Monday, April 29, 2013
A few months ago, my wife bought a lamp at an office-supply place to light up the table where my father-in-law plays dominoes with us. He’s 87 and his eyesight isn’t what it used to be, so having lots of light in the right place is important. The ceiling light doesn’t quite do the job.
I was impressed with her purchase. It’s an elegant-looking design that unfolds. When it’s folded it’s just an oblong white plastic pillar on a round stand, about ten inches tall. It unfolds like a book hinged at the top, and when you unfold it you find that the upper inside surface is lined with thirty white LEDs that turn on as the hinge opens up. You can set it at a convenient angle and it casts a smooth, even white light over several square feet.
It cost only twenty bucks or so, but it had a significant disadvantage in my view: it ran only on batteries, unless you bought a separate power supply (not provided). After finding that the batteries would last maybe four or five hours at the most, I did a quick calculation and concluded to buy a plug-in “wall wart” for the thing. I had to go to Radio Shack and assemble a custom one from their array of general-purpose power supplies, and spent about $25 on that. But once I got the lamp hooked up to the mains, it worked fine, and we have probably used it daily for the last six months or so. . .
Until one day last week, when I opened it up and it flashed for a second and went out. Well, I had to see what the problem was. Five minutes with a screwdriver in the garage revealed the cause. There are two small stranded wires leading from the base of the unit to the panel of LEDs in the upper part. One of the wires goes to a switch on the hinge that turns it off when you fold it up. The wire was soldered to the switch terminal and glued down to the case with some kind of silicone glue, so that the continual flexing at the hinge would not bend the wire where it goes into the solder joint at the stationary switch terminal. Experience has taught me that if stranded wire going to a solder joint bends back and forth, the strands will start to break after only a few bends. The glue holding down the wire had come loose, allowing the wire to move at the joint, and the wire eventually broke off.
I thought about fixing it, but in the meantime we needed something to light up the domino table. So I switched to a backup lamp.
The backup lamp has a bit of history attached to it. To the best of my knowledge, I bought it in the late 1960s at a Radio Shack in Fort Worth, Texas, back when there were only about ten Radio Shacks in the whole country. I guess you would call it a generic Tensor lamp. I find from a New York Times obituary that one Jay Monroe, a Cornell-educated engineer (like myself), liked to read in bed, but his wife objected to the large conventional lamp he used. So he took a twelve-volt automotive tail lamp, stuck it in a kitchen measuring cup for a reflector, and mounted it on an arm attached to a box containing a transformer that stepped the line voltage down to twelve volts and also served conveniently as a weight to keep the thing from tipping over. His invention, which he called the Tensor lamp, proved so popular that elite retail outfits such as Hammacher Schlemmer began to carry them, and the name “Tensor” briefly enjoyed so much popularity that any high-intensity low-voltage lamp was called a Tensor lamp, whether or not it was made under Mr. Monroe’s patent.
My Tensor-like lamp follows the same basic pattern: a round plastic base containing the transformer and a switch, a flexible spiral-steel “gooseneck” arm, and a conical black shade. During one of our several moves, it was packed so that something rubbed a hole in the shade in transit, but I patched it with some electrical tape. The thing is now about 45 years old, and still works fine.
Lamps evoke their eras. Kerosene lamps proclaim the 19th century just as clearly as incandescent lamps connote the 20th century. Many people of my grandparents’ generation could recall the day, usually sometime between 1900 and 1930, when their houses were first wired for electric lights. When the LED lamp was working, I would often meditate, during breaks in domino games, that it was the first of many more LED lamps we will use as incandescent lighting gradually becomes a thing of the past, just as kerosene lamps did for my grandparents.
I wonder if I should attach any significance to the fact that two lamps purchased 45 years apart for similar prices (in non-constant dollars: I think I paid something like $9.99 for the Tensor lamp) to fulfill similar purposes, had such radically different lifetimes. One is still working fine, having delivered many thousands of hours of service; the other worked for maybe a hundred hours and failed. The new lamp is more complex, true. But it doesn’t take a rocket scientist to figure out that silicone glue doesn’t stick to smooth plastic that well, and this kind of problem would have showed up in a series of reliability tests—say bending the hinge ten thousand times.
