

Radiographic evaluation of the canine elbow joint with special reference to the medial humeral condyle and the medial coronoid process

International Nuclear Information System (INIS)

Voorhout, G.; Hazewinkel, H.A.W.

1987-01-01

The results of radiographic examination of clinically affected elbow joints in 14 young, large-breed dogs, including standard and oblique projections and linear tomography, were compared with the findings of medial arthrotomy. Radiographs revealed arthrosis (13 dogs), osteochondrosis of the medial humeral condyle (2 dogs), fragmentation of the medial coronoid process (5 dogs), and a combination of osteochondrosis of the medial humeral condyle and fragmentation of the medial coronoid process (2 dogs). In one dog fissures in the medial coronoid process and in another dog a linear radiopacity along the articular surface of the medial coronoid process were found. In three dogs both medial humeral condyle and medial coronoid process appeared normal. The radiographic findings were confirmed during surgery in 11 dogs. Cartilage erosion of the medial humeral condyle in two dogs and of the medial coronoid process in one dog had not resulted in radiographically visible abnormalities. Radiographic examination of the elbow joints in young, large-breed dogs should include standard mediolateral and craniocaudal projections, a mediolateral projection with the joint maximally extended and the leg supinated 15°, and a craniolateral-to-caudomedial projection

The Relationship between Chondromalacia Patella, Medial Meniscal Tear and Medial Periarticular Bursitis in Patients with Osteoarthritis.

Science.gov (United States)

Resorlu, Mustafa; Doner, Davut; Karatag, Ozan; Toprak, Canan Akgun

2017-12-01

This study investigated the presence of bursitis in the medial compartment of the knee (pes anserine, semimembranosus-tibial collateral ligament, and medial collateral ligament bursa) in osteoarthritis, chondromalacia patella and medial meniscal tears. Radiological findings of 100 patients undergoing magnetic resonance imaging with a preliminary diagnosis of knee pain were retrospectively evaluated by two radiologists. The first radiologist assessed all patients in terms of osteoarthritis, chondromalacia patella and medial meniscal tear. The second radiologist was blinded to these results and assessed the presence of bursitis in all patients. Mild osteoarthritis (grade I and II) was determined in 55 patients and severe osteoarthritis (grade III and IV) in 45 cases. At retropatellar cartilage evaluation, 25 patients were assessed as normal, while 29 patients were diagnosed with mild chondromalacia patella (grade I and II) and 46 with severe chondromalacia patella (grade III and IV). Medial meniscus tear was determined in 51 patients. Severe osteoarthritis and chondromalacia patella were positively correlated with meniscal tear (p chondromalacia patella (p = 0.023 and p = 0.479, respectively). Evaluation of lateral compartment bursae revealed lateral collateral ligament bursitis in 2 patients and iliotibial bursitis in 5 patients. We observed a greater prevalence of bursitis in the medial compartment of the knee in patients with severe osteoarthritis and medial meniscus tear.

Influence of step rate and quadriceps load distribution on patellofemoral cartilage contact pressures during running.

Science.gov (United States)

Lenhart, Rachel L; Smith, Colin R; Vignos, Michael F; Kaiser, Jarred; Heiderscheit, Bryan C; Thelen, Darryl G

2015-08-20

Interventions used to treat patellofemoral pain in runners are often designed to alter patellofemoral mechanics. This study used a computational model to investigate the influence of two interventions, step rate manipulation and quadriceps strengthening, on patellofemoral contact pressures during running. Running mechanics were analyzed using a lower extremity musculoskeletal model that included a knee with six degree-of-freedom tibiofemoral and patellofemoral joints. An elastic foundation model was used to compute articular contact pressures. The lower extremity model was scaled to anthropometric dimensions of 22 healthy adults, who ran on an instrumented treadmill at 90%, 100% and 110% of their preferred step rate. Numerical optimization was then used to predict the muscle forces, secondary tibiofemoral kinematics and all patellofemoral kinematics that would generate the measured primary hip, knee and ankle joint accelerations. Mean and peak patella contact pressures reached 5.0 and 9.7MPa during the midstance phase of running. Increasing step rate by 10% significantly reduced mean contact pressures by 10.4% and contact area by 7.4%, but had small effects on lateral patellar translation and tilt. Enhancing vastus medialis strength did not substantially affect pressure magnitudes or lateral patellar translation, but did shift contact pressure medially toward the patellar median ridge. Thus, the model suggests that step rate tends to primarily modulate the magnitude of contact pressure and contact area, while vastus medialis strengthening has the potential to alter mediolateral pressure locations. These results are relevant to consider in the design of interventions used to prevent or treat patellofemoral pain in runners. Copyright © 2015 Elsevier Ltd. All rights reserved.

Contact Estimation in Robot Interaction

Directory of Open Access Journals (Sweden)

Filippo D'Ippolito

2014-07-01

Full Text Available In the paper, safety issues are examined in a scenario in which a robot manipulator and a human perform the same task in the same workspace. During the task execution, the human should be able to physically interact with the robot, and in this case an estimation algorithm for both interaction forces and a contact point is proposed in order to guarantee safety conditions. The method, starting from residual joint torque estimation, allows both direct and adaptive computation of the contact point and force, based on a principle of equivalence of the contact forces. At the same time, all the unintended contacts must be avoided, and a suitable post-collision strategy is considered to move the robot away from the collision area or else to reduce impact effects. Proper experimental tests have demonstrated the applicability in practice of both the post-impact strategy and the estimation algorithms; furthermore, experiments demonstrate the different behaviour resulting from the adaptation of the contact point as opposed to direct calculation.

The variable contact pressure influence on the tensile force in the process of strip sliding in the flat die in ironing

Directory of Open Access Journals (Sweden)

Milan Djordjević

2016-07-01

Full Text Available Possibilities to influence the deep drawing process during its duration are limited and generally consist of influences at the flange of the thin sheet, mainly by the contact pressure (the blank holding force. The common characteristics of previous investigations were setting of the fixed values of the blank holding force or the holder's pressure within the ironing tool. The objective of this investigation was the continuous setting of the variable pressure during the sliding process, via the preset functions, in order to analyze the variable pressure influence on the ironing process. This is why an experimental computerized device was designed and constructed for analyzing the influence of the variable contact pressure on the sliding process of the model strip during the flat-die test. The multi-parameter experiment was conducted; various materials of the tested pieces were applied (primarily thin sheet made of Al alloys and low-carbon steels sheet, with and without coating; different versions of the tool's contact elements were used, with various friction regimes and influential parameters (variable contact pressure during the sliding process, etc.. This experimental device practically represents a simulator for realization and studying of the physical model of an important segment of the ironing process in the completely realistic conditions (materials, tools, etc.. The aim was to find the optimal combination of the variable contact pressure and the tribological parameters, so that the punch force, as one of the process output parameters, would have the minimal value, as well as to avoid the undesired effects during the forming (difficult sliding of the flange, appearance of thin sheet's wrinkling, structural destruction, etc.. Understanding the mutual dependence of the holder's variable pressure and other influences should enable improvement of the ironing process control and should contribute to better understanding of the phenomena

Changes in motor unit recruitment strategy during pain alters force direction.

Science.gov (United States)

Tucker, Kylie J; Hodges, Paul W

2010-10-01

Motor unit (MU) recruitment is altered (decreased discharge rate and cessation of discharge in some units, and recruitment of new units) in force-matched contractions during pain compared to contractions performed before pain. As MU's within a motoneurone pool have different force direction properties we hypothesised that altered MU recruitment during experimental knee pain would change the force vector (total force (F(T)): amplitude and angle) generated by the quadriceps. Force was produced at two levels during 1 × 60-s and 3 × 10-s isometric contractions of knee extensors, and recorded by two force transducers at right angles. This enabled calculation of both F(E) (extension force) and F(T). MU recruitment was recorded from the medial and lateral vastii with four fine-wire electrodes. Pain was induced by hypertonic saline injection in the infra-patella fat pad. Nine subjects matched F(E) and six subjects also matched both medial and lateral forces (F(T)) before and during pain. Changes in MU discharge pattern (decreased discharge rate (Precruitment of new units) during pain were associated with a ∼5° change in absolute force angle. As force angle changed in both directions (left/right) for individual subjects with pain there was no change in average F(T) amplitude between conditions. When both medial and lateral forces were matched MU discharge rate decreased (Punits ceased firing or were newly recruited during pain. Change in motoneurone recruitment during pain alters direction of muscle force. This may be a strategy to avoid pain or protect the painful part. Copyright © 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.

Foot medial longitudinal-arch deformation during quiet standing and gait in subjects with medial tibial stress syndrome

DEFF Research Database (Denmark)

Bandholm, Thomas Quaade; Boysen, Lisbeth; Haugaard, Stine

2008-01-01

The objective of this study was to investigate (1) if subjects with medial tibial stress syndrome demonstrate increased navicular drop and medial longitudinal-arch deformation during quiet standing and gait compared with healthy subjects, and (2) the relationship between medial longitudinal-arch ...

The Relationship between Chondromalacia Patella, Medial Meniscal Tear and Medial Periarticular Bursitis in Patients with Osteoarthritis

Science.gov (United States)

Doner, Davut; Karatag, Ozan; Toprak, Canan Akgun

2017-01-01

Abstract Background This study investigated the presence of bursitis in the medial compartment of the knee (pes anserine, semimembranosus-tibial collateral ligament, and medial collateral ligament bursa) in osteoarthritis, chondromalacia patella and medial meniscal tears. Patients and methods Radiological findings of 100 patients undergoing magnetic resonance imaging with a preliminary diagnosis of knee pain were retrospectively evaluated by two radiologists. The first radiologist assessed all patients in terms of osteoarthritis, chondromalacia patella and medial meniscal tear. The second radiologist was blinded to these results and assessed the presence of bursitis in all patients. Results Mild osteoarthritis (grade I and II) was determined in 55 patients and severe osteoarthritis (grade III and IV) in 45 cases. At retropatellar cartilage evaluation, 25 patients were assessed as normal, while 29 patients were diagnosed with mild chondromalacia patella (grade I and II) and 46 with severe chondromalacia patella (grade III and IV). Medial meniscus tear was determined in 51 patients. Severe osteoarthritis and chondromalacia patella were positively correlated with meniscal tear (p chondromalacia patella (p = 0.023 and p = 0.479, respectively). Evaluation of lateral compartment bursae revealed lateral collateral ligament bursitis in 2 patients and iliotibial bursitis in 5 patients. Conclusions We observed a greater prevalence of bursitis in the medial compartment of the knee in patients with severe osteoarthritis and medial meniscus tear. PMID:29333118

Intraarticular arthrofibrosis of the knee alters patellofemoral contact biomechanics.

Science.gov (United States)

Mikula, Jacob D; Slette, Erik L; Dahl, Kimi D; Montgomery, Scott R; Dornan, Grant J; O'Brien, Luke; Turnbull, Travis Lee; Hackett, Thomas R

2017-12-19

Arthrofibrosis in the suprapatellar pouch and anterior interval can develop after knee injury or surgery, resulting in anterior knee pain. These adhesions have not been biomechanically characterized. The biomechanical effects of adhesions in the suprapatellar pouch and anterior interval during simulated quadriceps muscle contraction from 0 to 90° of knee flexion were assessed. Adhesions of the suprapatellar pouch and anterior interval were hypothesized to alter the patellofemoral contact biomechanics and increase the patellofemoral contact force compared to no adhesions. Across all flexion angles, suprapatellar adhesions increased the patellofemoral contact force compared to no adhesions by a mean of 80 N. Similarly, anterior interval adhesions increased the contact force by a mean of 36 N. Combined suprapatellar and anterior interval adhesions increased the mean patellofemoral contact force by 120 N. Suprapatellar adhesions resulted in a proximally translated patella from 0 to 60°, and anterior interval adhesions resulted in a distally translated patella at all flexion angles other than 15° (p patellofemoral contact forces were significantly increased by simulated adhesions in the suprapatellar pouch and anterior interval. Anterior knee pain and osteoarthritis may result from an increase in patellofemoral contact force due to patellar and quadriceps tendon adhesions. For these patients, arthroscopic lysis of adhesions may be beneficial.

Real-time deflection and friction force imaging by bimorph-based resonance-type high-speed scanning force microscopy in the contact mode.

Science.gov (United States)

Cai, Wei; Fan, Haiyun; Zhao, Jianyong; Shang, Guangyi

2014-01-01

We report herein an alternative high-speed scanning force microscopy method in the contact mode based on a resonance-type piezoelectric bimorph scanner. The experimental setup, the modified optical beam deflection scheme suitable for smaller cantilevers, and a high-speed control program for simultaneous data capture are described in detail. The feature of the method is that the deflection and friction force images of the sample surface can be obtained simultaneously in real time. Images of various samples (e.g., a test grating, a thin gold film, and fluorine-doped tin oxide-coated glass slides) are acquired successfully. The imaging rate is 25 frames per second, and the average scan speed reaches a value of approximately 2.5 cm/s. The method combines the advantages of both observing the dynamic processes of the sample surface and monitoring the frictional properties on the nanometer scale. 07.79.Lh; 07.79.Sp; 68.37.Ps.

Effect of graft shape in lateral column lengthening on tarsal bone position and subtalar and talonavicular contact pressure in a cadaveric flatfoot model.

Science.gov (United States)

Campbell, Sean T; Reese, Keri A; Ross, Steven D; McGarry, Michelle H; Leba, Thu-Ba; Lee, Thay Q

2014-11-01

Lateral column lengthening (LCL) has been used for correction of flatfoot deformity. The purpose of this study was to determine the effect of LCL graft shape on tarsal bone position and talonavicular and subtalar joint pressure. A flatfoot model was created in 6 cadaveric specimens. Corrective LCL was performed using a rectangular graft or a trapezoidal graft with the broad surface oriented dorsally, laterally, or plantarly. Bony surface markers were digitized to calculate angular parameters used in the evaluation of flatfoot deformity. Contact pressure and area in the subtalar and talonavicular joints were also recorded. All measurements were carried out under multiple axial loads in the intact and flatfoot conditions, and following LCL with each graft shape. Flatfoot creation resulted in significant changes in arch collapse and forefoot abduction. LCL with a rectangular graft best corrected these parameters, while a laterally oriented trapezoidal graft provided some correction. Talonavicular contact pressure was unchanged after flatfoot creation, and was significantly less than intact after LCL. Subtalar contact pressure decreased in some conditions after flatfoot creation, and decreased further after LCL. LCL with a rectangular graft best restored tarsal bone orientation in a cadaveric flatfoot model. The decreases in talonavicular pressure likely represent redistribution of force from the medial to lateral foot. When performing LCL for flatfoot deformity, increased bone graft volume medially better restores tarsal bone position. One way of achieving this is through the use of a rectangular graft as opposed to a trapezoidal graft. © The Author(s) 2014.

Effect of hoof angle on joint contact area in the equine metacarpophalangeal joint following simulated impact loading ex vivo.

Science.gov (United States)

McCarty, C A; Thomason, J J; Gordon, K; Hurtig, M; Bignell, W

2015-11-01

To add to the existing data on impact loading of the metacarpophalangeal (MCP) joint as a precursor to assessing the potential role of impact in joint disease. To examine the effect of impact loading on contact areas of the first phalanx (P1) and proximal sesamoids (PS) with the third metacarpal (McIII) under 3 hoof-strike conditions (toe-first, flat, heel-first). Randomised, repeated controlled experiment using cadaver material. Eight cadaver limbs were subjected to randomised, repeated controlled trials where the hoof was struck by a pendulum impact machine (impact velocity 3.55 m/s) under 3 strike conditions. Data from pressure sensitive film placed over medial and lateral McIII condyles and lateromedially across the dorsal aspect of McIII were quantified: total areas of P1 and PS contact (cm(2) ) at maximum recorded pressure; centroid locations of contact areas relative to the sagittal ridge (cm) and transverse ridge (cm) and dispersion of pixels (cm(4) ) for each McIII condyle (medial/lateral). The effect of the strike conditions on each variable were statistically tested using repeated-measures ANOVA (α = 0.05). Contact area between P1 and McIII condyles fell in well-defined areas bounded by the sagittal and transverse ridge, contact areas from PS were smaller and widely dispersed across McIII palmar border. Ratio of contact area of P1 to PS was 2.83 (Pcontact area (P>0.54) CONCLUSIONS: Contact at impact (primarily from P1 and distally situated on McIII), contrasts with contact areas at midstance from both P1 and PS, symmetrically placed. Under impact, the greatest contact area was on the dorsal aspect of the medial condyle and coincides with the area subjected to the greatest increase in subchondral bone stiffening in joint disease. © 2014 EVJ Ltd.

Sliding friction: From microscopic contacts to Amontons’ law

OpenAIRE

Weber, B.A.

2017-01-01

Most engineers describe sliding friction using the friction coefficient, the ratio of frictional force to normal force. While this proportionality is very simple, its origin is not trivial at all and has been subject of investigation for more than a century. The current consensus is that both frictional and normal force are proportional to the 'real contact area'. Surface roughness prevents surfaces from coming into full contact; the real contact area is simply the fraction of the apparent co...

UMAPRM: Uniformly sampling the medial axis

KAUST Repository

Yeh, Hsin-Yi Cindy

2014-05-01

© 2014 IEEE. Maintaining clearance, or distance from obstacles, is a vital component of successful motion planning algorithms. Maintaining high clearance often creates safer paths for robots. Contemporary sampling-based planning algorithms That utilize The medial axis, or The set of all points equidistant To Two or more obstacles, produce higher clearance paths. However, They are biased heavily Toward certain portions of The medial axis, sometimes ignoring parts critical To planning, e.g., specific Types of narrow passages. We introduce Uniform Medial Axis Probabilistic RoadMap (UMAPRM), a novel planning variant That generates samples uniformly on The medial axis of The free portion of Cspace. We Theoretically analyze The distribution generated by UMAPRM and show its uniformity. Our results show That UMAPRM\\'s distribution of samples along The medial axis is not only uniform but also preferable To other medial axis samplers in certain planning problems. We demonstrate That UMAPRM has negligible computational overhead over other sampling Techniques and can solve problems The others could not, e.g., a bug Trap. Finally, we demonstrate UMAPRM successfully generates higher clearance paths in The examples.

The relationship between chondromalacia patella, medial meniscal tear and medial periarticular bursitis in patients with osteoarthritis

OpenAIRE

Resorlu Mustafa; Doner Davut; Karatag Ozan; Toprak Canan Akgun

2017-01-01

Abstract Background This study investigated the presence of bursitis in the medial compartment of the knee (pes anserine, semimembranosus-tibial collateral ligament, and medial collateral ligament bursa) in osteoarthritis, chondromalacia patella and medial meniscal tears. Patients and methods Radiological findings of 100 patients undergoing magnetic resonance imaging with a preliminary diagnosis of knee pain were retrospectively evaluated by two radiologists. The first radiologist assessed al...

Effects of glovebox gloves on grip and key pinch strength and contact forces for simulated manual operations with three commonly used hand tools.

Science.gov (United States)

Sung, Peng-Cheng

2014-01-01

This study examined the effects of glovebox gloves for 11 females on maximum grip and key pinch strength and on contact forces generated from simulated tasks of a roller, a pair of tweezers and a crescent wrench. The independent variables were gloves fabricated of butyl, CSM/hypalon and neoprene materials; two glove thicknesses; and layers of gloves worn including single, double and triple gloving. CSM/hypalon and butyl gloves produced greater grip strength than the neoprene gloves. CSM/hypalon gloves also lowered contact forces for roller and wrench tasks. Single gloving and thin gloves improved hand strength performances. However, triple layers lowered contact forces for all tasks. Based on the evaluating results, selection and design recommendations of gloves for three hand tools were provided to minimise the effects on hand strength and optimise protection of the palmar hand in glovebox environments. To improve safety and health in the glovebox environments where gloves usage is a necessity, this study provides recommendations for selection and design of glovebox gloves for three hand tools including a roller, a pair of tweezers and a crescent wrench based on the results discovered in the experiments.

Medial structure generation for registration of anatomical structures

DEFF Research Database (Denmark)

Vera, Sergio; Gil, Debora; Kjer, Hans Martin

2017-01-01

structures. Methods for generation of medial structures, however, are prone to the generation of medial artifacts (spurious branches) that traditionally need to be pruned before the medial structure can be used for further computations. The act of pruning can affect main sections of the medial surface......Medial structures (skeletons and medial manifolds) have shown capacity to describe shape in a compact way. In the field of medical imaging, they have been employed to enrich the description of organ anatomy, to improve segmentation, or to describe the organ position in relation to surrounding...

Surface potential measurement on contact resistance of amorphous-InGaZnO thin film transistors by Kelvin probe force microscopy

Science.gov (United States)

Han, Zhiheng; Xu, Guangwei; Wang, Wei; Lu, Congyan; Lu, Nianduan; Ji, Zhuoyu; Li, Ling; Liu, Ming

2016-07-01

Contact resistance plays an important role in amorphous InGaZnO (a-IGZO) thin film transistors (TFTs). In this paper, the surface potential distributions along the channel have been measured by using Kelvin probe force microscopy (KPFM) on operating a-IGZO TFTs, and sharp potential drops at the edges of source and drain were observed. The source and drain contact resistances can be extracted by dividing sharp potential drops with the corresponding drain to source current. It is found that the contact resistances could not be neglected compared with the whole channel resistances in the a-IGZO TFT, and the contact resistances decrease remarkably with increasing gate biased voltage. Our results suggest that the contact resistances can be controlled by tuning the gate biased voltage. Moreover, a transition from gradual channel approximation to space charge region was observed through the surface potential map directly when TFT operating from linear regime to saturation regime.

Effect of time derivative of contact area on dynamic friction

OpenAIRE

Arakawa, Kazuo

2015-01-01

This study investigated dynamic friction during oblique impact of a golf ball by evaluating the ball’s angular velocity, contact force, and the contact area between the ball and target. The effect of the contact area on the angular velocities was evaluated, and the results indicated that the contact area plays an important role in dynamic friction. In this study, the dynamic friction force F was given by F= μN+μη.dA/dt, where μ is the coefficient of friction, N is the contact force, dA/dt is ...

Arrhythmia-free survival and pulmonary vein reconnection patterns after second-generation cryoballoon and contact-force radiofrequency pulmonary vein isolation.

Science.gov (United States)

Buist, Thomas J; Adiyaman, Ahmet; Smit, Jaap Jan J; Ramdat Misier, Anand R; Elvan, Arif

2018-06-01

The aim of this study was to compare second-generation cryoballoon and contact-force radiofrequency point-by-point pulmonary vein isolation (PVI) in atrial fibrillation (AF) patients with regard to pulmonary vein reconnection and arrhythmia-free survival. Altogether, 269 consecutive patients with drug-refractory AF undergoing PVI were included and randomly allocated to second-generation cryoballoon or contact-force point-by-point radiofrequency ablation. Median follow-up duration was 389 days (interquartile range 219-599). Mean age was 59 years (71% male); 136 patients underwent cryoballoon and 133 patients underwent radiofrequency ablation. Acute electrical PVI was 100% for both techniques. Procedure duration was significantly shorter in cryoballoon vs radiofrequency (166.5 vs 184.13 min P = 0.016). Complication rates were similar (6.0 vs 6.7%, P = 1.00). Single procedure freedom of atrial arrhythmias was significantly higher in cryoballoon as compared to radiofrequency (75.2 vs 57.4%, P = 0.013). In multivariate analysis, persistent AF, AF duration, and cryoballoon ablation were associated with freedom of atrial tachyarrhythmias. The number of repeat ablation procedures was significantly lower in the cryoballoon compared to radiofrequency (15.0 vs 24.3%, P = 0.045). At repeat ablation, pulmonary vein reconnection rate was significantly lower after cryoballoon as compared to radiofrequency ablation (36.8 vs 58.1%, P = 0.003). Improved arrhythmia-free survival and more durable pulmonary vein isolation is seen after PVI using second-generation cryoballoon as compared to contact-force radiofrequency, in patients with drug-refractory paroxysmal AF. Complication rates for both ablation techniques are low.

Contact angle and local wetting at contact line.

Science.gov (United States)

Li, Ri; Shan, Yanguang

2012-11-06

This theoretical study was motivated by recent experiments and theoretical work that had suggested the dependence of the static contact angle on the local wetting at the triple-phase contact line. We revisit this topic because the static contact angle as a local wetting parameter is still not widely understood and clearly known. To further clarify the relationship of the static contact angle with wetting, two approaches are applied to derive a general equation for the static contact angle of a droplet on a composite surface composed of heterogeneous components. A global approach based on the free surface energy of a thermodynamic system containing the droplet and solid surface shows the static contact angle as a function of local surface chemistry and local wetting state at the contact line. A local approach, in which only local forces acting on the contact line are considered, results in the same equation. The fact that the local approach agrees with the global approach further demonstrates the static contact angle as a local wetting parameter. Additionally, the study also suggests that the wetting described by the Wenzel and Cassie equations is also the local wetting of the contact line rather than the global wetting of the droplet.

In-vivo evaluation of the kinematic behavior of an artificial medial meniscus implant: A pilot study using open-MRI.

Science.gov (United States)

De Coninck, Tineke; Elsner, Jonathan J; Linder-Ganz, Eran; Cromheecke, Michiel; Shemesh, Maoz; Huysse, Wouter; Verdonk, René; Verstraete, Koenraad; Verdonk, Peter

2014-09-01

In this pilot study we wanted to evaluate the kinematics of a knee implanted with an artificial polycarbonate-urethane meniscus device, designed for medial meniscus replacement. The static kinematic behavior of the implant was compared to the natural medial meniscus of the non-operated knee. A second goal was to evaluate the motion pattern, the radial displacement and the deformation of the meniscal implant. Three patients with a polycarbonate-urethane implant were included in this prospective study. An open-MRI was used to track the location of the implant during static weight-bearing conditions, within a range of motion of 0° to 120° knee flexion. Knee kinematics were evaluated by measuring the tibiofemoral contact points and femoral roll-back. Meniscus measurements (both natural and artificial) included anterior-posterior meniscal movement, radial displacement, and meniscal height. No difference (P>0.05) was demonstrated in femoral roll-back and tibiofemoral contact points during knee flexion between the implanted and the non-operated knees. Meniscal measurements showed no significant difference in radial displacement and meniscal height (P>0.05) at all flexion angles, in both the implanted and non-operated knees. A significant difference (P ≤ 0.05) in anterior-posterior movement during flexion was observed between the two groups. In this pilot study, the artificial polycarbonate-urethane implant, indicated for medial meniscus replacement, had no influence on femoral roll-back and tibiofemoral contact points, thus suggesting that the joint maintains its static kinematic properties after implantation. Radial displacement and meniscal height were not different, but anterior-posterior movement was slightly different between the implant and the normal meniscus. Copyright © 2014 Elsevier Ltd. All rights reserved.

Lateral and medial epicondylitis: role of occupational factors.

Science.gov (United States)

Shiri, Rahman; Viikari-Juntura, Eira

2011-02-01

Epicondylitis is a common upper-extremity musculoskeletal disorder. It is most common at the age of 40-60 years. Epicondylitis seems to affect women more frequently than men. Diagnosis of epicondylitis is clinical and based on symptoms and findings of physical examination. The prevalence of lateral epicondylitis in the general populations is approximately 1.0-1.3% in men and 1.1-4.0% in women and that of medial epicondylitis is nearly 0.3-0.6% in men and 0.3-1.1% in women. The incidence rate of medical consultations has been estimated at 0.3-1.1 for lateral and 0.1 for medial epicondylitis per year per 100 subjects of general practice populations. Of occupational risk factors, forceful activities, high force combined with high repetition or awkward posture and awkward postures are associated with epicondylitis. The number of studies is limited to work-related psychosocial factors and the effects are not as consistent as those of physical load factors. Topical non-steroidal anti-inflammatory drugs, corticosteroid injections and acupuncture provide short-term beneficial effects. Workload modification should be considered, especially in manually strenuous jobs. According to clinical case series, surgical treatment has shown fair to good results; however, the efficacy of surgical treatment has not been evaluated in randomised controlled trials. Poorer prognosis of epicondylitis has been reported for individuals with high level of physical strain at work, non-neutral wrist postures during work activity and for those with the condition on the dominant elbow. Modification of physical factors could reduce the risk or improve the prognosis of epicondylitis. Copyright © 2011 Elsevier Ltd. All rights reserved.

A new distraction arthroplasty device using magnetic force; a cadaveric study.

Science.gov (United States)

Kamei, Goki; Ochi, Mitsuo; Okuhara, Atsushi; Fujimiya, Mineko; Deie, Masataka; Adachi, Nobuo; Nakamae, Atsuo; Nakasa, Tomoyuki; Ohkawa, Shingo; Takazawa, Kobun; Eguchi, Akio; Katou, Tomohiro; Takada, Tsuyoshi; Usman, Muhammad Andry

2013-04-01

It is difficult for an articular cartilage injury to repair spontaneously. There are many procedures for treating cartilage injury, however there is no standard procedure for middle-aged patients who have diffuse knee osteoarthritis, especially of the lateral compartment. Therefore, Ochi developed a new distraction device that uses magnetic power to enlarge a joint space and promote cartilage regeneration with microfracture. The purpose of this study is to evaluate this new distraction arthroplasty system by using the cadaveric knee. This study used ten knees from six cadavers that were embalmed by Thiel's methods. The medial and lateral joint space was measured by AP radiographic view before and after distraction, and after weight-bearing to evaluate the joint distraction. The contact pressure of the medial and lateral compartments at the knee extension position by using a prescale film system was measured before and after weight-bearing with a 15 or 30-kg weight-bearing load to evaluate the effectiveness of this device. The lateral joint space significantly increased from the pre-distraction to the post-distraction; however, it did not change significantly between post-distraction and post-weight-bearing. With a 15 or 30-kg weight-bearing load, the contact pressure of the lateral compartment significantly decreased from the pre-distraction to the post-distraction. The most important advantage of this device is that it maintains a continuous distraction tension and enables almost the full range of motion of the knee. We believe that joint distraction by using magnetic force can be a promising option for cartilage injury in middle-aged patients. Copyright © 2013 Elsevier Ltd. All rights reserved.

