Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Friction”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 793 records · Page 44Linked to original sources
PubMed1989

A mortality study of workers manufacturing friction materials: 1941-86.

The mortality of workers employed at a factory producing friction materials has been studied from 1941 to 1986, extending a previous study by seven years. Apart from two periods before 1944, when crocidolite asbestos was used on one particular contract, only chrysotile asbestos has been used. Thirteen deaths were attributed to mesothelioma and of these, 11 were of subjects who had known contact with crocidolite asbestos. Of the remaining two, in one instance the diagnosis is uncertain and in the other the occupational history of the subject is not well established. There was no excess of deaths from lung cancer or other asbestos related tumours, or from chronic respiratory disease. After 1950 hygienic control was progressively improved and from 1970 levels of asbestos in air have not exceeded 0.5-1.0 f/ml. It is concluded that with good environmental control chrysotile asbestos may be used in manufacture without causing excess mortality.

Asbestos↗
PubMed2000

Frictional properties of cattle hooves and their conformation after trimming.

The conformation of the hooves of nine heifers obtained from an abattoir was measured and their coefficient of static friction (mu) was determined for movement in forward, backward and sideways directions. The hooves were trimmed by the Dutch method and their conformation and p were measured again. Trimming increased mu, and decreased the length of the digit and the angle between it and the floor. The value of mu was considerably greater for movement in a forward or backwards direction than sideways. The relationship between the value of mu for sideways movement and hoof conformation was examined by using 52 lower limbs from a variety of cattle breeds. Although mu was greater for Belgian blue than other cattle breeds, there were no relationships between mu and hoof conformation, including a measure of the roughness of the sole.

Animal Husbandry↗
PubMed2002

Rheological aging and rejuvenation in solid friction contacts.

We study the low-velocity (0.1-100 microm s(-1)) frictional properties of interfaces between a rough glassy polymer and smooth silanized glass, a configuration which gives direct access to the rheology of the adhesive joints in which shear localizes. We show that these joints exhibit the full phenomenology expected for confined quasi-2D soft glasses: they strengthen logarithmically when aging at rest, and weaken (rejuvenate) when sliding. Rejuvenation is found to saturate at large velocities. Moreover, aging at rest is shown to be strongly accelerated when waiting under finite stress below the static threshold.

Journal Article↗
PubMed2005

Fracture and friction: Stick-slip motion.

We discuss the stick-slip motion of an elastic block sliding along a rigid substrate. We argue that for a given external shear stress this system shows a discontinuous nonequilibrium transition from a uniform stick state to uniform sliding at some critical stress which is nothing but the Griffith threshold for crack propagation. An inhomogeneous mode of sliding occurs when the driving velocity is prescribed instead of the external stress. A transition to homogeneous sliding occurs at a critical velocity, which is related to the critical stress. We solve the elastic problem for a steady-state motion of a periodic stick-slip pattern and derive equations of motion for the tip and resticking end of the slip pulses. In the slip regions we use the linear friction law and do not assume any intrinsic instabilities even at small sliding velocities. We find that, as in many other pattern forming system, the steady-state analysis itself does not select uniquely all the internal parameters of the pattern, especially the primary wavelength. Using some plausible analogy to first-order phase transitions we discuss a "soft" selection mechanism. This allows to estimate internal parameters such as crack velocities, primary wavelength and relative fraction of the slip phase as functions of the driving velocity. The relevance of our results to recent experiments is discussed.

Journal Article↗
PubMed1992

Iliotibial band friction syndrome: MR imaging findings.

Six patients with clinical histories and physical examination results consistent with iliotibial band friction syndrome (ITBFS) were examined with magnetic resonance (MR) imaging. Ill-defined decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images was present deep to the iliotibial band, adjacent to the lateral femoral epicondyle. Axial fast imaging with steady-state precession (FISP) gradient-echo sequences were essential in differentiating the ill-defined signal intensity abnormality associated with ITBFS from fluid in the lateral knee joint. None of these patients were found to have lateral meniscal tears, and all responded to conservative measures directed at treating ITBFS. The authors conclude that MR imaging may be useful in confirming or establishing the diagnosis of ITBFS in patients with the appropriate clinical history and distal lateral thigh or lateral knee pain.

