Letters.Tear down this wall "Tear down this wall" was the famous challenge from United States President Ronald Reagan to Soviet leader Mikhail Gorbachev to destroy the Berlin Wall. In a speech at the Brandenburg Gate, by the Berlin Wall, on June 12, 1987, Reagan challenged Gorbachev, then the General Contrary to "Debate over Alzheimer's enzyme flares up" (SN: 6/10/00 p. 374), animal cells do not possess "cell walls," as suggested by "proteases are usually much smaller and don't inhabit cell walls." Plants have cell walls; animal cells are bound by a single lipid bilayer A lipid bilayer or bilayer lipid membrane (BLM) is a membrane or zone of a membrane composed of lipid molecules (usually phospholipids). The lipid bilayer is a critical component of all biological membranes, including cell membranes, and so is absolutely essential for all membrane. David Winialski Tallahassee, Fla. Just a pill in the pool Regarding the article "Excreted drugs: Something looks fishy fish·y adj. fish·i·er, fish·i·est 1. Resembling or suggestive of fish, as in taste or odor. 2. Cold or expressionless: a fishy stare. 3. " (SN: 6/17/00, p. 388), just because chemical equipment can measure parts per trillion doesn't necessarily mean that they have any biological significance. If you took one pill of Tylenol and dissolved in an olympic-size swimming pool, that would roughly be 1 part per billion. One part per trillion would be one pill in 1,000 swimming pools. My point is that it is very hard to think in such fantastically small quantities, and it takes much more rigorous biological thinking to make scientific sense of the kinds of claims made in articles such as this one. Timothy Brac London, Ontario Research erosion? I think that your readers should be aware that the article on beach erosion Noun 1. beach erosion - the erosion of beaches eating away, eroding, erosion, wearing, wearing away - (geology) the mechanical process of wearing or grinding something down (as by particles washing over it) ("Enjoy the beach ... while it's still there," SN: 7/8/00, p. 20) is based upon a report by the Heinz Center for Science that's being widely disputed. Susan Halsey's opinion that nothing can be done to stop these losses is in direct conflict with a National Research Council report, "Beach Nourishment and Protection," that finds that "beach nourishment is a viable engineering alternative for shore protection and is the principal technique for beach restoration; its application is suitable for some, but not all, locations where erosion is occurring." Halsey's assessment that there isn't enough sand in the Sahara to renourish these eroding beaches appears to be nonscientific hyperbole. It's interesting to note that the Spanish government has actually imported sand from the Sahara to undertake more than 50 beach projects, including the construction of new beaches where none had existed before. Richard Seymour Scripps Institution of Oceanography Scripps Institution of Oceanography: see California, Univ. of. La Jolla, Calif. Not in my background In "Gene test probes Neandertal origins" (SN: 7/8/00, p. 21), Erik Trinkaus argues that fossil evidence shows signs of considerable interbreeding interbreeding crossbreeding, as between half-breds. of Neandertals and modern humans. However, I don't believe that proves we could have Neandertal ancestors. Couldn't crossbreeding crossbreeding /cross·breed·ing/ (-bred-ing) hybridization; the mating of organisms of different strains or species. crossbreeding hybridization; the mating of organisms of different strains or species, e.g. result in sterile offspring, such as is seen in mules? Anne Wittke Flagstaff Flagstaff, city (1990 pop. 45,857), seat of Coconino co., N Ariz., near the San Francisco Peaks; inc. 1894. Lumbering, ranching, and a lively tourist trade thrive in the region, where many ruined pueblos, numerous state parks, several lakes, and large pine forests , Ariz. Sure. Trinkaus argues, however, that the presence of Neandertal traits on the skeletons of Stone Age Homo sapiens reflects the fertility of hybrid offspring. --B. Bower |
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