But except for extraordinary jobs like satellites, nobody does that kind of testing any more, especially not for inexpensive consumer products. The long-term-reliability test for most such items is called the marketplace, and the test engineers are the people who buy the product first. And face it—99 out of a hundred people who buy an LED lamp like this that breaks will simply throw it out and buy a new one.
I finally had some time a few days ago to fix the LED lamp. It was a tricky job involving a utility knife, a soldering gun, and some bathroom caulk that will stick to ceramic tiles, so I’m pretty sure it will stick to the plastic inside the lamp. It’s working again now, and we are back in 2013 rather than 1967 as far as lighting the domino table is concerned. In the bargain, I’ve learned something about how the consumer market for lamps has changed over the last four decades. And I’m not too happy about what I’ve learned.
Sources: The New York Times article “Jay Monroe, 80, Engineer Who Invented Tensor Lamp, Dies” appeared on July 2, 2007 and can be found at http://www.nytimes.com/2007/07/02/nyregion/02monroe.html. The word “tensor,” by the way, would be familiar to a Cornell-educated engineer, who would know it as a type of mathematical object that transforms one vector into another vector.
Monday, April 22, 2013
Anyone who drives along Interstate 35 in Texas between Waco and Dallas or Fort Worth will pass through West, a small rural Texas town with a Czech heritage that was known, at least until last week, mainly for the pastries that you can buy at a bakery right next to the Interstate. It would not have surprised me to learn that a distributor of fertilizers to local farmers operated on the east edge of town, nor that one of the kinds of fertilizer sold by the dealer was ammonium nitrate. But when I learned of the tremendous explosion that killed at least 14 people, injured hundreds, and destroyed a good fraction of West’s built environment last Wednesday evening, April 17, my sadness was tinged with the knowledge that in warehousing large quantities of ammonium nitrate fertilizer, the firm was taking a chance that such a thing could happen.
Ammonium nitrate is a curious chemical. A “molecule” consists of an ammonium ion (four hydrogens arranged around a nitrogen) with a positive charge and a nitrate ion (a nitrogen atom surrounded by three oxygen atoms) with a negative charge. At room temperature, it is a solid, but its constituent elements are all gases. And the only thing holding it together are the opposite charges retained by the ammonium and nitrate ions. When heated gently in an open container, it breaks down into nitrous oxide (laughing gas) and water. But when it is in contact with easily oxidized materials, such as the fertilizer urea or even some metals, heating can cause it to release oxygen, which greatly increases the heat of the reaction and can lead to a fire. When confined by walls or even the pressure of a high stack of the material itself, burning ammonium nitrate can self-detonate. A detonation is an explosive shock wave that travels at very high speed through a volume of material, and differs from burning as traveling by jet aircraft differs from walking. This is apparently what happened a little after seven in the evening at the burning warehouse in West.
A back-of-the-envelope calculation of the power of the resulting blast can be done by beginning with an aerial view of the fertilizer plant before the explosion, which is still available on Google Maps. Comparison with views of the devastated explosion site indicate that the explosion was probably centered in a large, flat warehouse building that appeared to be one story high and measured about 60 feet by 110 feet. If we assume it was packed to a height of eight feet with ammonium nitrate (not an unreasonable assumption as distributors stock up for the summer growing season), the total mass of chemical in that building could have been as much as two thousand tons. Pure ammonium nitrate has about a fourth of the energy content per pound as TNT. Still, given these rough assumptions, if the whole mass went off at once, which it appears to have done, the force of the explosion could have been as great as a thousand tons of TNT, or one kiloton.
You may have run across the word “kiloton” in reference to nuclear explosions. While there were fortunately no nuclear weapons or radioactive materials involved in the West explosion, the nuclear weapon dropped on Hiroshima at the end of World War II had a yield of only about 16 kilotons of TNT. So what happened in West was one-sixteenth of a small nuclear bomb, in terms of destructive power. No wonder it showed up on seismographs as a magnitude-2 earthquake.
If ammonium nitrate is so dangerous, why isn’t handling and use of it more regulated? That’s a good question. The Wikipedia article on ammonium nitrate notes that in 2005, Australia passed a Dangerous Goods Regulation law which requires a license for the sale or use of the material. But if even licensed users store huge quantities of the stuff in places where it can catch fire and explode, licensing would not prevent disasters such as the one that happened to West last week, or Texas City in 1947, or over twenty other occasions since 1916 listed in a separate Wikipedia article devoted to ammonium nitrate disasters.
