Seven University of California, Davis, researchers will be presenting papers or chairing sessions at the annual meeting of the American Association for the Advancement of Science Feb. 18-23 in San Francisco. Emphasizing public education, the meeting will address such diverse topics as health-care reform and advances in medicine, the changing environment, and science education reform. Also offered will be two special seminars on mapping and modeling the brain, and extinction and evolution. The theme of this year's meeting is "Science and a Changing World." • In an overview of the most respected modern theories about how life on Earth began, David Deamer, UC Davis professor of molecular and cellular biology, will discuss possible cosmic connections to the origin of cells in a session beginning at 2 p.m. Saturday, Feb. 19, in Barcelona 1, Parc Fifty-Five. • Martin Kenney, an associate professor of applied behavioral sciences at UC Davis, organized a session assessing new directions in the organization of Japanese corporate research and design systems. It begins at 2:30 p.m. Saturday, Feb. 20, in Imperial Ballroom B, San Francisco Hilton & Towers. • Exploring song learning in birds, Peter Marler, UC Davis professor of neurobiology, physiology and behavior, will discuss an aspect of the relationship between behavior and heredity in a session beginning at 8:30 a.m. Sunday, Feb. 20, in Yosemite 3, San Francisco Hilton & Towers. • With a brief history of the changing nature of California agriculture, UC Davis history professor Morton Rothstein will open a session on agricultural production and environmental protection in light of the state's 25 percent population growth during the last decade. UC Davis political science researcher Alvin Sokolow will comment on the other presentations and discuss Central Valley farm protection patterns. The session begins at 8:30 a.m. Monday, Feb. 21, in Continental Parlor 3, San Francisco Hilton & Towers. • Hydrolic science professor Kenneth Tanji of UC Davis will review the implication of land use for water in a session about balancing conservation with the need for land and soil resources for future sustainability, 8:30 a.m. Tuesday, Feb. 22, in Toyan A-B, San Francisco Hilton & Towers. • In a session designed to give new economic, political, demographic and cultural perspectives on Mexican migration to the United States, UC Davis agricultural economics professor J. Edward Taylor will discuss the social and economic issues affecting Mexico-U.S. migration, at 2:30 p.m. Tuesday, Feb. 22, in Monterey, San Francisco Hilton & Towers. The AAAS is the world's largest federation of scientific societies, with more than 140,000 members and 300 affiliated science organizations. The association publishes the weekly peer-reviewed journal Science, which has the world's largest circulation of any multidisciplinary scientific journal.