Adolescent↗
PubMed1987

Frictional longitudinal melanonychia: a new entity.

Longitudinal melanonychia of the toes initiated by repeated trauma from the footwear is described as a new entity in a clinical study of 12 patients. Its proper recognition should help to rule out the brown streaks due to malignant melanoma. The nail pigmentation appears over the distal bony phalanx where the deep matrix covered by the proximal nail fold is exposed to friction or pressure of the narrowing portion of the tip of the shoe. Histological studies revealed hyperplasia of the matrix, some melanin granules in the upper dermis with increased pigmentation of the basal cell layer of the epithelium, and marked melanotic pigment in the nail plate.

Adult↗
PubMed2006

Effect of pre-strain on interfacial friction damping in carbon nanotube polymer composites.

This paper investigates the effect of mechanical pre-strain on interfacial friction damping in nanotube polymer composites. Oxidized single-walled carbon nanotubes were dispersed in a polycarbonate matrix using a solution mixing technique. To characterize the damping response, the material storage and loss modulus was measured by application of dynamic (sinusoidal) load to the nanocomposite in the uniaxial direction. A static pre-strain (in 0.35-0.85% range) was then superimposed on the dynamic strain to quantify its effect on the material response. The results indicate that application of pre-strain facilitates the activation of interfacial slip at the nanotube-polymer interfaces at relatively low dynamic strain amplitudes. This is because pre-strain raises the interfacial shear stress for the nanotube inclusions allowing the critical stress for tube-matrix interfacial slip to be reached at lower strain amplitudes. In this way pre-strain significantly improves the effectiveness of the nanotube-matrix sliding energy dissipation mechanism for damping enhancement in composite structures.

Carbon↗
PubMed1992

Coefficient of friction and subjective assessment of slippery work surfaces.

Research was conducted to determine how well subjects could distinguish between surfaces with different coefficient of friction (COF) values and to evaluate how well subjective ratings of slipperiness correlated with the actual COF values. Thirty-three ironworkers experienced in working and walking on steel surfaces and 23 university students inexperienced with these tasks participated in the study. Subjective slipperiness ratings for a variety of climbing and walking conditions were obtained from the subjects. It was found that subjects could identify differences in the slipperiness of four types of steel coatings tested in the study. There was a high correlation between the subjective ratings and the measured COF values. Subjects did not slip at a COF of 0.41 but did lose footing at a COF of 0.20.

Accidental Falls↗
PubMed1988

Treatment of urethral stricture disease by internal urethrotomy followed by intermittent 'low-friction' self-catheterization: preliminary communication.

The aim of this study was to determine whether the natural course of urethral stricture disease could be modified following urethrotomy by teaching patients intermittent self-catheterization. Preliminary results in 42 patients show that postoperative urine flow rates can be maintained if this method of 'low-friction' catheterization is adopted. The technique has been well received by an elderly group of patients and can be recommended for wider use.

Adult↗
PubMedDate not supplied

Iliotibial band friction syndrome in runners.

The iliotibial band friction syndrome is an overuse injury found in long-distance runners. It is characterized by pain on the outer aspect of the knee in close relation to the lateral femoral epicondyle. It is usually poorly localized, is aggravated by running long distances or excessive striding, and is more severe running downhill. It may be prevented by walking with a stiff knee. In a series of 100 consecutive knees, including 6 patients with the syndrome in both knees (age range, 19 to 48 years; average, 31 years), of which 73 were available for follow-up evaluation, only 30 patients were resolved on the initial regimen of a single injection of local steroid and reduction in the training program. Twenty-one patients had two injections and 8 patients required the third injection. The remaining 14 patients were placed on a regimen of total rest from running for 4 to 6 weeks. Nine patients returned to training and had no recurrence of pain. Five patients consented to surgery and returned to long-distance running between 2 and 7 weeks later. The syndrome apparently has a higher incidence in areas where long-distance running is the vogue, such as, South Africa, or where the climate is cool and running surfaces are slippery.

Adult↗
PubMedDate not supplied

Surgical treatment of the iliotibial band friction syndrome.

