PANTHER Sensor Quickly Detects Pathogens

Researchers at MIT Lincoln Laboratory have developed a powerful sensor that can detect airborne pathogens such as anthrax and smallpox in less than three minutes.

The new device, called PANTHER (for PAthogen Notification for THreatening Environmental Releases), represents a "significant advance" over any other sensor, says James Harper of Lincoln Lab's Biosensor and Molecular Technologies Group. Current sensors take at least 20 minutes to detect harmful bacteria or viruses in the air, but the PANTHER sensors can do detection and identification in less than 3 minutes.

The technology has been licensed to Innovative Biosensors, Inc. (IBI) of Rockville, Md. In January, IBI began selling a product, BioFlash, that uses the PANTHER technology.

"There is a real need to detect a pathogen in less than three minutes, so you have time to take action before it is too late," says Harper, the lead scientist developing the sensor.

The PANTHER sensor uses a cell-based sensor technology known as CANARY (after the birds sent into mines to detect dangerous gases), and can pick up a positive reading with only a few dozen particles per liter of air.

The device could be used in buildings, subways and other public areas, and can currently detect 24 pathogens, including anthrax, plague, smallpox, tularemia and E. coli.

"There's really nothing out there that compares with this," said Todd Rider of Lincoln Lab's Biosensor and Molecular Technologies Group, who invented the CANARY sensor technology.

Rider started developing CANARY in 1997 when he realized that there were no sensors available that could rapidly detect pathogens. His idea was to take advantage of nature's own defense system--specifically the B cells that target pathogens in the human body. "B cells in the body are very fast and very sensitive," Rider says.

The CANARY concept uses an array of B cells, each specific to a particular bacterium or virus. The cells are engineered to emit photons of light when they detect their target pathogen. The device then displays a list of any pathogens found.

CANARY is the only sensor that makes use of immune cells. Other available sensors are based on immunoassays or PCR (polymerase chain reaction), which take much longer and/or are not as sensitive as CANARY.

Rider and colleagues first reported the success of CANARY (which stands for Cellular Analysis and Notification of Antigen Risks and Yields) in the journal Science in 2003. Since then, they have been working to incorporate the technology into a portable device that could be used in a variety of settings where environmental threats might exist.

The new device, PANTHER, takes the CANARY technology and combines it with an air sampler that brings pathogens into contact with the detector cells. The prototype sensor is about a cubic foot and weighs 37 pounds and is well suited to building-protection applications. With minor modifications it could also enhance biological detection capabilities for emergency responders.

CANARY has been tested in rural and coastal environments as well as urban ones. It could eventually be used on farms or in food-processing plants to test for contamination by E. coli, salmonella, or other food-borne pathogens.

Another potential application is in medical diagnostics, where the technology could be used to test patient samples, giving rapid results without having to send samples to a laboratory.

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MIT Lecture Search Engine Aids Students

Imagine you are taking an introductory biology course. You're studying for an exam and realize it would be helpful to revisit the professor's explanation of RNA interference. Fortunately for you, a digital recording of the lecture is online, but the 10-minute explanation you want is buried in a 90-minute lecture you don't have time to watch.

A new lecture search engine developed at MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) could help with this dilemma. Created by a team of researchers and students led by MIT associate professor Regina Barzilay and principal research scientist James Glass, the web-based technology allows users to search hundreds of MIT lectures for key topics.
"Our goal is to develop a speech and language technology that will help educators provide structure to these video recordings, so it's easier for students to access the material," says Glass, who is head of CSAIL's Spoken Language Systems Group.

More than 200 MIT lectures are currently available on the site (web.sls.csail.mit.edu/lectures/). So far, most of the users are international students who access the lectures through MIT's OpenCourseWare (OCW) initiative, which makes curriculum materials for most MIT courses available to anyone with Internet access. Although the lecture-browsing system is still in the early development stages, a recent announcement in OCW's newsletter has drawn increased traffic to the site.

Barzilay and Glass expect the system will be most useful for OCW users and for MIT students who want to review lecture material. MIT World, a web site that provides video of significant MIT events such as lectures by speakers from MIT and around the world, is also participating in the project.

Many MIT professors record their lectures and post them online, but it's difficult to search them for specific topics. Because there is no way to easily scan audio, as you can with printed text, "you end up watching the whole thing, and it's hard to keep focused," says Barzilay, the Douglas T. Ross Career Development Associate Professor of Software Development in the Department of Electrical Engineering and Computer Science.

On the prototype web site, users can search lectures for any term they want and then play the relevant sections.

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Three Mile Island--Failure of Science or Spin?

By Stephanie Schorow

Since 1979, the words "Three Mile Island" have been synonymous with the words "nuclear disaster." But does a careful analysis of the timeline, aftermath and media coverage reveal that the accident at the Three Mile Island Nuclear Generating Station was really a public relations disaster and not a technical failure?

