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At least 703 records · Page 39Linked to original sources
PubMed1988

Frictional resistance to motions of bimane-labelled spinach calmodulin in response to ligand binding.

The single cysteinyl residue 26 of spinach calmodulin was labelled with the thiol-specific bimane fluorescence probe. Following application of stoichiometric quantities of Ca2+ or aluminum ions to the protein, temperature-dependent fluorescence changes (anisotropy, lifetime) could be monitored via the label. From these data the Y function could be constructed which, as a function of temperature, seems to consist of two linear regions which intersect at the critical temperature, Tc. From the Y function the thermal coefficient, b(T), of the frictional resistance to fluorophore rotation could be determined. b(T) was dependent on the type and stoichiometry of the ligand(s) bound to calmodulin. Changes of the thermal coefficient apparently resulted in part from ligand-triggered structural pertubations transmitted over a considerable distance to calmodulin region I, the site of the fluorophore.

Aluminum↗
PubMed1987

In vivo coefficient of kinetic friction: study of urinary catheter biocompatibility.

An animal model was developed to measure objectively the in vivo intrinsic coefficient of kinetic friction (COFk) of various catheter materials. Uncoated red rubber catheters had the highest COFk of the three materials tested. The Biocath catheter exhibited less COFk when compared with the standard silicone catheter. Although the etiology of urethral strictures is multifactorial, better biocompatibility as measured by in vivo COFk may be an important factor in the inevitable urethral trauma and irritation associated with indwelling catheterization and possibly with postcatheterization urethral stricture formation.

Animals↗
PubMed1992

Dislocation in low-friction arthroplasty.

In a series of 2,050 low-friction arthroplasties, 61 cases (2.97%) of dislocation were analyzed. The mechanism of production was malposition of the components (group 1, 33%), deficiency of the abductor mechanism (group 2, 34%), or the association of both (group 3, 26%). Failure to find a cause was even more rare (group 4, 7%). The best treatment is prevention by careful surgical technique, since good results with different procedures have only been attained in 51% of dislocated hips.

Adult↗
PubMed1994

Activity and socket wear in the Charnley low-friction arthroplasty.

A clinical study was undertaken to assess the influence of patient-related factors on wear of the socket in Charnley low-friction arthroplasty. One hundred nine arthroplasties in 79 patients were reviewed at an average of 10.3 years. A new method of activity assessment was designed and used to estimate the distance walked by each patient. This method was validated by a pedometer that recorded the time taken by each patient to walk 20 m. Activity level was related to the amount of movement at the level of the prosthetic articulation by calculating the sliding distance of a point at the center of the surface of the head of the femoral component. Wear was found to correlate with patient activity, but not with the physical characteristics of the patient or the time since operation.

Activities of Daily Living↗
PubMed1994

Bulk autograft for a deficient acetabulum in Charnley low-friction arthroplasty. A 2-9-year follow-up study.

The authors assessed 40 hips in 36 patients where a bulk femoral head autograft was used to supplement deficient acetabulum while performing Charnley low-friction arthroplasty. The majority of the hips were congenitally dysplastic or dislocated with secondary arthritis. The average age at surgery was 47.5 years and the average follow-up period was 4 years. The graft provided a cover between 10 and 42% (mean, 23%) of the socket hemisphere. Union of the graft was evident on the radiograph in 35 hips. There was no graft resorption in 28 hips. Mild graft resorption was seen in 11 cases, and moderate graft resorption was seen in 1 case. In 24 cases, there was no demarcation at the bone-cement interface of the socket. Asymptomatic demarcation of 1 mm thickness or less was seen in 16 hips, of which only 2 showed demarcation at the cement-graft interface. All 40 cases were clinically asymptomatic and successful thus far, with the mean d'Aubigne and Postel score improving from 3.1, 2.8, and 2.9 before surgery to 5.9, 5.4, and 4.9 after surgery for pain, function, and movement, respectively.

Acetabulum↗
PubMed1987

Frictional changes in force values caused by saliva substitution.

