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December 10, 2007

Happy Holidays!

I'll be away from my office until Wednesday, January 2, 2008. There will be no postings on this blog until the new year.

Have a happy holiday season!

December 07, 2007


Like other scientists and engineers, I try to keep current with technology, primarily so that the Young Turks won't show me up at meetings. This lifelong learning extends beyond trade magazines and scholarly journals to popular culture. One interesting element of this culture is Steampunk. Steampunk, per se refers to a type of science fiction writing in which modern machines are introduced before their time using available technology (e.g., a steam-powered computer), but engineers have elevated steampunk to an object style. Typically, an object such as a computer keyboard is remanufactured into an object that would not seem out of place in Victorian England. Typical embellishments include the use of polished wood and brass fixtures.

Actually, steampunk is not that much a stretch of reality. Precision instruments, such as those for xray crystallography, were sold in polished rosewood boxes (at least simulated rosewood boxes) when I was first introduced to them as a young scientist. The reasoning here is simple - you don't sell expensive jewelry in paper sacks, and such instruments were the price of a small house. The further reason is the need to protect the instruments between their sometimes infrequent use, and this was the era before foam-padded aluminum boxes.

Of course, an art form must have an ideology, at least in the mind of the media [1], so steampunk is supposed to be an expression of two ideals. The first is a yearning for a time when technology was not mass-produced, and was more crafted, personal, and beautiful. There is not argument that today's consumer electronic items are "little boxes all the same." The second is the durability and permanence of things past. As an example, my father's used Model A Ford lived a long life, unlike a modern automobile that rusts through at the end of its supposed decade of utility. The Ford body never rusted-through, since the steel was too thick, but such a design is not recommended in our hundred-dollar-a-barrel oil age. Mark Frauenfelder, editor in chief of Make magazine, says that "The Victorian era was the great age of the amateur, where nonprofessionals could contribute to the advancement of science, and because these amateurs were most often well-heeled gentlemen, great emphasis was placed on ornamental beauty in their equipment."[2]

The most popular steampunk web site is the Steampunk Workshop, "Wherein the craftsman demonstrates the construction of artifacts from an age of steam and brass," hosted by Sean Slattery (who goes by the steampunk name Hieronymus Isambard Jake von Slatt). Among his creations are a flat panel monitor modified with gas lamp arms and parts from a grandfather clock, looking like something Captain Nemo would use on the Nautilus. He's also transformed a computer keyboard by attaching the round keys from an old typewriter. His penchant for giving a retro look to computer components is not surprising, since Slattery is an information technologist.

For those of you interested in the roots of steampunk, Peter Bebergal of the Boston Globe has assembled the following reading list: [3]

• "The Warlord of the Air" (Michael Moorcock, 1971)
• "Lord Kelvin's Machine" (James P. Blaylock, 1992)
• "The Difference Engine" (William Gibson and Bruce Sterling, 1991)
• "Steampunk Trilogy" (Paul Di Filippo, 1995)
• "Mainspring," (Jay Lake, 2007)

For those more inclined to the new media, I suggest the film, "Brazil (Terry Gilliam, Director, 1985)." My favorite steampunk items from this film are small, bare CRT monitors fitted with lenses to enlarge the image.

1. Brian Braiker, "Steampunking Technology" (Newsweek, October 31, 2007).
2. John Brownlee, "Meet Mr. Steampunk: Jake von Slatt" (Wired News, June 29, 2007).
3. Peter Bebergal, "The age of steampunk" (Boston Globe, August 26, 2007).

December 06, 2007

The Pauli Effect

Wolfgang Pauli (1900-1958) was a preeminent theoretical physicist of the twentieth century. He is famous for the Pauli Exclusion Principle, which states, among other things, that electrons may occupy the same atomic orbitals if they have different spins. This effectively explains chemical bonding and some details of the Periodic Table of the Elements.

Pauli is associated with another law called the Pauli Effect. Theorist are good with paper and pencil, but their experiments are typically disasters. Pauli's excellence as a theorist was perfectly balanced by his ability to destroy laboratory apparatus. It wasn't necessary for him to even touch the apparatus. His presence in the room was enough. Otto Stern, a Nobel Prize winning experimental physicist and close fried of Pauli, banned Pauli from his laboratory. Pauli's supernormal powers in this regard were known to extend over great distances. Once, an experimental apparatus at the University of Göttingen stopped functioning. Pauli was suspected, but he was not at the University. Later it was found that he was on a train to Zürich that passed the university at the time.

It's been said that the Pauli Effect extends to technical managers, also, but there is only anecdotal evidence at this time.

