Readers share their thoughts on "Down with carbon" (SN: 5/10/08, p. 18), which describes carbon dioxide sequestration: Complex schemes The article repeatedly mentions liquid CO2, which has to be under high pressure to become a liquid. Has the CO2 released from burning fuel to run the necessary compressors and pumps been considered, or would those be powered with wind or solar energy? If so, why not just use those sources directly to replace fossil fuels and make less CO2 to begin with? Why keep devising complex technological schemes to fix problems rather than simply avoiding the techno...

Plants and rheumatism Some medical specialists in the field of rheumatology might find it useful to review the work of Ann M. Hirsch and Angie Lee, mentioned in the article by Susan Milius (SN: 4/12/08, p. 235). It describes a process in plant fixation of nitrogen involving biological action that seems to attract calcium. Perhaps a similar action occurs in human bone joints, causing the attraction of calcium in rheumatism. Roger W. Otto, San Mateo, Calif. A pervasive hidden influence “Dad’s Hidden Influence” (SN: 3/29/08, p. 200) states that, “Fathers 40 and older have an increas...