The objective of this study was to determine the magnitude of frictional force changes between several sizes of stainless steel orthodontic wires (0.018 inch round, 0.020 inch round, and 0.018 X 0.025 inch rectangular) and an edgewise bracket (0.022 X 0.028 inch slot) when an artificial saliva medium was introduced. The wires were secured in the bracket slots with a 0.010 inch polyurethane ligatures. The force values in the saliva substitute medium were compared with those produced in a dry control and in glycerin. Clinically significant differences among the environmental conditions and among the wire sizes were found. The introduction of saliva substitute provides a significant reduction in force values.

Dental Stress Analysis↗
PubMed2005

Friction force measurements relevant to de-inking by means of atomic force microscope.

In the pulping step of the de-inking process, the ink detaches from the fibers due to shear and physical chemical interaction. In order to get a better understanding of the forces involved between cellulose and ink, the atomic force microscope and the colloidal probe technique have been used in the presence of a model chemical dispersant (hexa-ethyleneglycol mono n-dodecyl ether, C12E6). A cellulose bead was used as the colloidal probe and three different lower surfaces have been used, an alkyd resin, mica and a cellulose sphere. The normal and lateral forces have been measured at a range of nonionic concentrations. It was found that the lateral sliding friction forces deceased with increasing surfactant concentration for both the alkyd resin and mica while no differences were observed for the cellulose surface. In addition, only a very small change in normal force could be detected for the alkyd surface as the concentration changed.

Journal Article↗
PubMed2006

Effects of cleaning procedures of silica wafers on their friction characteristics.

Silicon wafers with thermal silicon oxide layers were cleaned and hydrophilized by three different methods: (1) the remote chemical analysis (RCA) wet cleaning by use of ammonia and hydrogen peroxide mixture solutions, (2) water-vapor plasma cleaning, and (3) UV/ozone combined cleaning. All procedures were found to remove effectively organic contaminations on wafers and gave identical characteristics of the contact angle, the surface roughness and the normal force interactions, measured by atomic force microscopy (AFM). However, it is found that wafers cleaned by the RCA method have several times larger friction coefficients than those cleaned by the plasma and UV/ozone methods. The difference was explained by the atomic-scale topological difference induced during the RCA cleaning. This study reveals the lateral force microscopy as a very sensitive method to detect the microstructure of surfaces.

Journal Article↗
PubMed2004

Knee synovial cyst presenting as iliotibial band friction syndrome.

We present the case of a 28-year-old competitive runner with iliotibial band (ITB) friction syndrome associated with a synovial cyst. Magnetic resonance imaging (MRI) did not demonstrate a fluid collection. However, open exploration revealed a large cyst beneath the ITB arising from the capsule of the knee proximal to the lateral meniscus. The cyst disappeared on extension. The pre-operative MRI scan may have revealed the cyst, if it had been taken with the knee flexed.

Adult↗
PubMed2004

Friction generated ultrasound from geotechnical materials.

Drilling is a process involved with product manufacturing and for civil engineers, site preparation. The usual requirement is for efficient material removal. In this study, the friction pair interaction generated by a drilling process provides ultrasound information related to parameters for the geotechnical material being drilled, where the drill bit has non-degrading ultrasonic characteristics and no essential requirement for material removal. This study has considered monitoring the ultrasonic signal generated by a drilling process, with a view to characterising the parameters of the geotechnical material being drilled and provides a novel method to identify or characterise ground structures. Drilling of geotechnical material systems, typically involve the interaction of a rotating probe and a granular composite medium. The applied load and angular velocity are measured to determine their relevance to the ultrasonic signal. Samples of granular materials have been graded into controlled grain size ranges. Attention has been focused on determining the effects on the ultrasound signal of grain size, bulk density and the water content of the granular material. A comparison between the various granular samples of the different grain sizes, density, water content and the associated ultrasonic signal has been done. The effect of each variable, and existing theory for these effects is commented upon. The broad aim of this research is to evaluate ultrasonic monitoring of drilling and assess its potential for real-time geotechnical ground condition monitoring applications and offer it as an alternative to existing methods.

Journal Article↗
PubMed2006

Performance evaluation of traveling wave ultrasonic motor based on a model with visco-elastic friction layer on stator.