Friction and universal contact area law for randomly rough viscoelastic contacts.

Science.gov (United States)

Scaraggi, M; Persson, B N J

2015-03-18

We present accurate numerical results for the friction force and the contact area for a viscoelastic solid (rubber) in sliding contact with hard, randomly rough substrates. The rough surfaces are self-affine fractal with roughness over several decades in length scales. We calculate the contribution to the friction from the pulsating deformations induced by the substrate asperities. We also calculate how the area of real contact, A(v, p), depends on the sliding speed v and on the nominal contact pressure p, and we show how the contact area for any sliding speed can be obtained from a universal master curve A(p). The numerical results are found to be in good agreement with the predictions of an analytical contact mechanics theory.

Snapping Knee Caused by Medial Meniscal Cyst

Directory of Open Access Journals (Sweden)

Tsuyoshi Ohishi

2014-01-01

Full Text Available Snapping phenomenon around the medial aspect of the knee is rare. We present this case of snapping knee caused by the sartorius muscle over a large medial meniscal cyst in a 66-year-old female. Magnetic resonance images demonstrated a large medial meniscal cyst with a horizontal tear of the medial meniscus. Arthroscopic cyst decompression with limited meniscectomy resulted in the disappearance of snapping, and no recurrence of the cyst was observed during a 2-year follow-up period.

A Systematic Review of Clinical Functional Outcomes After Medial Stabilized Versus Non-Medial Stabilized Total Knee Joint Replacement

Directory of Open Access Journals (Sweden)

Tony Young

2018-04-01

Full Text Available Background Medial stabilized total knee joint replacement (TKJR construct is designed to closely replicate the kinematics of the knee. Little is known regarding comparison of clinical functional outcomes of patients utilising validated patient reported outcome measures (PROM after medial stabilized TKJR and other construct designs.PurposeTo perform a systematic review of the available literature related to the assessment of clinical functional outcomes following a TKJR employing a medial stabilized construct design.MethodsThe review was performed with a Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA algorithm. The literature search was performed using variouscombinations of keywords. The statistical analysis was completed using Review Manager (RevMan, Version 5.3.ResultsIn the nineteen unique studies identified, there were 2,448 medial stabilized TKJRs implanted in 2,195 participants, there were 1,777 TKJRs with non-medial stabilized design constructs implanted in 1,734 subjects. The final mean Knee Society Score (KSS value in the medial stabilized group was 89.92 compared to 90.76 in the non-medial stabilized group, with the final KSS mean value difference between the two groups was statistically significant and favored the non-medial stabilized group (SMD 0.21; 95% CI: 0.01 to 0.41; p = 004. The mean difference in the final WOMAC values between the two groups was also statistically significant and favored the medial stabilized group (SMD: −0.27; 95% CI: −0.47 to −0.07; p = 0.009. Moderate to high values (I2 of heterogeneity were observed during the statistical comparison of these functional outcomes.ConclusionBased on the small number of studies with appropriate statistical analysis, we are unable to reach a clear conclusion in the clinical performance of medial stabilized knee replacement construct.Level of EvidenceLevel II

Capillary force between wetted nanometric contacts and its application to atomic force microscopy.

Science.gov (United States)

Crassous, Jérôme; Ciccotti, Matteo; Charlaix, Elisabeth

2011-04-05

We extend to the case of perfect wetting the exact calculation of Orr et al. (J. Fluid. Mech. 1975, 67, 723) for a pendular ring connecting two dry surfaces. We derive an approximate analytical expression for the capillary force between two highly curved surfaces covered by a wetting liquid film. The domain of validity of this expression is assessed and extended by a custom-made numerical simulation based on the full exact mathematical description. In the case of attractive liquid-solid van der Waals interactions, the capillary force increases monotonically with decreasing vapor pressure up to several times its saturation value. This accurate description of the capillary force makes it possible to estimate the adhesion force between wet nanoparticles; it can also be used to quantitatively interpret pull-off forces measured by atomic force microscopy.

Head-disk interface nanotribology for Tbit/inch2 recording densities: near-contact and contact recording

Science.gov (United States)

Vakis, Antonis I.; Polycarpou, Andreas A.

2010-06-01

In the effort to achieve Tbit/inch2 recording densities, thermal fly-height control (TFC) nanotechnology was developed to effectively reduce the clearance (which is of the order of a few nanometres) at the head-disk interface (HDI) of hard-disk drives. In this work, we present a model of the HDI that can predict the dynamic flying and nanotribological contacting behaviour, allowing for accurate predictions and characterization of the operating regime as a function of TFC actuation. A geometric model for TFC is presented and an improved definition of contact at the interface is developed in the presence of nanoscale topographical roughness and dynamic microwaviness. A new methodology is proposed for the calculation of the nominal area of contact, which affects both near- and at-contact behaviour, while the stiffening of the air bearing force with TFC actuation is also accounted for. Slider behaviour is analysed by quantifying the approach, jump-to-contact, lubricant and solid contact regimes of operation and identifying the critical and optimum TFC actuations. The feasibility of near-contact, light molecularly thin lubricant contact versus solid contact recording is explored under the effect of the interfacial forces and stresses present at the HDI. The clearance and the state of vibrations are analysed and design guidelines are proposed for improved performance.

Head-disk interface nanotribology for Tbit/inch2 recording densities: near-contact and contact recording

International Nuclear Information System (INIS)

Vakis, Antonis I; Polycarpou, Andreas A

2010-01-01

In the effort to achieve Tbit/inch 2 recording densities, thermal fly-height control (TFC) nanotechnology was developed to effectively reduce the clearance (which is of the order of a few nanometres) at the head-disk interface (HDI) of hard-disk drives. In this work, we present a model of the HDI that can predict the dynamic flying and nanotribological contacting behaviour, allowing for accurate predictions and characterization of the operating regime as a function of TFC actuation. A geometric model for TFC is presented and an improved definition of contact at the interface is developed in the presence of nanoscale topographical roughness and dynamic microwaviness. A new methodology is proposed for the calculation of the nominal area of contact, which affects both near- and at-contact behaviour, while the stiffening of the air bearing force with TFC actuation is also accounted for. Slider behaviour is analysed by quantifying the approach, jump-to-contact, lubricant and solid contact regimes of operation and identifying the critical and optimum TFC actuations. The feasibility of near-contact, light molecularly thin lubricant contact versus solid contact recording is explored under the effect of the interfacial forces and stresses present at the HDI. The clearance and the state of vibrations are analysed and design guidelines are proposed for improved performance.

Abnormal tibiofemoral contact stress and its association with altered kinematics after center-center anterior cruciate ligament reconstruction: an in vitro study.

Science.gov (United States)

Imhauser, Carl; Mauro, Craig; Choi, Daniel; Rosenberg, Eric; Mathew, Stephen; Nguyen, Joseph; Ma, Yan; Wickiewicz, Thomas

2013-04-01

Abnormal tibiofemoral contact stress and aberrant kinematics may influence the progression of osteoarthritis in the anterior cruciate ligament (ACL)-deficient and the ACL-reconstructed knee. However, relationships between contact stress and kinematics after ACL reconstruction are poorly understood. Therefore, we posed the following research questions: (1) How do ACL deficiency and reconstruction affect the kinematics of and contact stress in the tibiofemoral joint? (2) What kinematic differences are associated with abnormal contact stress after ACL reconstruction? Center-center ACL reconstruction will not restore knee kinematics and contact stress. Correlations will exist between abnormal contact stress and aberrant kinematics after ACL reconstruction. Controlled laboratory study. Clinical tests of anterior and rotational stability were simulated on 11 cadaveric knees using an industrial robot. Tests were conducted with the ACL intact, sectioned, and after single-bundle ACL reconstruction using a quadrupled hamstring autograft with tunnels drilled through the center of the native footprints. Kinematics were recorded during the tests. Contact stress was continuously recorded from a stress transducer fixed to the tibial plateau, and mean contact stress was calculated regionally. ACL deficiency resulted in increased mean contact stress in the posterior sectors of the medial and lateral compartments under anterior and rotational loads, respectively. Reconstruction reduced stress in these locations; however, contact stress abnormalities remained. On average, kinematics were overconstrained after ACL reconstruction (≤1.8 mm and ≤2.6° in all directions). However, combinations of overconstrained and underconstrained motions in abduction/adduction and medial-lateral translation in response to combined moments, and anterior-posterior translation, medial-lateral translation, and axial rotation in response to an anterior load were associated with abnormal mean contact

Computational simulations of direct contact condensation as the driving force for water hammer

International Nuclear Information System (INIS)

Ceuca, Sabin-Cristian

2015-01-01

An analysis, based on Computer Simulations of the Direct Contact Condensation as the Driving Force for the Condensation Induced Water Hammer phenomenon is performed within this thesis. The goal of the work is to develop a mechanistic HTC model, with predictive capabilities for the simulation of horizontal or nearly horizontal two-phase ows with complex patterns including the e ect of interfacial heat and mass transfer. The newly developed HTC model was implemented into the system code ATHLET and into the CFD tools ANSYS CFX and OpenFOAM. Validation calculations have been performed for horizontal or nearly horizontal ows, where simulation results have been compared against the local measurement data such as void and temperature or area averaged data delivered by a wire mesh sensor.

Computational simulations of direct contact condensation as the driving force for water hammer

Energy Technology Data Exchange (ETDEWEB)

Ceuca, Sabin-Cristian

2015-04-27

An analysis, based on Computer Simulations of the Direct Contact Condensation as the Driving Force for the Condensation Induced Water Hammer phenomenon is performed within this thesis. The goal of the work is to develop a mechanistic HTC model, with predictive capabilities for the simulation of horizontal or nearly horizontal two-phase ows with complex patterns including the e ect of interfacial heat and mass transfer. The newly developed HTC model was implemented into the system code ATHLET and into the CFD tools ANSYS CFX and OpenFOAM. Validation calculations have been performed for horizontal or nearly horizontal ows, where simulation results have been compared against the local measurement data such as void and temperature or area averaged data delivered by a wire mesh sensor.

Static and kinetic friction force and surface roughness of different archwire-bracket sliding contacts.

Science.gov (United States)

Carrion-Vilches, Francisco J; Bermudez, María-Dolores; Fructuoso, Paula

2015-01-01

The aim of this study was to determine the static and kinetic friction forces of the contact bracket-archwire with different dental material compositions in order to select those materials with lower resistance to sliding. We carried out sliding friction tests by means of a universal testing machine following an experimental procedure as described in ASTM D1894 standard. We determined the static and kinetic friction forces under dry and lubricating conditions using an artificial saliva solution at 36.5ºC. The bracket-archwire pairs studied were: stainless steel-stainless steel; stainless steel-glass fiber composite; stainless steel-Nitinol 60; sapphire-stainless steel; sapphire-glass fiber composite; and sapphire-Nitinol 60. The best performance is obtained for Nitinol 60 archwire sliding against a stainless steel bracket, both under dry and lubricated conditions. These results are in agreement with the low surface roughness of Nitinol 60 with respect to the glass fiber composite archwire. The results described here contribute to establishing selection criteria for materials for dental archwire-brackets.

Attenuated increase in maximal force of rat medial gastrocnemius muscle after concurrent peak power and endurance training

NARCIS (Netherlands)

Furrer, R.; Jaspers, R.T.; Baggerman, H.L.; Bravenboer, N.; Lips, P.; de Haan, A.

2013-01-01

Improvement of muscle peak power and oxidative capacity are generally presumed to be mutually exclusive. However, this may not be valid by using fibre type-specific recruitment. Since rat medial gastrocnemius muscle (GM) is composed of high and low oxidative compartments which are recruited task

Medial cortex activity, self-reflection and depression.

Science.gov (United States)

Johnson, Marcia K; Nolen-Hoeksema, Susan; Mitchell, Karen J; Levin, Yael

2009-12-01

Using functional magnetic resonance imaging, we investigated neural activity associated with self-reflection in depressed [current major depressive episode (MDE)] and healthy control participants, focusing on medial cortex areas previously shown to be associated with self-reflection. Both the MDE and healthy control groups showed greater activity in anterior medial cortex (medial frontal gyrus, anterior cingulate gyrus) when cued to think about hopes and aspirations compared with duties and obligations, and greater activity in posterior medial cortex (precuneus, posterior cingulate) when cued to think about duties and obligations (Experiment 1). However, the MDE group showed less activity than controls in the same area of medial frontal cortex when self-referential cues were more ambiguous with respect to valence (Experiment 2), and less deactivation in a non-self-referential condition in both experiments. Furthermore, individual differences in rumination were positively correlated with activity in both anterior and posterior medial cortex during non-self-referential conditions. These results provide converging evidence for a dissociation of anterior and posterior medial cortex depending on the focus of self-relevant thought. They also provide neural evidence consistent with behavioral findings that depression is associated with disruption of positively valenced thoughts in response to ambiguous cues, and difficulty disengaging from self-reflection when it is appropriate to do so.

Loading of Hip Measured by Hip Contact Forces at Different Speeds of Walking and Running.

Science.gov (United States)

Giarmatzis, Georgios; Jonkers, Ilse; Wesseling, Mariska; Van Rossom, Sam; Verschueren, Sabine

2015-08-01

Exercise plays a pivotal role in maximizing peak bone mass in adulthood and maintaining it through aging, by imposing mechanical loading on the bone that can trigger bone mineralization and growth. The optimal type and intensity of exercise that best enhances bone strength remains, however, poorly characterized, partly because the exact peak loading of the bone produced by the diverse types of exercises is not known. By means of integrated motion capture as an input to dynamic simulations, contact forces acting on the hip of 20 young healthy adults were calculated during walking and running at different speeds. During walking, hip contact forces (HCFs) have a two-peak profile whereby the first peak increases from 4.22 body weight (BW) to 5.41 BW and the second from 4.37 BW to 5.74 BW, by increasing speed from 3 to 6 km/h. During running, there is only one peak HCF that increases from 7.49 BW to 10.01 BW, by increasing speed from 6 to 12 km/h. Speed related profiles of peak HCFs and ground reaction forces (GRFs) reveal a different progression of the two peaks during walking. Speed has a stronger impact on peak HCFs rather than on peak GRFs during walking and running, suggesting an increasing influence of muscle activity on peak HCF with increased speed. Moreover, results show that the first peak of HCF during walking can be predicted best by hip adduction moment, and the second peak of HCF by hip extension moment. During running, peak HCF can be best predicted by hip adduction moment. The present study contributes hereby to a better understanding of musculoskeletal loading during walking and running in a wide range of speeds, offering valuable information to clinicians and scientists exploring bone loading as a possible nonpharmacological osteogenic stimulus. © 2015 American Society for Bone and Mineral Research. © 2015 American Society for Bone and Mineral Research.

Force modulation for improved conductive-mode atomic force microscopy

NARCIS (Netherlands)

Koelmans, W.W.; Sebastian, Abu; Despont, Michel; Pozidis, Haris

We present an improved conductive-mode atomic force microscopy (C-AFM) method by modulating the applied loading force on the tip. Unreliable electrical contact and tip wear are the primary challenges for electrical characterization at the nanometer scale. The experiments show that force modulation

Abnormal tibiofemoral contact stress and its association with altered kinematics following center-center ACL reconstruction: an in vitro study

Science.gov (United States)

Imhauser, Carl; Mauro, Craig; Choi, Daniel; Rosenberg, Eric; Mathew, Stephen; Nguyen, Joseph; Ma, Yan; Wickiewicz, Thomas

2014-01-01

Background Abnormal tibiofemoral contact stress and aberrant kinematics may influence the progression of osteoarthritis in the ACL-deficient and the ACL-reconstructed knee. However, relationships between contact stress and kinematics following ACL reconstruction are poorly understood. Therefore, we posed the following research questions: (1) How do ACL deficiency and reconstruction affect kinematics of and contact stress in the tibiofemoral joint? (2) What kinematic differences are associated with abnormal contact stress following ACL reconstruction? Hypothesis/Purpose Center-center ACL reconstruction will not restore knee kinematics and contact stress. Correlations will exist between abnormal contact stress and aberrant kinematics following ACL reconstruction will exist. Study Design Controlled laboratory study Methods Clinical tests of anterior and rotational stability were simulated on eleven cadaveric knees using an industrial robot. Tests were conducted with the ACL intact, sectioned, and after single bundle ACL reconstruction using a quadrupled hamstring autograft with tunnels drilled through the center of the native footprints. Kinematics were recorded during the tests. Contact stress was continuously recorded from a stress transducer fixed to the tibial plateau and mean contact stress was calculated regionally. Results ACL deficiency resulted in increased mean contact stress in the posterior sectors of the medial and lateral compartments under anterior and rotational loads, respectively. Reconstruction reduced stress in these locations; however contact stress abnormalities remained. On average, kinematics were overconstrained following ACL reconstruction (≤1.8mm and ≤2.6° in all directions). However, combinations of overconstrained and underconstrained motions in ab/adduction and medial-lateral translation in response to combined moments, and axial rotation, anterior-posterior and medial-lateral translation in response to an anterior load were

Equilibrium contact angle or the most-stable contact angle?

Science.gov (United States)

Montes Ruiz-Cabello, F J; Rodríguez-Valverde, M A; Cabrerizo-Vílchez, M A

2014-04-01

It is well-established that the equilibrium contact angle in a thermodynamic framework is an "unattainable" contact angle. Instead, the most-stable contact angle obtained from mechanical stimuli of the system is indeed experimentally accessible. Monitoring the susceptibility of a sessile drop to a mechanical stimulus enables to identify the most stable drop configuration within the practical range of contact angle hysteresis. Two different stimuli may be used with sessile drops: mechanical vibration and tilting. The most stable drop against vibration should reveal the changeless contact angle but against the gravity force, it should reveal the highest resistance to slide down. After the corresponding mechanical stimulus, once the excited drop configuration is examined, the focus will be on the contact angle of the initial drop configuration. This methodology needs to map significantly the static drop configurations with different stable contact angles. The most-stable contact angle, together with the advancing and receding contact angles, completes the description of physically realizable configurations of a solid-liquid system. Since the most-stable contact angle is energetically significant, it may be used in the Wenzel, Cassie or Cassie-Baxter equations accordingly or for the surface energy evaluation. © 2013 Elsevier B.V. All rights reserved.

[SPECIFIC DIAGNOSTIC SIGNIFICANCE OF "RIPPLE SIGN" OF MEDIAL FEMORAL CONDYLE UNDER ARTHROSCOPE IN MEDIAL LONGITUDINAL MENISCAL TEARS].

Science.gov (United States)

Ren Shiyou; Sun, Limang; Chen, Guofei; Jiang, Changqing; Zhang, Xintao; Zhang Wentao

2015-01-01

To investigate the reliability of the "ripple sign" on the upper surface of the medial femoral condyle in the diagnosis of medial longitudinal meniscal tears under arthroscope. Between June 2013 and June 2014, 56 patients with knee injuries were included. There were 35 males and 21 females with an average age of 22.2 years (range, 12-38 years). The causes of injury were sports in 40 cases, falling in 10 cases, and traffic accident in 6 cases. The injury was located at the left knee in 22 cases and at the right knee in 34 cases. The disease duration was 10-40 days (mean, 20.2 days). Of 56 patients, 15 cases had simple medial meniscal injury; 41 cases had combined injuries, including anterior cruciate ligament injury in 38 cases, posterior cruciate ligament injury in 2 cases, and patellar dislocation in 1 case. The "ripple sign" was observed under arthroscope before operation. Repair of medial meniscal injury and reconstruction of cruciate ligament were performed. The positive "ripple sign" was seen under arthroscope in all patients, who were diagnosed to have longitudinal meniscal tears, including 23 cases of mild "ripple sign" , 28 cases of moderate "ripple sign", and 5 cases of severe "ripple sign". The "ripple sign" on the upper surface of the medial femoral condyle is a reliable diagnostic evidence of medial longitudinal meniscal tears.

A compact internal drum test rig for measurements of rolling contact forces between a single tread block and a substrate

NARCIS (Netherlands)

Lundberg, O.E.; Kari, L.; Lopez Arteaga, I.

2017-01-01

A novel test rig design is presented which enables detailed studies of the three force components generated in the impact and release phase of rolling contact between a tyre tread block and a substrate. The design of the compact internal drum test rig provides realistic impact and release angles for

The effect of elastic modulus on ablation catheter contact area.

Science.gov (United States)

Camp, Jon J; Linte, Cristian A; Rettmann, Maryam E; Sun, Deyu; Packer, Douglas L; Robb, Richard A; Holmes, David R

2015-02-21

Cardiac ablation consists of navigating a catheter into the heart and delivering RF energy to electrically isolate tissue regions that generate or propagate arrhythmia. Besides the challenges of accurate and precise targeting of the arrhythmic sites within the beating heart, limited information is currently available to the cardiologist regarding intricate electrode-tissue contact, which directly impacts the quality of produced lesions. Recent advances in ablation catheter design provide intra-procedural estimates of tissue-catheter contact force, but the most direct indicator of lesion quality for any particular energy level and duration is the tissue-catheter contact area, and that is a function of not only force, but catheter pose and material elasticity as well. In this experiment, we have employed real-time ultrasound (US) imaging to determine the complete interaction between the ablation electrode and tissue to accurately estimate contact, which will help to better understand the effect of catheter pose and position relative to the tissue. By simultaneously recording tracked position, force reading and US image of the ablation catheter, the differing material properties of polyvinyl alcohol cryogel [1] phantoms are shown to produce varying amounts of tissue depression and contact area (implying varying lesion quality) for equivalent force readings. We have shown that the elastic modulus significantly affects the surface-contact area between the catheter and tissue at any level of contact force. Thus we provide evidence that a prescribed level of catheter force may not always provide sufficient contact area to produce an effective ablation lesion in the prescribed ablation time.

Endoscopic medial maxillectomy breaking new frontiers.

Science.gov (United States)

Mohanty, Sanjeev; Gopinath, M

2013-07-01

Endoscopy has changed the perspective of rhinologist towards the nose. It has revolutionised the surgical management of sinonasal disorders. Sinus surgeries were the first to get the benefit of endoscope. Gradually the domain of endoscopic surgery extended to the management of sino nasal tumours. Traditionally medial maxillectomy was performed through lateral rhinotomy or mid facial degloving approach. Endoscopic medial maxillectomy has been advocated by a number of authors in the management of benign sino-nasal tumours. We present our experience of endoscopic medial maxillectomy in the management of sinonasal pathologies.

On the real-time estimation of the wheel-rail contact force by means of a new nonlinear estimator design model

Science.gov (United States)

Strano, Salvatore; Terzo, Mario

2018-05-01

The dynamics of the railway vehicles is strongly influenced by the interaction between the wheel and the rail. This kind of contact is affected by several conditioning factors such as vehicle speed, wear, adhesion level and, moreover, it is nonlinear. As a consequence, the modelling and the observation of this kind of phenomenon are complex tasks but, at the same time, they constitute a fundamental step for the estimation of the adhesion level or for the vehicle condition monitoring. This paper presents a novel technique for the real time estimation of the wheel-rail contact forces based on an estimator design model that takes into account the nonlinearities of the interaction by means of a fitting model functional to reproduce the contact mechanics in a wide range of slip and to be easily integrated in a complete model based estimator for railway vehicle.

Adhesive contact: from atomistic model to continuum model

International Nuclear Information System (INIS)

Fan Kang-Qi; Jia Jian-Yuan; Zhu Ying-Min; Zhang Xiu-Yan

2011-01-01

Two types of Lennard-Jones potential are widely used in modeling adhesive contacts. However, the relationships between the parameters of the two types of Lennard-Jones potential are not well defined. This paper employs a self-consistent method to derive the Lennard-Jones surface force law from the interatomic Lennard-Jones potential with emphasis on the relationships between the parameters. The effect of using correct parameters in the adhesion models is demonstrated in single sphere-flat contact via continuum models and an atomistic model. Furthermore, the adhesion hysteresis behaviour is investigated, and the S-shaped force-distance relation is revealed by the atomistic model. It shows that the adhesion hysteresis loop is generated by the jump-to-contact and jump-off-contact, which are illustrated by the S-shaped force-distance curve. (atomic and molecular physics)

Wear-less floating contact imaging of polymer surfaces

International Nuclear Information System (INIS)

Knoll, A; Rothuizen, H; Gotsmann, B; Duerig, U

2010-01-01

An atomic force microscopy (AFM) technique is described combining two operating modes that previously were mutually exclusive: gentle imaging of delicate surfaces requiring slow dynamic AFM techniques, and passive feedback contact mode AFM enabling ultra-fast imaging. A high-frequency force modulation is used to excite resonant modes in the MHz range of a highly compliant cantilever force sensor with a spring constant of 0.1 N m -1 . The high-order mode acts as a stiff system for modulating the tip-sample distance and a vibration amplitude of 1 nm is sufficient to overcome the adhesion interaction. The soft cantilever provides a force-controlled support for the vibrating tip, enabling high-speed intermittent contact force microscopy without feedback control of the cantilever bending. Using this technique, we were able to image delicate polymer surfaces and to completely suppress the formation of the ripple wear patterns that are commonly observed in contact AFM.

Minimizing tip-sample forces in jumping mode atomic force microscopy in liquid

Energy Technology Data Exchange (ETDEWEB)

Ortega-Esteban, A. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Horcas, I. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Hernando-Perez, M. [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Ares, P. [Nanotec Electronica S.L., Centro Empresarial Euronova 3, Ronda de Poniente 12, 28760 Tres Cantos, Madrid (Spain); Perez-Berna, A.J.; San Martin, C.; Carrascosa, J.L. [Centro Nacional de Biotecnologia (CNB-CSIC), Darwin 3, 28049 Madrid (Spain); Pablo, P.J. de [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Gomez-Herrero, J., E-mail: julio.gomez@uam.es [Departamento de Fisica de la Materia Condensada, C-3, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain)

2012-03-15

Control and minimization of tip-sample interaction forces are imperative tasks to maximize the performance of atomic force microscopy. In particular, when imaging soft biological matter in liquids, the cantilever dragging force prevents identification of the tip-sample mechanical contact, resulting in deleterious interaction with the specimen. In this work we present an improved jumping mode procedure that allows detecting the tip-sample contact with high accuracy, thus minimizing the scanning forces ({approx}100 pN) during the approach cycles. To illustrate this method we report images of human adenovirus and T7 bacteriophage particles which are prone to uncontrolled modifications when using conventional jumping mode. -- Highlights: Black-Right-Pointing-Pointer Improvement in atomic force microscopy in buffer solution. Black-Right-Pointing-Pointer Peak force detection. Black-Right-Pointing-Pointer Subtracting the cantilever dragging force. Black-Right-Pointing-Pointer Forces in the 100 pN range. Black-Right-Pointing-Pointer Imaging of delicate viruses with atomic force microscopy.

The Comparison of Forces Applied to the Knee Extensor Mechanism during Stance Phase of Gait in Flat Footed Females Three Different in-Shoe Orthotics

Directory of Open Access Journals (Sweden)

Mohsen Razeghi

2012-01-01

Full Text Available Objective: It has been postulated that subtalar position and movement would influence the function of the foot and the lower limb’s biomechanical alignment as a whole. The aim of this study was to compare the changes of force applied to the knee extensor mechanism of the female subjects while applying three different in-shoe orthotic appliances. Materials & Methods: Feiss Line test was used to assign a group of 10 healthy female subjects aged at 19-25 years as flat foot group. Retro reflective calibration and tracking markers were placed on the subjects over anatomically relevant locations. Kinematic and kinetic data were collected by employing a three dimensional motion capture system (Qualisys®Ltd, Sweden and a force platform (Kistler®, Switzerland respectively, while subjects walked at their preferred speed with 3 different in-shoe orthotics: simple insole, insole with medial arch support, insole with medial arch support and medial heel wedge, and insole with medial arch support and lateral forefoot wedge. Results: A statistically significant lower amount of the force applied to the extensor mechanism was found while applying medial arch support combined with lateral wedge (P=0.005. Conclusion: It could be concluded that changes of the different foot insoles would alter the force applied to the knee extensor mechanism. Results of this study emphasize the immediate effect of applying a medial arch support combined lateral wedge on reduction of the force applied to the extensor mechanism through which decrease a tendency towards musculoskeletal injuries.

An isolated dorso-medial dislocation of navicular bone: A case report.

