Yu-Chu Yang was born in China, grew up in Taiwan, and has lived in the United States since 1969. She holds a B.S. degree (1969) in Chemical Engineering from the National Taiwan University and a Ph.D. (1974) in Physical Chemistry from Tulane University. After graduation, she worked for Exxon Corp. both in Louisiana and in New Jersey for nearly 6 years. In 1983, she began research work in the decontamination of chemical warfare agents at the U.S. Army Edgewood Research, Development and Engineering Center in Maryland. For the past 5 years, she has focused her research on CW agent neutralization for the purpose of their safe disposal. She is now assigned to the U.S. Army European Research Office, serving as the Chief of Chemistry and Biological Sciences Branch.

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Both V-type nerve agents MeP(O)(OR)(SCH2CH2NR‘2), VX (R = C2H5; R‘ = i-C3H7) and its isomeric analog RVX (the “Russian V-agent”, R = i-C4H9; R‘ = C2H5), react slowly but completely with an equimolar amount of H2O via exclusive P−S cleavage to produce the corresponding phosphonic acid (MeP(O)(OR)OH) and 2-aminoethanethiol (HSCH2CH2NR‘2). The reaction is believed to be initiated by nucleophilic attack of the deprotonated phosphonic acid on the protonated V-agent to produce a diphosphonate intermediate ((MeP(O)(OR))2O) that rapidly hydrolyzes to regenerate the phosphonic acid. The autocatalytic ionic chain reaction is thus continued in the nearly nonaqueous reaction medium. The viscous final product mixture remains reactive toward freshly added trace amounts of the V-agent, giving the same final reaction half-life of 13−15 h at 23 °C. When water is insufficient and depleted, the diphosphonate intermediate accumulates and reacts with the aminoethanethiol to regenerate the V-agent. This autocatalytic hydrolysis process is not observed with a simpler phosphonothioate analog (MeP(O)(OC2H5)(SC2H5)), which suggests that the attack of the phosphonic acid on the V-agent is intramolecularly assisted by the protonated amino group.

Solid-state electrochemical cells with dense oriented thin film electrodes of La 0.5 Sr 0.5 CoO 3Ϫ␦ (LSCO) were prepared on (100) surfaces of single-crystal disks of yttria-stabilized zirconia (YSZ) by the pulsed laser deposition technique. Oxygen exchange at the electrodes was studied with alternating current impedance spectroscopy under various temperature and oxygen partial pressure conditions. Three distinctive features were observed in the impedance spectra from high to low frequency corresponding to contributions from the ionic conduction of the YSZ electrolyte, ionic transfer at the LSCO/YSZ interface, and the oxygen exchange on the LSCO electrode surface. An equivalent circuit model of the electrode process is used to fit the impedance data. The time constant for the oxygen surface exchange was derived from the impedance simulation. The surface chemical exchange coefficients, k chem , were calculated from the time constants as a function of temperature and pO 2 . k chem is 7 ϫ 10 Ϫ4 cm/s at T ϭ 700ЊC and pO 2 ϭ 1 atm. The activation energy at pO 2 ϭ 1 atm is Ϸ1.1 eV. The interfacial conductivity data were also derived from the impedance simulations as a function of temperature and pO 2 . The activation energy for the interfacial transport at pO 2 ϭ 1 atm is Ϸ1.6 eV.

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