FISCHETTI REPLIES: Numerous readers wrote to correct a common but faulty explanation of how an airplane wing creates lift, noting that it has somehow persisted for years, even in textbooks. We wrote, “...because the wing top is curved, air streaming over it must travel farther and thus faster than air passing underneath the flat bottom. According to Bernoulli's principle, the slower air below exerts more force on the wing than the faster air above, thereby lifting the plane.”
Or not. As Fritsch points out, the key factor is the wing's angle of attack, not its shape. As for the topside curvature of many wings, some readers noted that Bernoulli's principle can add a small amount of additional lift. Others pointed out that stunt planes and certain fighter aircraft have wings that are flat on top and bottom (or have equivalently curved surfaces) so they can better fly upside down. And yet the “third law” explanation is not the full story either: according to NASA, the complex “turning” of airflow, both below and above the wing, is the real driver. For a vetting of both the Newtonian and Bernoullian explanations, see www.grc.nasa.gov/WWW/K-12/airplane/bernnew.html
In “New Hope for Defeating Rotavirus,” Roger I. Glass indicated that two rotavirus vaccines, RotaTeq and Rotarix, have recently proved highly effective in clinical trials and are soon to be marketed in a number of countries. The RotaShield rotavirus vaccine has also been shown to be highly effective in clinical trials; his discussion on RotaShield is related only to its withdrawal from the market in 1999.
Now that new scientific evidence has demonstrated that RotaShield can be safely used in infants, BIOVIRx intends to bring RotaShield back to the market, subject to appropriate regulatory approvals. Our goal is to make it affordable, because we believe that is necessary for a rotavirus vaccine to have the greatest global impact on reducing morbidity and mortality.
Leonard P. Ruiz, Jr.
President and CEO, BIOVIRx, Inc.
With regard to “Computing with Quantum Knots,” by Graham P. Collins, is it possible to simulate a quantum computer on a conventional computer, at least in theory? If not, perhaps some of the difficulty in artificial intelligence is because biological systems have somehow discovered ways to use quantum effects.
John J. Boyer
God Touches Digital Ministry
COLLINS REPLIES: It is impossible to simulate a quantum computer efficiently on a conventional classical computer. The simulation would require a vast supply of hardware to run algorithms in parallel, or it would take an extremely long time. Some researchers, most notably mathematician Roger Penrose, have speculated that biological brains might use quantum computation, but physicist Max Tegmark has argued that in the physical environment of a brain, the quantum coherence required would decay far too quickly to have any effect on the firing of neurons.
ERRATA “An Antibiotic Resistance Fighter,” by Gary Stix, noted incorrectly that mice did not develop resistance to the antibiotic ciprofloxacin. The article should have stated that the bacterium Escherichia coli did not become resistant. It also remarked that blocking the cutting of the protein LexA might undermine “drug effectiveness” in other microbes besides E. coli. Rather preventing the clipping of LexA might undermine the evolution of drug resistance in other microbes.
“Sharp Shooter,” by Steven Ashley [Technicalities], stated that the APS sensor in the Sony R1 digital camera has a low signal-to-noise ratio. It has a high signal-to-noise ratio.
CLARIFICATIONS In “The Science behind Sudoku,” by Jean-Paul Delahaye [June], the grid for puzzle e in the “Variations on a Theme” box should have included outlines for the domino pieces. Without the lines, the puzzle has two solutions. To find the correct version, go to www.sciam.com/ontheweb; visit that same site for extra puzzles and solutions to the grids in the article. (The address given in the article was incomplete.)