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At least 613 records · Page 34Linked to original sources
PubMed2001

Frictional dermal melanosis (lifa disease) over bony prominences.

Seventy-one patients (70 females and one male) were studied. Their ages at presentation ranged from 16-43 years with a mean of 24.4 years. The duration of disease varied from three months to ten years with a median of 2.7 years. All patients were slim and had recorded using a washing agent (Lifa) during bathing with vigorous friction. Family history of the same disease was present in 11 (15.5%) patients. The pigmentation was brown-black with a rippled pattern and showed no contrast under Wood's light. The areas commonly affected were clavicles (71.8%), shins (36.6%), upper back (32.4%), Adam's apple (31%), lateral aspects of the arms (31%) and other areas. The histopathology of biopsies from 24 patients showed marked dermal melanosis. Amyloid deposits in the papillary dermis were present in one patient. This clinical and histopathological picture suggests that this common condition is related to frictional melanosis.

Adolescent↗
PubMed1999

Surgical treatment of iliotibial band friction syndrome. A retrospective study of 45 patients.

Iliotibial band friction syndrome is an overuse injury mainly affecting runners, but also other athletes. The treatment of choice is conservative. If this treatment is unsuccessful, surgical treatment can be performed. The posterior half of the iliotibial band is transsected where it passes over the lateral epicondyle of the femur. Optionally the underlying bursa is removed. Between 1989 and 1996 45 patients were operated in Trondheim. The mean age was 27 (14-46) years. Of the patients, 22 (48.9%) had excellent results, 16 (35.5%) had good results, 6 (13.3%) had fair results and 1 (2.2%) patient had a poor result. One patient had a minor postoperative infection. Had the postoperative result been known beforehand, 75.6% of the patients would have been operated on again. We conclude that surgical treatment of iliotibial band friction syndrome produces good results in patients with insufficient relief of symptoms after conservative treatment.

Adolescent↗
PubMed1995

Structural evaluation of ceramic femoral heads: effect of taper friction, support conditions and trunnion compliance.

The outcome of a nonlinear finite element stress analysis of ceramic heads for artificial hip joints is presented. The analysis mainly covers the influence of taper friction, support conditions and trunnion modulus of elasticity on the hoop stress distribution at the surface of the head bore. The paper quantifies how much the maximum tensile stress decreases with increasing frictional coefficient, with stiffening of the support and with stiffening of the trunnion material. An appreciable rise of the maximum tensile upon unloading of the head is also shown for the case of cup support. The computational results are found in close correspondence with photoelastic measurements of taper pressures and encourage the use, for preliminary design purposes, of an approximate theoretical model retrieved from the literature.

Biomechanical Phenomena↗
PubMed1990

Effects of friction on the unconfined compressive response of articular cartilage: a finite element analysis.

A finite element analysis is used to study a previously unresolved issue of the effects of platen-specimen friction on the response of the unconfined compression test; effects of platen permeability are also determined. The finite element formulation is based on the linear KLM biphasic model for articular cartilage and other hydrated soft tissues. A Galerkin weighted residual method is applied to both the solid phase and the fluid phase, and the continuity equation for the intrinsically incompressible binary mixture is introduced via a penalty method. The solid phase displacements and fluid phase velocities are interpolated for each element in terms of unknown nodal values, producing a system of first order differential equations which are solved using a standard numerical finite difference technique. An axisymmetric element of quadrilateral cross-section is developed and applied to the mechanical test problem of a cylindrical specimen of soft tissue in unconfined compression. These studies show that interfacial friction plays a major role in the unconfined compression response of articular cartilage specimens with small thickness to diameter ratios.

Biomechanical Phenomena↗
PubMed1992

Finite element stress analysis of a push-out test. Part II: Free interface with nonlinear friction properties.