Chemical companies that deal routinely with explosives know how to handle these materials so that when they explode, the explosions are limited to a small area that is sacrificed in order to protect the rest of the property and lives involved. You simply restrict the amount of explosive allowed in one place to a maximum amount that you can afford to blow up, and then physically isolate it from all other concentrations of explosive in a series of small bunkers. If the fertilizer stored in the West Fertilizer Company plant had been dispersed in this way, perhaps one of the small storage areas might have blown up, but with sufficient earth-berm isolation and other precautions, the explosion would not have spread.
That is small comfort for the survivors in West. And as a practical matter, you can handle ammonium nitrate in an ordinary way without special precautions, as it is done thousands of times each year around the world, and most of the time, nothing bad will happen. If the West firm had been required to invest in the additional storage facilities needed to treat ammonium nitrate as a true explosive, it would have gone out of business for sure. (News reports indicate the firm nearly went bankrupt a few years ago and was rescued at the last minute by the present owner.) So we face the dilemma of either requiring a huge investment in safety facilities on the part of fertilizer manufacturers and retailers everywhere to prevent disasters like West, or we leave things as they are and wait for the next one.
A compromise solution might be the rigorous training of anyone who deals with ammonium nitrate, enforced by a licensing law similar to the one on Australia. This would include mandatory evacuations based on scientific calculations of a worst-case explosion whenever a fire occurs near large quantities of the stuff. While regulations like this would not have prevented the damage caused by the West detonation, it could have reduced the death toll.
Our thoughts and prayers are with the residents of West, whose tragic experience may lead to changes that at least mitigate the dangers involved in dealing with ammonium nitrate in the future.
Sources: I referred to the Wikipedia articles “Energy density,” “Ammonium nitrate” and “Ammonium nitrate disasters” as well as Google maps of the vicinity and photographs in various publications of the disaster site, and the book The Science of High Explosives by Melvin A. Cook (Reinhold, 1958).
Monday, April 15, 2013
Not long after I chose electrical engineering as a major in college, someone asked me if I was planning to take the EIT exam. What was that? It stands for “engineer in training” and it is the customary first step in obtaining a Professional Engineer (PE) license. To the best of my recollection, it didn’t cost that much and I went ahead and took it, not so much because I wanted a license but because I was the kind of nerd who couldn’t turn down a chance to see how well he did on standardized tests. By the time I graduated, I had learned that you had to “practice” for a specified number of years to take the next exam to become a full-blown PE, and in the meantime I had not been able to find anyone who could tell me what good it would do to have a PE license. So I dropped the whole thing.
Doctors and lawyers in Texas, just to choose a state I’m familiar with, must have licenses issued respectively by the Texas Medical Board (a government agency) or the State Bar of Texas (a private organization authorized to grant licenses to practice law). You can go to jail for practicing medicine without a license, and the penalties for violating legal codes of ethics include “disbarment,” which effectively ends your career as a lawyer. But the codes of ethics of most engineering organizations do not have the force of law, and the great majority of practicing engineers are not licensed, at least not in the U. S. (The laws of many other countries for licensing engineers more closely resemble those of the medical and legal professions here in the U. S.)
Why can you practice engineering without a license here, but not doctoring or lawyering? The doctors and lawyers have to answer for themselves, but it turns out that for engineers, every state (that I know of, anyway) has something in their laws concerning the engineering profession called an “industrial exemption.” The gist of the exemption is this. If an engineer works for a private firm whose products are sold outside the state where the engineer is employed, then the state regulations don’t apply. The federal government is not in the business of licensing engineers, so that is the reason why you don’t need a PE license to work as an engineer in most firms.
The industrial exemption doesn’t cover everyone. Public works such as roads, bridges, and buildings that are all in one state are not regarded as interstate commerce, and so many engineers working for certain civil-engineering firms must sign off on plans as licensed engineers. Also, there are situations in which engineers who work directly for the public, such as consulting engineers, find it helpful if not essential to be licensed. And there is the prestige factor of being able to list “P. E.” after your name, but that’s a pretty silly reason by itself.
The National Society of Professional Engineers, for one, would like it if every engineer were licensed. That organization performs a function similar to the state bars for lawyers, in that it operates the examination system for licensing of engineers and investigates alleged cases of unethical behavior by engineers. However, the power to revoke licenses lies not with NSPE, but with the state boards of professional engineers who issue a person’s license in a given state.
