Channeling the future
Your "JACS at 125" article on Lars Onsager (C&EN, Nov. 17, 2003, page 70) made me read his Nobel lecture, held in 1968, titled "The motion of ions: principles and concepts" (http://www.nobel.se/chemistry/laureates/1968/onsager-lecture.pdf). He ends his lecture with an amazing prophecy of the experimental proof for which the 2003 Chemistry Nobel Prize was awarded: "Many of the things I have told you have a bearing on problems in biology. For example, how do ions get through in cell membrane? Observations on poisoning suggest fixed facilities for such transport. Let me just toss on the screen what I think might be an essential element of such a facility.
"This is speculation, but one which is not yet refuted by observations and seems generally compatible with physical principles. The hope that it might be right adds interests to the exploration of ice and other protonic semiconductors."
I went on to read his contribution (on pages 75 to 79) in "The Neurosciences" (edited by Gardner C. Quarton, Theodore Melnechuk, and Francis O. Schmitt), which begins with a brilliant and authoritative summary of the foundations of the theory of thermodynamics of equilibrium systems and ends with a foresight on how water molecules and ions may pass, one by one, a seemingly unsurpassable obstacle such as a biological membrane. In his Figure 1, you see strings of polar amino acid side chains aligned so as to transiently but effectively stabilize polar molecules or ions within a hostile, lipophilic environment. One option even shows a "negative bonding effect" situation where a string of hydrogen bonds in a hydroxyl channel is interrupted through a single lone pair-to-lone pair arrangement.
William G. Hime was right that the alkalinity and chromium content of the cement dust from the World Trade Center collapse contributed to respiratory problems in workers and residents (C&EN, Jan. 12, page 2). But many of the activists like myself who were involved were well aware of chromium as a factor, not only from the cement but from many other sources. The problem was that the Environmental Protection Agency did not report chromium and other contaminants. It concentrated on asbestos, lead, and a few other substances.
When a better analysis of the dust was published by Paul J. Lioy and his colleagues [Environ. Health Perspect., 110, 703 (2002)], they documented chromium and 25 other metals. A number of these metals were more toxic and/or sensitizing than the chromium, including nickel, beryllium, manganese, cobalt, gallium, arsenic, cadmium, cesium, barium, mercury, lead, and uranium.
In addition to the cement, there was shattered glass and fiberglass in almost all samples. And in many samples, there were significant amounts of asbestos. Then there were the pesticides, a flock of PCBs, PAHs, and about 85 other organic compounds of various types, none of which is good for you.
This was a dust like none other seen in the occupational setting. It is why we now see unresolved respiratory problems such as reactive airway disease syndrome and adult-onset asthma in thousands of clean-up workers, 2,400 firefighters on disability, and more than 6,000 workers in offices and businesses below Canal Street. Google up the studies at Mount Sinai Hospital and Downstate Medical Center in Brooklyn, the Queen's College study of immigrant laborers, and the "firefighter's cough" studied at several hospitals. It will break your heart.
Most of these illnesses could have been prevented if EPA had not assured New Yorkers that the air was safe and encouraged them to clean up homes and businesses without professional help. Ground Zero workers were also encouraged to overwork and were not required to wear respiratory protection. As a result, there will be many more casualties from the Sept. 11, 2001, attack in time.
New York City
I am incredulous that the U.S. Treasury Department's Office of Foreign Assets Control (OFAC) deems it essential to place an embargo on the publication of scientific material coming from countries we are seeking to convert to a democratic form of government (C&EN, Jan. 26, page 5). This action tends to weaken our argument that ours is a free and open society. Contact with the scientific and intellectual members of those hostile countries can only demonstrate the advantages of free and open exchanges.
Publication is the medium through which ideas are transferred. To place an embargo on this seems contrary to our basic goal in those countries.
C. A. Carroll<br > Woodcliff Lake, N.J.
The censorship of the scientific enterprise by the Treasury Department's self-appointed watchdogs is painful to encounter and would have previously been inconceivable in our country. Review of scientific papers and publication after rigorous examination is a process that, while frequently lacking in grace, is always ultimately vindicated. Science in the countries now interdicted can only benefit by publication in Western journals. In Cuba, for example, there are a number of original discoveries that are unavailable to Americans: in cancer therapeutics, in pediatric vaccines, and in humanized monoclonals. We in the U.S. are being deprived of these potentially life-saving agents by the blind ignorance of OFAC in not allowing them the full scrutiny of peer-reviewed literature. By comparison, the Luddites were enlightened activists.
Little Rock, Ark.
All that glitters ...
I enjoyed your article on synthetic diamonds and their possible future in the gem and electronics markets (C&EN, Feb. 2, page 26). Are you aware of Cree Research (http://www.cree.com) in North Carolina? They manufacture single-crystal silicon carbide for gemstones (their spin-off company is Charles & Colvard, makers of Moissanite gems, http://www.cthr.com), and they already make and market n-type semiconductors, light-emitting diodes, rectifiers, etcetera, for exactly the same reasons as you postulate are the advantages of diamond: high thermal conductivity, optical clarity, and radiation resistance. Moreover, as gemstones, SiC gems have a higher dispersion than diamond and are tougher than diamond. Moissanite is harder than any gemstone other than diamond (about 9.3 Mohs).