Science.gov (United States)

Singh, Varun Kumar; Kashyap, Abhishek; Vargaonkar, Gauresh; Kumar, Ramesh

2015-03-01

An isolated dislocation of tarsal navicular is extremely rare injury. Usually it is associated with fracture of navicular itself or other tarsal bones of foot along with disruption of medial or lateral column of foot. Mechanism of injury is complex but usually a severe abduction force is required to produce such injury in a planter flexed foot. A 30 year old male presented with isolated navicular dislocation. Management required open reduction and fixation with k-wires. These injuries have specific complications including avascular necrosis of navicular and post-traumatic arthritis.

A comparison of hamstring muscle activity during different screening tests for non-contact ACL injury

DEFF Research Database (Denmark)

Husted, Rasmus S; Bencke, Jesper; Andersen, Lars Louis

2016-01-01

phenomenon and thereby observable independently of the type of clinical screening tests used is not known. This cross sectional study investigated the rank correlation of knee joint neuromuscular activity between three different ACL injury risk screening tests. METHODS: Sixty-two adolescent female elite......BACKGROUND: Reduced ability to activate the medial hamstring muscles during a sports-specific sidecutting movement has been found to be a potential risk factor for non-contact ACL injury. However, whether a reduced ability to activate the medial hamstring muscle is a general neuromuscular...... football and handball players (16.7±1.3years) participated in the study. Using surface electromyography (EMG) assessment, the neuromuscular activity of medial hamstring muscle (semitendinosus, ST), lateral hamstring muscle (biceps femoris, BF) and quadriceps muscle (vastus lateralis, VL) were monitored...

On the relationship between lower extremity muscles activation and peak vertical and posterior ground reaction forces during single leg drop landing.

Science.gov (United States)

Mahaki, M; Mi'mar, R; Mahaki, B

2015-10-01

Anterior cruciate ligament (ACL) injury continues to be an important medical issue for athletes participating in sports. Vertical and posterior ground reaction forces have received considerable attention for their potential influence on ACL injuries. The purpose of this study was to examine the relationship between electromyographic activity of lower extremity muscles and the peak vertical and posterior ground reaction forces during single leg drop landing. Thirteen physical education male students participated in this correlation study. Electromyographic activities of gluteus medius, biceps femoris, medial gastrocnemius, soleus as well as anterior tibialis muscles along with ground reaction forces were measured. Participants performed single-leg landing from a 0.3 m height on to a force platform. Landing was divided into two phases: 100 ms preceding ground contact and 100 ms proceeding ground contact. Pearson correlation test was used to determine the relationships between these muscles activity and peak vertical and posterior ground reaction forces. The results of the study indicated that the activity of soleus and tibialis anterior in pre-landing phase were positively correlated with peak vertical ground reaction force ([P≤0.04], [P≤0.008], respectively). However, no significant correlation was found between the activities of other muscles in pre-landing phase and peak vertical as well as peak posterior ground reaction forces. Also, no significant correlation was found between the activities of muscles in post-landing phase and peak vertical as well as peak posterior ground reaction forces. Soleus loading shifts the proximal tibia posterior at the knee joint and tibialis anterior prevent hyperporonation of the ankle, a mechanisms of ACL injury. Hence, neuromuscular training promoting preparatory muscle activity in these muscles may reduce the incidence of ACL injuries.

Medial collateral ligament healing one year after a concurrent medial collateral ligament and anterior cruciate ligament injury: an interdisciplinary study in rabbits.

Science.gov (United States)

Yamaji, T; Levine, R E; Woo, S L; Niyibizi, C; Kavalkovich, K W; Weaver-Green, C M

1996-03-01

The optimal treatment for concurrent injuries to the medial collateral and anterior cruciate ligaments has not been determined, despite numerous clinical and laboratory studies. The objective of this study was to examine the effect of surgical repair of the medial collateral ligament on its biomechanical and biochemical properties 52 weeks after such injuries. In the left knee of 12 skeletally mature New Zealand White rabbits, the medial collateral ligament was torn and the anterior cruciate ligament was transected and then reconstructed. This is an experimental model previously developed in our laboratory. In six rabbits, the torn ends of the medial collateral ligament were repaired, and in the remaining six rabbits, the ligament was not repaired. Fifty-two weeks after injury, we examined varus-valgus and anterior-posterior knee stability; structural properties of the femur-medial collateral ligament-tibia complex; and mechanical properties, collagen content, and mature collagen crosslinking of the medial collateral ligament. We could not detect significant differences between repair and nonrepair groups for any biomechanical or biochemical property. Our data support clinical findings that when the medial collateral and anterior cruciate ligaments are injured concurrently and the anterior cruciate ligament is reconstructed, conservative treatment of the ruptured medial collateral ligament can result in successful healing.

Sliding force measurements of the LHC RF contact Plug In Modules at 15 K and in UHV

CERN Document Server

Artoos, K; Renaglia, T; CERN. Geneva. TS Department

2008-01-01

Some sliding RF contacts mounted in the Plug In Modules in the LHC interconnects failed during a thermal cycle between 4.2 K and room temperature. Some of the gold-coated copper-beryllium RF fingers buckled during the warm up of the machine, indicating that one or more parameters during operation (e.g. the friction coefficient) could be different from what was used in the calculations. This report describes the measurement of the longitudinal forces acting on the sliding RF fingers at operating vacuum and temperatures.

Sliding force measurements on the LHC RF contact Plug In Modules at 15 K and in UHV

CERN Document Server

Artoos, K; Renaglia, T

2008-01-01

Some sliding RF contacts mounted in the Plug In Modules in the LHC interconnects failed during a thermal cycle between 4.2 K and room temperature. Gold-coated copperberyllium RF fingers buckled during the warm up of the machine, indicating that one or more parameters during operation (e.g. the friction coefficient under vacuum) could be different from what was used in the calculations. This report describes the measurement of the longitudinal forces acting on the sliding RF fingers at operating vacuum and temperatures.

Contact stiffness considerations when simulating tyre/road noise

Science.gov (United States)

Winroth, Julia; Kropp, Wolfgang; Hoever, Carsten; Höstmad, Patrik

2017-11-01

Tyre/road simulation tools that can capture tyre vibrations, rolling resistance and noise generation are useful for understanding the complex processes that are involved and thereby promoting further development and optimisation. The most detailed tyre/road contact models use a spatial discretisation of the contact and assume an interfacial stiffness to account for the small-scale roughness within the elements. This interfacial stiffness has been found to have a significant impact on the simulated noise emissions but no thorough investigations of this sensitivity have been conducted. Three mechanisms are thought to be involved: The horn effect, the modal composition of the vibrational field of the tyre and the contact forces exciting the tyre vibrations. This study used a numerical tyre/road noise simulation tool based on physical relations to investigate these aspects. The model includes a detailed time-domain contact model with linear or non-linear contact springs that accounts for the effect of local tread deformation on smaller length scales. Results confirm that an increase in contact spring stiffness causes a significant increase of the simulated tyre/road noise. This is primarily caused by a corresponding increase in the contact forces, resulting in larger vibrational amplitudes. The horn effect and the modal composition are relatively unaffected and have minor effects on the radiated noise. A more detailed non-linear contact spring formulation with lower stiffness at small indentations results in a reduced high-frequency content in the contact forces and the simulated noise.

Typing of MRI in medial meniscus degeneration in relation to radiological grade in medial compartmental osteoarthritis of the knee

Energy Technology Data Exchange (ETDEWEB)

Nagata, Nobuhito; Koshino, Tomihisa; Saito, Tomoyuki; Sakai, Naotaka; Takagi, Toshitaka; Takeuchi, Ryohei [Yokohama City Univ. (Japan). School of Medicine

1998-10-01

The advancement of degeneration of 50 medial menisci in patients with medial compartmental osteoarthritic knees (OA) were evaluated with magnetic resonance imaging (MRI). The average age of the patients was 66.6 years (range, 39 to 86). According to a radiographical grading system, 6 knees were classified as Grade 1, 24 as Grade 2, 16 as Grade 3, and 4 as Grade 4. The extent and the location of a high intensity region in MRI were observed in 3 parts of the meniscus, namely, the anterior, middle and posterior part. In Grade 1, no high intensity region was observed in 3 knees, and a high intensity region was observed only in the posterior part in 2 knees. A high intensity region was observed from the medial to the posterior part in 13 knees, and only in the posterior part in 10 knees of Grade 2; from the medial to the posterior part in 12 knees, and only in the posterior part in 3 knees of Grade 3, and from the anterior to the posterior part in 2 knees of Grade 4. The shape of the high intensity region in the medial meniscus was classified into 5 types, as follows: Type 1, there was no high intensity region; Type 2, the high intensity region was observed to be restricted within the meniscus; Type 3, the high intensity region resembled a horizontal tear; Type 4, the high intensity region was observed as all of the medial joint space without a marginal area; Type 5, the high intensity region was observed as all of the medial joint space. In Grade 1, 3 knees were classified as Type 1, and 2 knees as Type 2; in Grade 2, 7 knees as Type 2, and 13 knees as Type 3, and 4 knees into Type 4; in Grade 3, 6 knees as Type 3, and 7 knees as Type 4; and in Grade 4, 2 knees as Type 4, and 2 knees as Type 5. These findings might suggest that the degeneration of medial meniscus in the medial type of OA was accelerated by mechanical stress due to varus deformity. (author)

Typing of MRI in medial meniscus degeneration in relation to radiological grade in medial compartmental osteoarthritis of the knee

International Nuclear Information System (INIS)

Nagata, Nobuhito; Koshino, Tomihisa; Saito, Tomoyuki; Sakai, Naotaka; Takagi, Toshitaka; Takeuchi, Ryohei

1998-01-01

The advancement of degeneration of 50 medial menisci in patients with medial compartmental osteoarthritic knees (OA) were evaluated with magnetic resonance imaging (MRI). The average age of the patients was 66.6 years (range, 39 to 86). According to a radiographical grading system, 6 knees were classified as Grade 1, 24 as Grade 2, 16 as Grade 3, and 4 as Grade 4. The extent and the location of a high intensity region in MRI were observed in 3 parts of the meniscus, namely, the anterior, middle and posterior part. In Grade 1, no high intensity region was observed in 3 knees, and a high intensity region was observed only in the posterior part in 2 knees. A high intensity region was observed from the medial to the posterior part in 13 knees, and only in the posterior part in 10 knees of Grade 2; from the medial to the posterior part in 12 knees, and only in the posterior part in 3 knees of Grade 3, and from the anterior to the posterior part in 2 knees of Grade 4. The shape of the high intensity region in the medial meniscus was classified into 5 types, as follows: Type 1, there was no high intensity region; Type 2, the high intensity region was observed to be restricted within the meniscus; Type 3, the high intensity region resembled a horizontal tear; Type 4, the high intensity region was observed as all of the medial joint space without a marginal area; Type 5, the high intensity region was observed as all of the medial joint space. In Grade 1, 3 knees were classified as Type 1, and 2 knees as Type 2; in Grade 2, 7 knees as Type 2, and 13 knees as Type 3, and 4 knees into Type 4; in Grade 3, 6 knees as Type 3, and 7 knees as Type 4; and in Grade 4, 2 knees as Type 4, and 2 knees as Type 5. These findings might suggest that the degeneration of medial meniscus in the medial type of OA was accelerated by mechanical stress due to varus deformity. (author)

Design and fabrication stable LNF contact for future IC application

International Nuclear Information System (INIS)

Bhuiyan, M M I; Bhuiyan, M; Rashid, M M; Ahmed, Sayem; Kajihara, M

2013-01-01

Enable the design of a small contact spring for applications requiring high density, high speed and high durability. A low normal force (LNF) contact spring with high performance is fabricated using a unique combined MEMS photo resist lithography and electro fine forming (EFF) technology. Reducing a total contact material cost of a connector, a high-Hertz stress with LNF contact will be a key technology in the future. Only radius R 5μm tip with 0.1N force contact provides an excellent electrical performance which is much sharper than conventional contact. 0.30million cycle's durability test was passed at 300μm displacement and the contact resistance was ≤50mΩ

Frictional Compliant Haptic Contact and Deformation of Soft Objects

Directory of Open Access Journals (Sweden)

Naci Zafer

2016-05-01

Full Text Available This paper is concerned with compliant haptic contact and deformation of soft objects. A human soft fingertip model is considered to act as the haptic interface and is brought into contact with and deforms a discrete surface. A nonlinear constitutive law is developed in predicting normal forces and, for the haptic display of surface texture, motions along the surface are also resisted at various rates by accounting for dynamic Lund-Grenoble (LuGre frictional forces. For the soft fingertip to apply forces over an area larger than a point, normal and frictional forces are distributed around the soft fingertip contact location on the deforming surface. The distribution is realized based on a kernel smoothing function and by a nonlinear spring-damper net around the contact point. Experiments conducted demonstrate the accuracy and effectiveness of our approach in real-time haptic rendering of a kidney surface. The resistive (interaction forces are applied at the user fingertip bone edge. A 3-DoF parallel robotic manipulator equipped with a constraint based controller is used for the implementation. By rendering forces both in lateral and normal directions, the designed haptic interface system allows the user to realistically feel both the geometrical and mechanical (nonlinear properties of the deforming kidney.

Effect of Tabor parameter on hysteresis losses during adhesive contact

Science.gov (United States)

Ciavarella, M.; Greenwood, J. A.; Barber, J. R.

2017-01-01

The Tabor parameter μ is conventionally assumed to determine the range of applicability of the classical 'JKR' solution for adhesive elastic contact of a sphere and a plane, with the variation of the contact area and approach with load, and in particular the maximum tensile force (the pull-off force) being well predicted for μ > 5 . Here we show that the hysteretic energy loss during a contact separation cycle is significantly overestimated by the JKR theory, even at quite large values of μ. This stems from the absence of long-range tensile forces in the JKR theory, which implies that jump into contact is delayed until the separation α = 0 . We develop an approximate solution based on the use of Wu's solution with van der Waals interactions for jump-in, and the JKR theory for jump out of contact, and show that for μ > 5 , the predicted hysteresis loss is then close to that found by direct numerical solutions using the Lennard-Jones force law. We also show how the same method can be adapted to allow for contact between bodies with finite support stiffness.

VOF simulations of the contact angle dynamics during the drop spreading: standard models and a new wetting force model.

Science.gov (United States)

Malgarinos, Ilias; Nikolopoulos, Nikolaos; Marengo, Marco; Antonini, Carlo; Gavaises, Manolis

2014-10-01

In this study,a novel numerical implementation for the adhesion of liquid droplets impacting normally on solid dry surfaces is presented. The advantage of this new approach, compared to the majority of existing models, is that the dynamic contact angle forming during the surface wetting process is not inserted as a boundary condition, but is derived implicitly by the induced fluid flow characteristics (interface shape) and the adhesion physics of the gas-liquid-surface interface (triple line), starting only from the advancing and receding equilibrium contact angles. These angles are required in order to define the wetting properties of liquid phases when interacting with a solid surface. The physical model is implemented as a source term in the momentum equation of a Navier-Stokes CFD flow solver as an "adhesion-like" force which acts at the triple-phase contact line as a result of capillary interactions between the liquid drop and the solid substrate. The numerical simulations capture the liquid-air interface movement by considering the volume of fluid (VOF) method and utilizing an automatic local grid refinement technique in order to increase the accuracy of the predictions at the area of interest, and simultaneously minimize numerical diffusion of the interface. The proposed model is validated against previously reported experimental data of normal impingement of water droplets on dry surfaces at room temperature. A wide range of impact velocities, i.e. Weber numbers from as low as 0.2 up to 117, both for hydrophilic (θadv=10°-70°) and hydrophobic (θadv=105°-120°) surfaces, has been examined. Predictions include in addition to droplet spreading dynamics, the estimation of the dynamic contact angle; the latter is found in reasonable agreement against available experimental measurements. It is thus concluded that theimplementation of this model is an effective approach for overcoming the need of a pre-defined dynamic contact angle law, frequently adopted as

Frictional forces between cohesive powder particles studied by AFM

International Nuclear Information System (INIS)

Jones, Robert; Pollock, Hubert M; Geldart, Derek; Verlinden-Luts, Ann

2004-01-01

A range of commercially important powders (hydrated alumina, limestone, titania and zeolite) and glass ballotini were attached to atomic force microscope cantilevers, and inter-particle friction forces studied in air using lateral force microscopy (LFM). The in situ calibration procedure for friction forces is described. LF images, line profiles, LF histograms, surface roughness, pull-off forces, and the load dependence of friction in the range 0-25 nN were studied for both particle-particle and particle-wall (steel) contacts. The single-particle friction results are discussed in terms of contact mechanics theory. Particle-particle contacts showed load-dependent friction, involving single asperity contacts (non-linear behaviour) or multi-asperity contacts (linear behaviour). Particle-wall contacts usually showed little load dependence and were more adhesive. The results are also related to shear stress-normal stress data (yield loci) for the same materials from bulk shear testers

Vocal fold injection medialization laryngoplasty.

Science.gov (United States)

Modi, Vikash K

2012-01-01

Unilateral vocal fold paralysis (UVFP) can cause glottic insufficiency that can result in hoarseness, chronic cough, dysphagia, and/or aspiration. In rare circumstances, UVFP can cause airway obstruction necessitating a tracheostomy. The treatment options for UVFP include observation, speech therapy, vocal fold injection medialization laryngoplasty, thyroplasty, and laryngeal reinnervation. In this chapter, the author will discuss the technique of vocal fold injection for medialization of a UVFP. Copyright © 2012 S. Karger AG, Basel.

Modeling of contact theories for the manipulation of biological micro/nanoparticles in the form of circular crowned rollers based on the atomic force microscope

International Nuclear Information System (INIS)

Korayem, M. H.; Khaksar, H.; Taheri, M.

2013-01-01

This article has dealt with the development and modeling of various contact theories for biological nanoparticles shaped as cylinders and circular crowned rollers for application in the manipulation of different biological micro/nanoparticles based on Atomic Force Microscope. First, the effective contact forces were simulated, and their impact on contact mechanics simulation was investigated. In the next step, the Hertz contact model was simulated and compared for gold and DNA nanoparticles with the three types of spherical, cylindrical, and circular crowned roller type contact geometries. Then by reducing the length of the cylindrical section in the circular crowned roller geometry, the geometry of the body was made to approach that of a sphere, and the results were compared for DNA nanoparticles. To anticipatory validate the developed theories, the results of the cylindrical and the circular crowned roller contacts were compared with the results of the existing spherical contact simulations. Following the development of these contact models for the manipulation of various biological micro/nanoparticles, the cylindrical and the circular crowned roller type contact theories were modeled based on the theories of Lundberg, Dowson, Nikpur, Heoprich, and Hertz for the manipulation of biological micro/nanoparticles. Then, for a more accurate validation, the results obtained from the simulations were compared with those obtained by the finite element method and with the experimental results available in previous articles. The previous research works on the simulation of nanomanipulation have mainly investigated the contact theories used in the manipulation of spherical micro/nanoparticles. However since in real biomanipulation situations, biological micro/nanoparticles of more complex shapes need to be displaced in biological environments, this article therefore has modeled and compared, for the first time, different contact theories for use in the biomanipulation of

Tibiofemoral joint contact area and pressure after single- and double-bundle anterior cruciate ligament reconstruction.

Science.gov (United States)

Morimoto, Yusuke; Ferretti, Mario; Ekdahl, Max; Smolinski, Patrick; Fu, Freddie H

2009-01-01

The purpose of this study was to compare the tibiofemoral contact area and pressure after single-bundle (SB) and double-bundle (DB) anterior cruciate ligament (ACL) reconstruction by use of 2 femoral and 2 tibial tunnels in intact cadaveric knees. Tibiofemoral contact area and mean and maximum pressures were measured by pressure-sensitive film (Fujifilm, Valhalla, NY) inserted between the tibia and femur. The knee was subjected to a 1,000-N axial load by use of a uniaxial testing machine at 0 degrees , 15 degrees , 30 degrees , and 45 degrees of flexion. Three conditions were evaluated: (1) intact ACL, (2) SB ACL reconstruction (n = 10 knees), and (3) DB ACL reconstruction (n = 9 knees). When compared with the intact knee, DB ACL reconstruction showed no significant difference in tibiofemoral contact area and mean and maximum pressures. SB ACL reconstruction had a significantly smaller contact area on the lateral and medial tibiofemoral joints at 30 degrees and 15 degrees of flexion. SB ACL reconstruction also had significantly higher mean pressures at 15 degrees of flexion on the medial tibiofemoral joint and at 0 degrees and 15 degrees of flexion on the lateral tibiofemoral joint, as well as significantly higher maximum pressures at 15 degrees of flexion on the lateral tibiofemoral joint. SB ACL reconstruction resulted in a significantly smaller tibiofemoral contact area and higher pressures. DB ACL more closely restores the normal contact area and pressure mainly at low flexion angles. Our findings suggest that the changes in the contact area and pressures after SB ACL reconstruction may be one of the causes of osteoarthritis on long-term follow-up. DB ACL reconstruction may reduce the incidence of osteoarthritis by closely restoring contact area and pressure.

Influence of wheel-rail contact modelling on vehicle dynamic simulation

Science.gov (United States)

Burgelman, Nico; Sichani, Matin Sh.; Enblom, Roger; Berg, Mats; Li, Zili; Dollevoet, Rolf

2015-08-01

This paper presents a comparison of four models of rolling contact used for online contact force evaluation in rail vehicle dynamics. Until now only a few wheel-rail contact models have been used for online simulation in multibody software (MBS). Many more models exist and their behaviour has been studied offline, but a comparative study of the mutual influence between the calculation of the creep forces and the simulated vehicle dynamics seems to be missing. Such a comparison would help researchers with the assessment of accuracy and calculation time. The contact methods investigated in this paper are FASTSIM, Linder, Kik-Piotrowski and Stripes. They are compared through a coupling between an MBS for the vehicle simulation and Matlab for the contact models. This way the influence of the creep force calculation on the vehicle simulation is investigated. More specifically this study focuses on the influence of the contact model on the simulation of the hunting motion and on the curving behaviour.

Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

Energy Technology Data Exchange (ETDEWEB)

Ambroziński, Łukasz [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); AGH University of Science and Technology, Krakow 30059 (Poland); Pelivanov, Ivan, E-mail: ivanp3@uw.edu [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Song, Shaozhen; Yoon, Soon Joon; Gao, Liang; O' Donnell, Matthew [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Li, David [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Chemical Engineering, University of Washington Seattle, Washington 98195 (United States); Shen, Tueng T.; Wang, Ruikang K. [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Ophthalmology, University of Washington, Seattle, Washington 98104 (United States)

2016-07-25

A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

Tyre-road contact using a particle-envelope surface model

Science.gov (United States)

Pinnington, Roger J.

2013-12-01

Determination of the contact forces is the central problem in all aspects of road-tyre interaction: i.e. noise, energy loss and friction. A procedure to find the contact forces under a rolling tyre is presented in four stages. First, the contact stiffness of a uniform peak array from indentations in the rubber tread, and also tyre carcass deflection, is described by some new simplified expressions. Second, a routine divides a single surface profile into equal search intervals, in which the highest peaks are identified. These are used to obtain the parameters for the interval, i.e. the mean envelope and the mean interval. The process is repeated at geometrically decreasing search intervals until the level of the data resolution, thereby describing the profile by a set of envelopes. The ‘strip profile’ ultimately used to describe the surface, is obtained by selecting the highest points across the profiles of one stone's width. The third stage is to combine the strip profile envelopes with the contact stiffness expressions, yielding the nonlinear stiffness-displacement, and force-displacement relationships for the chosen road-tyre combination. Finally the contact pressure distribution from a steady-state rolling tyre model is applied to the strip profile, via the force-displacement relationship, giving the local tyre displacements on the road texture. This displacement pattern is shown to be proportional to the time and space varying contact pressure, which then is incorporated into a wave equation for rolling contact.

Isolated partial tear and partial avulsion of the medial head of gastrocnemius tendon presenting as posterior medial knee pain

OpenAIRE

Watura, Christopher; Ward, Anthony; Harries, William

2010-01-01

We present a case of medial head of gastrocnemius tendon tear. The type of injury widely reported in the literature is tear of the medial head of gastrocnemius muscle or ‘tennis leg’. We previously reported an isolated partial tear and longitudinal split of the tendon to the medial head of gastrocnemius at its musculotendinous junction. The case we now present has notable differences; the tear was interstitial and at the proximal (femoral attachment) part of the tendon, the patient’s symptoms...

Modelling atomic scale manipulation with the non-contact atomic force microscope

International Nuclear Information System (INIS)

Trevethan, T; Watkins, M; Kantorovich, L N; Shluger, A L; Polesel-Maris, J; Gauthier, S

2006-01-01

We present the results of calculations performed to model the process of lateral manipulation of an oxygen vacancy in the MgO(001) surface using the non-contact atomic force microscope (NC-AFM). The potential energy surfaces for the manipulation as a function of tip position are determined from atomistic modelling of the MgO(001) surface interacting with a Mg terminated MgO tip. These energies are then used to model the dynamical evolution of the system as the tip oscillates and at a finite temperature using a kinetic Monte Carlo method. The manipulation process is strongly dependent on the lateral position of the tip and the system temperature. It is also found that the expectation value of the point at which the vacancy jumps depends on the trajectory of the oscillating cantilever as the surface is approached. The effect of the manipulation on the operation of the NC-AFM is modelled with a virtual dynamic AFM, which explicitly simulates the entire experimental instrumentation and control loops. We show how measurable experimental signals can result from a single controlled atomic scale event and suggest the most favourable conditions for achieving successful atomic scale manipulation experimentally

Direct measurements of intermolecular forces by chemical force microscopy

Science.gov (United States)

Vezenov, Dmitri Vitalievich

1999-12-01

Detailed description of intermolecular forces is key to understanding a wide range of phenomena from molecular recognition to materials failure. The unique features of atomic force microscopy (AFM) to make point contact force measurements with ultra high sensitivity and to generate spatial maps of surface topography and forces have been extended to include measurements between well-defined organic molecular groups. Chemical modification of AFM probes with self-assembled monolayers (SAMs) was used to make them sensitive to specific molecular interactions. This novel chemical force microscopy (CFM) technique was used to probe forces between different molecular groups in a range of environments (vacuum, organic liquids and aqueous solutions); measure surface energetics on a nanometer scale; determine pK values of the surface acid and base groups; measure forces to stretch and unbind a short synthetic DNA duplex and map the spatial distribution of specific functional groups and their ionization state. Studies of adhesion forces demonstrated the important contribution of hydrogen bonding to interactions between simple organic functionalities. The chemical identity of the tip and substrate surfaces as well as the medium had a dramatic effect on adhesion between model monolayers. A direct correlation between surface free energy and adhesion forces was established. The adhesion between epoxy polymer and model mixed SAMs varied with the amount of hydrogen bonding component in the monolayers. A consistent interpretation of CFM measurements in polar solvents was provided by contact mechanics models and intermolecular force components theory. Forces between tips and surfaces functionalized with SAMs terminating in acid or base groups depended on their ionization state. A novel method of force titration was introduced for highly local characterization of the pK's of surface functional groups. The pH-dependent changes in friction forces were exploited to map spatially the

Men pressured and forced into sexual experience.

Science.gov (United States)

Struckman-Johnson, C; Struckman-Johnson, D

1994-02-01

A predominantly heterosexual sample of 204 college men were asked to report incidents of pressured or forced sexual touch or intercourse since age 16. About 34% indicated they had received coercive sexual contact: 24% from women, 4% from men, and 6% from both sexes. Contact involved only sexual touching for 12% and intercourse for 22%. Sexual contact was pressured in 88% of the 81 reported incidents by tactics of persuasion, intoxication, threat of love withdrawal, and bribery. In 12% of the incidents, sexual contact was forced through physical restraint, physical intimidation, threat of harm, or harm. Contact was initiated by an acquaintance or intimate in 77% of incidents. The negative emotional impact of male contact was rated significantly higher than the impact of female contact. Men with and without coercion experience did not differ, however, for scale scores on sexual esteem, depression, and preoccupation. Interviews with 10 subjects revealed complex reactions to coercive male and female contact, including doubts about one's sexuality, resentment of unexpected or forceful contact, and fear of telling others about the event.

Wide range local resistance imaging on fragile materials by conducting probe atomic force microscopy in intermittent contact mode

Energy Technology Data Exchange (ETDEWEB)

Vecchiola, Aymeric [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Concept Scientific Instruments, ZA de Courtaboeuf, 2 rue de la Terre de Feu, 91940 Les Ulis (France); Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Chrétien, Pascal; Schneegans, Olivier; Mencaraglia, Denis; Houzé, Frédéric, E-mail: frederic.houze@geeps.centralesupelec.fr [Laboratoire de Génie électrique et électronique de Paris (GeePs), UMR 8507 CNRS-CentraleSupélec, Paris-Sud and UPMC Universities, 11 rue Joliot-Curie, Plateau de Moulon, 91192 Gif-sur-Yvette (France); Delprat, Sophie [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); UPMC, Université Paris 06, 4 place Jussieu, 75005 Paris (France); Bouzehouane, Karim; Seneor, Pierre; Mattana, Richard [Unité Mixte de Physique CNRS-Thales UMR 137, 1 avenue Augustin Fresnel, 91767 Palaiseau (France); Tatay, Sergio [Molecular Science Institute, University of Valencia, 46980 Paterna (Spain); Geffroy, Bernard [Lab. Physique des Interfaces et Couches minces (PICM), UMR 7647 CNRS-École polytechnique, 91128 Palaiseau (France); Lab. d' Innovation en Chimie des Surfaces et Nanosciences (LICSEN), NIMBE UMR 3685 CNRS-CEA Saclay, 91191 Gif-sur-Yvette (France); and others

2016-06-13

An imaging technique associating a slowly intermittent contact mode of atomic force microscopy (AFM) with a home-made multi-purpose resistance sensing device is presented. It aims at extending the widespread resistance measurements classically operated in contact mode AFM to broaden their application fields to soft materials (molecular electronics, biology) and fragile or weakly anchored nano-objects, for which nanoscale electrical characterization is highly demanded and often proves to be a challenging task in contact mode. Compared with the state of the art concerning less aggressive solutions for AFM electrical imaging, our technique brings a significantly wider range of resistance measurement (over 10 decades) without any manual switching, which is a major advantage for the characterization of materials with large on-sample resistance variations. After describing the basics of the set-up, we report on preliminary investigations focused on academic samples of self-assembled monolayers with various thicknesses as a demonstrator of the imaging capabilities of our instrument, from qualitative and semi-quantitative viewpoints. Then two application examples are presented, regarding an organic photovoltaic thin film and an array of individual vertical carbon nanotubes. Both attest the relevance of the technique for the control and optimization of technological processes.