A new visco-elastic contact model of traveling wave ultrasonic motor (TWUSM) is proposed. In this model, the rotor is assumed to be rigid body and the friction material on stator teeth surface to be visco-elastic body. Both load characteristics of TWUSM, such as rotation speed, torque and efficiency, and effects of interface parameters between stator and rotor on output characteristic of TWUSM can be calculated and simulated numerically by using MATLAB method based on this model. This model is compared with that one of compliant slider and rigid stator. The results show that this model can obtain bigger stall torque. The simulated results are compared with test results, and found that their load characteristics have good agreement.

Journal Article↗
PubMed1998

Pulmonary vein injury through repetitive clip friction: an unusual cause of hemothorax.

Massive hemothorax developed in a 58-year-old man 12 hours after a left pneumonectomy. The source of bleeding was a tear in the pulmonary vein stump caused by a titanium clip that had been used during mediastinal lymphadenectomy. Postoperatively, the clip progressively sawed through the vascular wall of the pulmonary vein due to friction during the cardiac cycle.

Hemothorax↗
PubMed1995

Estimating friction coefficients of mixed globular/chain molecules, such as protein/DNA complexes.

Existing methods for predicting translational friction properties of complex molecules start by explicitly building up their three-dimensional shape with spherical subunits. This treatment has been used especially for two types of systems: rigid assemblies and flexible chain molecules. However, many protein/DNA complexes such as chromatin consist of a small number of globular, relatively rigid, bound protein interspersed by long stretches of flexible DNA chain. I present a higher level of treatment of such macromolecules that avoids explicit subunit modeling as much as possible. An existing analytical formulation of the hydrodynamics equations is shown to be accurate when used with the present treatment. Thus the approach is fast and can be applied to hydrodynamic studies of highly degenerate multiple equilibria, such as those encountered in problems of the regulation of chromatin structure. I demonstrate the approach by predicting the effect of a hypothetical unwinding process in dinucleosomes and by simulating the distribution of sedimentation coefficients for cooperative and random models for a chromatin saturation process.

Chromatin↗
PubMed2006

Intelligent compensation of friction, ripple, and hysteresis via a regulated chatter.

In this paper, a hybrid control scheme utilizing a PID feedback control with an additional regulated chatter signal is developed to compensate motion impeding influences such as the effects due to friction, force ripples, and hysteresis in linear piezoelectric motor. The regulated chatter signal is a pulse sequence superimposed on the PID control signal. It has a fixed amplitude, and a pulse width regulated via iterative learning control. As such, the scheme is expected to be useful for applications involving iterative motion sequences. An analysis of the closed-loop performance is presented in the paper. Simulation and experimental results are also furnished to demonstrate that the proposed control scheme can reduce tracking errors significantly.

Algorithms↗
PubMed2003

Cake consolidation in a compression-permeability cell: effect of side-wall friction.

A simulation study was made to investigate the transient state stresses, strains, and void ratio distributions in the formation of a filter cake in a compression-permeability cell (C-P cell). A finite-element software package, ABAQUS, was used for the simulation and emphasis was placed on the effect of the cake/cell-surface friction. The validity of the simulation was assessed by comparing simulation results with available experimental data.

Journal Article↗
PubMed2002

A study on the friction of a self-correction ultrasonic stepping motor.

An experiment has been carried out to investigate the self-correction function of a self-correction ultrasonic stepping motor. When a slider (rotor) is placed on a vibrating beam (stator), it will stay at a stable equilibrium position. If the slider is slightly moved off the equilibrium position, a restoring force will urge the slider back towards its equilibrium position. The experimental result shows that the position of the maximum restoring force on the slider differs from that predicted by using the linear theory. Study found that when a quadratic form is assumed for the dynamic friction coefficient, the theoretical and experimental results are in good agreement.

Journal Article↗
PubMed1982

A salvage procedure in the treatment of the boutonnière deformity caused by contact burn and friction injury.

Contact burns and friction injuries to the dorsum of the finger denude it of full thickness of skin and central extensor tendon tissue, rendering the primary repair of the resultant boutonnière deformity difficult. A salvage procedure that offers both functional restoration and cosmesis is described. Here the unaffected lateral band attachments are transposed en-masses, as a composite flap, to the dorsum of the finger to establish active extension of the proximal interphalangeal joint.

Adult↗