Why don't you do a follow-up article about single-crystal SiC? It is a fascinating tale. We are inundated with silicon carbide, all of it manufactured as carborundum. It only occurs naturally in meteorites. SiC occurs as 152 "polytypes." In single crystals, it has been available for about 17 years, only from Cree. SiC for electronics is an industry in rapid growth, unlike basic research on synthetic diamond.
Jim Johnston<br > Salt Lake City
"Man-made": I was shocked to see the use of such an outdated phrase on the cover of the magazine and even further shocked by the fact that the author was a woman.
The ACS Style Guide takes a very strong stance on the use of gendered language such as "man-made." It specifically suggests alternatives to gendered language, with "synthetic" and "artificial" as two possible replacements for the word man-made. Such outdated language is not appropriate for C&EN.
R. Lee Penn
I saw the article about ricin found in a Washington, D.C., Senate office (C&EN, Feb. 9, page 11). I wanted to let you know that the Centers for Disease Control & Prevention (CDC) has a resource available to your readers who may have questions or concerns about ricin or other bioterrorism issues. The CDC Public Response Service, a toll-free, nationwide resource, can be contacted at (888) 246-2675 (English), (888) 246-2857 (Spanish), or (866) 874-2646 (TTY). Our website, http://www.cdcresponse.org, provides additional information about our services.
Edgar G. Villanueva
First, regarding the attainable rates of either the hypothetical machine-phase or more conventional reactive-molecule chemistry, it is said that a "million reactions per second is hard to imagine being practical." In fact, turnover numbers (also called turnover frequencies in the literature of catalytic chemistry) of this order of magnitude are achieved by the catalase and carbonic anhydrase enzymes in aqueous solutions as well as by reactive intermediates in organic systems. Examples of the latter class involving chain reactions with neat substrates are provided by propagating carbenium ions in the free-ion cationic polymerization of olefins [see, for example, J. Polym. Sci., Part A: Polym. Chem., 37, 4467 (1999)]. In this case, the turnover numbers given by the product of the bimolecular propagation rate constant and olefin concentration are in the range of 105 to 109 s–1.
Second, Mezei's "back-of-the-envelope" estimate that it would take a nanomachine with a turnover number of 106 s-1 more than a 100 million years to generate 1 mole of product applies, of course, only to the operation of a single molecular machine. Clearly, any type of useful mechanosynthesis would require a significant number density of such nanomachines. However, even a nanomolar concentration of reactive species with a turnover number of 106 s–1 generates product at a rate of 10–3 M s–1 or 3.6 M h–1. Thus, practical chemical processes can indeed be based on the utilization of microscopically low concentrations of highly reactive species participating in chain reactions.
Thomas F. Williams
More on Taiwan
I am writing in reference to Charng-Ming Liu's letter "An ugly misnomer" (C&EN, Jan. 19, page 7). While the letter is informative on Taiwan's efforts to restore the island's natural beauty, two points come to mind that, in my view, make the letter weaker.
The author used the word "nation" to describe Taiwan at three places. This introduces a controversial political topic into a nonpolitical issue and is clearly not warranted in an association newsmagazine such as C&EN. The current U.S. policy on the China-Taiwan relationship is "one nation, one China." No matter what one thinks about the relationship, there is no need whatsoever to advocate and propel, directly or subtly, one's view in a society newsmagazine. The letter has clearly crossed the line.
The author has also given as an example of the many "good things" that happened in Taiwan that, as a result of regulation changes, "reckless polluters moved their operations to neighboring countries like China." Politics aside, exporting polluters out of the island cannot be a good solution to the problem, can it? Or maybe we could all simply do so to each other, and the problem will be resolved? Pollution in general is a local as well as a global problem. Moving polluting industries somewhere else is, at best, a temporary solution to Taiwan's problem, but not to the problem itself. The example serves to show, though, that the island still has a long way to go, as does the rest of the world.
As a chemist and a football fan, I was interested in the report in "Roomy Crystals," in which the surface area per gram of MOF-177 was given as 4,500 m2 or "roughly equivalent to four football fields" (C&EN, Feb. 9, page 10). A football field measures 360 feet by 160 feet, which translates to about 5,350 m2. Clearly the comparison of the surface area in the roomy crystal to the field area was in error.
Larry L. Funck
The recent article about highly porous materials is quite fascinating, and a nice example of rational design. My only quibble is that the specific surface area is stated completely without qualification as to how it was measured.
I am assuming that the classic BET nitrogen adsorption method was used here, though this is not explicitly stated. Anyone experienced in the art of measuring surface area knows that at this size scale fractal concepts apply, with the apparent (accessible) surface area strongly impacted by the size of the "yardstick" (typically some molecule adsorbed onto the surface, the most common being nitrogen, mercury, and various alkanes) used to measure it, in the same way that the length of the Maine coastline varies depending how you measure it (by the mile, by the yard, or by the grain of sand).
Mark R. Timmins