Determinants of the frequency of contact lens wear

To characterize and discover the determinants of the frequency of wear (FOW) of contact lenses. Survey forms were sent to contact lens fitters in up to 40 countries between January and March every year for 5 consecutive years (2007–2011). Practitioners were asked to record data relating to the first 10 contact lens fits or refits performed after receiving the survey form. Only data for daily wear lens fits were analyzed. Data were collected in relation to 74,510 and 9,014 soft and rigid lens fits, respectively. Overall, FOW was 5.9±1.7 days per week (DPW). When considering the proportion of lenses worn between one to seven DPW, the distribution for rigid lenses is skewed toward full-time wear (7 DPW), whereas the distribution for soft daily disposable lenses is perhaps bimodal, with large and small peaks at seven and two DPW, respectively. There is a significant variation in FOW among nations (P<0.0001), ranging from 6.8±1.0 DPW in Greece to 5.1±2.5 DPW in Kuwait. For soft lenses, FOW increases with decreasing age. Females (6.0±1.6 DPW) wear lenses more frequently than males (5.8±1.7 DPW) (P=0.0002). FOW is greater among those wearing presbyopic corrections (6.1±1.4 DPW) compared with spherical (5.9±1.7 DPW) and toric (5.9±1.6 DPW) designs (P<0.0001). FOW with hydrogel peroxide systems (6.4±1.1 DPW) was greater than that with multipurpose systems (6.2±1.3 DPW) (P<0.0001).

Studies of a wear resistant cast iron

 The objective of this investigation was to set down (on the base of the results obtained by the examination of white cast iron alloys with different content of the alloying elements) a correlation between chemical composition and microstructure, on one hand, and the properties relevant for this group of materials, i.e., abrasion wear resistance and fracture toughness, on the other. Experimental results indicate that the volume fracture of the carbide phase, carbide size and distribution, as well as the morphology of eutectic colonies, had an important influence on the wear resistance of white cast iron alloys under low-stress abrasion conditions, whereas fracture toughness was determined largely by the matrix microstructure.

Sliding wear behavior of plasma sprayed Fe3Al–Al2O3 graded coatings

Fe3Al–Al2O3 double-layer coatings (DC), Fe3Al-Fe3Al/50%Al2O3–Al2O3 triple-layer coatings (TC) and Fe3Al-Al2O3 graded coatings (GC) were produced from a series of Fe3Al/Al2O3 composite powders with different compositions on low carbon steel substrate using PLAXAIR plasma spraying equipment. Friction behaviors and wear resistance of the three kinds of coatings have been investigated under different loads. Tests were carried out using an MRH-3 standard machine, in lineal contact sliding under dry condition against hardmetal, at a sliding velocity of about 1.57 ms−1. Wear rates under different loads were measured and the friction coefficients were recorded. SEM analysis was carried out to identify the wear mechanisms. The results show that the GC has higher wear-resistance than DC and TC. The tribological characteristics of graded coating were different along the depth of the coatings, and the surface of coatings with pure Al2O3 does not show the best wear resistance. The wear rate and friction coefficients were also different under different loads. The failure types of plasma-sprayed Fe3Al-Al2O3 graded coatings in lineal contact were: loosening of ceramic particles, crack nucleation and propagation, brittle fracture, plastic deformation, and adhesive wear.

Wear of permanent incisors with age on commercial Australian Angora goat farms

OBJECTIVE: To quantify if, and to what extent, permanent incisor wear differed with age of goat and farm of origin on commercial Australian Angora goat farms. DESIGN: Observations were made on three Angora goat farms in the wheat-sheep zone of Victoria, each managed according to the farmer's practices. Farmers provided a representative flock of does. METHODS: The proportion and pattern of wear of permanent incisors were recorded and percentage wear calculated. After log(y + 10) transformation, a parsimonious general linear model was developed to relate wear to farm and age, with age considered as a continuous variate. RESULTS: The range in wear of the permanent incisors was 0-100%. For each farm, the most parsimonious model for permanent first incisor wear and average wear of all permanent incisors was a separate straight line relating the transformed incisor wear to the age of doe. The models accounted for 66-73% of variance. On each farm the incisor wear was similar and low for ages up to approximately 4 years. On all farms, the amount of incisor wear increased dramatically with age, although the rate of increase differed with each farm. CONCLUSIONS: Permanent incisor wear increased with age of goat and differed with farm of origin. Angora goat farmers need to be aware of the potential for incisor wear to affect doe production and health.