PURPOSE To investigate thickness profile changes of the corneal epithelium and Bowman's layer at the vertical and horizontal meridians with overnight myopia orthokeratology (OK) lenses. METHODS Twenty subjects (age range: 19-33 years) wore reverse-geometry rigid gas-permeable OK lenses in both eyes for 30 days. Before lens wear and after 1, 7, and 30 days of overnight lens wear, evaluation of...

Since screw compressor rotors are of a helical shape and tool points engaged in their manufacturing pass different cutting length, the tools do not wear uniformly along the rotor profiles. The nonuniformity depends on a difference between the rotor point angle and pressure angle and on the rotor helix angle. A difference in relative movement between the tool and the rotors with and without the ...

OBJECTIVES The goal of resident selection is twofold: (1) select candidates who will be successful residents and eventually successful practitioners and (2) avoid selecting candidates who will be unsuccessful residents and/or eventually unsuccessful practitioners. Traditional tools used to select residents have well-known limitations. The Hartman Value Profile (HVP) is a proven adjuvant tool to...

Hip simulators have been used for ten years to determine the tribological performance of large-head metal-on-metal devices using traditional test conditions. However, the hip simulator protocols were originally developed to test metal-on-polyethylene devices. We have used patient activity data to develop a more physiologically relevant test protocol for metal-on-metal devices. This includes sto...

The surface degradation of composite resins caused by accelerated aging was studied. Accelerated aging for 900 hours caused erosion of the resin matrices and exposure of filler particles. Differences in surface profiles after aging suggest that the materials eroded at different rates. Accelerated aging may model erosive wear of composites.

Traditionally, thick enamel has often been used to infer durophagy (i.e., hard nut and seed consumption) in extinct hominins. These inferences are based on the hypothesis that thick enamel is primarily an adaptation to prevent tooth fracture or chipping resulting from high-stress loads produced during the mastication of large hard foods. An alternative view argues that thick enamel may aid in m...

Experimental and theoretical studies are made of a typical snap-action rocker switch, to establish the wear mechanisms in the pivoting contact. The rocker switch, used extensive~ in consumer goods, operates in the medium duty current range, (1 30 Amps). Highspeed photographic studies have shown that the main cause of wear is arcing, occurri~ during separation and bounce at the pivot contacts. T...

Introduction: Ultra High Molecular Weight Polyethylene (PE) remains the primary bearing surface of choice in total knee replacements (TKR). Traditionally Archard’s Law is used to predict wear rates in hip and knee prostheses. This assumes that the volume of wear between two articulating surfaces is proportional to the applied load and sliding distance. However it has been shown that this is a s...

OBJECTIVE To investigate the abrasive wear of surface sealants (Seal&Protect and K-0184 (experimental sealant)) and the influence of pre-treatment with mineral deposit forming prophylaxis pastes (NUPRO Sensodyne and NUPRO) on this wear. METHODS One hundred and eight bovine dentine samples were randomly allocated to nine groups (1-9). Pre-treatment (10 s): groups 1-3: untreated, groups 4-6: NU...