Membrane reactors enable synthesis-gas production from methane and air while a®oiding the need for separation of the nitrogen either before or after the reaction. A stable membrane was de®eloped by spray deposition of a dense thin film of La Sr Fe Ga O on a high-purity porous ␣ -alumina tube. The oxygen per-0 .5 0 .5 0 .8 0 .2 3 y ␦ meation rate at 850ЊC was 2.5 = 10 y 7 mol ؒ cm y 2 ؒ s y 1 . A quartz tube was placed coaxially around the membrane and the shell filled with a rhodium catalyst. Air was fed to the tube and methane to the shell. At 850ЊC the methane con®ersion was 97% and the selecti®ity to carbon monoxide approached 100%. Rapid radial mixing of the oxygen in the shell is essential to pre®ent coking and undesirable reactions. The membrane decomposes at 780ЊC in pure CH , but remains stable up to 970ЊC in a mixture of 4 90-mol % CH and 10-mol % CO .

Transient electric fields of up to 1.5 V were generated during the high temperature oxidation of pure metals (Mg, Al, Ti, Zr, Hf, Cr, Mn, Fe, Co, and Ni) either by gaseous oxygen or by solid peroxides or perchlorates. These time-varying fields are most probably due to ion formation and motion in and behind the moving high temperature reaction zone, which creates an electric double layer within individual particles. The shape and magnitude of the induced temporal electric signal depends upon the reactant properties, mode of the front propagation, and mobility of the ions formed. Unsteady combustion front propagation (occurring during the oxidation of Mg, Al, and Nb) generates an oscillatory electrical signal. Metals belonging to the same group in the periodic table (Ti, Zr, and Hf; Ni and Co) and whose products have the same oxidation state generate qualitatively similar electrical signals. The sign and magnitude of the transient electric potential generated during metal oxidation by perchlorates or peroxides are dominated by the chemoionization processes involved in the decomposition of a solid oxidizer. © 2001 The Electrochemical Society. All rights reserved.

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Major ampullate (dragline) silk is attracting significant attention as a potentially useful engineering fiber. This interest is motivated by reports that the silk exhibits high mean strength, stiffness and toughness as measured in tensile tests. However, the typical testing conditions (constant strain rate; experiment completed within less than an hour) imposed during such assessments do not reflect typical demands (e.g. ability to support constant load for long times) made on real high-tensile materials. We demonstrate here that Nephila ciavipes major ampullate silk subjected to constant loads performs poorly: its breaking strength is significantly lower than that measured in conventional constant strain rate tests, and even very small constant loads can cause elongation to increase appreciably over long timescales.

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