Fragmentation of the medial malleolus of dogs with and without tarsal osteochondrosis

International Nuclear Information System (INIS)

Newell, S.M.; Mahaffey, M.B.; Aron, D.N.

1994-01-01

Fragmentation of the medial malleolus of the tibia was found radiographically in 5 canine tarsi which did not have evidence of osteochondrosis of the medial trochlear ridge. An additional 5 tarsi were found where both medial malleolar fragmentation and osteochondrosis of the medial trochlear ridge were present. Radiographic evidence of degenerative joint disease was present in 3 of 5 dogs with medial malleolar fragmentation alone, and 5 of 5 dogs with medial malleolar fragmentation and medial trochlear ridge osteochondrosis. Eight of the 9 dogs were Rottweilers. Considering the sites of occurrence of osteochondrosis in other species, the authors propose that medial malleolar fragmentation could be secondary to osteochondrosis of the medial malleolus. Osteochondrosis of the medial malleolus has not been previously reported in dogs. Histological examination of the medial malleolar fragmentation was unavailable because surgery was not performed, therefore the hypothesis that the medial malleolar fragmentation is due to osteochondrosis was not proven

Contact behavior analysis of elastomeric x-ring under uniform squeeze rate and internal pressure before and after forcing-out using the photoelastic experimental hybrid method

Energy Technology Data Exchange (ETDEWEB)

Bernard, Alunda Ouma [Dedan Kimathi University of Technology, Nyeri (Kenya); Hawong, Jai Sug; Dong, Bai [Yeungnam University, Gyeongsan (Korea, Republic of); Shin, Dong Chul [Koje College, Geoje (Korea, Republic of)

2015-05-15

Many different types of elastomeric rings have been developed to suit various needs in industry. The X-ring was introduced as a result of the limitations of O-rings that twist, especially during dynamic application. A better understanding of the behavior and the stress distribution of the X-ring under a uniform squeeze rate and internal pressure is needed. We analyzed the contact stresses and internal stresses developed in an X-ring before and after forcing-out by using the photoelastic experimental hybrid method, ascertained the packing ability of an X-ring, and studied the failure criterion of an X-ring under uniform squeeze rate and internal pressure. Forcing-out in the X-ring occurred when the internal pressure was 3.92 MPa. After forcing-out, at an internal pressure of 5.88 MPa, the two lobes on the upper contact surface merged one contact side of the upper side immensely. Even after extrusion of the X-ring, the X-ring can be used to effectively contain the fluid. This is because the effects of extrusion on the X-ring affected the stress distribution of only two lobes close to the assembly gap and the two lobes are merge into one lobe. In addition, our experimental results show that the maximum shear failure criterion is suitable for the prediction of failure in X-ring seals.

Functional results after external vocal fold medialization thyroplasty with the titanium vocal fold medialization implant.

Science.gov (United States)

Schneider, Berit; Denk, Doris-Maria; Bigenzahn, Wolfgang

2003-04-01

A persistent insufficiency of glottal closure is mostly a consequence of a unilateral vocal fold movement impairment. It can also be caused by vocal fold atrophy or scarring processes with regular bilateral respiratory vocal fold function. Because of consequential voice, breathing, and swallowing impairments, a functional surgical treatment is required. The goal of the study was to outline the functional results after medialization thyroplasty with the titanium vocal fold medialization implant according to Friedrich. In the period of 1999 to 2001, an external vocal fold medialization using the titanium implant was performed on 28 patients (12 women and 16 men). The patients were in the age range of 19 to 84 years. Twenty-two patients had a paralysis of the left-side vocal fold, and six patients, of the right-side vocal fold. Detailed functional examinations were executed on all patients before and after the surgery: perceptive voice sound analysis according to the "roughness, breathiness, and hoarseness" method, judgment of the s/z ratio and voice dysfunction index, voice range profile measurements, videostroboscopy, and pulmonary function tests. In case of dysphagia/aspiration, videofluoroscopy of swallowing was also performed. The respective data were statistically analyzed (paired t test, Wilcoxon-test). All patients reported on improvement of voice, swallowing, and breathing functions postoperatively. Videostroboscopy revealed an almost complete glottal closure after surgery in all of the patients. All voice-related parameters showed a significant improvement. An increase of the laryngeal resistance by the medialization procedure could be excluded by analysis of the pulmonary function test. The results confirm the external medialization of the vocal folds as an adequate method in the therapy of voice, swallowing, and breathing impairment attributable to an insufficient glottal closure. The titanium implant offers, apart from good tissue tolerability, the

Mixed Finite Element Method for Static and Dynamic Contact Problems with Friction and Initial Gaps

Directory of Open Access Journals (Sweden)

Lanhao Zhao

2014-01-01

Full Text Available A novel mixed finite element method is proposed for static and dynamic contact problems with friction and initial gaps. Based on the characteristic of local nonlinearity for the problem, the system of forces acting on the contactor is divided into two parts: external forces and contact forces. The displacement of structure is chosen as the basic variable and the nodal contact force in contact region under local coordinate system is selected as the iteration variable to confine the nonlinear iteration process in the potential contact surface which is more numerically efficient. In this way, the sophisticated contact nonlinearity is revealed by the variety of the contact forces which are determined by the external load and the contact state stick, slip, or separation. Moreover, in the case of multibody contact problem, the flexibility matrix is symmetric and sparse; thus, the iterative procedure becomes easily carried out and much more economical. In the paper, both the finite element formulations and the iteration process are given in detail for static and dynamic contact problems. Four examples are included to demonstrate the accuracy and applicability of the presented method.

Biomechanical comparison of four double-row speed-bridging rotator cuff repair techniques with or without medial or lateral row enhancement.

Science.gov (United States)

Pauly, Stephan; Fiebig, David; Kieser, Bettina; Albrecht, Bjoern; Schill, Alexander; Scheibel, Markus

2011-12-01

Biomechanical comparison of four different Speed-Bridge configurations with or without medial or lateral row reinforcement. Reinforcement of the knotless Speed-Bridge double-row repair technique with additional medial mattress- or lateral single-stitches was hypothesized to improve biomechanical repair stability at time zero. Controlled laboratory study: In 36 porcine fresh-frozen shoulders, the infraspinatus tendons were dissected and shoulders were randomized to four groups: (1) Speed-Bridge technique with single tendon perforation per anchor (STP); (2) Speed-Bridge technique with double tendon perforation per anchor (DTP); (3) Speed-Bridge technique with medial mattress-stitch reinforcement (MMS); (4) Speed-Bridge technique with lateral single-stitch reinforcement (LSS). All repairs were cyclically loaded from 10-60 N up to 10-200 N (20 N stepwise increase) using a material testing device. Forces at 3 and 5 mm gap formation, mode of failure and maximum load to failure were recorded. The MMS-technique with double tendon perforation showed significantly higher ultimate tensile strength (338.9 ± 90.0 N) than DTP (228.3 ± 99.9 N), LSS (188.9 ± 62.5 N) and STP-technique (122.2 ± 33.8 N). Furthermore, the MMS-technique provided increased maximal force resistance until 3 and 5 mm gap formation (3 mm: 77.8 ± 18.6 N; 5 mm: 113.3 ± 36.1 N) compared with LSS, DTP and STP (P row defect by tendon sawing first, then laterally. No anchor pullout occurred. Double tendon perforation per anchor and additional medial mattress stitches significantly enhance biomechanical construct stability at time zero in this ex vivo model when compared with the all-knotless Speed-Bridge rotator cuff repair.

Contact pressure measurement in hand tool evaluation studies

NARCIS (Netherlands)

Kuijt-Evers, L.F.M.; Bosch, T.

2006-01-01

In hand tool evaluation studies, several objective measurements are used. Grip force distribution and grip force are important as they give feedback about the force which has to be performed with the hand on the handle. A measurement technique -which is related to grip force measurement- is contact

Stimulation of the medial amygdala enhances medial preoptic dopamine release: implications for male rat sexual behavior.

Science.gov (United States)

Dominguez, J M; Hull, E M

2001-11-02

Increased dopamine (DA) in the medial preoptic area (MPOA) facilitates male sexual behavior. A major source of innervation to the MPOA is the medial amygdala (MeA). We now report that chemical stimulation of the MeA enhanced levels of extracellular MPOA DA in anesthetized male rats. These results suggest that DA activity in the MPOA can be regulated by input from the MeA to the MPOA.

Posterior labral injury in contact athletes.

Science.gov (United States)

Mair, S D; Zarzour, R H; Speer, K P

1998-01-01

Nine athletes (seven football offensive linemen, one defensive lineman, and one lacrosse player) were found at arthroscopy to have posterior labral detachment from the glenoid. In our series, this lesion is specific to contact athletes who engage their opponents with arms in front of the body. All patients had pain with bench pressing and while participating in their sport, diminishing their ability to play effectively. Conservative measures were ineffective in relieving their symptoms. Examination under anesthesia revealed symmetric glenohumeral translation bilaterally, without evidence of posterior instability. Treatment consisted of glenoid rim abradement and posterior labral repair with a bioabsorbable tack. All patients returned to complete at least one full season of contact sports and weightlifting without pain (minimum follow-up, > or = 2 years). Although many injuries leading to subluxation of the glenohumeral joint occur when an unanticipated force is applied, contact athletes ready their shoulder muscles in anticipation of impact with opponents. This leads to a compressive force at the glenohumeral joint. We hypothesize that, in combination with a posteriorly directed force at impact, the resultant vector is a shearing force to the posterior labrum and articular surface. Repeated exposure leads to posterior labral detachment without capsular injury. Posterior labral reattachment provides consistently good results, allowing the athlete to return to competition.

Effect of Ankle Joint Contact Angle and Ground Contact Time on Depth Jump Performance.

Science.gov (United States)

Phillips, Joshua H; Flanagan, Sean P

2015-11-01

Athletes often need to both jump high and get off the ground quickly, but getting off the ground quickly can decrease the vertical ground reaction force (VGRF) impulse, impeding jump height. Energy stored in the muscle-tendon complex during the stretch-shortening cycle (SSC) may mitigate the effects of short ground contact times (GCTs). To take advantage of the SSC, several coaches recommend "attacking" the ground with the foot in a dorsiflexed (DF) position at contact. However, the efficacy of this technique has not been tested. This investigation tested the hypotheses that shorter GCTs would lead to smaller vertical depth jump heights (VDJH), and that this difference could be mitigated by instructing the athletes to land in a DF as opposed to a plantar flexed (PF) foot position. Eighteen healthy junior college athletes performed depth jumps from a 45-cm box onto force platforms under instruction to achieve one of the 2 objectives (maximum jump height [hmax] or minimal GCT [tmin]), with one of the 2 foot conditions (DF or PF). These variations created 4 distinct jump conditions: DF-hmax, DF-tmin, PF-hmax, and PF-tmin. For all variables examined, there were no significant interactions. For all 4 conditions, the ankle was PF during landing, but the DF condition was 28.87% less PF than the PF condition. The tmin conditions had a 23.48% shorter GCT than hmax. There were no significant main effects for jump height. The peak impact force for tmin was 22.14% greater than hmax and 19.11% greater for DF compared with PF conditions. A shorter GCT did not necessitate a smaller jump height, and a less PF foot did not lead to improvements in jump height or contact time during a depth jump from a 45-cm box. The same jump height was attained in less PF and shorter GCT conditions by larger impact forces. To decrease contact time while maintaining jump height, athletes should be instructed to "get off the ground as fast as possible." This cue seems to be more important than foot

Contact mechanical characteristics of Nb3Sn strands under transverse electromagnetic loads in the CICC cross-section

International Nuclear Information System (INIS)

Zhu Jiyue; Luo Wei; Zhou Youhe; Zheng Xiaojing

2012-01-01

This paper presents a new code for the two-dimensional discrete element method (DEM) and relevant simulations to quantitatively characterize the contact force behavior of the Nb 3 Sn strands in the ITER CICC cross-section under a transverse electromagnetic load. In order to obtain the essential parameters in the contact force model employed in the DEM, a simulation of the experiments conducted by Nijhuis et al (2004 IEEE Trans. Appl. Supercond. 14 1489–94) is first performed, where the load–displacement curve predicted by the code is in good agreement with the measurements. After that, the contact force chain between strands and its distribution is quantitatively analyzed by the code. It is found that the contact force distribution among strands is heterogeneous and strongly anisotropic. In other words, the force chain distribution, which determines the behavior of the assembly of strands with discrete media, and the distribution of area average magnitude of the contact force are obviously inhomogeneous. To describe this inhomogeneity, here, the probability density function (PDF) is used in the statistical analysis. The numerical results show that the PDFs of the magnitudes of the resultant contact force, normal contact force, and tangential contact force all decay with an exponential law, and that PDFs of the directions of the contact forces are all anisotropic and exhibit about six periodic changes in which the peak values in the direction parallel to the applied electromagnetic load are appreciably larger than the other peaks. (paper)

Dynamic Contact Angle at the Nanoscale: A Unified View.

Science.gov (United States)

Lukyanov, Alex V; Likhtman, Alexei E

2016-06-28

Generation of a dynamic contact angle in the course of wetting is a fundamental phenomenon of nature. Dynamic wetting processes have a direct impact on flows at the nanoscale, and therefore, understanding them is exceptionally important to emerging technologies. Here, we reveal the microscopic mechanism of dynamic contact angle generation. It has been demonstrated using large-scale molecular dynamics simulations of bead-spring model fluids that the main cause of local contact angle variations is the distribution of microscopic force acting at the contact line region. We were able to retrieve this elusive force with high accuracy. It has been directly established that the force distribution can be solely predicted on the basis of a general friction law for liquid flow at solid surfaces by Thompson and Troian. The relationship with the friction law provides both an explanation of the phenomenon of dynamic contact angle and a methodology for future predictions. The mechanism is intrinsically microscopic, universal, and irreducible and is applicable to a wide range of problems associated with wetting phenomena.

Mathematical Modeling of Contact Problems of Elasticity Theory with Continuous Unilateral Contact

Directory of Open Access Journals (Sweden)

I. V. Stankevich

2015-01-01

Full Text Available The work [1] presents the formulation and numerical solution of the problem concerning the unilateral discrete contact interaction of an elastic body and a rigid half-space. However, many parts and components of engineering structures have a pronounced continuous contact within a given surface [2, 3]. In this paper we consider a special case of this option of contact interaction when, the elastic body of finite size, subjected to external forces, is based on a rigid half-space. Contact occurs through a dedicated contact surface, which in general can change their sizes.Developed to solve this problem, a numerical algorithm is a further adaptation and development of the approaches described in [1]. The paper shows results of solving the model problem of the elasticity theory with and without taking friction into account. In the latter case, were additionally obtained numerical data characterizing the convergence of the solution.

Medial stabilized and posterior stabilized TKA affect patellofemoral kinematics and retropatellar pressure distribution differently.

Science.gov (United States)

Glogaza, Alexander; Schröder, Christian; Woiczinski, Matthias; Müller, Peter; Jansson, Volkmar; Steinbrück, Arnd

2018-06-01

Patellofemoral kinematics and retropatellar pressure distribution change after total knee arthroplasty (TKA). It was hypothesized that different TKA designs will show altered retropatellar pressure distribution patterns and different patellofemoral kinematics according to their design characteristics. Twelve fresh-frozen knee specimens were tested dynamically in a knee rig. Each specimen was measured native, after TKA with a posterior stabilized design (PS) and after TKA with a medial stabilized design (MS). Retropatellar pressure distribution was measured using a pressure sensitive foil which was subdivided into three areas (lateral and medial facet and patellar ridge). Patellofemoral kinematics were measured by an ultrasonic-based three-dimensional motion system (Zebris CMS20, Isny Germany). Significant changes in patellofemoral kinematics and retropatellar pressure distribution were found in both TKA types when compared to the native situation. Mean retropatellar contact areas were significantly smaller after TKA (native: 241.1 ± 75.6 mm 2 , MS: 197.7 ± 74.5 mm 2 , PS: 181.2 ± 56.7 mm 2 , native vs. MS p patellofemoral kinematics were found in both TKA designs when compared to the native knee during flexion and extension with a more medial patella tracking. Patellofemoral kinematics and retropatellar pressure change after TKA in different manner depending on the type of TKA used. Surgeons should be aware of influencing the risks of patellofermoral complications by the choice of the prosthesis design.

Gastrocnemius recession leads to medial shift of gait line, impairment of muscle strength and improved dorsal extension in forefoot overload syndrome

DEFF Research Database (Denmark)

Schmal, Hagen; Walther, Markus; Hirschmüller, Anja

2018-01-01

. A strength power analysis of plantar flexors and a pedobarography was performed. Clinical outcome was measured by Foot Function Index (FFI). RESULTS: Plantarflexors are impaired about 40% six weeks and around 10% 24 weeks following GR compared to the contralateral side. Patients experienced a pain relief...... and an improvement of ankle dorsiflexion from 2° to 15°. An increased contact time of the heel (15%) and a shift of metatarsal plantar pressure from lateral to medial could be demonstrated. CONCLUSIONS: This study suggests that GR leads to pain reduction by an increase in heel contact time and a shift of gait line...

Time domain contact model for tyre/road interaction including nonlinear contact stiffness due to small-scale roughness

Science.gov (United States)

Andersson, P. B. U.; Kropp, W.

2008-11-01

Rolling resistance, traction, wear, excitation of vibrations, and noise generation are all attributes to consider in optimisation of the interaction between automotive tyres and wearing courses of roads. The key to understand and describe the interaction is to include a wide range of length scales in the description of the contact geometry. This means including scales on the order of micrometres that have been neglected in previous tyre/road interaction models. A time domain contact model for the tyre/road interaction that includes interfacial details is presented. The contact geometry is discretised into multiple elements forming pairs of matching points. The dynamic response of the tyre is calculated by convolving the contact forces with pre-calculated Green's functions. The smaller-length scales are included by using constitutive interfacial relations, i.e. by using nonlinear contact springs, for each pair of contact elements. The method is presented for normal (out-of-plane) contact and a method for assessing the stiffness of the nonlinear springs based on detailed geometry and elastic data of the tread is suggested. The governing equations of the nonlinear contact problem are solved with the Newton-Raphson iterative scheme. Relations between force, indentation, and contact stiffness are calculated for a single tread block in contact with a road surface. The calculated results have the same character as results from measurements found in literature. Comparison to traditional contact formulations shows that the effect of the small-scale roughness is large; the contact stiffness is only up to half of the stiffness that would result if contact is made over the whole element directly to the bulk of the tread. It is concluded that the suggested contact formulation is a suitable model to include more details of the contact interface. Further, the presented result for the tread block in contact with the road is a suitable input for a global tyre/road interaction model

Interface bonding in silicon oxide nanocontacts: interaction potentials and force measurements

Science.gov (United States)

Wierez-Kien, M.; Craciun, A. D.; Pinon, A. V.; Le Roux, S.; Gallani, J. L.; Rastei, M. V.

2018-04-01

The interface bonding between two silicon-oxide nanoscale surfaces has been studied as a function of atomic nature and size of contacting asperities. The binding forces obtained using various interaction potentials are compared with experimental force curves measured in vacuum with an atomic force microscope. In the limit of small nanocontacts (typically contact area which is altered by stretching speeds. The mean unbinding force is found to decrease as the contact spends time in the attractive regime. This contact weakening is featured by a negative aging coefficient which broadens and shifts the thermal-induced force distribution at low stretching speeds.

Arthroscopic treatment of symptomatic type D medial plica

OpenAIRE

Uysal, Mustafa; Asik, Mehmet; Akpinar, Sercan; Ciftci, Feyyaz; Cesur, Necip; Tandogan, Reha N.

2007-01-01

We aimed to review the results of subtotal arthroscopic resection of symptomatic type D medial plica. We retrospectively evaluated 23 knees with symptomatic type D medial plica in 22 patients without other intra-articular pathology. All patients complained of chronic knee pain that had not been alleviated by medical treatment or physical therapy. In only three (13%) of the patients studied was the plica diagnosed pre-operatively with magnetic resonance imaging. The type D medial plicae in our...

Medial gastrocnemius and soleus muscle-tendon unit, fascicle, and tendon interaction during walking in children with cerebral palsy.

Science.gov (United States)

Barber, Lee; Carty, Chris; Modenese, Luca; Walsh, John; Boyd, Roslyn; Lichtwark, Glen

2017-08-01

This study investigates the in vivo function of the medial gastrocnemius and soleus muscle-tendon units (MTU), fascicles, and tendons during walking in children with cerebral palsy (CP) and an equinus gait pattern. Fourteen children with CP (9 males, 5 females; mean age 10y 6mo, standard deviation [SD] 2y 11mo; GMFCS level I=8, II=6), and 10 typically developing (6 males, 4 females; mean age 10y, SD 2y 1mo) undertook full body 3D gait analysis and simultaneous B-mode ultrasound images of the medial gastrocnemius and soleus fascicles during level walking. Fascicle lengths were analysed using a semi-automated tracking algorithm and MTUs using OpenSim. Statistical parametric mapping (two-sample t-test) was used to compare differences between groups (ppower during push-off (p=0.015) and positive work (ppower and positive work in the children with CP may be attributed to reduced active medial gastrocnemius fascicle shortening. These findings suggest a reliance on passive force generation for forward propulsion during equinus gait. © 2017 Mac Keith Press.

Centralization of extruded medial meniscus delays cartilage degeneration in rats.

Science.gov (United States)

Ozeki, Nobutake; Muneta, Takeshi; Kawabata, Kenichi; Koga, Hideyuki; Nakagawa, Yusuke; Saito, Ryusuke; Udo, Mio; Yanagisawa, Katsuaki; Ohara, Toshiyuki; Mochizuki, Tomoyuki; Tsuji, Kunikazu; Saito, Tomoyuki; Sekiya, Ichiro

2017-05-01

Meniscus extrusion often observed in knee osteoarthritis has a strong correlation with the progression of cartilage degeneration and symptom in the patients. We recently reported a novel procedure "arthroscopic centralization" in which the capsule was sutured to the edge of the tibial plateau to reduce meniscus extrusion in the human knee. However, there is no animal model to study the efficacy of this procedure. The purposes of this study were [1] to establish a model of centralization for the extruded medial meniscus in a rat model; and [2] to investigate the chondroprotective effect of this procedure. Medial meniscus extrusion was induced by the release of the anterior synovial capsule and the transection of the meniscotibial ligament. Centralization was performed by the pulled-out suture technique. Alternatively, control rats had only the medial meniscus extrusion surgery. Medial meniscus extrusion was evaluated by micro-CT and macroscopic findings. Cartilage degeneration of the medial tibial plateau was evaluated macroscopically and histologically. By micro-CT analysis, the medial meniscus extrusion was significantly improved in the centralization group in comparison to the extrusion group throughout the study. Both macroscopically and histologically, the cartilage lesion of the medial tibial plateau was prevented in the centralization group but was apparent in the control group. We developed medial meniscus extrusion in a rat model, and centralization of the extruded medial meniscus by the pull-out suture technique improved the medial meniscus extrusion and delayed cartilage degeneration, though the effect was limited. Centralization is a promising treatment to prevent the progression of osteoarthritis. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Endoscopic Medial Maxillectomy Breaking New Frontiers

OpenAIRE

Mohanty, Sanjeev; Gopinath, M.

2011-01-01

Endoscopy has changed the perspective of rhinologist towards the nose. It has revolutionised the surgical management of sinonasal disorders. Sinus surgeries were the first to get the benefit of endoscope. Gradually the domain of endoscopic surgery extended to the management of sino nasal tumours. Traditionally medial maxillectomy was performed through lateral rhinotomy or mid facial degloving approach. Endoscopic medial maxillectomy has been advocated by a number of authors in the management ...

A soft-contact model for computing safety margins in human prehension.

Science.gov (United States)

Singh, Tarkeshwar; Ambike, Satyajit

2017-10-01

The soft human digit tip forms contact with grasped objects over a finite area and applies a moment about an axis normal to the area. These moments are important for ensuring stability during precision grasping. However, the contribution of these moments to grasp stability is rarely investigated in prehension studies. The more popular hard-contact model assumes that the digits exert a force vector but no free moment on the grasped object. Many sensorimotor studies use this model and show that humans estimate friction coefficients to scale the normal force to grasp objects stably, i.e. the smoother the surface, the tighter the grasp. The difference between the applied normal force and the minimal normal force needed to prevent slipping is called safety margin and this index is widely used as a measure of grasp planning. Here, we define and quantify safety margin using a more realistic contact model that allows digits to apply both forces and moments. Specifically, we adapt a soft-contact model from robotics and demonstrate that the safety margin thus computed is a more accurate and robust index of grasp planning than its hard-contact variant. Previously, we have used the soft-contact model to propose two indices of grasp planning that show how humans account for the shape and inertial properties of an object. A soft-contact based safety margin offers complementary insights by quantifying how humans may account for surface properties of the object and skin tissue during grasp planning and execution. Copyright © 2017 Elsevier B.V. All rights reserved.

The Effect of Foot Progression Angle on Knee Joint Compression Force during Walking

DEFF Research Database (Denmark)

Baldvinsson, Henrik Koblauch; Heilskov-Hansen, Thomas; Alkjær, Tine

2013-01-01

males walked at a fixed speed of 4.5 km/h under three conditions: Normal walking, internally rotated and externally rotated. All gait-trials were recorded by six infrared cameras. Net joint moments were calculated by 3D inverse dynamics. The results revealed that the medial knee joint compartment......It is unclear how rotations of the lower limb affect the knee joint compression forces during walking. Increases in the frontal plane knee moment have been reported when walking with internally rotated feet and a decrease when walking with externally rotated feet. The aim of this study...... was to investigate the knee joint compressive forces during walking with internal, external and normal foot rotation and to determine if the frontal plane knee joint moment is an adequate surrogate for the compression forces in the medial and lateral knee joint compartments under such gait modifications. Ten healthy...

Two-Polarisation Physical Model of Bowed Strings with Nonlinear Contact and Friction Forces, and Application to Gesture-Based Sound Synthesis

Directory of Open Access Journals (Sweden)

Charlotte Desvages

2016-05-01

Full Text Available Recent bowed string sound synthesis has relied on physical modelling techniques; the achievable realism and flexibility of gestural control are appealing, and the heavier computational cost becomes less significant as technology improves. A bowed string sound synthesis algorithm is designed, by simulating two-polarisation string motion, discretising the partial differential equations governing the string’s behaviour with the finite difference method. A globally energy balanced scheme is used, as a guarantee of numerical stability under highly nonlinear conditions. In one polarisation, a nonlinear contact model is used for the normal forces exerted by the dynamic bow hair, left hand fingers, and fingerboard. In the other polarisation, a force-velocity friction curve is used for the resulting tangential forces. The scheme update requires the solution of two nonlinear vector equations. The dynamic input parameters allow for simulating a wide range of gestures; some typical bow and left hand gestures are presented, along with synthetic sound and video demonstrations.

Effects of ballet training of children in Turkey on foot anthropometric measurements and medial longitudinal arc development.

Science.gov (United States)

Ozdinc, Sevgi Anar; Turan, Fatma Nesrin

2016-07-01

To investigate the effects of ballet training on foot structure and the formation of the medial longitudinal arc in childhood, and the association of body mass index with structural change secondary to ballet training. This study was conducted at Öykü Ballet and Dance School and Trakya University, Edirne, Turkey, from September 2007 to November 2008, and comprised girl students who were taking ballet classes, and a group of those who were not taking such who acted as the controls. Static footprints of both feet of all participants were taken with an ink paedogram. Parameters evaluated from footprints included foot length, metatarsal width, heel width and medial longitudinal arch. The relationship between the parameters, the ballet starting age, training duration and body mass index was investigated. Of the 67 participants, there were 36(53.7%) in the experimental group and 31(48.3%) in the control group. The difference between age, height, weight and body mass index between the two groups was insignificant (p>0.05). The average ballet starting age was 6.47±1.55 years and duration was 4.36±2.002 years. Positive correlations were found between body mass index and foot length, metatarsal width, heel width, medial longitudinal arch contact width and halluxvalgus angle; between ballet starting age and metatarsal width, heel width; between duration of training and foot length, metatarsal width and hallux valgus angle (p?0.05 each). Evidence supporting the education in children on foot anthropometric measurements and medial longitudinal arc development could not be found.