In this second part of a two-part paper, nonlinear frictional properties measured at the bone/porous-surfaced metal interface are used to perform the stress analysis of a push-out test assuming free interface. In this case, the friction at the interface is the only mechanism to resist the externally applied load. Similar to the part I, the model is axisymmetric and consists of two cylinders in contact with each other through the interface. Various relative material properties and boundary conditions are simulated in order to examine their effects on the interface stresses and overall push-out resistance. The role of the force-fit and the load direction (push-out versus pull-out) on the results is also investigated. The computed radial and shear stresses are found to markedly vary both with location along the interface and with the testing configuration. The ultimate push-out resistance is also found to significantly alter as the material arrangement and boundary conditions change. The predicted push-out load augments with an increase in the force-fit and diminishes to nil in the absence of a press-fit. For the cases studied here, there is a relative difference of as large as 13 percent between the push-out response and the pull-out response so far as the interface stresses and the maximum resistance are concerned. Therefore, any comparison between the results of push-out (or pull-out) tests performed with different design configurations appears to be invalid.

Biomechanical Phenomena↗
PubMed2000

Determination of the dynamic elastic moduli and internal friction using thin resonant bars

Analysis of the data from the resonant-bar technique for determining wave speed and internal friction is presented. Internal friction has been included in the longitudinal and torsional wave equations and the analytical solution has been obtained. In determining the acoustical constants of lossy materials, a broad frequency spectrum is used that includes many resonances and not just data at or near the individual resonances. Corrections due to the mass, length, stiffness, and damping of the transducers are also presented. The theoretical solutions are compared with the measured magnitude and phase response data for torsional, longitudinal, and flexural measurements and are shown to be in good agreement.

Journal Article↗
PubMed2005

High frictional anisotropy of periodic and aperiodic directions on a quasicrystal surface.

Strong friction anisotropy is found when the twofold surface of an atomically clean aluminum-nickel-cobalt quasicrystal slides against a thiol-passivated titanium-nitride tip. Friction along the aperiodic direction is one-eighth as much as that along the periodic direction. This anisotropy, which is about three times as large as the highest value observed in anisotropic crystalline surfaces, disappears after the surface is oxidized in air. These results reveal a strong connection between interface atomic structure and the mechanisms by which energy is dissipated, which likely include electronic or phononic contributions, or both.

Journal Article↗
PubMed2006

Atomic-scale control of friction by actuation of nanometer-sized contacts.

Stiction and wear are demanding problems in nanoelectromechanical devices, because of their large surface-to-volume ratios and the inapplicability of traditional liquid lubricants. An efficient way to switch friction on and off at the atomic scale is achieved by exciting the mechanical resonances of the sliding system perpendicular to the contact plane. The resulting variations of the interaction energy reduce friction below 10 piconewtons in a finite range of excitation and load, without any noticeable wear. Without actuation, atomic stick-slip motion, which leads to dissipation, is observed in the same range. Even if the normal oscillations require energy to actuate, our technique represents a valuable way to minimize energy dissipation in nanocontacts.

Journal Article↗
PubMed2006

Frictional afterslip following the 2005 Nias-Simeulue earthquake, Sumatra.

Continuously recording Global Positioning System stations near the 28 March 2005 rupture of the Sunda megathrust [moment magnitude (Mw) 8.7] show that the earthquake triggered aseismic frictional afterslip on the subduction megathrust, with a major fraction of this slip in the up-dip direction from the main rupture. Eleven months after the main shock, afterslip continues at rates several times the average interseismic rate, resulting in deformation equivalent to at least a M(w) 8.2 earthquake. In general, along-strike variations in frictional behavior appear to persist over multiple earthquake cycles. Aftershocks cluster along the boundary between the region of coseismic slip and the up-dip creeping zone. We observe that the cumulative number of aftershocks increases linearly with postseismic displacements; this finding suggests that the temporal evolution of aftershocks is governed by afterslip.