1. One of my professors in graduate school got his Ph.D. in Physics from the University of Göttingen

December 05, 2007

Mechanical Resonators

Quartz crystal resonators are the principal frequency-determining element in electronic circuitry. Quartz has two physical properties that are advantageous for this application. First, it's a piezoelectric material, which means it will mechanically deform in the presence of an electric field and likewise produce an electric field by charging its crystal faces in response to a mechanical force. Second, it is mechanically stiff, which means it will "ring" at high frequencies in response to an impulse force. By depositing electrodes on opposite faces of a quartz crystal, it can be wired into a positive feedback circuit to form an oscillator. Fortunately, quartz is a common mineral in the Earth's crust, second only to feldspar in natural abundance, so natural quartz has been mined for this application. The piezoelectric property is partly a consequence of its unusual rhombohedral crystal structure, and this crystal structure also allows for temperature compensation of the resonator by selecting certain wafer orientations. These crystal orientations are called "cuts," and the most popular of these for frequency generation are "AT" and "ST," for which "T" indicates temperature-compensation.

The Roman naturalist, Pliny the Elder, who observed the great eruption of Mount Vesuvius in 79 AD and died as a result, thought that quartz was permanently frozen water. This is understandable, since quartz crystals superficially resemble ice crystals, and Pliny knew that that quartz is never found atop volcanoes. Volcanic rock is igneous, whereas quartz is crystallized from water solution. Although quartz is a common mineral, perfect crystals of quartz, from which the best resonators are made, are not. Robert Laudise of Bell Laboratories perfected the hydrothermal synthesis of highly perfect quartz crystals [1]. One of my first projects at Honeywell (then Allied Corporation) was the characterization of the piezoelectric properties of the quartz analog, Berlinite (AlPO4).

MEMS technology has allowed the development of non-quartz resonators [2]. In this case, direct electrostatic attraction, rather than piezoelectricity, is used as the coupling between electrical fields and the mechanical structure. MEMS resonators have been able to match or exceed the "Q" and frequency of quartz resonators, although temperature compensation is still a problem. Of course, the idea of moving a mechanical device billions of times a second for very long times seems to be inviting disaster. There is the concept of "fatigue limit" which specifies a stress level below which materials will not fatigue, but the trillions of cycles required in MEMS resonators is beyond any laboratory experience. Additionally, MEMS manufacturing, especially precise etching of the mechanical features, is a more complex process than quartz resonator manufacturing.

Recently, physicists at the University of Colorado (Boulder) and the US National Institute of Standards and Technology (NIST) have investigated a new type of MEMS resonator. Their resonators are gallium nitride wires prepared by molecular beam epitaxy [3]. Pure gallium nitride is a piezoelectric material. These cantilever nanowires are about 30-500 nm in diameter and 5-20 micrometers long. The resonance frequencies of these wires ranged from 0.4-2.8 MHz, and in a good vacuum, where damping effects of air are not important, the Q values were above 10,000. Some wires exhibited a Q of more than 60,000. A Q of 10,000 at 1 MHz means that most of the resonance energy is contained in a 100 Hz bandwidth.

Doping the gallium nitride to diminish the piezoelectric effect had the expected consequence of preventing resonance. At this time, the only way to excite these wires at high Q is with an electron beam, but these Q values are an order of magnitude greater than nano-resonators made from carbon nanotubes and silicon MEMS devices with similar surface-to-volume ratio. This research is reported in the November 16, 2007, issue of Applied Physics Letters [4].

1. Hydrothermal Crystal Growth - Quartz.
2. Aaron Partridge and John McDonald, "MEMS Resonators look to displace Quartz resonators," MEMS Manufacturing (July, 2006).
3. Laura Ost, "High Q NIST nanowires may be practical oscillators" (NIST Press Release, November 27, 2007).
4. S. M. Tanner, J. M. Gray, C. T. Rogers, K. A. Bertness and N. A. Sanford, "High-Q GaN nanowire resonators and oscillators," Appl. Phys. Lett., vol. 91 (November 16, 2007), 203117.

December 04, 2007

Pink/Blue/Yellow Packets

Over the years, in my efforts to avoid too much sugar, I've tried various sugar substitutes. One acceptably tasting substitute, calcium cyclamate, the calcium salt of cyclohexanesulfamic acid, had a small problem. Although it was declared to be a safe food additive in the late 1950s, a research study in 1966 showed that intestinal bacteria can desulfonate cyclamate to form cyclohexylamine, a compound implicated in bladder cancer and testicular atrophy in mice. Cyclamate was banned as a food additive in the US in 1969 [1].

For many years, the only commonly available sugar-substitutes were the infamous pink packets, containing a mixture of saccharin, dextrose and cream of tartar; and the blue packets, containing aspartame, dextrose and maltodextrin. Neither of these really tasted like sugar, and they were certainly not to my liking, although I preferred blue over pink. Then along came the yellow packet, something like the ambrosia of the gods - but, perhaps I exaggerate. In any case, I found it much more to my liking than the pink and blue packets.