Multipoint contact modeling of nanoparticle manipulation on rough surface

Energy Technology Data Exchange (ETDEWEB)

Zakeri, M., E-mail: m.zakeri@tabrizu.ac.ir; Faraji, J.; Kharazmi, M. [University of Tabriz, School of Engineering Emerging Technologies (Iran, Islamic Republic of)

2016-12-15

In this paper, the atomic force microscopy (AFM)-based 2-D pushing of nano/microparticles investigated on rough substrate by assuming a multipoint contact model. First, a new contact model was extracted and presented based on the geometrical profiles of Rumpf, Rabinovich and George models and the contact mechanics theories of JKR and Schwartz, to model the adhesion forces and the deformations in the multipoint contact of rough surfaces. The geometry of a rough surface was defined by two main parameters of asperity height (size of roughness) and asperity wavelength (compactness of asperities distribution). Then, the dynamic behaviors of nano/microparticles with radiuses in range of 50–500 nm studied during their pushing on rough substrate with a hexagonal or square arrangement of asperities. Dynamic behavior of particles were simulated and compared by assuming multipoint and single-point contact schemes. The simulation results show that the assumption of multipoint contact has a considerable influence on determining the critical manipulation force. Additionally, the assumption of smooth surfaces or single-point contact leads to large error in the obtained results. According to the results of previous research, it anticipated that a particles with the radius less than about 550 nm start to slide on smooth substrate; but by using multipoint contact model, the predicted behavior changed, and particles with radii of smaller than 400 nm begin to slide on rough substrate for different height of asperities, at first.

Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator.

Science.gov (United States)

Raabe, D; Harrison, A; Ireland, A; Alemzadeh, K; Sandy, J; Dogramadzi, S; Melhuish, C; Burgess, S

2012-03-01

This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator

Improved single- and multi-contact life-time testing of dental restorative materials using key characteristics of the human masticatory system and a force/position-controlled robotic dental wear simulator

International Nuclear Information System (INIS)

Raabe, D; Dogramadzi, S; Melhuish, C; Harrison, A; Alemzadeh, K; Burgess, S; Ireland, A; Sandy, J

2012-01-01

This paper presents a new in vitro wear simulator based on spatial parallel kinematics and a biologically inspired implicit force/position hybrid controller to replicate chewing movements and dental wear formations on dental components, such as crowns, bridges or a full set of teeth. The human mandible, guided by passive structures such as posterior teeth and the two temporomandibular joints, moves with up to 6 degrees of freedom (DOF) in Cartesian space. The currently available wear simulators lack the ability to perform these chewing movements. In many cases, their lack of sufficient DOF enables them only to replicate the sliding motion of a single occlusal contact point by neglecting rotational movements and the motion along one Cartesian axis. The motion and forces of more than one occlusal contact points cannot accurately be replicated by these instruments. Furthermore, the majority of wear simulators are unable to control simultaneously the main wear-affecting parameters, considering abrasive mechanical wear, which are the occlusal sliding motion and bite forces in the constraint contact phase of the human chewing cycle. It has been shown that such discrepancies between the true in vivo and the simulated in vitro condition influence the outcome and the quality of wear studies. This can be improved by implementing biological features of the human masticatory system such as tooth compliance realized through the passive action of the periodontal ligament and active bite force control realized though the central nervous system using feedback from periodontal preceptors. The simulator described in this paper can be used for single- and multi-occlusal contact testing due to its kinematics and ability to exactly replicate human translational and rotational mandibular movements with up to 6 DOF without neglecting movements along or around the three Cartesian axes. Recorded human mandibular motion and occlusal force data are the reference inputs of the simulator

Air Force Senior Leaders

Science.gov (United States)

Force TV Radio Week in Photos About Us Air Force Senior Leaders SECAF CSAF CMSAF Biographies Adjunct Professors Senior Mentor Biographies Fact Sheets Commander's Call Topics CCT Archive CSAF Reading List 2017 Media Sites Site Registration Contact Us Search AF.mil: Home > About Us > Air Force Senior Leaders

Contact mechanical analysis of O-ring stresses

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyung Kyu

2007-02-15

The purpose of this project is to develop the approximate solutions of contact traction and internal stress of an O-ring by using a two dimensional elasticity for enhancing the design and failure prediction technology. Investigated were the applicability of Lindley's formulae of contact force prediction and the Hertz theory. Three cases of O-ring installation were considered. The approximate solution of contact tractions and internal stresses of each case were derived. The key results are summarized as follows: 1. It is verified that Lindley's formulae predicts the relationship between the fractional compression and contact force. 2. In the case of Case I, II and III without internal pressure, it is found that a function form of the contact traction is the Hertzian. So it is possible to express the traction with a Hertzian form and correction factors. 3. The internal stresses are derived in the case of the Hertzian traction profile. The stresses at the center of O-ring show a satisfactory result when compared with the finite element result.

Differential roles for medial prefrontal and medial temporal cortices in schema-dependent encoding: From congruent to incongruent

OpenAIRE

Kesteren, M.T.R. van; Beul, S.F.; Takashima, A.; Henson, R.N.; Ruiter, D.J.

2013-01-01

Information that is congruent with prior knowledge is generally remembered better than incongruent information. This effect of congruency on memory has been attributed to a facilitatory influence of activated schemas on memory encoding and consolidation processes, and hypothesised to reflect a shift between processing in medial temporal lobes (MTL) towards processing in medial prefrontal cortex (mPFC). To investigate this shift, we used functional magnetic resonance imaging (fMRI) to compare ...

Defining forces that are associated with shoulder dystocia: the use of a mathematic dynamic computer model.

Science.gov (United States)

Gonik, Bernard; Zhang, Ning; Grimm, Michele J

2003-04-01

A computer model was modified to study the impact of maternal endogenous and clinician-applied exogenous delivery loads on the contact force between the anterior fetal shoulder and the maternal symphysis pubis. Varying endogenous and exogenous loads were applied, and the contact force was determined. Experiments also examined the effect of pelvic orientation and the direction of load application on contact force behind the symphysis pubis. Exogenous loading forces (50-100 N) resulted in anterior shoulder contact forces of 107 to 127 N, with delivery accomplished at 100 N of applied load. Higher contact forces (147-272 N) were noted for endogenously applied loads (100-400 N), with delivery occurring at 400 N of maternal force. Pelvic rotation from lithotomy to McRoberts' positioning resulted in reduced contact forces. Downward lateral flexion of the fetal head led to little difference in contact force but required 30% more exogenous load to achieve delivery. Compared with clinician-applied exogenous force, larger maternally derived endogenous forces are needed to clear the impacted anterior fetal shoulder. This is associated with >2 times more contact force by the obstructing symphysis pubis. McRoberts' positioning reduces shoulder-symphysis pubis contact force. Lateral flexion of the fetal head results in the larger forces that are needed for delivery but has little effect on contact force. Model refinements are needed to examine delivery forces and brachial plexus stretching more specifically.

Opening the medial tibiofemoral compartment by pie-crusting the superficial medial collateral ligament at its tibial insertion: a cadaver study.

Science.gov (United States)

Roussignol, X; Gauthe, R; Rahali, S; Mandereau, C; Courage, O; Duparc, F

2015-09-01

Arthroscopic treatment of tears in the middle and posterior parts of the medial meniscus can be difficult when the medial tibiofemoral compartment is tight. Passage of the instruments may damage the cartilage. The primary objective of this cadaver study was to perform an arthroscopic evaluation of medial tibiofemoral compartment opening after pie-crusting release (PCR) of the superficial medial collateral ligament (sMCL) at its distal insertion on the tibia. The secondary objective was to describe the anatomic relationships at the site of PCR (saphenous nerve, medial saphenous vein). We studied 10 cadaver knees with no history of invasive procedures. The femur was held in a vise with the knee flexed at 45°, and the medial aspect of the knee was dissected. PCR of the sMCL was performed under arthroscopic vision, in the anteroposterior direction, at the distal tibial insertion of the sMCL, along the lower edge of the tibial insertion of the semi-tendinosus tendon. Continuous 300-N valgus stress was applied to the ankle. Opening of the medial tibiofemoral compartment was measured arthroscopically using graduated palpation hooks after sequential PCR of the sMCL. The compartment opened by 1mm after release of the anterior third, 2.3mm after release of the anterior two-thirds, and 3.9mm after subtotal release. A femoral fracture occurred in 1 case, after completion of all measurements. Both the saphenous nerve and the medial saphenous vein were located at a distance from the PCR site in all 10 knees. PCR of the sMCL is chiefly described as a ligament-balancing method during total knee arthroplasty. This procedure is usually performed at the joint line, where it opens the compartment by 4-6mm at the most, with some degree of unpredictability. PCR of the sMCL at its distal tibial insertion provides gradual opening of the compartment, to a maximum value similar to that obtained with PCR at the joint space. The lower edge of the semi-tendinosus tendon is a valuable landmark

Cartilage Delamination Flap Mimicking a Torn Medial Meniscus

Directory of Open Access Journals (Sweden)

Gan Zhi-Wei Jonathan

2016-01-01

Full Text Available We report a case of a chondral delamination lesion due to medial parapatellar plica friction syndrome involving the medial femoral condyle. This mimicked a torn medial meniscus in clinical and radiological presentation. Arthroscopy revealed a chondral delamination flap, which was debrided. Diagnosis of chondral lesions in the knee can be challenging. Clinical examination and MRI have good accuracy for diagnosis and should be used in tandem. Early diagnosis and treatment of chondral lesions are important to prevent progression to early osteoarthritis.

Impaired Varus-Valgus Proprioception and Neuromuscular Stabilization in Medial Knee Osteoarthritis

Science.gov (United States)

Chang, Alison H.; Lee, Song Joo; Zhao, Heng; Ren, Yupeng; Zhang, Li-Qun

2014-01-01

Impaired proprioception and poor muscular stabilization in the frontal plane may lead to knee instability during functional activities, a common complaint in persons with knee osteoarthritis (KOA). Understanding these frontal plane neuromechanical properties in KOA will help elucidate the factors contributing to knee instability and aid in the development of targeted intervention strategies. The study objectives were to compare knee varus-valgus proprioception, isometric muscle strength, and active muscular contribution to stability between persons with medial KOA and healthy controls. We evaluated knee frontal plane neuromechanical parameters in 14 participants with medial KOA and 14 age- and gender-matched controls, using a joint driving device (JDD) with a customized motor and a 6-axis force sensor. Analysis of covariance with BMI as a covariate was used to test the differences in varus-valgus neuromechanical parameters between these two groups. The KOA group had impaired varus proprioception acuity (1.08 ± 0.59° vs. 0.69 ± 0.49°, p < 0.05), decreased normalized varus muscle strength (1.31 ± 0.75% vs. 1.79 ± 0.84% body weight, p < 0.05), a trend toward decreased valgus strength (1.29 ± 0.67% vs. 1.88 ± 0.99%, p = 0.054), and impaired ability to actively stabilize the knee in the frontal plane during external perturbation (4.67 ± 2.86 vs. 8.26 ± 5.95 Nm/degree, p < 0.05). The knee frontal plane sensorimotor control system is compromised in persons with medial KOA. Our findings suggest varus-valgus control deficits in both the afferent input (proprioceptive acuity) and muscular effectors (muscle strength and capacity to stabilize the joint). PMID:24321442

Medial branch neurotomy in low back pain

International Nuclear Information System (INIS)

Masala, Salvatore; Mammucari, Matteo; Simonetti, Giovanni; Nano, Giovanni; Marcia, Stefano

2012-01-01

This study aimed to assess the effectiveness of pulsed radiofrequency medial branch dorsal ramus neurotomy in patients with facet joint syndrome. From January 2008 to April 2010, 92 patients with facet joint syndrome diagnosed by strict inclusion criteria and controlled diagnostic blocks undergone medial branch neurotomy. We did not exclude patients with failed back surgery syndrome (FBSS). Electrodes (20G) with 5-mm active tip were placed under fluoroscopy guide parallel to medial branch. Patients were followed up by physical examination and by Visual Analog Scale and Oswestry Disability Index at 1, 6, and 12 months. In all cases, pain improvement was statistically significant and so quality of life. Three non-FBSS patients had to undergo a second neurotomy because of non-satisfactory pain decrease. Complications were reported in no case. Medial branch radiofrequency neurotomy has confirmed its well-established effectiveness in pain and quality of life improvement as long as strict inclusion criteria be fulfilled and nerve ablation be accomplished by parallel electrode positioning. This statement can be extended also to FBSS patients. (orig.)

Medial branch neurotomy in low back pain

Energy Technology Data Exchange (ETDEWEB)

Masala, Salvatore; Mammucari, Matteo; Simonetti, Giovanni [Interventional Radiology and Radiotherapy University ' ' Tor Vergata' ' , Department of Diagnostic and Molecular Imaging, Rome (Italy); Nano, Giovanni [Interventional Radiology and Radiotherapy University ' ' Tor Vergata' ' , Department of Diagnostic and Molecular Imaging, Rome (Italy); University ' ' Tor Vergata' ' , Department of Radiology, Rome (Italy); Marcia, Stefano [S. Giovanni di Dio Hospital, Department of Diagnostic and Molecular Imaging, Cagliari (Italy)

2012-07-15

This study aimed to assess the effectiveness of pulsed radiofrequency medial branch dorsal ramus neurotomy in patients with facet joint syndrome. From January 2008 to April 2010, 92 patients with facet joint syndrome diagnosed by strict inclusion criteria and controlled diagnostic blocks undergone medial branch neurotomy. We did not exclude patients with failed back surgery syndrome (FBSS). Electrodes (20G) with 5-mm active tip were placed under fluoroscopy guide parallel to medial branch. Patients were followed up by physical examination and by Visual Analog Scale and Oswestry Disability Index at 1, 6, and 12 months. In all cases, pain improvement was statistically significant and so quality of life. Three non-FBSS patients had to undergo a second neurotomy because of non-satisfactory pain decrease. Complications were reported in no case. Medial branch radiofrequency neurotomy has confirmed its well-established effectiveness in pain and quality of life improvement as long as strict inclusion criteria be fulfilled and nerve ablation be accomplished by parallel electrode positioning. This statement can be extended also to FBSS patients. (orig.)

The effects of neuromuscular exercise on medial knee joint load post-arthroscopic partial medial meniscectomy: 'SCOPEX', a randomised control trial protocol

DEFF Research Database (Denmark)

Hall, Michelle; Hinman, Rana S; Wrigley, Tim V

2012-01-01

Meniscectomy is a risk factor for knee osteoarthritis, with increased medial joint loading a likely contributor to the development and progression of knee osteoarthritis in this group. Therefore, post-surgical rehabilitation or interventions that reduce medial knee joint loading have the potential...... to reduce the risk of developing or progressing osteoarthritis. The primary purpose of this randomised, assessor-blind controlled trial is to determine the effects of a home-based, physiotherapist-supervised neuromuscular exercise program on medial knee joint load during functional tasks in people who have...

Prediction of static friction coefficient in rough contacts based on the junction growth theory

Science.gov (United States)

Spinu, S.; Cerlinca, D.

2017-08-01

The classic approach to the slip-stick contact is based on the framework advanced by Mindlin, in which localized slip occurs on the contact area when the local shear traction exceeds the product between the local pressure and the static friction coefficient. This assumption may be too conservative in the case of high tractions arising at the asperities tips in the contact of rough surfaces, because the shear traction may be allowed to exceed the shear strength of the softer material. Consequently, the classic frictional contact model is modified in this paper so that gross sliding occurs when the junctions formed between all contacting asperities are independently sheared. In this framework, when the contact tractions, normal and shear, exceed the hardness of the softer material on the entire contact area, the material of the asperities yields and the junction growth process ends in all contact regions, leading to gross sliding inception. This friction mechanism is implemented in a previously proposed numerical model for the Cattaneo-Mindlin slip-stick contact problem, which is modified to accommodate the junction growth theory. The frictionless normal contact problem is solved first, then the tangential force is gradually increased, until gross sliding inception. The contact problems in the normal and in the tangential direction are successively solved, until one is stabilized in relation to the other. The maximum tangential force leading to a non-vanishing stick area is the static friction force that can be sustained by the rough contact. The static friction coefficient is eventually derived as the ratio between the latter friction force and the normal force.

Natural history of medial clavicle fractures.

Science.gov (United States)

Salipas, Andrew; Kimmel, Lara A; Edwards, Elton R; Rakhra, Sandeep; Moaveni, Afshin Kamali

2016-10-01

Fractures of the medial third of the clavicle comprise less than 3% of all clavicle fractures. The natural history and optimal management of these rare injuries are unknown. The aim of our study is to describe the demographics, management and outcomes of patients with medial clavicle fractures treated at a Level 1 Trauma Centre. A retrospective review was conducted of patients presenting to our institution between January 2008 and March 2013 with a medial third clavicle fracture. Clinical and radiographic data were recorded including mechanism of injury, fracture pattern and displacement, associated injuries, management and complications. Functional outcomes were assessed using the Glasgow Outcome Scale Extended (GOS-E) scores from the Victorian Orthopaedic Trauma Outcomes Registry (VOTOR). Shoulder outcomes were assessed using two patient reported outcomes scores, the American Shoulder and Elbow Society Score (ASES) and the Subjective Shoulder Value (SSV). Sixty eight medial clavicle fractures in 68 patients were evaluated. The majority of patients were male (n=53), with a median age of 53.5 years (interquartile range (IQR) 37.5-74.5 years). The most common mechanism of injury was motor vehicle accident (n=28). The in-hospital mortality rate was 4.4%. The fracture pattern was almost equally distributed between extra articular (n=35) and intra-articular (n=33). Fifty-five fractures (80.9%) had minimal or no displacement. Associated injuries were predominantly thoracic (n=31). All fractures were initially managed non-operatively, with a broad arm sling. Delayed operative fixation was performed for painful atrophic delayed union in two patients (2.9%). Both patients were under 65 years of age and had a severely displaced fracture of the medial clavicle. One intra-operative vascular complication was seen, with no adverse long-term outcome. Follow-up was obtained in 85.0% of the surviving cohort at an average of three years post injury (range 1-6 years). The mean ASES

Evaluation of a musculoskeletal model with prosthetic knee through six experimental gait trials.

Science.gov (United States)

Kia, Mohammad; Stylianou, Antonis P; Guess, Trent M

2014-03-01

Knowledge of the forces acting on musculoskeletal joint tissues during movement benefits tissue engineering, artificial joint replacement, and our understanding of ligament and cartilage injury. Computational models can be used to predict these internal forces, but musculoskeletal models that simultaneously calculate muscle force and the resulting loading on joint structures are rare. This study used publicly available gait, skeletal geometry, and instrumented prosthetic knee loading data [1] to evaluate muscle driven forward dynamics simulations of walking. Inputs to the simulation were measured kinematics and outputs included muscle, ground reaction, ligament, and joint contact forces. A full body musculoskeletal model with subject specific lower extremity geometries was developed in the multibody framework. A compliant contact was defined between the prosthetic femoral component and tibia insert geometries. Ligament structures were modeled with a nonlinear force-strain relationship. The model included 45 muscles on the right lower leg. During forward dynamics simulations a feedback control scheme calculated muscle forces using the error signal between the current muscle lengths and the lengths recorded during inverse kinematics simulations. Predicted tibio-femoral contact force, ground reaction forces, and muscle forces were compared to experimental measurements for six different gait trials using three different gait types (normal, trunk sway, and medial thrust). The mean average deviation (MAD) and root mean square deviation (RMSD) over one gait cycle are reported. The muscle driven forward dynamics simulations were computationally efficient and consistently reproduced the inverse kinematics motion. The forward simulations also predicted total knee contact forces (166Nphysiological motor control patterns during gait. Consequently, the simulations did not accurately predict medial/lateral tibio-femoral force distribution and muscle activation timing. Copyright

Usefullness of three-dimensional templating software to quantify the contact state between implant and femur in total hip arthroplasty.

Science.gov (United States)

Inoue, Daisuke; Kabata, Tamon; Maeda, Toru; Kajino, Yoshitomo; Fujita, Kenji; Hasegawa, Kazuhiro; Yamamoto, Takashi; Takagi, Tomoharu; Ohmori, Takaaki; Tsuchiya, Hiroyuki

2015-12-01

It would be ideal if surgeons could precisely confirm whether the planned femoral component achieves the best fit and fill of implant and femur. However, the cortico-cancellous interfaces can be difficult to standardize using plain radiography, and therefore, determining the contact state is a subjective decision by the examiner. Few reports have described the use of CT-based three-dimensional templating software to quantify the contact state of stem and femur in detail. The purpose of this study was to use three-dimensional templating software to quantify the implant-femur contact state and develop a technique to analyze the initial fixation pattern of a cementless femoral stem. We conducted a retrospective review of 55 hips in 53 patients using a short proximal fit-and-fill anatomical stem (APS Natural-Hip™ System). All femurs were examined by density mapping which can visualize and digitize the contact state. We evaluated the contact state of implant and femur by using density mapping. The varus group (cases that had changed varus 2° by 3 months after surgery) consisted of 11 hips. The varus group showed no significant difference with regard to cortical contact in the proximal medial portion (Gruen 7), but the contact area in the distal portion (Gruen 3 and Gruen 5) was significantly lower than that of non-varus group. Density mapping showed that the stem only has to be press-fit to the medial calcar, but also must fill the distal portion of the implant in order to achieve the ideal contact state. Our results indicated that quantifying the contact state of implant and femur by using density mapping is a useful technique to accurately analyze the fixation pattern of a cementless femoral stem.

Determination of the nano-scaled contact area of staphylococcal cells.

Science.gov (United States)

Spengler, Christian; Thewes, Nicolas; Jung, Philipp; Bischoff, Markus; Jacobs, Karin

2017-07-20

Bacterial adhesion is a crucial step during the development of infections as well as the formation of biofilms. Hence, fundamental research of bacterial adhesion mechanisms is of utmost importance. So far, less is known about the size of the contact area between bacterial cells and a surface. This gap will be filled by this study using a single-cell force spectroscopy-based method to investigate the contact area between a single bacterial cell of Staphylococcus aureus and a solid substrate. The technique relies on the strong influence of the hydrophobic interaction on bacterial adhesion: by incrementally crossing a very sharp hydrophobic/hydrophilic interface while performing force-distance curves with a single bacterial probe, the bacterial contact area can be determined. Assuming circular contact areas, their radii - determined in our experiments - are in the range from tens of nanometers to a few hundred nanometers. The contact area can be slightly enlarged by a larger load force, yet does not resemble a Hertzian contact, rather, the enlargement is a property of the individual bacterial cell. Additionally, Staphylococcus carnosus has been probed, which is less adherent than S. aureus, yet both bacteria exhibit a similar contact area size. This corroborates the notion that the adhesive strength of bacteria is not a matter of contact area, but rather a matter of which and how many molecules of the bacterial species' cell wall form the contact. Moreover, our method of determining the contact area can be applied to other microorganisms and the results might also be useful for studies using nanoparticles covered with soft, macromolecular coatings.

Ulnohumeral chondral and ligamentous overload: biomechanical correlation for posteromedial chondromalacia of the elbow in throwing athletes.

Science.gov (United States)

Osbahr, Daryl C; Dines, Joshua S; Breazeale, Nathan M; Deng, Xiang-Hua; Altchek, David W

2010-12-01

Previous studies have documented increased posteromedial contact forces with the elbow at lower flexion angles associated with valgus extension overload; however, the authors believe that posteromedial elbow impingement in association with valgus laxity is a complex pathological process that may occur throughout the entire throwing motion in the form of ulnohumeral chondral and ligamentous overload. Valgus laxity with the elbow at 90° of flexion may lead to chondromalacia secondary to a subtle shift in the contact point between the tip of the olecranon and the distal humeral trochlea. Controlled laboratory study. Six fresh human cadaveric elbows were dissected and subjected to a static valgus load. Pressure-sensitive Fuji film measured the contact pressure, contact area, and shift in contact area across the posteromedial elbow before and after sectioning the anterior bundle of the ulnar collateral ligament. The contact pressure between the tip of the olecranon process and the medial crista of the posterior humeral trochlea significantly increased, from an average of 0.27 ± 0.06 kg/cm² to 0.40 ± 0.08 kg/cm². The contact area also significantly decreased, from an average of 30.34 ± 9.17 mm² to 24.59 ± 6.44 mm², and shifted medially on the medial humeral crista, which corresponds to the position of the posteromedial chondral lesions that was observed in throwing athletes in the authors' clinical practice. While simulating the early acceleration phase of the throwing motion with the elbow in 90° of flexion, the results illustrate that abnormal contact may occur as a result of valgus laxity through increased contact pressures across the posteromedial elbow between the medial tip of the olecranon and medial crista of the humeral trochlea. In addition, congruency of the ulnohumeral joint changed, as there was a statistically significant medial shift of the olecranon on the posterior humeral trochlea with the elbow at 90° of flexion after sectioning the anterior

Adding Value to Force Diagrams: Representing Relative Force Magnitudes

Science.gov (United States)

Wendel, Paul

2011-05-01

Nearly all physics instructors recognize the instructional value of force diagrams, and this journal has published several collections of exercises to improve student skill in this area.1-4 Yet some instructors worry that too few students perceive the conceptual and problem-solving utility of force diagrams,4-6 and over recent years a rich variety of approaches has been proposed to add value to force diagrams. Suggestions include strategies for identifying candidate forces,6,7 emphasizing the distinction between "contact" and "noncontact" forces,5,8 and the use of computer-based tutorials.9,10 Instructors have suggested a variety of conventions for constructing force diagrams, including approaches to arrow placement and orientation2,11-13 and proposed notations for locating forces or marking action-reaction force pairs.8,11,14,15

The steady-state tangential contact problem for a falling drop type of contact area on corrugated rail by simplified theory of rolling contact

Science.gov (United States)

Piotrowski, Jerzy

1991-10-01

Investigation of contact mechanical nonlinearities of a mathematical model of corrugation revealed that the typical shape of contact patch resembles a falling drop of water. A contact patch of that shape was approximated with a figure composed of two parts of ellipses with different eccentricities. The contact pressure distribution was assumed as a smoothing ensemble of two paraboloidal distributions. The description of a general case of double half elliptical contact area was given but a special case of double half elliptical contact is more interesting as it possesses some Hertzian properties. It was shown how three geometrical parameters of double half elliptical contact can be chosen when actual, non-Hertzian contact is known. A linear theory was written which indicates that the lateral vibrations of the rail may be excited only due to shape variation on corrugation even if any other cause for these vibrations does not exist. For nonlinear theory a computer program, based on FASTSIM algorithm by Kalker, was written. The aim is to calculate the creep forces and frictional power density distribution over the contact area. Also, a graphic program visualizing the solution was written. Numerical results are not provided; unattended and unsolved problems relevant for this type of contact are listed.

The effect of different depths of medial heel skive on plantar pressures

Directory of Open Access Journals (Sweden)

Bonanno Daniel R

2012-08-01

Full Text Available Abstract Background Foot orthoses are often used to treat lower limb injuries associated with excessive pronation. There are many orthotic modifications available for this purpose, with one being the medial heel skive. However, empirical evidence for the mechanical effects of the medial heel skive modification is limited. This study aimed to evaluate the effect that different depths of medial heel skive have on plantar pressures. Methods Thirty healthy adults (mean age 24 years, range 18–46 with a flat-arched or pronated foot posture and no current foot pain or deformity participated in this study. Using the in-shoe pedar-X® system, plantar pressure data were collected for the rearfoot, midfoot and forefoot while participants walked along an 8 metre walkway wearing a standardised shoe. Experimental conditions included a customised foot orthosis with the following 4 orthotic modifications: (i no medial heel skive, (ii a 2 mm medial heel skive, (iii a 4 mm medial heel skive and (iv a 6 mm medial heel skive. Results Compared to the foot orthosis with no medial heel skive, statistically significant increases in peak pressure were observed at the medial rearfoot – there was a 15% increase (p = 0.001 with the 4 mm skive and a 29% increase (p  Conclusions This study found that a medial heel skive of 4 mm or 6 mm increases peak pressure under the medial rearfoot in asymptomatic adults with a flat-arched or pronated foot posture. Plantar pressures at the midfoot and forefoot were not altered by a medial heel skive of 2, 4 or 6 mm. These findings provide some evidence for the effects of the medial heel skive orthotic modification.