Journal Article↗
PubMed1998

Frictional melting during the rupture of the 1994 bolivian earthquake

The source parameters of the 1994 Bolivian earthquake (magnitude Mw = 8.3) suggest that the maximum seismic efficiency eta was 0.036 and the minimum frictional stress was 550 bars. Thus, the source process was dissipative, which is consistent with the observed slow rupture speed, only 20% of the local S-wave velocity. The amount of nonradiated energy produced during the Bolivian rupture was comparable to, or larger than, the thermal energy of the 1980 Mount St. Helens eruption and was sufficient to have melted a layer as thick as 31 centimeters. Once rupture was initiated, melting could occur, which reduces friction and promotes fault slip.

Journal Article↗
PubMed2000

Low-friction nanoscale linear bearing realized from multiwall carbon nanotubes

We demonstrate the controlled and reversible telescopic extension of multiwall carbon nanotubes, thus realizing ultralow-friction nanoscale linear bearings and constant-force nanosprings. Measurements performed in situ on individual custom-engineered nanotubes inside a high-resolution transmission electron microscope demonstrated the anticipated van der Waals energy-based retraction force and enabled us to place quantitative limits on the static and dynamic interwall frictional forces between nested nanotubes. Repeated extension and retraction of telescoping nanotube segments revealed no wear or fatigue on the atomic scale. Hence, these nanotubes may constitute near perfect, wear-free surfaces.

Journal Article↗
PubMed1978

Iliotibial tract friction syndrome in athletes--an uncommon exertion syndrome on the lateral side of the knee.

An uncommon exertion pain on the lateral side of the knee is described in 88 patients, in four of whom it was bilateral. The disorder is a result of the friction of the iliotibial tract over the lateral femoral epicondyle. The syndrome is the iliotibial tract friction syndrome of ITFS. All the patients in the material were active athletes or middle-aged joggers in regular training. The cases were seen over four years and four months. The mean age of them was approximately 25 years, and there were only nine women in the series. Th pain appeared usually after running and was localised on the outer femoral condyle, and often radiated downwards along the iliotibial tract. Conservative treatment and changes in training habits cured most cases. The disorder has not often been described in the literature, and seems to appear only in physically very active people, such as athletes or military recruits.

Adolescent↗
PubMed1979

The treatment of iliotibial band friction syndrome.

Iliotibial band friction syndrome is a common cause of knee pain in long distance runners. The pain is caused by friction of the iliotibial band over the lateral epicondyle of the femur. Two hundred and twenty one cases were seen in a two year period. Tenderness over the lateral epicondyle associated with pain at 30 degrees of flexion on compressing the iliotibial band against the lateral epicondyle is diagnostic. Conservative treatment consisted of treating the cause, mostly training irregularities and the local inflammation mostly with steroid injections and rest. Nine cases failed to respond to conservative treatment and these were treated by surgical release of the posterior fibres of the iliotibial band.

Athletic Injuries↗
PubMedDate not supplied

Treatment of a heel blister caused by pressure and friction.

The treatment of heel blisters caused by pressure, friction, and shear is a complex subject. Issues such as whether to aspirate the blister, how to protect it from further pressure, friction, and shear, and which dressing to choose, need to be considered. As nurses are increasingly aware of the emphasis that has been placed on the importance of ensuring that clinical practice is based on evidence, this article attempts to shed some light on these areas of debate. It is important to highlight that during the literature search very little research was found to exist on blister care and it became clear that further research into the nursing care of a blister caused by pressure would be useful to aid nursing care and patient comfort.

Aged↗
PubMed1997

Progression of radiolucent lines adjacent to the acetabular component and factors influencing migration after Charnley low-friction total hip arthroplasty.