All this seems rather obscure and complicated, but most political things are. Would we be better off if the federal government, for example, issued engineering licenses, and no one could be hired as an engineer even by a private firm without possessing such a license? That is similar to what’s happening in the medical profession today, as more and more doctors join clinics and hospital-run HMOs rather than try to make it alone in private practice.
If such a thing were to come about, there would be some good effects and some bad effects. The good effect, for engineers, anyway, is that average salaries for engineers would probably increase, simply because the supply of engineers would go down while the demand stayed the same. However, a bad effect might be that universal licensing requirements for U. S. engineers might encourage the ongoing trend to outsource engineering to countries outside the U. S. Of course, you could try passing laws about that too, but you might succeed only in making an entire firm wash its hands of the U. S. altogether, if it got too expensive to do engineering here.
Would we enjoy better-engineered products under a universal licensing law? Somehow I suspect that competition and quality control give us products that are the best our money can buy most of the time already. Microscopic state control of every aspect of manufacturing, from engineering to marketing and distribution, was tried for decades in the old Soviet Union. And the products that resulted were not renowned for their attractive characteristics, although there were exceptions.
Much later in life, when I was contemplating a move from Massachusetts to Texas and wanted to get a job teaching in the latter state, I found out that some schools encouraged their applicants to have a PE license. So I looked into what would be involved in getting one in Massachusetts. It turned out that for someone with enough years of experience, you could avoid taking an exam altogether and simply assemble a lot of documentation on your career and appear in person before the state board of licensure. I did so, and I remember one of the members asking me if I intended to practice engineering or just teach it. I told him frankly what my reasons were, and he said something like, “Well, if that’s all you’re going to do with it, I guess it’s OK.” So I walked out of the hearing with a PE license, which I have maintained to this day.
As it happened, nobody much cared at Texas State University (or Southwest Texas State, as it was called then) whether I had a PE license or not. But the certificate looks nice on my wall, and I get to put “P. E.” after my name, for what that is worth.
Should every engineer be licensed? On the whole, I think such a law would cause more problems than it would solve, even for the engineers who might think they would benefit from the restricted market of engineering talent that would result. But at the same time, I think it is a good idea for every engineer at the start of his or her career to consider becoming licensed, because it can’t hurt you, and it might help both you and the people you are obliged to serve.
Sources: I referred to the Wikipedia article “Regulation and licensure in engineering” and the websites of the Texas Bar Association and the Texas Medical Board.
Monday, April 08, 2013
Long-time readers of this blog know that I have been less than complimentary to NASA, the International Space Station, and manned space flight in general. So it’s only fair that when NASA-sponsored teams do something good, I should mention that too. A few days ago, representatives of an international effort that produced a cosmic-ray detector that made it to the International Space Station on the next-to-last-ever Shuttle flight held a news conference. They announced the first batch of results from their detector, and while they didn’t come right out and say they have figured out what dark matter is, they did say they found strikingly clear evidence that something funny is going on out there in interstellar space. Dark matter, by the way, is what 80% of the universe is made of, only we don’t know what it is because it’s, well, dark, and most of it is far away. The only way we know it’s there is because of its gravitational effects.
While experimental physicists don’t like to admit it, a whole lot of what they do is just engineering: figuring out how to do a technical thing within a budget. In the case of the Alpha Magnetic Spectrometer (AMS), the budget was about $2 billion, and involved the work of hundreds of scientists at dozens of institutions all around the world. I counted the number of authors on the Physical Review Letters paper announcing the discovery, and there are 350 of them (349 if you leave out the researcher who died before it was published).
The AMS had a rocky road into space. Pieces of it were assembled as long ago as 1997, and I’m sure the planning took place well before then. Just as it was about to be loaded aboard a shuttle for transport to the International Space Station in 2003, the shuttle Columbia disintegrated on re-entry, and the resulting delays knocked AMS off the shuttle’s manifest. But the scientists pulled strings in Washington, and eventually got a special Congressional resolution passed in 2008 ordering NASA to get the thing up there somehow. Finally, in May 2011, AMS flew on the penultimate shuttle flight and began collecting data.
