Azotobacter vinelandii can grow with a variety of organic carbon sources and fix N2 without the need for added H2. However, due to an active H2-oxidizing system, H2-dependent mixotrophic growth in an N-free medium was demonstrated when mannose was provided as the carbon source. There was no appreciable growth with either H2 or mannose alone. Both the growth rate and the cell yield were dependent on the concentrations of both substrates, H2 and mannose. Cultures growing mixotrophically with H2 and mannose consumed approximately 4.8 mmol of 02 and produced 4.6 mmol of CO2 per mmol of mannose consumed. In the absence of H2, less CO2 was produced, less 02 was consumed, and cell growth was negligible. The rate of acetylene reduction in mixotrophic cultures was comparable to the rate in cultures grown in N-free sucrose medium. The rate of ['4C]mannose uptake of cultures with H2 was greater than with argon, whereas

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Data from a 1989 CBS News/New York Times survey are used to examine the effect that the framing of questions on abortion has on estimates of what proportions of the population support various legal positions. The nationwide data and results from six state polls show that general questions with only two or three options overestimate the proportions of respondents who either favor a ban on all abortion or who would allow abortion under all circumstances. Questions that pose specific circumstances result in movement of respondents out of extreme categories and into more moderate ones. Even respondents who indicate they would favor abortion in all specific circumstances and those who favor abortion in none are likely to moderate their views when asked if they support restrictions that have been proposed in a number of states.

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