Two crops, only one pops In “Let’s get vertical” (SN: 10/11/08, p. 16), writer Rachel Ehrenberg reports that “increased demand for a single crop, such as corn, is felt from movie theaters to hog farms.” It is important to note, however, that the corn fed to moviegoers and the corn fed to farm animals aren’t the same thing. In fact, they are two distinct and different varieties. Popcorn is Zea mays averta, a type of flint corn. The corn used as animal feed, called dent corn or field corn, is Zea mays indentata. Try to pop field corn, and you’ll just get hard, tough, hot corn. Je...

Testosterone proxy In the study on the correlation of high levels of serum calcium with fatal prostate cancer (“Cancer-calcium connection,” SN: 9/27/08, p. 12), were testosterone and vitamin D levels also measured simultaneously? Since low levels of both are related to osteoporosis in men, and testosterone is known to be a fuel of cancer, wasn’t perhaps calcium just a proxy for testosterone? Edward Kausel, Cambridge, Mass. Participants were given vitamin D and calcium supplements as part of the study. But the researchers didn’t measure blood levels of vitamin D, and they acknowled...

Defining death Allowing doctors to absolutely define death (“Doctors debate death definition for transplants,” SN: 9/13/08, p. 5) as “irreversible brain damage” is a slippery slope. There is a lot of pressure from transplant coordinators for body parts. While there is no absolute point in brain damage, heart stoppage is an absolute point. Allowing a vague definition will certainly lead to earlier and earlier use of such a definition. Temptation—the need for organs to maintain transplant programs and the cost of caring for a dying child—will certainly increase the pressure to back...

Only in the north It is not clear in the fine article on volcanoes (“Disaster goes global,” SN: 8/30/08, p. 16) how dust from the eruption of Huaynaputina, well south of the equator, in 1600 could affect only the Northern Hemisphere. David Bronson, Biddeford Pool, Maine For one thing, there’s less real estate in the Southern Hemisphere to have been affected. Also, the apparent lack of agricultural effects probably stems from population distribution at the time this eruption popped off. Australia was inhabited only by Aborigines until 1787 or so, and Cape Town, South Africa, wasn’t...

A climate tipping point In Janet Raloff’s article “Forest invades tundra” (SN: 7/5/08, p. 26), there seems to be a paradox. Raloff says that the albedo from normal snow coverage of the tundra “helps maintain the region’s chilly temperatures,” implying that the coverage also preserves the mats of plant matter. A little later in the article, Ken Tape explains how the arrival of tiny shrubs traps snow, insulating and warming the soil beneath and stimulating the growth of bacteria. At what point does snow’s effect change from a chilling blanket that preserves the tundra ecology to...

Disturbing numbers I found the “Sizing up science” Science Stat (SN: 8/2/08, p. 4) somewhat disconcerting with regard to the opinion about medicine. Basic medical research, in which ties to pharmaceutical companies and the like are not limited, may be “scientific” in the usual sense, but once you enter the arena of clinical research, the “scientific” is scarcely applicable. Objectivity and truth in reporting are not exactly encouraged in the current clinical medical research climate. It should be unsettling that a paper reporting an important negative result — one that ne...

Disturbing numbers I found the “Sizing up science” Science Stat (SN: 8/2/08, p. 4) somewhat disconcerting with regard to the opinion about medicine. Basic medical research, in which ties to pharmaceutical companies and the like are not limited, may be “scientific” in the usual sense, but once you enter the arena of clinical research, the “scientific” is scarcely applicable. Objectivity and truth in reporting are not exactly encouraged in the current clinical medical research climate. It should be unsettling that a paper reporting an important negative result — one that ne...

Starry details The article “Astronomers find distant star with a whole set of superEarths” (SN: 7/05/08, p. 7) leaves out some of the most interesting and important information. Is HD 40307 a G-type star like our sun? Which method was used to detect the planets? The article implies Doppler was used, but Doppler could not give the specific masses of planets in the article. John Myers, San Diego, Calif. HD 40307 is a K-type star, spectral class K2.5V . You could call this an orange dwarf star. The researchers used the Doppler method. Technically their measurements give minimum masses. T...

Iridescent shortcut I was disappointed with your diagram of a Morpho wing in the June 7 issue (“How they shine,” SN: 6/7/08, p. 26). Rather than properly show different wavelengths of light interfering differently, you instead chose to cheat by keeping the wavelength the same in the two pictures and reversing the phase of the reflection from “Surface 2.” By doing this, you failed to illustrate the physics and lost an opportunity to elucidate it to the reader, who may instead come away with confusion or even an incorrect understanding of the phenomenon. Mike Speciner, Acton, Mass. ...

For the record We read with interest your article on superatoms (“Small, but super,” SN: 6/21/08, p. 14) and would like to add a note on the experimental discovery. In the mid-1970s the late Walter Knight decided to investigate small metallic particles with a molecular beam apparatus. When Walt de Heer joined the group in 1979, Knight gave him the freedom to redesign the apparatus. De Heer built a new cluster source and a quadrupole mass analyzer with a range from 1–10,000 amu; clusters were ionized using a broadband UV arc lamp — all features that later proved to be essential f...