Embodied Archives as Contact Zones

Directory of Open Access Journals (Sweden)

Judit Vidiella

2015-02-01

Full Text Available This article proposes a reflection about affective politics from locating some theoretical and conceptual genealogies like «emotion», «affection», «zones of contact»…, that understand them as action and force fields. These contributions allow us to rethink the relation of affects with politics and strategies of archive linked to performance, and understood as zones of friction, collision, circulation and contact: performative writing, repertoire, memes…

Correlations between deformations, surface state and leak rate in metal to metal contact; Correlations entre deformations, etat de surface et debit de fuite au contact metal-metal

Energy Technology Data Exchange (ETDEWEB)

Armand, G; Lapujoulade, J; Paigne, J [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1963-07-01

The study of metal to metal contact from the stand-point of the leak rate has been carried on a copper ring located between two hard-steel flanges. The analysis of the results confirms the hysteresis phenomenon already seen. Some curves (leak rate versus force and leak rate versus true deformation) in semi-logarithmic coordinates are straight lines. Likewise some curves (electrical contact resistance versus force) in bi-logarithmic coordinates are straight lines. All these results can be understood by looking at the conductance introduced by the deformations of the micro-geometry of the surfaces in contact. Some tests carried out in rising the temperature confirm these hypothesis. (authors) [French] L'etude du contact metal-metal du point de vue debit de fuite a ete poursuivie en utilisant un anneau de cuivre place entre brides d'acier dur. L'analyse des resultats confirme le phenomene d'hysteresis deja constate, montre l'influence de l'etat de surface des brides et du joint. Certaines courbes (debit de fuite/force et debit de fuite/deformation rationnelle), en coordonnees semi-logarithmiques, sont des droites. De meme, certaines courbes (resistance de contact/force) en coordonnees bi-logarithmiques, sont des droites. Ces resultats s'interpretent en considerant la conductance produite par la deformation des microgeometries des surfaces en contact. Quelques essais d'elevation de temperature confirment ces resultats. (auteurs)

The Use of Contact Mode Atomic Force Microscopy in Aqueous Medium for Structural Analysis of Spinach Photosynthetic Complexes

Energy Technology Data Exchange (ETDEWEB)

Phuthong, Witchukorn; Huang, Zubin; Wittkopp, Tyler M.; Sznee, Kinga; Heinnickel, Mark L.; Dekker, Jan P.; Frese, Raoul N.; Prinz, Fritz B.; Grossman, Arthur R.

2015-07-28

To investigate the dynamics of photosynthetic pigment-protein complexes in vascular plants at high resolution in an aqueous environment, membrane-protruding oxygen-evolving complexes (OECs) associated with photosystem II (PSII) on spinach (Spinacia oleracea) grana membranes were examined using contact mode atomic force microscopy. This study represents, to our knowledge, the first use of atomic force microscopy to distinguish the putative large extrinsic loop of Photosystem II CP47 reaction center protein (CP47) from the putative oxygen-evolving enhancer proteins 1, 2, and 3 (PsbO, PsbP, and PsbQ) and large extrinsic loop of Photosystem II CP43 reaction center protein (CP43) in the PSII-OEC extrinsic domains of grana membranes under conditions resulting in the disordered arrangement of PSII-OEC particles. Moreover, we observed uncharacterized membrane particles that, based on their physical characteristics and electrophoretic analysis of the polypeptides associated with the grana samples, are hypothesized to be a domain of photosystem I that protrudes from the stromal face of single thylakoid bilayers. Our results are interpreted in the context of the results of others that were obtained using cryo-electron microscopy (and single particle analysis), negative staining and freeze-fracture electron microscopy, as well as previous atomic force microscopy studies.

Abnormalities of the First Three Steps of Gait Initiation in Patients with Parkinson's Disease with Freezing of Gait

Directory of Open Access Journals (Sweden)

Yohei Okada

2011-01-01

Full Text Available The purpose of this study was to investigate abnormalities of the first three steps of gait initiation in patients with Parkinson's disease (PD with freezing of gait (FOG. Ten PD patients with FOG and 10 age-matched healthy controls performed self-generated gait initiation. The center of pressure (COP, heel contact positions, and spatiotemporal parameters were estimated from the vertical pressures on the surface of the force platform. The initial swing side of gait initiation was consistent among the trials in healthy controls but not among the trials in PD patients. The COP and the heel contact position deviated to the initial swing side during the first step, and the COP passed medial to each heel contact position during the first two steps in PD patients. Medial deviation of the COP from the first heel contact position had significant correlation with FOG questionnaire item 5. These findings indicate that weight shifting between the legs is abnormal and that medial deviation of the COP from the first heel contact position sensitively reflects the severity of FOG during the first three steps of gait initiation in PD patients with FOG.

On multiscale moving contact line theory.

Science.gov (United States)

Li, Shaofan; Fan, Houfu

2015-07-08

In this paper, a multiscale moving contact line (MMCL) theory is presented and employed to simulate liquid droplet spreading and capillary motion. The proposed MMCL theory combines a coarse-grained adhesive contact model with a fluid interface membrane theory, so that it can couple molecular scale adhesive interaction and surface tension with hydrodynamics of microscale flow. By doing so, the intermolecular force, the van der Waals or double layer force, separates and levitates the liquid droplet from the supporting solid substrate, which avoids the shear stress singularity caused by the no-slip condition in conventional hydrodynamics theory of moving contact line. Thus, the MMCL allows the difference of the surface energies and surface stresses to drive droplet spreading naturally. To validate the proposed MMCL theory, we have employed it to simulate droplet spreading over various elastic substrates. The numerical simulation results obtained by using MMCL are in good agreement with the molecular dynamics results reported in the literature.

TCDD alters medial epithelial cell differentiation during palatogenesis

International Nuclear Information System (INIS)

Abbott, B.D.; Birnbaum, L.S.

1989-01-01

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widely distributed, persistent environmental contaminant that is teratogenic in mice, where it induces hydronephrosis and cleft palate. The incidence of clefting has been shown to be dose dependent after exposure on either gestation Day (GD) 10 or 12, although the embryo is more susceptible on GD 12. TCDD-exposed palatal shelves meet but do not fuse, and programmed cell death of the medial epithelial cells is inhibited. The mechanism of action through which TCDD alters the program of medial cell development has not been examined in earlier studies, and it is not known whether the mechanism is the same regardless of the dose or developmental stage of exposure. In this study, C57BL/6N mice, a strain sensitive to TCDD, were dosed orally on GD 10 or 12 with 0, 6, 12, 24, or 30 micrograms/kg body wt, in 10 ml corn oil/kg. Embryonic palatal shelves were examined on GD 14, 15, or 16. The degree of palatal closure, epithelial surface morphology, and cellular ultrastructure, the incorporation of [3H]TdR, the expression of EGF receptors, and the binding of 125I-EGF were assessed. After exposure on GD 10 or 12, TCDD altered the differentiation pathway of the medial epithelial cells. The palatal shelves were of normal size and overall morphology, but fusion of the medial epithelia of the opposing shelves did not occur. TCDD prevented programmed cell death of the medial peridermal cells. The expression of EGF receptors by medial cells continued through Day 16 and the receptors were able to bind ligand. The medial cells differentiated into a stratified, squamous, keratinizing epithelium. The shift in phenotype to an oral-like epithelium occurred after exposure on either GD 10 or 12. At the lower dose (6 micrograms/kg), fewer cleft palates were produced, but those shelves which did respond had a fully expressed shift in differentiation

Non-contacting "snubber bearing" for passive magnetic bearing systems

Science.gov (United States)

Post, Richard F

2017-08-22

A new non-contacting magnetic "snubber" bearing is provided for application to rotating systems such as vehicular electromechanical battery systems subject to frequent accelerations. The design is such that in the equilibrium position the drag force of the snubber is very small (milliwatts). However in a typical case, if the rotor is displaced by as little as 2 millimeters a large restoring force is generated without any physical contact between the stationary and rotating parts of the snubber bearing.

Medial shoe-ground pressure and specific running injuries

DEFF Research Database (Denmark)

Brund, René B K; Rasmussen, Sten; Nielsen, Rasmus O

2017-01-01

pressure. Foot balance was categorized into those which presented a higher lateral shod pressure (LP) than medial pressure, and those which presented a higher medial shod pressure (MP) than lateral pressure during the stance phase. A time-to-event model was used to compare differences in incidence between...

Effect of surface tension on the behavior of adhesive contact based on Lennard-Jones potential law

Science.gov (United States)

Zhu, Xinyao; Xu, Wei

2018-02-01

The present study explores the effect of surface tension on adhesive contact behavior where the adhesion is interpreted by long-range intermolecular forces. The adhesive contact is analyzed using the equivalent system of a rigid sphere and an elastic half space covered by a membrane with surface tension. The long-range intermolecular forces are modeled with the Lennard‒Jones (L‒J) potential law. The current adhesive contact issue can be represented by a nonlinear integral equation, which can be solved by Newton‒Raphson method. In contrast to previous studies which consider intermolecular forces as short-range, the present study reveals more details of the features of adhesive contact with surface tension, in terms of jump instabilities, pull-off forces, pressure distribution within the contact area, etc. The transition of the pull-off force is not only consistent with previous studies, but also presents some new interesting characteristics in the current situation.

Effect of cranial cruciate ligament deficiency, tibial plateau leveling osteotomy, and tibial tuberosity advancement on contact mechanics and alignment of the stifle in flexion.

Science.gov (United States)

Kim, Stanley E; Pozzi, Antonio; Banks, Scott A; Conrad, Bryan P; Lewis, Daniel D

2010-04-01

To assess contact mechanics and 3-dimensional (3-D) joint alignment in cranial cruciate ligament (CCL)-deficient stifles before and after tibial plateau leveling osteotomy (TPLO) and tibial tuberosity advancement (TTA) with the stifle in 90 degrees of flexion. In vitro biomechanical study. Cadaveric pelvic limb pairs (n=8) from dogs weighing 28-35 kg. Contralateral limbs were assigned to receive TPLO or TTA. Digital pressure sensors were used to measure femorotibial contact area, peak and mean contact pressure, and peak pressure location with the limb under a load of 30% body weight and stifle flexion angle of 90 degrees . 3-D poses were obtained using a Microscribe digitizer. Specimens were tested under normal, CCL deficient, and treatment conditions. Significant disturbances in alignment were not observed after CCL transection, although medial contact area was 10% smaller than normal (P=.003). There were no significant differences in contact mechanics or alignment between normal and TTA conditions; TPLO induced 6 degrees varus angulation (PCranial tibial subluxation is nominal in CCL-deficient stifles loaded in flexion. Stifle alignment and contact mechanics are not altered by TTA, whereas TPLO causes mild varus and a subsequent increase in medial compartment loading. Cranial tibial subluxation of CCL-deficient stifles may not occur during postures that load the stifle in flexion. The significance of minor changes in loading patterns after TPLO is unknown.

Contact dynamics math model

Science.gov (United States)

Glaese, John R.; Tobbe, Patrick A.

1986-01-01

The Space Station Mechanism Test Bed consists of a hydraulically driven, computer controlled six degree of freedom (DOF) motion system with which docking, berthing, and other mechanisms can be evaluated. Measured contact forces and moments are provided to the simulation host computer to enable representation of orbital contact dynamics. This report describes the development of a generalized math model which represents the relative motion between two rigid orbiting vehicles. The model allows motion in six DOF for each body, with no vehicle size limitation. The rotational and translational equations of motion are derived. The method used to transform the forces and moments from the sensor location to the vehicles' centers of mass is also explained. Two math models of docking mechanisms, a simple translational spring and the Remote Manipulator System end effector, are presented along with simulation results. The translational spring model is used in an attempt to verify the simulation with compensated hardware in the loop results.

The Impact of Nitinol Staples on the Compressive Forces, Contact Area, and Mechanical Properties in Comparison to a Claw Plate and Crossed Screws for the First Tarsometatarsal Arthrodesis.

Science.gov (United States)

Aiyer, Amiethab; Russell, Nicholas A; Pelletier, Matthew H; Myerson, Mark; Walsh, William R

2016-06-01

Background The optimal fixation method for the first tarsometatarsal arthrodesis remains controversial. This study aimed to develop a reproducible first tarsometatarsal testing model to evaluate the biomechanical performance of different reconstruction techniques. Methods Crossed screws or a claw plate were compared with a single or double shape memory alloy staple configuration in 20 Sawbones models. Constructs were mechanically tested in 4-point bending to 1, 2, and 3 mm of plantar displacement. The joint contact force and area were measured at time zero, and following 1 and 2 mm of bending. Peak load, stiffness, and plantar gapping were determined. Results Both staple configurations induced a significantly greater contact force and area across the arthrodesis than the crossed screw and claw plate constructs at all measurements. The staple constructs completely recovered their plantar gapping following each test. The claw plate generated the least contact force and area at the joint interface and had significantly greater plantar gapping than all other constructs. The crossed screw constructs were significantly stiffer and had significantly less plantar gapping than the other constructs, but this gapping was not recoverable. Conclusions Crossed screw fixation provides a rigid arthrodesis with limited compression and contact footprint across the joint. Shape memory alloy staples afford dynamic fixation with sustained compression across the arthrodesis. A rigid polyurethane foam model provides an anatomically relevant comparison for evaluating the interface between different fixation techniques. Clinical Relevance The dynamic nature of shape memory alloy staples offers the potential to permit early weight bearing and could be a useful adjunctive device to impart compression across an arthrodesis of the first tarsometatarsal joint. Therapeutic, Level V: Bench testing. © 2015 The Author(s).

Response function of a moving contact line

Science.gov (United States)

Perrin, H.; Belardinelli, D.; Sbragaglia, M.; Andreotti, B.

2018-04-01

The hydrodynamics of a liquid-vapor interface in contact with a heterogeneous surface is largely impacted by the presence of defects at the smaller scales. Such defects introduce morphological disturbances on the contact line and ultimately determine the force exerted on the wedge of liquid in contact with the surface. From the mathematical point of view, defects introduce perturbation modes, whose space-time evolution is governed by the interfacial hydrodynamic equations of the contact line. In this paper we derive the response function of the contact line to such generic perturbations. The contact line response may be used to design simplified one-dimensional time-dependent models accounting for the complexity of interfacial flows coupled to nanoscale defects, yet offering a more tractable mathematical framework to explore contact line motion through a disordered energy landscape.

The medial patellofemoral complex.

Science.gov (United States)

Loeb, Alexander E; Tanaka, Miho J

2018-06-01

The purpose of this review is to describe the current understanding of the medial patellofemoral complex, including recent anatomic advances, evaluation of indications for reconstruction with concomitant pathology, and surgical reconstruction techniques. Recent advances in our understanding of MPFC anatomy have found that there are fibers that insert onto the deep quadriceps tendon as well as the patella, thus earning the name "medial patellofemoral complex" to allow for the variability in its anatomy. In MPFC reconstruction, anatomic origin and insertion points and appropriate graft length are critical to prevent overconstraint of the patellofemoral joint. The MPFC is a crucial soft tissue checkrein to lateral patellar translation, and its repair or reconstruction results in good restoration of patellofemoral stability. As our understanding of MPFC anatomy evolves, further studies are needed to apply its relevance in kinematics and surgical applications to its role in maintaining patellar stability.

Quantification of the Contact Area at the Head-Stem Taper Interface of Modular Hip Prostheses.

Science.gov (United States)

Witt, Florian; Gührs, Julian; Morlock, Michael M; Bishop, Nicholas E

2015-01-01

Corrosion of modular taper junctions of hip implants may be associated with clinical failure. Taper design parameters, as well as the intraoperatively applied assembly forces, have been proposed to affect corrosion. Fretting corrosion is related to relative interface shear motion and fluid ingress, which may vary with contact force and area. It was hypothesised in this study that assembly forces modify the extent and distribution of the surface contact area at the taper interface between a cobalt chrome head and titanium stem taper with a standard threaded surface profile. Local abrasion of a thin gold coating applied to the stem taper prior to assembly was used to determine the contact area after disassembly. Profilometry was then used to assess permanent deformation of the stem taper surface profile. With increasing assembly force (500 N, 2000 N, 4000 N and 8000 N) the number of stem taper surface profile ridges in contact with the head taper was found to increase (9.2±9.3%, 65.4±10.8%, 92.8±6.0% and 100%) and the overall taper area in contact was also found to increase (0.6±0.7%, 5.5±1.0%, 9.9±1.1% and 16.1±0.9%). Contact was inconsistently distributed over the length of the taper. An increase in plastic radial deformation of the surface ridges (-0.05±0.14 μm, 0.1±0.14 μm, 0.21±0.22 μm and 0.96±0.25 μm) was also observed with increasing assembly force. The limited contact of the taper surface ridges at lower assembly forces may influence corrosion rates, suggesting that the magnitude of the assembly force may affect clinical outcome. The method presented provides a simple and practical assessment of the contact area at the taper interface.

Contact angle change during evaporation of near-critical liquids

Science.gov (United States)

Nikolayev, Vadim; Hegseth, John; Beysens, Daniel

1998-11-01

An unexpected change of the dynamic contact angle was recently observed in a near-critical liquid-gas system in a space experiment. While the near-critical liquid completely wets a solid under equilibrium conditions, the apparent contact angle changed from 0^circ to about 120^circ during evaporation. We propose an explanation for this phenomenon by taking into account vapor recoil due to evaporation (motion of the vapor from the free liquid surface). This force is normal to the vapor-liquid interface and is directed towards the liquid. It increases sharply near the triple contact line. Near the critical point, where the surface tension force is very weak, the vapor recoil force can be important enough to change the apparent contact angle. A similar effect can also explain the drying of a heater during boiling at high heat flux. The drying greatly reduces the heat transfer to the liquid causing the heater to melt. This phenomenon is called ``boiling crisis", ``burnout" or ``Departure from Nuclear Boiling". We report the preliminary results of the numerical simulation of the liquid evaporation by the Boundary Element method.

Intrinsic factors associated with medial tibial stress syndrome in ...

African Journals Online (AJOL)

Intrinsic factors associated with medial tibial stress syndrome in athletes: A large case-control study. ... Medial tibial stress syndrome (MTSS) is the most common lower-leg injury in athletes, and is thought to be caused by ... from 32 Countries:.

Epidemiology of lateral and medial epicondylitis in a military population.

Science.gov (United States)

Wolf, Jennifer Moriatis; Mountcastle, Sally; Burks, Robert; Sturdivant, Rodney X; Owens, Brett D

2010-05-01

To determine the epidemiology of lateral and medial epicondylitis in the U.S. military. The Defense Medical Epidemiology Database was queried for ICD-9 codes 726.32 (lateral epicondylitis) and 726.33 (medial epicondylitis) for the years 1998-2006. Multivariate Poisson regression was used to calculate incidence rates (IR) and rate ratios (RR) among demographic groups. The IRs for lateral and medial epicondylitis were 2.98 and 0.81 per 1000 person-years. For lateral epicondylitis, women had a higher incidence (RR = 1.22, 95% CI 1.19-1.26). In both groups, analysis by age showed higher incidence in the > or = 40-year-old group. White compared with black race was a risk factor for both lateral (RR = 1.68, 95% CI, 1.63-1.74) and medial epicondylitis (RR = 1.11, 95% CI 1.05-1.17). Female gender was a risk factor for lateral but not medial epicondylitis. Age greater than 40 and white race were significant risk factors for both conditions.

Ultrastructure of medial rectus muscles in patients with intermittent exotropia.

Science.gov (United States)

Yao, J; Wang, X; Ren, H; Liu, G; Lu, P

2016-01-01

PURPOSE To study the ultrastructure of the medial rectus in patients with intermittent exotropia at different ages.PATIENTS AND METHODS The medial recti were harvested surgically from 20 patients with intermittent exotropia. Patients were divided into adolescent (age18 years, n=10). The normal control group included five patients without strabismus and undergoing eye enucleation. Hematoxylin and eosin staining and transmission electron microscopy were used to visualize the medial recti. Western blot was used to determine the levels of myosin and actin.RESULTS Varying fiber thickness, atrophy, and misalignment of the medial recti were visualized under optical microscope in patients with exotropia. Electron microscopy revealed sarcomere destruction, myofilament disintegration, unclear dark and light bands, collagen proliferation, and fibrosis. The adolescent group manifested significantly higher levels of myosin and actin than the adult group (Pstronger contraction of the medial recti compared with older patients. Our findings suggest that childhood was the appropriate time for surgery as the benefit of the intervention was better than in adulthood.

Source/drain electrodes contact effect on the stability of bottom-contact pentacene field-effect transistors

Directory of Open Access Journals (Sweden)

Xinge Yu

2012-06-01

Full Text Available Bottom-contact pentacene field-effect transistors were fabricated with a PMMA dielectric layer, and the air stability of the transistors was investigated. To characterize the device stability, the field-effect transistors were exposed to ambient conditions for 30 days and subsequently characterized. The degradation of electrical performance was traced to study the variation of field-effect mobility, saturation current and off-state current. By investigating the morphology variance of the pentacene film at the channel and source/drain (S/D contact regions by atomic force microscopy, it was clear that the morphology of the pentacene film adhered to the S/D degenerated dramatically. Moreover, by studying the variation of contact resistance in detail, it was found that the S/D contact effect was the main reason for the degradation in performance.

Mathematical Modeling of Contact Problems of Elasticity Theory with Unilateral Discrete Contact

Directory of Open Access Journals (Sweden)

I. V. Stankevich

2015-01-01

Full Text Available Development and operation of modern machinery and latest technology require reliable estimates of the strength characteristics of the critical elements of structures and technological equipment under the impact of high-intensity thermomechanical loading, accompanied, as a rule, by complex contact interaction. Mathematical modeling of stress-strain state of such parts and components in the contact area, based on adequate mathematical models, modern numerical methods and efficient algorithms that implement the direct determination of displacement fields, strains and stresses, is the main tool that allows fast acquisition of data required for the calculations of strength and durability. The paper considers an algorithm for constructing the numerical solution of the contact problem of elasticity theory in relation to the body, which has an obvious one-sided discrete contact interaction with an elastic half-space. The proposed algorithm is specially designed to have a correction of the tangential forces at discrete contact points, allowing us to achieve sufficiently accurate implementation of the adopted law of friction. The algorithm is embedded in a general finite element technology, with which the application code is generated. Numerical study of discrete unilateral contact interaction of an elastic plate and a rigid half-space showed a high efficiency of the developed algorithm and the application code that implements it.

Subquadratic medial-axis approximation in $\\mathbb{R}^3$

Directory of Open Access Journals (Sweden)

Christian Scheffer

2015-09-01

Full Text Available We present an algorithm that approximates the medial axis of a smooth manifold in $\\mathbb{R}^3$ which is given by a sufficiently dense point sample. The resulting, non-discrete approximation is shown to converge to the medial axis as the sampling density approaches infinity. While all previous algorithms guaranteeing convergence have a running time quadratic in the size $n$ of the point sample, we achieve a running time of at most $\\mathcal{O}(n\\log^3 n$. While there is no subquadratic upper bound on the output complexity of previous algorithms for non-discrete medial axis approximation, the output of our algorithm is guaranteed to be of linear size.

Predictive Simulations of Neuromuscular Coordination and Joint-Contact Loading in Human Gait.

Science.gov (United States)

Lin, Yi-Chung; Walter, Jonathan P; Pandy, Marcus G

2018-04-18

We implemented direct collocation on a full-body neuromusculoskeletal model to calculate muscle forces, ground reaction forces and knee contact loading simultaneously for one cycle of human gait. A data-tracking collocation problem was solved for walking at the normal speed to establish the practicality of incorporating a 3D model of articular contact and a model of foot-ground interaction explicitly in a dynamic optimization simulation. The data-tracking solution then was used as an initial guess to solve predictive collocation problems, where novel patterns of movement were generated for walking at slow and fast speeds, independent of experimental data. The data-tracking solutions accurately reproduced joint motion, ground forces and knee contact loads measured for two total knee arthroplasty patients walking at their preferred speeds. RMS errors in joint kinematics were joint kinematics, ground forces, knee contact loads and muscle activation patterns measured for slow and fast walking. The results demonstrate the feasibility of performing computationally-efficient, predictive, dynamic optimization simulations of movement using full-body, muscle-actuated models with realistic representations of joint function.

Effect of radial meniscal tear on in situ forces of meniscus and tibiofemoral relationship.

Science.gov (United States)

Tachibana, Yuta; Mae, Tatsuo; Fujie, Hiromichi; Shino, Konsei; Ohori, Tomoki; Yoshikawa, Hideki; Nakata, Ken

2017-02-01

To clarify the effect of the radial tear of the lateral meniscus on the in situ meniscus force and the tibiofemoral relationship under axial loads and valgus torques. Ten intact porcine knees were settled to a 6-degree of freedom robotic system, while the force and 3-dimensional path of the knees were recorded via Universal Force Sensor (UFS) during 3 cycles of 250-N axial load and 5-Nm valgus torque at 15°, 30°, 45°, and 60° of knee flexion. The same examination was performed on the following 3 meniscal states sequentially; 33, 66, and 100% width of radial tears at the middle segment of the lateral meniscus, while recording the force and path of the knees via UFS. Finally, all paths were reproduced after total lateral meniscectomy and the in situ force of the lateral meniscus were calculated with the principle of superposition. The radial tear of 100% width significantly decreased the in situ force of the lateral meniscus and caused tibial medial shift and valgus rotation at 30°-60° of knee flexion in both testing protocols. Under a 250-N axial load at 60° of knee flexion, the in situ force decreased to 36 ± 29 N with 100% width of radial tear, which was 122 ± 38 N in the intact state. Additionally, the tibia shifted medially by 2.1 ± 0.9 mm and valgusrotated by 2.5 ± 1.9° with the complete radial tear. However, the radial tear of 33 or 66% width had little effect on either the in situ force or the tibial position. A radial tear of 100% width involving the rim significantly decreased the in situ force of the lateral meniscus and caused medial shift and valgus rotation of the tibia, whereas a radial tear of up to 66% width produced only little change. The clinical relevance is that loss of meniscal functions due to complete radial tear can lead to abnormal stress concentration in a focal area of cartilage and can increase the risk of osteoarthritis in the future.

Effect of skin hydration on the dynamics of fingertip gripping contact.

Science.gov (United States)

André, T; Lévesque, V; Hayward, V; Lefèvre, P; Thonnard, J-L

2011-11-07

The dynamics of fingertip contact manifest themselves in the complex skin movements observed during the transition from a stuck state to a fully developed slip. While investigating this transition, we found that it depended on skin hydration. To quantify this dependency, we asked subjects to slide their index fingertip on a glass surface while keeping the normal component of the interaction force constant with the help of visual feedback. Skin deformation inside the contact region was imaged with an optical apparatus that allowed us to quantify the relative sizes of the slipping and sticking regions. The ratio of the stuck skin area to the total contact area decreased linearly from 1 to 0 when the tangential force component increased from 0 to a maximum. The slope of this relationship was inversely correlated to the normal force component. The skin hydration level dramatically affected the dynamics of the contact encapsulated in the course of evolution from sticking to slipping. The specific effect was to reduce the tendency of a contact to slip, regardless of the variations of the coefficient of friction. Since grips were more unstable under dry skin conditions, our results suggest that the nervous system responds to dry skin by exaggerated grip forces that cannot be simply explained by a change in the coefficient of friction.

Case report - curved femoral osteotomy for management of medial patellar luxation

DEFF Research Database (Denmark)

Allpass, Maja; Miles, James Edward

2015-01-01

Medial patellaluxation kan forårsages af femoral varus hos hund. Førhen har patienter med excessiv femoralvarus været korrigeret ved en lateralt placeret femoral kile-ostektomi. Her præsenteres en case, hvor en buet osteotomi blev anvendt til behandling af medial patellaluxation.......Medial patellaluxation kan forårsages af femoral varus hos hund. Førhen har patienter med excessiv femoralvarus været korrigeret ved en lateralt placeret femoral kile-ostektomi. Her præsenteres en case, hvor en buet osteotomi blev anvendt til behandling af medial patellaluxation....

The contact area and sliding friction in nanotribological systems

International Nuclear Information System (INIS)

Wolloch, M.

2014-01-01

Although friction, wear, and lubrication have been investigated for hundreds of years, many important questions in the field, now dubbed tribology, remain open. Two of these are the determination of the real area of contact and the direction dependence of friction forces on the nanoscale, which are investigated in this thesis. The invention of the atomic force microscope (AFM) in 1986 by Binnig , Quate, and Gerber was invaluable for the investigation of frictional forces on the atomic scale, giving a boost to the emerging field of nanotribology. While experimental AFM set-ups where quickly modeled with classical molecular dynamic (MD) simulations, the use of 'ab-initio' methods on tribological problems remained scarce until recently. In this thesis density functional theory (DFT) is used to develop parameter free methods in the field of nanotribology. Since the discovery that the apparent area of contact can be orders of magnitude larger than the true area of contact, the definition and determination of the latter has been an important topic of research. While classical contact mechanics provides satisfactory theories and results for various macroscopic systems, the application of these methods to atomistic systems is dubious, as the contacting bodies are not continuous at this length scale. We developed a parameter free approach to define and calculate the real area of contact between two bodies depending on distance. Strong relaxations at distinct distances, like the j ump to contact , which is often observed in AFM experiments, are used to define the onset of contact and Bader-s Quantum Theory of Atoms in Molecules is used to calculate the real area of contact at a given distance. Bader's method partitions the charge density ρ unambiguously into atoms, which theoretically fill all space and thus give non zero contact areas for all distances. It is therefore necessary to use a density cutoff ρ cut which assigns all regions in space where ρ < �

Contact-resonance atomic force microscopy for nanoscale elastic property measurements: Spectroscopy and imaging

International Nuclear Information System (INIS)

Stan, G.; Krylyuk, S.; Davydov, A.V.; Vaudin, M.D.; Bendersky, L.A.; Cook, R.F.

