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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Biometrika Trust is collaborating with JSTOR to digitize, preserve and extend access to Biometrika. SUMMARYIn this paper we consider the problem of sequentially applying v treatments to n experimental units over time or space where there may be an unknown trend effect which can be expressed as a polynomial function of the order in which the observations are taken. A method is given for constructing ordered applications of treatments to experimental units which produce easily computed and optimal estimates for treatment differences that are orthogonal to the unknown trend effect.Some key words: A-optimal; Run order; Treatment; Trend free.

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The Taguchi analysis method along with a nanoindentation technique were used to study the effects of alloy chemistry, pH and halide ion concentrations on the mechanical fracture of electrochemically grown passive films formed at a metastable pitting potential. Three austenitic stainless steels, 304L, 316L and 904L, were potentiostatically polarised in hydrochloric acid solutions. The load at film fracture during nanoindentation was primarily dominated by both alloy chemistry and the salt concentration. Passive films mechanically weakened as the ratio of iron to the total metallic atoms increased in the film; an estimate of the applied tensile stress that caused fracture increased from 0 . 8 GPa to 1 . 18 GPa as the alloy was changed from 304L to 904L. Increasing the salt concentration present during film growth from 0 . 01M to 0 . 2M reduced the applied stress for fracture by a factor of two. Prolonged anodic aging times at 40uC decreased the fracture load of these passive films.

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