Study of astronaut capabilities to perform extravehicular maintenance and assembly functions in weightless conditions

Analysis of astronaut capabilities to perform extravehicular maintenance and assembly functions under simulated weightlessnes

A review of friction models in interacting joints for durability design.

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting systems. Friction is a complex phenomenon and occurs at the interface of two components in relative motion. Over the last several decades, the effects of friction and its modelling techniques have been of significant interests in terms of industrial applications. There is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational conditions. Classical dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity behaviour. Therefore, the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully analysed. Previously the dynamics and impact models used in mechanical joints with clearance have also been examined. The inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational conditions. The revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding surfaces. The presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces, would in turn affect the performance of revolute joints, and puts both reliability and durability of the systems at greater risks of failure. Key literature is identified and a review on the latest developments of the science of friction modelling is presented here. This review is based on a large volume of knowledge. Gaps in the relevant field have been identified to capitalise on for future developments. Therefore, this review will bring significant benefits to researchers, academics and industrial professionals

Urinary metabolite profile of phenyl and o-cresyl glycidyl ether in rats: identification of a novel pathway leading to N-acetylserine O-conjugates.

The urinary excretion of metabolites of phenyl glycidyl ether (PGE) and o-cresyl glycidyl ether (o-CGE) was investigated in rats. Urine was collected, in fractions, from rats intraperitoneally administered PGE or o- CGE in doses ranging from 0.033 to 1.0 mmol/kg. The metabolites were extracted from acidified urine with ethyl acetate or diethyl ether, and their identity was elucidated by GC/MS analysis. The epoxide of PGE can be inactivated by glutathione (GSH) conjugation or epoxide hydrolysis. After further metabolites, these routes lead to the urinary excretion of phenyl glycidyl ether mercapturic acid (PGEMA) and 3-(phenyloxy)lactic acid (POLA). The excretion of PGEMA and POLA was described before and is confirmed in this study. Additionally, a new metabolite was identified as N-acetyl-O- phenylserine (NAPS), which is proposed to be formed from POLA by subsequent oxidation, transamination, and N-acetylation. For PGEMA a linear dose- excretion relationship was found (