Cosmic rays have been somewhat of a mystery ever since their discovery around 1910, when it became possible to measure them accurately. Here at the bottom of the atmosphere, all you see is the decay products of the original rays, which are high-energy particles (mainly protons and atomic nuclei) that crash into air molecules and produce a shower of lower-energy particles. While scientists can tell some things about cosmic rays from ground-based observations, it’s clear that to get the best idea of where they come from and what they are, you need to hoist yourself above the atmosphere and look at the things before they slam into air molecules.
That is exactly what AMS does. It uses five different kinds of particle detectors and a great big magnet to bend the particle’s paths slightly in order to figure out energy, mass, and charge. While it might have theoretically been possible to put such a machine into unmanned orbit by itself, the size of the thing (it’s about ten feet on a side, roughly) and its power consumption made it a prime candidate for installation on the International Space Station. I read the original paper describing the device, and while I don’t pretend to understand it all, I was impressed by the sheer magnitude of the task: using over 600 microprocessors to compress 300,000 raw data inputs into a data stream that runs only 10 megabits per second, for instance. They catch an average of about 600 particles (of all kinds) each second, and the paper describes results from eighteen months’ worth of data.
Now that you have the world’s greatest cosmic ray detector, what do you do with it? Look for positrons, it turns out. Why positrons, which are the electron’s antiparticle? When a positron hits an electron, they both turn into energy and release gamma rays. And the theorists say that when two hypothetical dark-matter particles called WIMPs (I did not make this up—it stands for “weakly interacting massive particle”) hit each other, they disappear and make a positron-electron pair. Or something like that. Anyway, according to reports, if you find a lot of high-energy positrons in cosmic rays, that is evidently strong evidence for something we don’t fully understand, and dark-matter collisions making positrons are one of the prime candidates for that something.
It’s sort of like if you lock up your house when you leave and the door is standing open when you come back: you know something unusual is going on, but you don’t know exactly what yet. That’s about where the AMS scientists are now.
They are not the first people to discover these high-energy positrons. We are talking truly high-energy here: they are concerned with energies from 10 billion electron volts (GeV) up to 350 GeV. And the higher the energy they look at, the more positrons they see, as a fraction of the total of electrons and positrons together. Obviously the trend has to poop out somewhere, but the size and shape of the curve has got them more excited than a cat who wanders into a dog park by mistake.
The AMS experiment is not the first one to find this trend (an unmanned satellite instrument called PAMELA found similar results in 2008), but the AMS data covers a larger energy range and is more accurate. The data will keep theorists busy for many months or years, and because AMS was designed to operate for at least 20 years, as time goes on they will have even more to work with in the future.
Was AMS worth the $2 billion it took to do it? Supposedly, when Ben Franklin witnessed the first balloon ascension in Paris in 1783, he was asked what good it was. His reply? “What use is a newborn baby?” I can find a reference to this only on the Scientific Urban Legends webpage, so it may be apocryphal, but Franklin really did witness the first balloon flight, which was the first time a human being left the ground under control (as opposed to falling out of a fifth-story window, for example). Here 230 years later, more than a century after balloons were used for some of the first cosmic-ray experiments around 1910, we are still hoisting instruments high above the ground to look for the things. Only this time, we may be closer to figuring out where some of them come from, and in the process we may learn more about what four-fifths of the material universe is made of. Personally, I’d say that is worth $2 billion, especially if it was spread out over most of the world the way it was.
Sources: The website Space.com carried an article “Potential dark matter discovery a win for space station science” at http://www.space.com/20499-dark-matter-space-station-ams.html on Apr. 3, 2013. I also referred to Wikipedia articles on dark matter, WIMPs, PAMELA, and cosmic rays.
Monday, April 01, 2013
No, that’s not a typo in the headline. I’m not talking about the founder of Microsoft, though he is no doubt the reason that biotechnology researcher Drew Endy decided to name his new computer-in-a-cell devices Boolean Integrase Logic gates (BIL for short). The technology, which I’ll get to in a minute, is fascinating on its own. But what is even more interesting is the thing Prof. Endy has done with it: he has put the intellectual property relating to it in the hands of the BioBrick Foundation, where it can apparently be used by anybody free of charge—anybody, that is, who knows how to use it. That knocks out most of us right there, but the idea itself is intriguing, to say the least.
