Web edition: September 21, 2004
Print edition: September 25, 2004; Vol.166 #13 (p. 207)

More of less is more

The counterintuitive finding that atrazine is more likely to kill tadpoles when it is highly diluted ("Just a Tad Is Too Much: Less is worse for tadpoles exposed to chemicals," SN: 7/10/04, p. 20: http://www.sciencenews.org/articles/20040710/fob3.asp) reminds me of a similar phenomenon in the alternative health care practice of homeopathy.

Tracy Sellers
Rowlett, Texas

Attractive offer

The otherwise well-written and fascinating article "Diatom Menagerie" (SN: 7/17/04, p. 42: http://www.sciencenews.org/articles/20040717/bob9.asp) contains an error. You write, "Because magnesium is more strongly attracted to oxygen than to silicon, magnesium atoms elbow out the silicon . . . ." The correct statement would be, "Because magnesium is more strongly attracted to oxygen than silicon is attracted to oxygen, magnesium atoms elbow out the silicon . . . ."

Fred Kohler
Ashland, Ore.

Either sentence is correct, but Mr. Kohler's is probably better. Both silicon and magnesium are competing for oxygen, and the goal of the researchers is to produce magnesium oxide.—A. Goho

Donation incentive?

Might donating blood reduce blood concentrations of organochlorines, once the body has time to regenerate blood ("A Toxic Side of Weight Loss: Pollutants may slow body's metabolism," SN: 7/17/04, p. 35: http://www.sciencenews.org/articles/20040717/fob2.asp)?

Bill Waller
Dallas, Texas

Researchers Catherine Pelletier and Angelo Tremblay of Laval University in Quebec City, Quebec, say this question is interesting but that the small quantity of donated blood wouldn't significantly affect the overall concentration of organochlorines.—C. Lock

Dues and don'ts

"The high cost of staying current" (SN: 7/17/04, p. 45: http://www.sciencenews.org/articles/20040717/note12.asp) didn't mention that professional journals usually charge exorbitant page charges, require that a paper be sent in a format that can be directly typeset, and price print and electronic subscriptions identically. What I conclude from this is that greed is as prevalent at professional societies as it is in the commercial world.

Edmond Murad
Newton, Mass.