The yellow packets contain Sucralose; or, more precisely, 1,6-Dichloro-1,6-dideoxy-β-D-fructofuranosyl-4-chloro-4-deoxy-α-D-galactopyranoside (C12H19Cl3O8, CAS number 56038-13-2) [2]. The yellow packets are sold under the trade name, Splenda. Sucralose is about six hundred time sweeter than cane sugar (sucrose), it's twice as sweet as saccharin, and four times as sweet as aspartame. Many people agree with my taste assessment of the colored packets. Splenda was introduced less than ten years ago, and it's already the market leader. According to the Wall Street Journal [3], yellow packet sales in 2006 were $212 million, compared with the $48.7 million for sales of the blue packet runner-up. Splenda was so successful that its rivals did what is usually expected these days when you lose market share - They called in the lawyers, not the scientists.

Splenda was marketed under the slogan, "Made from sugar, so it tastes like sugar." Indeed, the synthesis of sucralose starts with pure cane sugar, and the sugar is chlorinated in order to modify its caloric value. The industry rivals complained that the typical consumer would believe that Splenda actually contains sugar, along with something to reduce its caloric content; but consumers are really buying a chemical compound. When it looked as if a Philadelphia jury was preparing to rule against Splenda's maker, an out-of-court settlement was reached [4]. Unfortunately, this one trial is not the end of this, since there is at least one other case pending. I'll likely pay a little more for my yellow packets this year, and perhaps a little more the next.

1. Cyclamate (Wikipedia).
2. Sucralose (Wikipedia).
3. Avery Johnson, "How Sweet It Isn't," Wall Street Journal (April 6, 2007), p.B1.
4. Splenda settles lawsuit over 'sugar' claim (MSNBC, May 11, 2007).

December 03, 2007


OK, that's not how it's spelled, but that's the way US President George W. Bush pronounces it, and reportedly the way many presidents of the nuclear age, including Eisenhower, Carter (who should know better, since he has a BS in physics from the United States Naval Academy), and Clinton, pronounced it as well [1]. Webster's dictionary even gives nucular as an alternative pronunciation, although it insists that this is not the proper pronunciation [2]. As an erstwhile physicist, I should cringe every time I hear nucular, but it hardly registers anymore. The founders of the field of nuclear physics generally called it Kernphysics, but there may have been some chancellor or two who said Kornphysics.

Whether you say nuclear or nucular, this first week of December is an important time in history. On December 2, 1942, the first controlled nuclear reaction was initiated, of all places, in Chicago, Illinois, adjacent to the Alonzo Stagg Field stadium, at the University of Chicago [3]. The reaction was in Chicago Pile-1 (CP-1), a primitive nuclear reactor, and the world's first. This reactor, an actual pile of uranium pellets and graphite bricks, was the creation of the Italian physicist Enrico Fermi. The graphite bricks acted as moderators; that is, they slowed the neutrons enough to allow a more complete chain reaction. There were also cadmium-coated control rods whose function was to absorb neutrons and dampen the reaction. As a safety precaution, three men were stationed above the pile with buckets of a cadmium salt solution. They would pour these onto the pile if things got out of hand. The first controlled reaction was allowed to proceed for about half an hour.

On that same date fifteen years later, there was another event of nuclear significance. On December 2, 1957, the first US commercial nuclear reactor, located in Shippingport, PA (near Pittsburgh), achieved initial criticality [4]. Starting December 18, 1957, this reactor supplied electricity to the Pittsburgh area and continued for twenty-five years. The Shippingport reactor was part of the US "Atoms for Peace" program of the 1950s. The reactor, designed by the Westinghouse Electric Corporation, was originally intended for an aircraft carrier, and it's no wonder that the "Father of the modern nuclear navy," Admiral Hyman Rickover was involved in the construction of the power plant. The reactor produced 68 megawatts of electricity, or about a third the amount produced by modern nuclear reactors.

Shippingport was closed in 1982, and the reactor vessel was transported to the Hanford low-level radioactive waste disposal facility (Richland, Washington State) in a picturesque journey down the Ohio River, to the Mississippi River, and through the Panama Canal. Site remediation cost nearly $100 million and was completed in 1987.

1. Kate Taylor, "Why Does Bush Go Nucular?" (Slate Magazine, Sept. 18, 2002).
2. Webster's standard response to readers inquiring about 'nucular' (Slate Magazine, Sept. 18, 2002).
3. Chicago Pile-1 (Wikipedia).
4. Don Hopey, "50 years on, 'Atoms for Peace' is remembered" (Pittsburgh Post-Gazette, December 2, 2007).