A selected group of 23 patients underwent surgery for iliotibial band friction syndrome. Among the patients presenting with this exertional pain syndrome were runners, football players, and cyclists. Diagnosis was clinical since radiographs were negative and an ultrasound examination was positive in only one case, showing an aberrant picture around the lateral femoral epicondyle. Although conservative treatment is effective in most cases, an alternative is needed for patients with complaints that are resistant to conservative means. Surgery was done with the knee held in 60 degrees of flexion and consisted of a limited resection of a small triangular piece at the posterior part of the iliotibial band covering the lateral femoral epicondyle. The uniform good results, low morbidity, and quick return to sports demonstrate that this type of surgery offers a solution for selected cases of failed prolonged conservative treatment.

Adult↗
PubMed1999

The valuation of productivity costs due to premature mortality: a comparison of the human-capital and friction-cost methods for schizophrenia.

OBJECTIVE: To compare productivity-cost estimates for schizophrenia-related premature mortality in Canada in 1996 using the human-capital (HC) approach and friction-cost (FC) method. METHODS: The number of deaths directly attributed to schizophrenia was combined with the estimated number of deaths attributable to schizophrenia from suicide. These premature deaths were valued using 2 methods: 1) the traditional HC approach, based on "potential" lost output to normal age of retirement, and 2) the FC method, based on finding a replacement worker. RESULTS: In 1996, there were 342 male and female preretirement deaths attributed to schizophrenia, directly or indirectly by suicide, in Canada. Most deaths were in males (78%) and by suicide (97%). The productivity cost of these deaths was estimated to be $105 million using the HC approach but only $1.53 million using the FC method. CONCLUSIONS: Productivity-cost estimates from the HC approach are substantially higher than those obtained from the FC method (69 times higher). In circumstances of unemployment, the HC approach is an overestimate of future productivity losses for premature mortality.

Adolescent↗
PubMedDate not supplied

New graft for low friction tunneling in vascular access surgery.

PURPOSE: Prosthetic accesses of the upper extremity have been in use for more than 25 years. Many different conduits have been employed; investigators have continually searched for a graft with superior properties. METHODS: We describe a prospective randomized study comparing the new Slider Graft (Atrium) with the Hybrid PTFE Graft (Atrium); the latter has been used for a number of years. The Slider Graft is also made of PTFE. For this study, both grafts were 6 mm in diameter and 40 cm in length. The Slider Graft has a low friction polyethylene sheath over its entire length. This sheath expedites the passage of the graft through the tunnel. At one end, the graft and the polyethylene sheath are attached to a metal tip. This tip has male threads, which may be inserted firmly into a Kelly Wyck, Atrium, or any standard non-sheath tunneling system. This alleviates graft separation, turning, and slipping during tunneling. The primary objective of this trial was to determine the safety and efficacy of the Slider Graft as compared to the Hybrid Graft in vascular access surgery. The secondary objective was to evaluate how tunneling effects graft performance. We randomized 60 subjects for this study with two equal arms. During surgery we measured various parameters including ease of tunneling, tunnel bleeding, anastomotic bleeding, graft sweating, and immediate patency. To assess arm edema we measured circumference 7.5 cm and 20 cm above the wrist, prior to surgery and in follow-up visits at 1 week, 1 month, and 3 months. Primary patency was also assessed at these visits and at 6, 9, and 12 months. RESULTS: Our results show tunneling with the Slider Graft is easier to accomplish (p = 0.0001) with reduced tunnel bleeding (p = 0.0047) and anastomotic bleeding (p = 0.042). Further, the Slider Graft virtually eliminated the complication of graft sweating and seroma development (p = 0.0005). This may be due to reduced stretching and graft wetting during insertion. At 180 days the Slider Graft demonstrated improved primary patency, which was statistically significant (p = 0.047). At 360 and 720 days the Slider Graft continued to demonstrate a trend toward improved primary patency (p = 0.160). CONCLUSIONS: This study suggests the Slider Graft has significant advantages when compared to the Hybrid Graft and highlights the importance of tunneling in creating prosthetic accesses.

Journal Article↗
PubMed1997

Evaluation of the frictional properties of an elastomer with enhanced lipid-adsorbing ability.