We analyzed the progression of radiolucent lines around the acetabular cup after 452 Charnley low-friction arthroplasties that had been performed in 392 patients between 1971 and 1976. The average duration of follow-up was twenty years (range, eleven to twenty-five years) for the 442 hips (382 patients) that had the original component in place at ten years. The demarcation of the bone-cement interface was classified according to the system of Hodgkinson et al. We sought to determine if there was a relationship between the progression of the radiolucent line and the age, gender, and weight of the patient; the level of activity; the preoperative diagnosis; or the amount of wear of the acetabular cup. The demarcation increased over time in 138 (31 per cent) of the 452 hips. Radiographs made at the time of the latest follow-up showed migration of eleven (5 per cent) of the 233 acetabular cups with no demarcation on the initial postoperative radiograph, eighteen (11 per cent) of the 167 cups with type-1 demarcation, twelve (35 per cent) of the thirty-four cups with type-2 demarcation, and thirteen of the eighteen cups with type-3 demarcation. Preoperative acetabular protrusion, inflammatory arthritis, and severe acetabular dysplasia as well as a previous operation were associated with the extent of the radiolucent line on the most recent radiograph (p < or = 0.05 for all). A high level of activity and more than two millimeters of wear of the acetabular cup also were related to the progression of the radiolucent line (p = 0.0004 and p < 0.0001, respectively). Kaplan-Meier survivorship analysis demonstrated that the greater the demarcation on the initial postoperative radiograph, the greater the risk of migration (p < 0.0001, Mantel-Cox test). Our data suggest that, after a Charnley low-friction arthroplasty, any cemented cup, even one with the least amount of demarcation (types 0 and 1), can migrate. As the type of the initial postoperative demarcation increases, so does the risk of migration of the cup, particularly when there is loss of the acetabular bone stock.

Acetabulum↗
PubMed2006

Stormwater quality benefits of a porous friction course and its effect on pollutant removal by roadside shoulders.

This project has two main objectives; the first is to documents the effect of a porous friction course overlay on the quality of highway stormwater runoff, and the second is to assess pollutant removal of a vegetated area along the side of a road from both conventional and porous pavements. The quantity and quality of stormwater runoff from a four-lane divided highway in the Austin, Texas, area was monitored before and after the installation of a porous friction course (PFC). Observed concentrations of suspended solids and pollutants associated with particulate material were much lower in the runoff from the PFC compared with runoff from the conventional asphalt surface. The vegetated highway shoulder reduced the concentrations of many stormwater constituents from the conventional asphalt surface; however, the concentrations of these constituents in runoff produced by the PFC were so low that the vegetated area produced no further reduction in concentration.

Construction Materials↗
PubMed1990

Long-term survival of the Charnley low-friction total hip arthroplasty.

A survivorship analysis of 1,151 Charnley low-friction total hip arthroplasties performed as a primary procedure showed the following 15-year failure probabilities: hip revision 13%, cup revision 8%, femoral revision 12%, radiographic femoral loosening 13%, and radiographic cup loosening 49%. Pain scores diminished gradually with time so that at 15 years, the probability of a Charnley pain score less than 5 was 70%. The data suggest that the Charnley low-friction hip arthroplasty has a finite life span.

Adolescent↗
PubMed1999

Effect of activity levels on polyethylene wear in Charnley low-friction arthroplasty.

Polyethylene wear debri has been implicated as a major cause of aseptic loosening following total hip replacement. The purpose of this study is to classify patient activity levels following total hip replacement and determine if it has an effect on radiographic wear of the socket. 97 patients (115 hips) with osteoarthritis who underwent Charnley low-friction arthroplasty with a minimum of 10 year follow-up were selected. Nine patients had died. Eighty-eight questionnaires were sent of which 59 replied. However, only 40 patients (45 hips) with a complete set of x-rays were finally studied. Activity levels were classified according to post-operative occupation and activities into 'active' and 'less active' groups. Radiographic wear was measured by studying the post-operative and the 10-year review radiograph. There was a significant difference in acetabular wear between the active and the less active group (p = 0.024). No correlation was found between weight and acetabular wear (p = 0.475) or between age and acetabular wear (p = 0.278). It was concluded, therefore, that surgeons who advise their patients to avoid heavy or high intensity activities for prolonged periods, after Charnley low-friction arthroplasty, are justified in this approach.

Acetabulum↗