2009-01-01

Quantitative measurements of the elastic modulus of nanosize systems and nanostructured materials are provided with great accuracy and precision by contact-resonance atomic force microscopy (CR-AFM). As an example of measuring the elastic modulus of nanosize entities, we used the CR-AFM technique to measure the out-of-plane indentation modulus of tellurium nanowires. A size-dependence of the indentation modulus was observed for the investigated tellurium nanowires with diameters in the range 20-150 nm. Over this diameter range, the elastic modulus of the outer layers of the tellurium nanowires experienced significant enhancement due to a pronounced surface stiffening effect. Quantitative estimations for the elastic moduli of the outer and inner parts of tellurium nanowires of reduced diameter are made with a core-shell structure model. Besides localized elastic modulus measurements, we have also developed a unique CR-AFM imaging capability to map the elastic modulus over a micrometer-scale area. We used this CR-AFM capability to construct indentation modulus maps at the junction between two adjacent facets of a tellurium microcrystal. The clear contrast observed in the elastic moduli of the two facets indicates the different surface crystallography of these facets.

The effects of neuromuscular exercise on medial knee joint load post-arthroscopic partial medial meniscectomy: 'SCOPEX', a randomised control trial protocol.

Science.gov (United States)

Hall, Michelle; Hinman, Rana S; Wrigley, Tim V; Roos, Ewa M; Hodges, Paul W; Staples, Margaret; Bennell, Kim L

2012-11-27

Meniscectomy is a risk factor for knee osteoarthritis, with increased medial joint loading a likely contributor to the development and progression of knee osteoarthritis in this group. Therefore, post-surgical rehabilitation or interventions that reduce medial knee joint loading have the potential to reduce the risk of developing or progressing osteoarthritis. The primary purpose of this randomised, assessor-blind controlled trial is to determine the effects of a home-based, physiotherapist-supervised neuromuscular exercise program on medial knee joint load during functional tasks in people who have recently undergone a partial medial meniscectomy. 62 people aged 30-50 years who have undergone an arthroscopic partial medial meniscectomy within the previous 3 to 12 months will be recruited and randomly assigned to a neuromuscular exercise or control group using concealed allocation. The neuromuscular exercise group will attend 8 supervised exercise sessions with a physiotherapist and will perform 6 exercises at home, at least 3 times per week for 12 weeks. The control group will not receive the neuromuscular training program. Blinded assessment will be performed at baseline and immediately following the 12-week intervention. The primary outcomes are change in the peak external knee adduction moment measured by 3-dimensional analysis during normal paced walking and one-leg rise. Secondary outcomes include the change in peak external knee adduction moment during fast pace walking and one-leg hop and change in the knee adduction moment impulse during walking, one-leg rise and one-leg hop, knee and hip muscle strength, electromyographic muscle activation patterns, objective measures of physical function, as well as self-reported measures of physical function and symptoms and additional biomechanical parameters. The findings from this trial will provide evidence regarding the effect of a home-based, physiotherapist-supervised neuromuscular exercise program on medial knee

A clinical evaluation of alternative fixation techniques for medial malleolus fractures.

Science.gov (United States)

Barnes, Hayley; Cannada, Lisa K; Watson, J Tracy

2014-09-01

Medial malleolus fractures have traditionally been managed using partially threaded screws and/or Kirschner wire fixation. Using these conventional techniques, a non-union rate of as high as 20% has been reported. In addition too many patients complaining of prominent hardware as a source of pain post-fixation. This study was designed to assess the outcomes of medial malleolar fixation using a headless compression screw in terms of union rate, the need for hardware removal, and pain over the hardware site. Saint Louis University and Mercy Medical Center, Level 1 Trauma Centers, St. Louis, MO. After IRB approval, we used billing records to identify all patients with ankle fractures involving the medial malleolus. Medical records and radiographs were reviewed to identify patients with medial malleolar fractures treated with headless compression screw fixation. Our inclusion criteria included follow-up until full weight bearing and a healed fracture. Follow-up clinical records and radiographs were reviewed to determine union, complication rate and perception of pain over the site of medial malleolus fixation. Sixty-four ankles were fixed via headless compression screws and 44 had adequate follow-up for additional evaluation. Seven patients had isolated medial malleolar fractures, 23 patients had bimalleolar fractures, and 14 patients had trimalleolar fractures. One patient (2%) required hardware removal due to cellulitis. One patient (2%) had a delayed union, which healed without additional intervention. Ten patients (23%) reported mild discomfort to palpation over the medial malleolus. The median follow-up was 35 weeks (range: 12-208 weeks). There were no screw removals for painful hardware and no cases of non-union. Headless compression screws provide effective compression of medial malleolus fractures and result in good clinical outcomes. The headless compression screw is a beneficial alternative to the conventional methods of medial malleolus fixation. Copyright �

Spontaneous Spreading of a Droplet: The Role of Solid Continuity and Advancing Contact Angle.

Science.gov (United States)

Jiang, Youhua; Sun, Yujin; Drelich, Jaroslaw W; Choi, Chang-Hwan

2018-05-01

Spontaneous spreading of a droplet on a solid surface is poorly understood from a macroscopic level down to a molecular level. Here, we investigate the effect of surface topography and wettability on spontaneous spreading of a water droplet. Spreading force is measured for a suspended droplet that minimizes interference of kinetic energy in the spontaneous spreading during its contact with solid surfaces of discontinuous (pillar) and continuous (pore) patterns with various shapes and dimensions. Results show that a droplet cannot spread spontaneously on pillared surfaces regardless of their shapes or dimensions because of the solid discontinuity. On the contrary, a droplet on pored surfaces can undergo spontaneous spreading whose force increases with a decrease in the advancing contact angle. Theoretical models based on both the system free energy and capillary force along the contact line validate the direct and universal dependency of the spontaneous spreading force on the advancing contact angle.

Modified tension band wiring of medial malleolar ankle fractures.

Science.gov (United States)

Georgiadis, G M; White, D B

1995-02-01

Twenty-two displaced medial malleolar ankle fractures that were treated surgically using the modified tension band method of Cleak and Dawson were retrospectively reviewed at an average follow-up of 25 months. The technique involves the use of a screw to anchor a figure-of-eight wire. There were no malreductions and all fractures healed. Problems with the technique included technical errors with hardware placement, medial ankle pain, and asymptomatic wire migration. Despite this, modified tension band wiring remains an acceptable method for fixation of selected displaced medial malleolar fractures. It is especially suited for small fracture fragments and osteoporotic bone.

Bucket handle tears of the medial meniscus: meniscal intrusion rather than meniscal extrusion

International Nuclear Information System (INIS)

Schlossberg, S.; Umans, H.; Flusser, G.; DiFelice, G.S.; Lerer, D.B.

2007-01-01

To determine the frequency of medial meniscal extrusion (MME) versus ''medial meniscal intrusion'' in the setting of bucket handle tears. Images were evaluated for previously reported risk factors for MME, including: medial meniscal root tear, radial tear, degenerative joint disease and joint effusion. Forty-one consecutive cases of bucket handle tear of the medial meniscus were reviewed by consensus by two musculoskeletal radiologists. Imaging was performed using a 1.5 GE Signa MR unit. Patient age, gender, medial meniscal root integrity, MME, medial meniscal intrusion, degenerative joint disease, effusion and anterior cruciate ligament (ACL) tear were recorded. Thirteen females and 27 males (age 12-62 years, median=30 years) were affected; one had bucket handle tear of each knee. Effusion was small in 13, moderate in 9 and large in 18. Degenerative joint disease was mild in three, moderate in two and severe in one. 26 ACL tears included three partial and three chronic. Medial meniscal root tear was complete in one case and partial thickness in two. None of the 40 cases with an intact or partially torn medial meniscal root demonstrated MME. MME of 3.1 mm was seen in the only full-thickness medial meniscal root tear, along with chronic ACL tear, moderate degenerative joint disease and large effusion. Medial meniscal intrusion of the central bucket handle fragment into the intercondylar notch was present in all 41 cases. Given an intact medial meniscal root in the setting of a ''pure'' bucket handle tear, there is no MME. (orig.)

The medial tibial stress syndrome. A cause of shin splints.

Science.gov (United States)

Mubarak, S J; Gould, R N; Lee, Y F; Schmidt, D A; Hargens, A R

1982-01-01

The medial tibial stress syndrome is a symptom complex seen in athletes who complain of exercise-induced pain along the distal posterior-medial aspect of the tibia. Intramuscular pressures within the posterior compartments of the leg were measured in 12 patients with this disorder. These pressures were not elevated and therefore this syndrome is a not a compartment syndrome. Available information suggests that the medial tibial stress syndrome most likely represents a periostitis at this location of the leg.

Atomic force microscopy employed as the final imaging stage for soft x-ray contact microscopy

International Nuclear Information System (INIS)

Cotton, R.A.; Stead, A.D.; Ford, T.W.; Fletcher, J.H.

1993-01-01

Soft X-ray contact microscopy (SXCM) enables a high resolution image of a living biological specimen to be recorded in an X-ray sensitive photoresist at unity magnification. Until recently scanning electron microscopes (SEM) have been employed to obtain the final magnified image. Although this has been successful in producing many high resolution images, this method of viewing the resist has several disadvantages. Firstly, a metallic coating has to be applied to the resist surface to provide electrical conductivity, rendering further development of the resist impossible. Also, electron beam damage to the resist surface can occur, in addition to poor resolution and image quality. Atomic force microscopy (AFM) allows uncoated resists to be imaged at a superior resolution, without damage to the surface. The use of AFM is seen as a major advancement in SXCM. The advantages and disadvantages of the two technologies are discussed, with illustrations from recent studies of a wide variety of hydrated biological specimens imaged using SXCM

Immobilization method of yeast cells for intermittent contact mode imaging using the atomic force microscope

International Nuclear Information System (INIS)

De, Tathagata; Chettoor, Antony M.; Agarwal, Pranav; Salapaka, Murti V.; Nettikadan, Saju

2010-01-01

The atomic force microscope (AFM) is widely used for studying the surface morphology and growth of live cells. There are relatively fewer reports on the AFM imaging of yeast cells (Kasas and Ikai, 1995), (Gad and Ikai, 1995). Yeasts have thick and mechanically strong cell walls and are therefore difficult to attach to a solid substrate. In this report, a new immobilization technique for the height mode imaging of living yeast cells in solid media using AFM is presented. The proposed technique allows the cell surface to be almost completely exposed to the environment and studied using AFM. Apart from the new immobilization protocol, for the first time, height mode imaging of live yeast cell surface in intermittent contact mode is presented in this report. Stable and reproducible imaging over a 10-h time span is observed. A significant improvement in operational stability will facilitate the investigation of growth patterns and surface patterns of yeast cells.

Default network connectivity in medial temporal lobe amnesia.

Science.gov (United States)

Hayes, Scott M; Salat, David H; Verfaellie, Mieke

2012-10-17

There is substantial overlap between the brain regions supporting episodic memory and the default network. However, in humans, the impact of bilateral medial temporal lobe (MTL) damage on a large-scale neural network such as the default mode network is unknown. To examine this issue, resting fMRI was performed with amnesic patients and control participants. Seed-based functional connectivity analyses revealed robust default network connectivity in amnesia in cortical default network regions such as medial prefrontal cortex, posterior medial cortex, and lateral parietal cortex, as well as evidence of connectivity to residual MTL tissue. Relative to control participants, decreased posterior cingulate cortex connectivity to MTL and increased connectivity to cortical default network regions including lateral parietal and medial prefrontal cortex were observed in amnesic patients. In contrast, somatomotor network connectivity was intact in amnesic patients, indicating that bilateral MTL lesions may selectively impact the default network. Changes in default network connectivity in amnesia were largely restricted to the MTL subsystem, providing preliminary support from MTL amnesic patients that the default network can be fractionated into functionally and structurally distinct components. To our knowledge, this is the first examination of the default network in amnesia.

Joint contact loading in forefoot and rearfoot strike patterns during running.

Science.gov (United States)

Rooney, Brandon D; Derrick, Timothy R

2013-09-03

Research concerning forefoot strike pattern (FFS) versus rearfoot strike pattern (RFS) running has focused on the ground reaction force even though internal joint contact forces are a more direct measure of the loads responsible for injury. The main purpose of this study was to determine the internal loading of the joints for each strike pattern. A secondary purpose was to determine if converted FFS and RFS runners can adequately represent habitual runners with regards to the internal joint loading. Using inverse dynamics to calculate the net joint moments and reaction forces and optimization techniques to estimate muscle forces, we determined the axial compressive loading at the ankle, knee, and hip. Subjects consisted of 15 habitual FFS and 15 habitual RFS competitive runners. Each subject ran at a preferred running velocity with their habitual strike pattern and then converted to the opposite strike pattern. Plantar flexor muscle forces and net ankle joint moments were greater in the FFS running compared to the RFS running during the first half of the stance phase. The average contact forces during this period increased by 41.7% at the ankle and 14.4% at the knee joint during FFS running. Peak ankle joint contact force was 1.5 body weights greater during FFS running (pstrike pattern. Copyright © 2013 Elsevier Ltd. All rights reserved.

Vocal fold contact patterns based on normal modes of vibration.

Science.gov (United States)

Smith, Simeon L; Titze, Ingo R

2018-05-17

The fluid-structure interaction and energy transfer from respiratory airflow to self-sustained vocal fold oscillation continues to be a topic of interest in vocal fold research. Vocal fold vibration is driven by pressures on the vocal fold surface, which are determined by the shape of the glottis and the contact between vocal folds. Characterization of three-dimensional glottal shapes and contact patterns can lead to increased understanding of normal and abnormal physiology of the voice, as well as to development of improved vocal fold models, but a large inventory of shapes has not been directly studied previously. This study aimed to take an initial step toward characterizing vocal fold contact patterns systematically. Vocal fold motion and contact was modeled based on normal mode vibration, as it has been shown that vocal fold vibration can be almost entirely described by only the few lowest order vibrational modes. Symmetric and asymmetric combinations of the four lowest normal modes of vibration were superimposed on left and right vocal fold medial surfaces, for each of three prephonatory glottal configurations, according to a surface wave approach. Contact patterns were generated from the interaction of modal shapes at 16 normalized phases during the vibratory cycle. Eight major contact patterns were identified and characterized by the shape of the flow channel, with the following descriptors assigned: convergent, divergent, convergent-divergent, uniform, split, merged, island, and multichannel. Each of the contact patterns and its variation are described, and future work and applications are discussed. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Anatomic Midpoint of the Attachment of the Medial Patellofemoral Complex.

Science.gov (United States)

Tanaka, Miho J; Voss, Andreas; Fulkerson, John P

2016-07-20

The medial patellofemoral ligament varies in attachment of its fibers to the patella and vastus intermedius tendon. Our aim was to identify and describe its anatomic midpoint. To account for the variability of the attachment site, we refer to it as the medial patellofemoral complex. Using AutoCAD software, we identified the midpoint of the medial patellofemoral complex attachment on photographs of 31 cadaveric knee dissections. The midpoint was referenced relative to the superior articular surface of the patella (P1) and was described in terms of the percentage of the patellar articular length distal to this point. A second point, at the junction of the medial border of the vastus intermedius tendon with the superior articular border of the patella, was identified (P2). The distances of the midpoint to P1 and P2 were calculated and were compared using paired t tests. Twenty-five images had appropriate quality and landmarks for digital analysis. The midpoint of the medial patellofemoral complex was located a mean (and standard deviation) of 2.3% ± 15.8% of the patellar articular length distal to the superior pole and was at or proximal to P1 in 12 knees. In all knees, the midpoint was at or proximal to P2. After exclusion of 2 knees with vastus intermedius tendon attachments only, the medial patellofemoral complex midpoint was closer to P2 (5.3% ± 8.6% of the patellar articular length) than to P1 (9.3% ± 8.5% of the patellar articular length) (p = 0.06). The midpoint of the medial patellofemoral complex was 2.3% of the articular length distal to the superior pole of the patella. Additionally, we describe an anatomic landmark at the junction of the medial border of the vastus intermedius tendon and the articular border of the patella that approximates the midpoint of this complex. Our study shows that the anatomic midpoint of the attachment of the medial patellofemoral complex is proximal to the junction of the medial vastus intermedius tendon and the articular

Association of medial meniscal extrusion with medial tibial osteophyte distance detected by T2 mapping MRI in patients with early-stage knee osteoarthritis.

Science.gov (United States)

Hada, Shinnosuke; Ishijima, Muneaki; Kaneko, Haruka; Kinoshita, Mayuko; Liu, Lizu; Sadatsuki, Ryo; Futami, Ippei; Yusup, Anwajan; Takamura, Tomohiro; Arita, Hitoshi; Shiozawa, Jun; Aoki, Takako; Takazawa, Yuji; Ikeda, Hiroshi; Aoki, Shigeki; Kurosawa, Hisashi; Okada, Yasunori; Kaneko, Kazuo

2017-09-12

Medial meniscal extrusion (MME) is associated with progression of medial knee osteoarthritis (OA), but no or little information is available for relationships between MME and osteophytes, which are found in cartilage and bone parts. Because of the limitation in detectability of the cartilage part of osteophytes by radiography or conventional magnetic resonance imaging (MRI), the rate of development and size of osteophytes appear to have been underestimated. Because T2 mapping MRI may enable us to evaluate the cartilage part of osteophytes, we aimed to examine the association between MME and OA-related changes, including osteophytes, by using conventional and T2 mapping MRI. Patients with early-stage knee OA (n = 50) were examined. MRI-detected OA-related changes, in addition to MME, were evaluated according to the Whole-Organ Magnetic Resonance Imaging Score. T2 values of the medial meniscus and osteophytes were measured on T2 mapping images. Osteophytes surgically removed from patients with end-stage knee OA were histologically analyzed and compared with findings derived by radiography and MRI. Medial side osteophytes were detected by T2 mapping MRI in 98% of patients with early-stage knee OA, although the detection rate was 48% by conventional MRI and 40% by radiography. Among the OA-related changes, medial tibial osteophyte distance was most closely associated with MME, as determined by multiple logistic regression analysis, in the patients with early-stage knee OA (β = 0.711, p T2 values of the medial meniscus were directly correlated with MME in patients with early-stage knee OA, who showed ≥ 3 mm of MME (r = 0.58, p = 0.003). The accuracy of osteophyte evaluation by T2 mapping MRI was confirmed by histological analysis of the osteophytes removed from patients with end-stage knee OA. Our study demonstrates that medial tibial osteophyte evaluated by T2 mapping MRI is frequently observed in the patients with early-stage knee OA, showing

Effect of medial arch support foot orthosis on plantar pressure distribution in females with mild-to-moderate hallux valgus after one month of follow-up.

Science.gov (United States)

Farzadi, Maede; Safaeepour, Zahra; Mousavi, Mohammad E; Saeedi, Hassan

2015-04-01

Higher plantar pressures at the medial forefoot are reported in hallux valgus. Foot orthoses with medial arch support are considered as an intervention in this pathology. However, little is known about the effect of foot orthoses on plantar pressure distribution in hallux valgus. To investigate the effect of a foot orthosis with medial arch support on pressure distribution in females with mild-to-moderate hallux valgus. Quasi-experimental. Sixteen female volunteers with mild-to-moderate hallux valgus participated in this study and used a medial arch support foot orthosis for 4 weeks. Plantar pressure for each participant was assessed using the Pedar-X(®) in-shoe system in four conditions including shoe-only and foot orthosis before and after the intervention. The use of the foot orthosis for 1 month led to a decrease in peak pressure and maximum force under the hallux, first metatarsal, and metatarsals 3-5 (p hallux and the first metatarsal head by transferring the load to the other regions. It would appear that this type of foot orthosis can be an effective method of intervention in this pathology. Findings of this study will improve the clinical knowledge about the effect of the medial arch support foot orthosis used on plantar pressure distribution in hallux valgus pathology. © The International Society for Prosthetics and Orthotics 2014.

U.S. Preventive Services Task Force

Science.gov (United States)

... USPSTF Our Members Conflict of Interest Disclosures Task Force Resources Our Partners Reports to Congress Contact Us ... effort to make the U.S. Preventive Services Task Force (USPSTF) recommendations clearer and its processes more transparent, ...

Optimization of a piezoelectric linear motor in terms of the contact parameters

International Nuclear Information System (INIS)

Ko, Hyun-Phill; Kim, Sangsig; Kang, Chong-Yun; Kim, Hyun-Jai; Yoon, Seok-Jin

2005-01-01

The contact kinetics of piezoelectric linear motors determines the operational characteristics like speed and torque or transmitted mechanical power and efficiency. Piezoelectric linear motors are driven by tangential stress in the interface between tip of shaking beam and slider. A good contact between the tip and slider is necessary for a reliable analysis of the motor, which is needed for the optimization of its performance. The piezoelectric linear motor was fabricated and the characteristics of the motor were investigated by external conditions such as tip shape with different curvatures and contact force between the tip and the slider. It was found in this investigation that the optimal curvature of the tip and the contact force are curvature of 1 and 10, respectively, for the high actuating speed, and curvature of 1 and 40 N, respectively, for the high actuating force. Finally, tip shape has an influence on the characteristics of linear motor

Radiographic anatomy of the medial coronoid process of dogs

International Nuclear Information System (INIS)

Miyabayashi, T.; Takiguchi, M.; Schrader, S.C.; Biller, D.S.

1995-01-01

Mediolateral, flexed mediolateral, mediocaudal-laterocranial 15 degrees oblique (extended and supinated mediolateral), and craniolateral-caudomedial 20 degrees to 30 degrees oblique radiographs of 16 elbow-joint specimens were produced to study the radiographic anatomy of the medial coronoid process. On the mediolateral view, the cranial point of the coronoid process was at the level of the distal one-third of the radial epiphysis. Degree of superimposition of the proximal radius and ulna determined how the medial coronoid process was projected on the radiographs. Mediocaudal-laterocranial oblique radiographs best showed the cranial outline of the medial coronoid process with moderate superimposition of the proximal radius and ulna

Adaptive contact elements for three-dimensional fluid-structure interfaces

International Nuclear Information System (INIS)

Kulak, R.F.

1985-01-01

A finite element method is developed for treating the mechanics of contact between two deformable bodies which occurs, for example, at fluid-structure interfaces. The method uses a family of adaptive contact elements, which are based upon the penalty method, to handle all of the possible contact configurations that can occur between the discretized contacting bodies. The contact element's nodal connectivity is allowed to change during the computations in order to accommodate finite sliding. The infusion of these elements in the interface results in satisfying the force equilibrium condition during contact. The methodology has been implemented into the NEPTUNE code. Results are presented for an illustrative problem

Adaptive contact elements for three-dimensional fluid-structure interfaces

Energy Technology Data Exchange (ETDEWEB)

Kulak, R.F.

1985-01-01

A finite element method is developed for treating the mechanics of contact between two deformable bodies which occurs, for example, at fluid-structure interfaces. The method uses a family of adaptive contact elements, which are based upon the penalty method, to handle all of the possible contact configurations that can occur between the discretized contacting bodies. The contact element's nodal connectivity is allowed to change during the computations in order to accommodate finite sliding. The infusion of these elements in the interface results in satisfying the force equilibrium condition during contact. The methodology has been implemented into the NEPTUNE code. Results are presented for an illustrative problem.

The effects of neuromuscular exercise on medial knee joint load post-arthroscopic partial medial meniscectomy: ‘SCOPEX’ a randomised control trial protocol

Science.gov (United States)

2012-01-01

Background Meniscectomy is a risk factor for knee osteoarthritis, with increased medial joint loading a likely contributor to the development and progression of knee osteoarthritis in this group. Therefore, post-surgical rehabilitation or interventions that reduce medial knee joint loading have the potential to reduce the risk of developing or progressing osteoarthritis. The primary purpose of this randomised, assessor-blind controlled trial is to determine the effects of a home-based, physiotherapist-supervised neuromuscular exercise program on medial knee joint load during functional tasks in people who have recently undergone a partial medial meniscectomy. Methods/design 62 people aged 30–50 years who have undergone an arthroscopic partial medial meniscectomy within the previous 3 to 12 months will be recruited and randomly assigned to a neuromuscular exercise or control group using concealed allocation. The neuromuscular exercise group will attend 8 supervised exercise sessions with a physiotherapist and will perform 6 exercises at home, at least 3 times per week for 12 weeks. The control group will not receive the neuromuscular training program. Blinded assessment will be performed at baseline and immediately following the 12-week intervention. The primary outcomes are change in the peak external knee adduction moment measured by 3-dimensional analysis during normal paced walking and one-leg rise. Secondary outcomes include the change in peak external knee adduction moment during fast pace walking and one-leg hop and change in the knee adduction moment impulse during walking, one-leg rise and one-leg hop, knee and hip muscle strength, electromyographic muscle activation patterns, objective measures of physical function, as well as self-reported measures of physical function and symptoms and additional biomechanical parameters. Discussion The findings from this trial will provide evidence regarding the effect of a home-based, physiotherapist

The effects of neuromuscular exercise on medial knee joint load post-arthroscopic partial medial meniscectomy: ‘SCOPEX’ a randomised control trial protocol

Directory of Open Access Journals (Sweden)

Hall Michelle

2012-11-01

Full Text Available Abstract Background Meniscectomy is a risk factor for knee osteoarthritis, with increased medial joint loading a likely contributor to the development and progression of knee osteoarthritis in this group. Therefore, post-surgical rehabilitation or interventions that reduce medial knee joint loading have the potential to reduce the risk of developing or progressing osteoarthritis. The primary purpose of this randomised, assessor-blind controlled trial is to determine the effects of a home-based, physiotherapist-supervised neuromuscular exercise program on medial knee joint load during functional tasks in people who have recently undergone a partial medial meniscectomy. Methods/design 62 people aged 30–50 years who have undergone an arthroscopic partial medial meniscectomy within the previous 3 to 12 months will be recruited and randomly assigned to a neuromuscular exercise or control group using concealed allocation. The neuromuscular exercise group will attend 8 supervised exercise sessions with a physiotherapist and will perform 6 exercises at home, at least 3 times per week for 12 weeks. The control group will not receive the neuromuscular training program. Blinded assessment will be performed at baseline and immediately following the 12-week intervention. The primary outcomes are change in the peak external knee adduction moment measured by 3-dimensional analysis during normal paced walking and one-leg rise. Secondary outcomes include the change in peak external knee adduction moment during fast pace walking and one-leg hop and change in the knee adduction moment impulse during walking, one-leg rise and one-leg hop, knee and hip muscle strength, electromyographic muscle activation patterns, objective measures of physical function, as well as self-reported measures of physical function and symptoms and additional biomechanical parameters. Discussion The findings from this trial will provide evidence regarding the effect of a home

The mechanical benefit of medial support screws in locking plating of proximal humerus fractures.

Directory of Open Access Journals (Sweden)

Wen Zhang

Full Text Available BACKGROUND: The purpose of this study was to evaluate the biomechanical advantages of medial support screws (MSSs in the locking proximal humeral plate for treating proximal humerus fractures. METHODS: Thirty synthetic left humeri were randomly divided into 3 subgroups to establish two-part surgical neck fracture models of proximal humerus. All fractures were fixed with a locking proximal humerus plate. Group A was fixed with medial cortical support and no MSSs; Group B was fixed with 3 MSSs but without medial cortical support; Group C was fixed with neither medial cortical support nor MSSs. Axial compression, torsional stiffness, shear stiffness, and failure tests were performed. RESULTS: Constructs with medial support from cortical bone showed statistically higher axial and shear stiffness than other subgroups examined (P<0.0001. When the proximal humerus was not supported by medial cortical bone, locking plating with medial support screws exhibited higher axial and torsional stiffness than locking plating without medial support screws (P ≤ 0.0207. Specimens with medial cortical bone failed primarily by fracture of the humeral shaft or humeral head. Specimens without medial cortical bone support failed primarily by significant plate bending at the fracture site followed by humeral head collapse or humeral head fracture. CONCLUSIONS: Anatomic reduction with medial cortical support was the stiffest construct after a simulated two-part fracture. Significant biomechanical benefits of MSSs in locking plating of proximal humerus fractures were identified. The reconstruction of the medial column support for proximal humerus fractures helps to enhance mechanical stability of the humeral head and prevent implant failure.

The Prevalence of Medial Epicondylitis Among Patients With C6 and C7 Radiculopathy

Science.gov (United States)

Lee, Aaron Taylor; Lee-Robinson, Ayse L.