Wear particle production in load-bearing orthopaedic implants is one of the major factors currently limiting the service life of the implant. Most of the research carried out to date in attempting to solve this problem has used the approach of finding more wear-resistant biocompatible material pairs. In contrast, other researchers have attempted to reduce wear by encouraging elastohydrodynamic film formation through the use of elastomeric bearing surfaces. Unfortunately, these elastomeric bearing surfaces have poor tribological properties when a fluid film is not present. Boundary lubrication of an elastomeric orthopaedic bearing may alleviate some of these difficulties. The purpose of this research was to fabricate and characterize an elastomeric material that had a surface capable of specifically adsorbing a naturally occurring boundary lubricant. Dipalmitoyl phosphatidylcholine (DPPC) has been previously shown to be able to act as a boundary lubricant at stresses that occur in human load-bearing joints such as the hip and knee; therefore, DPPC was chosen for use in this study. It was expected that in an aqueous liposome suspension the static coefficient of friction microseconds of such a material would be lower, and increase less quickly over time, than a similar material without an ability to adsorb specifically DPPC when articulated against a polished chrome steel ball bearing. The lipid-adsorbing elastomer did not possess the desired tribological properties. This result was attributed to the polymer adsorbing the DPPC in the liposome phase and not in the bilayer phase, and interaction among the polymeric surface, DPPC and water. This approach to lubricating orthopaedic bearings was shown to have some merit, but a great deal of work needs to be done before such an approach can be used on a clinically available material.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1991

Short stem in Charnley low-friction arthroplasty--a review of 100 cases.

One hundred cases of the Charnley low-friction arthroplasties using shorter (75-110 mm) than standard length stems, both in primary and revision surgery were reviewed. The average follow up was five years and three months. Eleven had cortical thickening that could be attributed to the predicted increase in the stresses within the femoral cortex. There were no cases of cortical thickening when the stem was 100 mm or longer. One stem in the 80-84 mm group was revised for loosening. The findings suggest that other than cortical thickening, which has not progressed during the period of the follow-up, there is no need to fear the use of shorter stems if indicated for technical reasons and provided good stem fixation can be achieved.

Adult↗
PubMed1995

Etiology of iliotibial band friction syndrome in distance runners.

The objectives of our study were: 1) to examine differences between a noninjured cohort of runners (N = 70) and runners afflicted with iliotibial band friction syndrome (ITBFS) (N = 56) according to selected anthropometric, biomechanical, muscular strength, and training measures; 2) to explore multivariate relationships among these measures in both the well and injured groups; and 3) to develop specific hypotheses concerning risk factors for injury that will later be tested in a prospective observational study. High speed videography (200 fps), a force platform (500 Hz), and a Cybex II+ isokinetic dynamometer were used to assess rearfoot motion, ground reaction forces, and knee muscular strength and endurance, respectively. A linear discriminant function analysis of the training data revealed weekly mileage, training pace, number of months using current training protocol, % time spent swimming, and % time spent running on a track to be significant (P < 0.10). Height was a significant anthropometric discriminator, while seven isokinetic strength and endurance measures were found to discriminate significantly between the groups. Calcaneal to vertical touchdown angle, and maximum supination velocity were significant rearfoot movement discriminators. Maximum braking force was the only significant kinetic discriminator. A combined discriminant analysis using those variables found to be significant in the previous analyses revealed weekly mileage, and maximum normalized braking force to be the best discriminators (model P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1977

Conversion of fused hips to low friction arthroplasty.

Fifty-four hips converted to low friction arthroplasty between 1965 and 1975 have been reviewed one to eleven years after operation. In many cases malposition had led to degenerative changes in the opposite hip, the lumbar spine or the knee, often with severe loss of function due to pain. It was found that total replacement could give useful relief of pain and improved function, though the range of movement obtained was not as good as in primary replacement. An outstanding feature was the correction of inequality of leg length. In general, the results were much better in cases of ankylosis acquired in adult life than in cases of spontaneous fusion after sepsis in childhood. The most important complication was a single case of sciatic palsy.

Adult↗
PubMed1978

Low-friction arthroplasty after fracture-dislocations of the hip.

Sixty-six patients are presented who have had a total hip replacement by the Charnley low-friction technique after injuries of the hip, the majority of which were fracture-dislocations. The clinical results of the arthroplasties in this relatively young group of patients are shown to be very good. The selection of young patients for total hip replacement arthroplasty is discussed.

Adult↗