What is a BIL gate? Bear in mind that this is being written by a person who successfully avoided taking even a single biology course, all the way through high school, college, and graduate school. (I couldn’t stand the idea of cutting up frogs.) But the San Jose Mercury-News item that brought Prof. Endy’s work to my attention had a nice little ten-minute PowerPoint-type presentation attached, evidently narrated by the professor himself, and I gleaned enough from it to give you a brief idea of BIL gates.
The basic idea is that these BIL gates work just like normal electronic logic gates, taking in inputs and sending out outputs that are logical functions of the inputs. A two-input AND gate, for instance, puts out a HI (or Yes, or 1, whatever you want to call it) if and only if both of its inputs are HI. Otherwise it sends out a LO. Devices like these form the essential building blocks of all digital computers.
The same logical functions are performed by BIL gates, except instead of wires and transistors you have paths that biological molecules can travel, and places where the molecules can either pass by or be blocked. The passing-by or blocking is done by another control molecule. The description is vague on exactly where all this happens, and what the things look like. But if you make the same thing happen in a whole bunch of cells, you can tell it works when they all light up because of a fluorescent tracer molecule, for instance.
Prof. Endy has demonstrated all the basic combinatorial logic operations, and says we are now set to do simple computations inside cells. You can imagine, for instance, rigging liver cells to count how many times they divide. If the number of divisions gets so high that the cell is probably cancerous, you could trip a biological switch so that the cell would self-destruct. Result: no liver cancer. Or you can detect chemicals, infectious agents, and so on, and send an unambiguous digital signal so that further action can be taken.
Sounds pretty neat, huh? What is even more remarkable than the technology itself, is that Prof. Endy has essentially donated it to an organization (of which he is board president) named the BioBrick Foundation. From what I can tell from their website, the foundation is aimed at seeing that synthetic biology (of which BIL gates are an example) is used “in an open and ethical manner to benefit all people and the planet,” as they say on their homepage. They have a registry of standard biological parts that seem to have enough detail for interested parties to use them. And while I haven’t hired a lawyer to go through their fine print (if they have any), their stated principle that “fundamental scientific knowledge belongs to all of us and must be freely available for ethical, open innovation” is clear enough.
Wikipedia’s article on Prof. Endy cites his strong support for “open-source biology." The open-source philosophy presumes certain conditions that do not always exist. Suppose you went up to an old-style nineteenth-century entrepreneur-inventor like Thomas Edison, for instance, and said to him, “Mr. Edison, I think you ought to donate your invention of the light bulb to humanity for free, instead of patenting it and building a giant corporation called General Electric around it.” After he got up from the floor where he fell down laughing, he’d throw you out and probably call you a Communist to boot. But thousands of technically savvy people, including everybody who writes for Wikipedia, now do something that amounts to that every day, and the world hasn’t come to an end yet. The conditions that open sourcing requires include a bunch of smart people who have day jobs as professors, engineers, or members of other professions that allow them enough slack to do “free” work. Of course, their employers are indirectly subsidizing all this free work, and sometimes their organizations they work for benefit from it as well. There is a basically open-source microcomputer platform called Arduino, for instance, which is increasingly being incorporated in commercial products. So in the proper circumstances, the economics of open-source technology works well. But it seems to work best with things of value that are easily reproducible: software, for example, or other forms of intellectual property. On the other hand, open-source gold mining does not have much of a future, I don’t think.
We may be seeing a fundamental economic shift that is in a way a secular working-out of the Christian injunction that “to give is better than to receive.” After all, simply as a matter of mathematics, if everybody gave away only twenty percent of what they get, and that twenty percent was judiciously distributed among the needy, we could eliminate poverty in short order. But it takes special circumstances to bring that about voluntarily, and doing it involuntarily (through taxes, for example) causes other problems.
Nevertheless, in software, and now maybe in synthetic biology, we have seen that people with both intellectual power and good hearts can be generous with their discoveries and not end up losing everything. It is a fragile arrangement, and hard times, or even just the perception of hard times, could make everyone pull their horns in and get selfish again, and the whole thing could come crashing down. But Prof. Endy and his BioBrick Foundation are to be congratulated for at least trying to get the trend started, and history will show whether they succeed.
Sources: The San Jose Mercury-News website carried the article “Biological computer created at Stanford” on Mar. 29 at http://www.mercurynews.com/science/ci_22891433/biological-computer-created-at-stanford. I consulted the BioBrick Foundation website at biobrick.org and the Wikipedia articles on “BioBrick” and “Drew Endy.”