Received for publication 16 Dec. 1986. Work funded by NASA Cooperative Agreement NCC-2-139 and Utah Agr. Expt. Sta., UAES paper 3301. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product and does not imply its approval to the exclusion of other products or vendors that also may be suitable. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.
Presently Research Scientist, NASA Ames Research Center, MS 239-4, Moffett Field, CA 94035.