Effects of Extreme Sleep Deprivation on Human Performance

Sleep is a fundamental recuperative process for the nervous system. Disruption of this homeostatic drive can lead to severe impairments of the operator’s ability to perceive, recognize, and respond to emergencies and/or unanticipated events, putting the operator at risk. Therefore, establishing a comprehensive understanding of how sleep deprivation influences human performance is essential in order to counter fatigue or to develop mitigation strategies. The goal of the present study was to examine the psychological effects of prolonged sleep deprivation (approx. 75 hrs) over a four-day span on a general aviation pilot flying a fixed-based flight simulator. During the study, a series of tasks were employed every four hours in order to examine the pilot’s perceptual and higher level cognitive abilities. Overall, results suggest that the majority of cognitive and perceptual degradation occurs between 30-40 hours into the flight. Limitations and future research directions are also discussed

Influence of head size on the development of metallic wear and on the characteristics of carbon layers in metal-on-metal hip joints

Background and purpose Particles originating from the articulating surfaces of hip endoprostheses often induce an inflammatory response, which can be related to implant failure. We therefore analyzed the metal content in capsular tissue from 44 McKee-Farrar metal-on-metal hip prostheses (with 3 different head sizes) and we also analyzed the morphological structure of layers located on articulating surfaces

Structural profile of ultra-high molecular weight polyethylene in acetabular cups worn on hip simulators characterized by confocal Raman spectroscopy

We applied a Raman confocal spectroscopic technique to quantitatively assess the structural features of two kinds of acetabular cups made of ultra-high molecular weight polyethylene. We wanted to know whether polyethylene cups belonging to different generations, and thus manufactured by different procedures, possess different molecular structures and how those differences affected their wear resistance. Emphasis was placed on oxidation profiles developed along the cross-sectional depth of the cups in the main wear zone developed during testing in a hip simulator. The micrometric lateral resolution of the laser beam, focused at surface or sub-surface sectional planes, enabled the visualization of highly resolved microstructural property profiles, including crystalline and amorphous phase fractions. Oxidation profiles retrieved from polyethylene cups belonging to different generations greatly differed after wear testing. The highly cross-linked polyethylene showed a lower degree of crystallinity and oxidation at an appreciably slower rate as compared to that belonging to an earlier generation. (C) 2011 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:893-899, 201