2010-01-01

Background: Medial epicondylitis, or golfer’s/pitcher’s elbow, develops as a result of medial stress overload on the flexor muscles at the elbow and presents as pain at the medial epicondyle. Cervical radiculopathy has been associated with lateral epicondylitis, but few associations between the cervical spine and medial epicondylitis have been made. Researchers propose that there is an association, suggesting that the weakness and imbalance in the elbow flexor and extensor muscles from C6 and C7 radiculopathy allow for easy onset of medial epicondylitis. Hypothesis: Medial epicondylitis will present in over half the patients diagnosed with C6 and C7 radiculopathy. Methodology: A total of 102 patients initially presenting with upper extremity or neck symptoms were diagnosed with cervical radiculopathy. They were then examined for medial epicondylitis. Data were collected by referring to patient charts from February 2008 until June 2009. Results: Fifty-five patients were diagnosed with medial epicondylitis. Of these, 44 had C6 and C7 radiculopathy whereas 11 presented with just C6 radiculopathy. Conclusion: Medial epicondylitis presented with cervical radiculopathy in slightly more than half the patients. Weakening of the flexor carpi radialis and pronator teres and imbalance of the flexor and extensor muscles from the C6 and C7 radiculopathy allow for easy onset of medial epicondylitis. Patients with medial epicondylitis should be examined for C6 and C7 radiculopathy to ensure proper treatment. Physicians dealing with golfers, pitchers, or other patients with medial epicondylitis should be aware of the association between these 2 diagnoses to optimize care. PMID:23015956

Contact Stress Generation on the UHMWPE Tibial Insert

Directory of Open Access Journals (Sweden)

S. Petrović Savić

2014-12-01

Full Text Available Total knee replacement (TKR is considered, during last years, as a very successful surgical technique for removing knee joint deformities and eliminating pain caused by cartilage damage. In literature, as primary causes for knee joint endoprothesis damage are cited complex movements which cause occurrences of complex stress conditions, sagital radius conformity, sliding, types of materials etc. Aim of this study is analysis of contact stresses that occur on tibial implant for 15°, 45° and 60° knee flexion and 50 kg, 75 kg, 100 kg and 125 kg weight. Knee joint prosthesis model and finite elements method (FEM analysis are done in software Catia V5. For this analysis we used ultra-high molecular weight polyethylene (UHMWPE for tibial implant material and AISI 316, AISI 317, AISI 321, 17-4PH, CoCrMo, Ti6Al4V and SAE A-286 for femoral component materials. Results show that area of maximal contact stress is identified in medial and lateral part of tibial implant. Von Mises stress values vary regarding of flexion degree and weight, but values are approximate for types of chosen materials. Contact stress location corresponds to damage that occur on tibial implant during exploitation.

Labral reconstruction with iliotibial band autografts and semitendinosus allografts improves hip joint contact area and contact pressure: an in vitro analysis.

Science.gov (United States)

Lee, Simon; Wuerz, Thomas H; Shewman, Elizabeth; McCormick, Frank M; Salata, Michael J; Philippon, Marc J; Nho, Shane J

2015-01-01

Labral reconstruction using iliotibial band (ITB) autografts and semitendinosus (Semi-T) allografts has recently been described in cases of labral deficiency. To characterize the joint biomechanics with a labrum-intact, labrum-deficient, and labrum-reconstructed acetabulum in a hip cadaveric model. The hypothesis was that labral resection would decrease contact area, increase contact pressure, and increase peak force, while subsequent labral reconstruction with ITB autografts or Semi-T allografts would restore these values toward the native intact labral state. Controlled laboratory study. Ten fresh-frozen human cadaveric hips were analyzed utilizing thin-film piezoresistive load sensors to measure contact area, contact pressure, and peak force (1) with the native intact labrum, (2) after segmental labral resection, and (3) after graft labral reconstruction with either ITB autografts or Semi-T allografts. Each specimen was examined at 20° of extension and 60° of flexion. Statistical analysis was conducted through 1-way analysis of variance with post hoc Games-Howell tests. For the ITB group, labral resection significantly decreased contact area (at 20°: 73.2%±5.38%, P=.0010; at 60°: 78.5%±6.93%, P=.0063) and increased contact pressure (at 20°: 106.7%±4.15%, P=.0387; at 60°: 103.9%±1.15%, P=.0428). In addition, ITB reconstruction improved contact area (at 20°: 87.2%±12.3%, P=.0130; at 60°: 90.5%±8.81%, P=.0079) and contact pressure (at 20°: 98.5%±5.71%, P=.0476; at 60°: 96.6%±1.13%, P=.0056) from the resected state. Contact pressure at 60° of flexion was significantly lower compared with the native labrum (P=.0420). For the Semi-T group, labral resection significantly decreased contact area (at 20°: 68.1%±12.57%, P=.0002; at 60°: 67.5%±6.70%, P=.0002) and increased contact pressure (at 20°: 105.3%±3.73%, P=.0304; at 60°: 106.8%±4.04%, P=.0231). Semi-T reconstruction improved contact area (at 20°: 87.9%±7.95%, P=.0087; at 60°: 92.9%±13

Fuel rod-to-support contact pressure and stress measurement for CHASNUPP-1(PWR) fuel

International Nuclear Information System (INIS)

Waseem; Elahi, N.; Siddiqui, A.; Murtaza, G.

2011-01-01

Research highlights: → A detailed finite element model of spacer grid cell with fuel rod-to-support has been developed to determine the contact pressure between the supports of the grid and fuel rod cladding. → The spring hold-down force is calculated using the contact pressure obtained from the FE model. → Experiment has also been conducted in the same environment for the measurement of this force. → The spring hold-down force values obtained from both studies confirm the validation of this analysis. → The stress obtained through this analysis is less than the yield strength of spacer grid material, thus fulfils the structural integrity criteria of grid. - Abstract: This analysis has been made in an attempt to measure the contact pressure of the PWR fuel assembly spacer grid spring and to verify its structural integrity at room temperature in air. A detailed finite element (FE) model of spacer grid cell with fuel rod-to-support has been developed to determine the contact pressure between the supports of the grid and fuel rod cladding. The FE model of a fuel rod-to-support system is produced with shell and contact elements. The spring hold-down force is calculated using the contact pressure obtained from the FE model. Experiment has also been conducted in the same environment for the measurement of this force. The spring hold-down force values obtained from both studies are compared, which show good agreement, and in turn confirm the validation of this analysis. The Stress obtained through this analysis is less than the yield strength of spacer grid material (Inconel-718), thus fulfils the structural integrity criteria of grid.

Fuel rod-to-support contact pressure and stress measurement for CHASNUPP-1(PWR) fuel

Energy Technology Data Exchange (ETDEWEB)

Waseem, E-mail: wazim_me@hotmail.co [Directorate General Nuclear Power Fuel, Pakistan Atomic Energy Commission, P.O. Box No. 1847, Islamabad 44000 (Pakistan); Elahi, N.; Siddiqui, A.; Murtaza, G. [Directorate General Nuclear Power Fuel, Pakistan Atomic Energy Commission, P.O. Box No. 1847, Islamabad 44000 (Pakistan)

2011-01-15

Research highlights: A detailed finite element model of spacer grid cell with fuel rod-to-support has been developed to determine the contact pressure between the supports of the grid and fuel rod cladding. The spring hold-down force is calculated using the contact pressure obtained from the FE model. Experiment has also been conducted in the same environment for the measurement of this force. The spring hold-down force values obtained from both studies confirm the validation of this analysis. The stress obtained through this analysis is less than the yield strength of spacer grid material, thus fulfils the structural integrity criteria of grid. - Abstract: This analysis has been made in an attempt to measure the contact pressure of the PWR fuel assembly spacer grid spring and to verify its structural integrity at room temperature in air. A detailed finite element (FE) model of spacer grid cell with fuel rod-to-support has been developed to determine the contact pressure between the supports of the grid and fuel rod cladding. The FE model of a fuel rod-to-support system is produced with shell and contact elements. The spring hold-down force is calculated using the contact pressure obtained from the FE model. Experiment has also been conducted in the same environment for the measurement of this force. The spring hold-down force values obtained from both studies are compared, which show good agreement, and in turn confirm the validation of this analysis. The Stress obtained through this analysis is less than the yield strength of spacer grid material (Inconel-718), thus fulfils the structural integrity criteria of grid.

Nanoscale elasticity mappings of micro-constituents of abalone shell by band excitation-contact resonance force microscopy

Science.gov (United States)

Li, Tao; Zeng, Kaiyang

2014-01-01

The macroscopic mechanical properties of the abalone shell have been studied extensively in the literature, but the in situ nanoscale elasticity of various micro-constituents in the shell have not been characterized and reported yet. In this study, the nanoscale elasticity mappings including different micro-constituents in abalone shell were observed by using the Contact Resonance Force Microscopy (CR-FM) technique. CR-FM is one of the advanced scanning probe microscopy techniques that is able to quantify the local elastic moduli of various materials in a non-destructive manner. Instead of an average value, an elasticity mapping that reveals the nanoscale variations of elastic moduli with location can be extracted and correlated with the topography of the structure. Therefore in this study, by adopting the CR-FM technique that is incorporated with the band excitation technique, the elasticity variations of the abalone shell caused by different micro-constituents and crystal orientations are reported, and the elasticity values of the aragonite and calcite nanograins are quantified.The macroscopic mechanical properties of the abalone shell have been studied extensively in the literature, but the in situ nanoscale elasticity of various micro-constituents in the shell have not been characterized and reported yet. In this study, the nanoscale elasticity mappings including different micro-constituents in abalone shell were observed by using the Contact Resonance Force Microscopy (CR-FM) technique. CR-FM is one of the advanced scanning probe microscopy techniques that is able to quantify the local elastic moduli of various materials in a non-destructive manner. Instead of an average value, an elasticity mapping that reveals the nanoscale variations of elastic moduli with location can be extracted and correlated with the topography of the structure. Therefore in this study, by adopting the CR-FM technique that is incorporated with the band excitation technique, the

Solving conformal contacts using multi-Hertzian techniques

Science.gov (United States)

Pascal, Jean-Pierre; Soua, Brahim

2016-06-01

Recently, publications aiming at wheel-rail contact surveys let readers think that multi-Hertzian methods present severe drawbacks with respect to 'virtual penetration' methods. These surveys criticise multi-Hertzian solutions mainly because presenting 'larger contacts overlaps' and 'frequent secondary contacts near the border of the first contact', both obvious geometric possibilities of which the practical occurrence and eventual inconvenience would remain purely theoretical unless established over definite methods demonstrating poor practical results. Recent surveys all quote Piotrowski-Chollet 2005 survey of wheel-rail contact models that attempted to illustrate defective multi-Hertzian techniques by concentrating on the method initiated by Sauvage in the 1990s and further developed by Pascal. The 2005 paper not only gives no evidence of practical inconveniences of Sauvage's method but also confuses static geometric contact overlaps with the dynamical overlapping of forces. In reality it mixes Sauvage method up with a quite different technique. Thus a clarification is now necessary by reminding what the proper Sauvage technique really is and by showing some of its practical successful applications. The present paper, focusing on determination of normal contact forces in conformal situations, intends to explain clearly the advantages of the unequivocal localisation of secondary ellipses in that multi-Hertzian method which has been developed in INRETS VOCO codes in the 1990s and successfully used by SNCF and ALSTOM in the INRETS-SNCF code, VOCODYM, and later in Pascal's online calculation of railway elastic contacts code. It proved its effectiveness for studying freight wagons derailments as well as rail wear and head-check, unrounded wheels wear, high-speed lines' deformations or TGV comfort. While simulating American ACELA trainsets' behaviour on the US North-East Corridor tracks, prior to actual tests, as part of the commercial contract. It has been also a

[Application of pie-crusting the medial collateral ligament release in arthroscopic surgery for posterior horn of 
medial meniscus in knee joint].

Science.gov (United States)

Zhu, Weihong; Tang, Qi; Liao, Lele; Li, Ding; Yang, Yang; Chen, You

2017-09-28

To explore the effectiveness and safety of pie-crusting the medial collateral ligament release (MCL) in treating posterior horn of medial meniscus (PHMM) tear in tight medial tibiofemoral compartment of knee joint.
 Methods: Thirty-two consecutive patients with PHMM tear in tight medial tibiofemoral compartment of knee joint were admitted to our department from January, 2013 to December, 2014. All patients were performed pie-crusting the MCL release at its tibial insertion with 18-gauge intravenous needle. All patients were evaluated by valgus stress test and bilateral valgus stress radiograph at postoperative 1st day, 4th week and 12th week. Visual Analogue Scales (VAS), Lysholm scores, Tegner scores and International Knee Documentation Committee (IKDC) scores were recorded at the 1st, 3th, 6th month follow-up, then follow-up every 6 months.
 Results: The mean follow-up was 28 (24-36) months. All cases were negative in valgus stress test. MCL rupture, femoral fracture, articular cartilage lesion and neurovascular injury were not found at the last follow-up. The median medial joint space width of affected side and unaffected side for valgus stress radiographs were 6.8 mm and 4.3 mm (P0.05) at the 12th week, respectively. VAS scores was changed from 4.5±1.5 preoperatively to 1.7±1.0 at the final follow-up (t=16.561, Pjoint.

A superellipsoid-plane model for simulating foot-ground contact during human gait.

Science.gov (United States)

Lopes, D S; Neptune, R R; Ambrósio, J A; Silva, M T

2016-01-01

Musculoskeletal models and forward dynamics simulations of human movement often include foot-ground interactions, with the foot-ground contact forces often determined using a constitutive model that depends on material properties and contact kinematics. When using soft constraints to model the foot-ground interactions, the kinematics of the minimum distance between the foot and planar ground needs to be computed. Due to their geometric simplicity, a considerable number of studies have used point-plane elements to represent these interacting bodies, but few studies have provided comparisons between point contact elements and other geometrically based analytical solutions. The objective of this work was to develop a more general-purpose superellipsoid-plane contact model that can be used to determine the three-dimensional foot-ground contact forces. As an example application, the model was used in a forward dynamics simulation of human walking. Simulation results and execution times were compared with a point-like viscoelastic contact model. Both models produced realistic ground reaction forces and kinematics with similar computational efficiency. However, solving the equations of motion with the surface contact model was found to be more efficient (~18% faster), and on average numerically ~37% less stiff. The superellipsoid-plane elements are also more versatile than point-like elements in that they allow for volumetric contact during three-dimensional motions (e.g. rotating, rolling, and sliding). In addition, the superellipsoid-plane element is geometrically accurate and easily integrated within multibody simulation code. These advantages make the use of superellipsoid-plane contact models in musculoskeletal simulations an appealing alternative to point-like elements.

MR imaging findings of medial tibial crest friction

International Nuclear Information System (INIS)

Klontzas, Michail E.; Akoumianakis, Ioannis D.; Vagios, Ilias; Karantanas, Apostolos H.

2013-01-01

Objective: Medial tibial condyle bone marrow edema (BME), associated with soft tissue edema (STe) surrounding the medial collateral ligament, was incidentally observed in MRI examinations of young and athletic individuals. The aim of the present study was to 1. Prospectively investigate the association between these findings and coexistence of localized pain, and 2. Explore the possible contribution of the tibial morphology to its pathogenesis. Methods: The medial tibial condyle crest was evaluated in 632 knee MRI examinations. The angle and depth were measured by two separate evaluators. The presence of STe and BME was recorded. A third evaluator blindly assessed the presence of pain at this site. Results: BME associated with STe was found in 24 patients (with no history of previous trauma, osteoarthritis, tumor or pes anserine bursitis). The mean crest angle was 151.3° (95%CI 147.4–155.3°) compared to 159.4° (95%CI 158.8–160°) in controls (Mann–Whitney test, P < 0.0001). MRI findings were highly predictive of localized pain (sensitivity 92% specificity 99%, Fisher's exact test, P < 0.0001). Conclusion: Friction at the medial tibial condyle crest is a painful syndrome. MRI is a highly specific and sensitive imaging modality for its diagnosis

MR imaging findings of medial tibial crest friction

Energy Technology Data Exchange (ETDEWEB)

Klontzas, Michail E., E-mail: miklontzas@gmail.com; Akoumianakis, Ioannis D., E-mail: ioannis.akoumianakis@gmail.com; Vagios, Ilias, E-mail: iliasvagios@gmail.com; Karantanas, Apostolos H., E-mail: akarantanas@gmail.com

2013-11-01

Objective: Medial tibial condyle bone marrow edema (BME), associated with soft tissue edema (STe) surrounding the medial collateral ligament, was incidentally observed in MRI examinations of young and athletic individuals. The aim of the present study was to 1. Prospectively investigate the association between these findings and coexistence of localized pain, and 2. Explore the possible contribution of the tibial morphology to its pathogenesis. Methods: The medial tibial condyle crest was evaluated in 632 knee MRI examinations. The angle and depth were measured by two separate evaluators. The presence of STe and BME was recorded. A third evaluator blindly assessed the presence of pain at this site. Results: BME associated with STe was found in 24 patients (with no history of previous trauma, osteoarthritis, tumor or pes anserine bursitis). The mean crest angle was 151.3° (95%CI 147.4–155.3°) compared to 159.4° (95%CI 158.8–160°) in controls (Mann–Whitney test, P < 0.0001). MRI findings were highly predictive of localized pain (sensitivity 92% specificity 99%, Fisher's exact test, P < 0.0001). Conclusion: Friction at the medial tibial condyle crest is a painful syndrome. MRI is a highly specific and sensitive imaging modality for its diagnosis.

Efficiency of Medial Rectus Advancement Surgery in Consecutive Exotropia

Directory of Open Access Journals (Sweden)

Kemal Yar

2015-12-01

Full Text Available Purpose: To evaluate the efficiency of medial rectus advancement surgery in consecutive exotropia. Material and Methods: The study group consisted of 20 cases, 10 male, 10 female, who were diagnosed as consecutive exotropia and underwent surgery between 2008-2013 at Cukurova University Medical Faculty Ophthalmology Department. Records of the patients were investigated retrospectively. We evaluated best corrected visual acuity, existence of ambliopia, postoperative duration following the first surgery and applied surgical procedures. Postoperative deviation lower than 10 PD were assesed as successful. Mean follow up period was 29,8 +/- 21,36 (8-80 months, patients with inadequate follow up period were dismissed from the study group. Results: We only applied bilateral medial rectus advancement surgery to 6 and unilateral medial rectus advancement surgery to 5 patients and obtained intended surgical result in these 11 cases. The other patients underwent lateral rectus recession or/and medial rectus resection operations inorder to reach projected deviation degrees. Deviation was found to be 46,4+/-9,24 (40-70 PD in cases who only underwent advancement surgery and was 65,56 +/- 18,78 (40-90 PD in cases who underwent additional surgical procedure. 16 (%80 of the cases had hypermetropi various dioptries and 7 (%35 had ambliopia. Discussion: Consecutive exotropia can appear years after surgery and is an important late period complication. In this study achievement of %55 success with medial rectus advancement surgery indicates that this is a preferable procedure. But in wide angle deviations additional lateral rectus recession or/and medial rectus resection operations can be applied inorder to reach intended adjustment. Accurrate prediction of the propotion of advancement surgery and adjustment is not always possible because of intensive fybrosis in operated muscles and enviroment tissue. [Cukurova Med J 2015; 40(4.000: 707-713

Magnetic resonance imaging findings in patients with medial epicondylitis

Energy Technology Data Exchange (ETDEWEB)

Kijowski, Richard; Smet, Arthur A. De [University of Wisconsin Hospital, Department of Radiology, Madison (United States)

2005-04-01

To compare the MR imaging findings of 13 patients with clinically diagnosed medial epicondylitis with the MR imaging findings of 26 patients of similar age with no clinical evidence of medial epicondylitis. The study group consisted of 13 patients with clinically diagnosed medial epicondylitis. The control group consisted of 26 patients of similar age with no clinical evidence of medial epicondylitis. The medical records and MR imaging findings of these patients were retrospectively reviewed by two fellowship-trained musculoskeletal radiologists. Eleven of the 13 patients in the study group had thickening and increased signal intensity of the common flexor tendon on both T1-weighted and T2-weighted images. The remaining two patients in the study group had soft tissue edema around a normal-appearing common flexor tendon. Twenty-one of the 26 patients in the control group had a normal-appearing common flexor tendon on MR imaging. Three patients in the control group had a thickened common flexor tendon which was of intermediate signal intensity on T1-weighted images but of uniform low signal intensity on T2-weighted images. Two patients in the control group had a thickened common flexor tendon which was of intermediate signal intensity on both T1-weighted and T2-weighted images. None of the patients in the control group had soft tissue edema around the common flexor tendon. MR imaging findings of patients with clinically diagnosed medial epicondylitis included thickening and increased T1 and T2 signal intensity of the common flexor tendon and soft tissue edema around the common flexor tendon. The presence of intermediate to high T2 signal intensity or high T2 signal intensity within the common flexor tendon and the presence of paratendinous soft tissue edema were the most specific findings of medial epicondylitis on MR imaging. (orig.)

White matter organization in cervical spinal cord relates differently to age and control of grip force in healthy subjects.

Science.gov (United States)

Lindberg, Påvel G; Feydy, Antoine; Maier, Marc A

2010-03-17

Diffusion tensor imaging (DTI) can be used to elucidate relations between CNS structure and function. We hypothesized that the degree of spinal white matter organization relates to the accuracy of control of grip force. Healthy subjects of different age were studied using DTI and visuomotor tracking of precision grip force. The latter is a prime component of manual dexterity. A regional analysis of spinal white matter [fractional anisotropy (FA)] across multiple cervical levels (C2-C3, C4-C5, and C6-C7) and in different regions of interest (left and right lateral or medial spinal cord) was performed. FA was highest at the C2-C3 level, higher on the right than the left side, and higher in the lateral than in the medial spinal cord (p level in the lateral spinal cord, in which the corticospinal tract innervates spinal circuitry controlling hand and digit muscles. FA of the medial spinal cord correlated consistently with age across all cervical levels, whereas FA of the lateral spinal cord did not. The results suggest (1) a functionally relevant specialization of lateral spinal cord white matter and (2) an increased sensitivity to age-related decline in medial spinal cord white matter in healthy subjects.

Anatomical and magnetic resonance imaging study of the medial ...

African Journals Online (AJOL)

Introduction: The medial collateral ligament of the ankle joint also known as the deltoid ligament, is a multifascicular group of ligaments. It can be divided into a superficial and deep group of fibers originating from the medial malleolus to insert in the talus, calcaneus, and navicular bones. Wide variations have been noted in ...

Contact lens wear by Royal Air Force aircrew in World War II.

Science.gov (United States)

Pearson, Richard M

2014-04-01

To provide an overview of the use of contact lenses by RAF aircrew in World War II by identifying some of the fitters and wearers and appraising the clinical results that they achieved. A wide-ranging literature search was undertaken that encompassed peer-reviewed journals, non-refereed publications, books, official publications, newspapers and archived documents. Thirty-one aircrew are known to have worn sealed scleral lenses in order to meet the required visual standards. Of these, only two were considered to be completely unsuccessful, one of whom was unilaterally aphakic. One additional case of undisclosed contact lens wear was found and the identity of this officer was established. Brief biographies of a few pilots establish the context of their contact lens wear. Overall, the results of scleral lens wear were variable reflecting those achieved by civilian patients of the period. While three men complained of discomfort due to heat and glare, one pilot experienced no photophobia when flying above white clouds in brilliant sunshine and another found no difficulty caused by altitude or tropical climate. Wearing time ranged from about 2h to 16, or more, hours. In about a third of the cases, wearing time was limited due to the onset of a form of contact lens induced-epithelial oedema known as Sattler's veil and effective solutions to this problem were not implemented until after the war. Copyright © 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Medial Amygdala and Aggressive Behavior : Interaction Between Testosterone and Vasopressin

NARCIS (Netherlands)

Koolhaas, J.M.; Roozendaal, B.; Boorsma, F.; Van Den Brink, T.H.C.

1990-01-01

This paper considers the functional significance of the testosterone-dependent vasopressinergic neurons of the medial amygdala (Ame) in intermale aggressive behavior of rats. Local microinfusion of vasopressin into the medial amygdala causes an increase in offensive behavior both in gonadally intact

Evaluation of changes in vertical ground reaction forces as indicators of meniscal damage after transection of the cranial cruciate ligament in dogs.

Science.gov (United States)

Trumble, Troy N; Billinghurst, R Clark; Bendele, Alison M; McIlwraith, C Wayne

2005-01-01

To determine whether decreases in peak vertical force of the hind limb after transection of the cranial cruciate ligament (CrCL) would be indicative of medial meniscal damage in dogs. 39 purpose-bred adult male Walker Hounds. The right CrCL was transected arthroscopically. Force plate measurements of the right hind limb were made prior to and 2, 4, 10, and 18 weeks after transection of the CrCL. Only dogs with > or =10% decreases in peak vertical force after week 2 were considered to have potential meniscal damage. Dogs that did not have > or =10% decreases in peak vertical force at any time point after week 2 were assigned to group 1. Group 2 dogs had > or =10% decreases in peak vertical force from weeks 2 to 4 only. Group 3 and 4 dogs had > or =10% decreases in peak vertical force from weeks 4 to 10 only or from weeks 10 to 18 only, respectively. Damage to menisci and articular cartilage was graded at week 18, and grades for groups 2 to 4 were compared with those of group 1. The percentage change in peak vertical force and impulse area was significantly different in groups 2 (n = 4), 3 (4), and 4 (4) at the end of each measurement period (weeks 4, 10, and 18, respectively) than in group 1 (27). The meniscal grade for groups 2 to 4 was significantly higher than for group 1. A > or =10% decrease in peak vertical force had sensitivity of 52% and accuracy of 72% for identifying dogs with moderate to severe medial meniscal damage. In dogs with transected or ruptured CrCLs, force plate analysis can detect acute exacerbation of lameness, which may be the result of secondary meniscal damage, and provide an objective noninvasive technique that delineates the temporal pattern of medial meniscal injury.

Contact-free handling using actively controlled electrostatic levitating fields

NARCIS (Netherlands)

Woo, S.J.

2012-01-01

In general electric field forces have the distinctive property of being able to mediate forces to virtually any material in a fully non-invasive and contact-free fashion. Based on this property, electrostatic levitation holds great promise for the semiconductor, solar panel, and flat-panel display

Endoscopic partial medial maxillectomy with mucosal flap for maxillary sinus mucoceles.

Science.gov (United States)

Durr, Megan L; Goldberg, Andrew N

2014-01-01

To describe a technique of endoscopic medial maxillectomy with mucosal flap for postoperative maxillary sinus mucoceles and to present a case series of subjects who underwent this procedure. This case series includes four subjects with postoperative maxillary sinus mucoceles who underwent resection via endoscopic partial medial maxillectomy with a mucosal flap. We will discuss the clinical presentation, imaging characteristics, operative details, and outcomes. Four subjects are included in this study. The average age at the time of medial maxillectomy was 52 years (range 35-65 years). Three subjects (75%) were female. One subject (25%) had bilateral postoperative maxillary sinus mucoceles. Two subjects (50%) had unilateral right sided mucoceles, and the remaining subject had a unilateral left sided mucocele. All subjects had a history of multiple sinus procedures for chronic sinusitis including Caldwell-Luc procedures ipsilateral to the postoperative mucocele. All subjects underwent endoscopic medial maxillectomy without complication and were symptom free at the last follow up appointment, average 24 months (range 3-71 months) after medial maxillectomy. For postoperative maxillary sinus mucoceles in locations that are difficult to access via the middle meatus antrostomy, we recommend endoscopic medial maxillectomy with mucosal flap. Our preliminary experience with four subjects demonstrates complete resolution of symptoms after this procedure. Copyright © 2014 Elsevier Inc. All rights reserved.

Fracture of an unossified humeral medial epicondyle: use of magnetic resonance imaging for diagnosis

International Nuclear Information System (INIS)

Tanabe, Katsuhisa; Miyamoto, Nao

2016-01-01

Fracture of the humeral medial epicondyle is a relatively common injury in children. Surgery is a good option for treatment, but correct diagnosis is important. Most fractures occur after the ossification of the medial epicondylar apophysis. If a fracture occurs before the ossification of the medial epicondyle, it is undetectable by radiographs. Here we report a case of an unossified medial epicondyle fracture of the humerus. A 9-year-old boy had persistent pain in the medial side of the right elbow after a fall. Despite his pain, he could move his injured elbow with a range from 60 to 90 . Radiographs and computed tomography showed neither fracture nor dislocation in the injured elbow, and soft tissue swelling was the only finding. Neither the trochlea nor the medial epicondyle was ossified. Magnetic resonance imaging showed that the medial epicondyle was separated from the medial metaphysis and displaced. This clear finding led us to surgical fixation. Under general anesthesia, valgus stress showed gross instability of the injured elbow. Two years after the operation, he had no complaints and could play sports with the same range of motion as the left elbow. It is important to keep in mind that medial epicondylar fractures may be hidden in a normal radiograph before the ossification of the medial epicondylar apophysis. (orig.)

Fracture of an unossified humeral medial epicondyle: use of magnetic resonance imaging for diagnosis

Energy Technology Data Exchange (ETDEWEB)

Tanabe, Katsuhisa; Miyamoto, Nao [Nishinomiya Municipal Central Hospital, Department of Orthopaedic Surgery, Nishinomiya (Japan)

2016-10-15

Fracture of the humeral medial epicondyle is a relatively common injury in children. Surgery is a good option for treatment, but correct diagnosis is important. Most fractures occur after the ossification of the medial epicondylar apophysis. If a fracture occurs before the ossification of the medial epicondyle, it is undetectable by radiographs. Here we report a case of an unossified medial epicondyle fracture of the humerus. A 9-year-old boy had persistent pain in the medial side of the right elbow after a fall. Despite his pain, he could move his injured elbow with a range from 60 to 90 . Radiographs and computed tomography showed neither fracture nor dislocation in the injured elbow, and soft tissue swelling was the only finding. Neither the trochlea nor the medial epicondyle was ossified. Magnetic resonance imaging showed that the medial epicondyle was separated from the medial metaphysis and displaced. This clear finding led us to surgical fixation. Under general anesthesia, valgus stress showed gross instability of the injured elbow. Two years after the operation, he had no complaints and could play sports with the same range of motion as the left elbow. It is important to keep in mind that medial epicondylar fractures may be hidden in a normal radiograph before the ossification of the medial epicondylar apophysis. (orig.)

A thermodynamic model of contact angle hysteresis.