That was the provocative question posed by Andrew Kadak, professor of the practice of nuclear engineering, in his Jan. 22 two-part IAP seminar about five crucial days in March 1979 at the plant near Harrisburg, Pa.

In the morning session of "Three Mile Island--Colossal Failure or Colossal Success?" Kadak concluded there were failures all around--except for the most important aspect: The melted nuclear core was contained and any radiation released was minimal. Thus, the plant design and safety protocols actually worked, despite numerous operator mistakes. Kadak's arguments met with lively opposition, as session participants zeroed in on technical glitches.

Just as lively was the afternoon session on "Three Mile Island Communications--Good, Bad or Ugly?" in which Kadak discussed the role of local reporters, the plant spokesman, members of the Nuclear Regulatory Commission and Pennsylvania Gov. Dick Thornburgh (R).

"What do you say when people want answers even if you don't have them?" he asked participants.

"You can't handle the truth!" was one humorous response, but the humor underscored the difficulty in explaining technical issues to a media or frightened public that demanded easy, immediate answers

Kadak set the framework for analysis by identifying four aspects of "failure": technical, financial, perception and consequences.

One of the key technical issues in running a nuclear plant is managing heat: radiation decay means that 7 percent of full heat continues even after the plant is "shut down," he explained.

The nuclear core has to be covered with water at all times.

On March 28, through a series of errors around 4 a.m.--including a valve that was supposed to close but didn't and a known leak that led operators to conclude high temperatures readings were false--water escaped from the core, which began heating up without a way to remove the heat. Within a matter of minutes, things went from bad to worse as operators continued to believe water was circulating through the core and they had a "bottled-up system."

By 5 a.m. "all hell broke loose," Kadak said. "In my assessment, (operators) had no real idea what was going on … They were not able to deal with all these events at the same time."

By 7 a.m. a site emergency was called; by 7:30 a.m. a general emergency was called, amid concerns that a hydrogen bubble had formed in the core. It had not, Kadak said, although months later cleanup crews were astonished to see how much of the core had actually melted.

Reports that radiation had been released--later found to be inaccurate--led Gov. Thornburgh to order a partial evacuation. A plant spokesman, technically skilled but inexperienced in media relations, gave the impression of a cover-up. Eventually a visit to the plant by then President Jimmy Carter, who had studied nuclear physics, helped calm the public and the cleanup process began. The release of the nuclear accident film "The China Syndrome" 12 days earlier was eerily coincidental.

As a result of the Three Mile Island incident, nuclear plant construction was halted throughout the United States, "killing the nuclear industry for 30 years," Kadak said, and many became convinced nuclear energy was unsafe. Yet Kadak said, despite ominous newspaper photos of (completely safe) steam being released from the plant's cooling towers, radiation was "contained"--the supreme goal of the design. Could that not be considered a success?

Not to Miklos Porkolab, MIT physics professor and director of the Plasma Science and Fusion Center. "I would say they were damn lucky,'' he said. "It reminds me of my Pontiac." That is, everything has failed at one time or another.

Physics graduate student Roark Marsh suggested removing the word "colossal" to make the assessment more accurate. But activist James Williamson, a frequent participant in MIT events, would have none of it, saying that not only did systems fail, but plant operators failed to err on the side of caution and call for an evacuation, even if they were unsure of the risk. "Yes, there was inaccurate information, but who cares?" he said.

But, noted Ian Hutchinson, head of MIT's Department of Nuclear Science and Engineering, evacuations are not without costs--people can be killed in traffic trying to flee.
Other participants said they saw all kind of places where "all systems failed." Some cited lack of user interface; others the lack of fail-safe mechanisms or "redundant sensors to know what's going on," as Joshua Stillerman, systems program analyst in the Plasma Science and Fusion Center, put it.

While experts wrongly concluded that hydrogen in the core would form a dangerous bubble (rather than safely recombine with oxygen), "isn't the lesson to imagine things even worse than they can imagine?" Hutchinson asked.

But bottom line: No one was killed in the accident and subsequent studies have turned up no conclusive evidence on health problems. Three Mile Island could have been a huge disaster; because of safety protocols, it was not, Kadak concluded. The real hero, he argued, was Gov. Thornburgh, who took the attitude, "I'm not going to do anything until I get the facts."

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Suburbia Gets Neo-New Deal

An international architecture journal has devoted an entire issue to the results of an MIT urban design studio--results that were further developed by a team of architects, planners, publishers and MIT faculty--addressing how to rescue suburbia after a coming economic crash, according to the university.

Led by Alexander D'Hooghe, assistant professor in MIT's Department of Architecture, the studio took as its premise the possibility that, because of rising debt, the decline of the dollar, burgeoning oil prices and the burst of the real estate bubble, the United States may soon experience an economic setback on a par with the Great -Depression.

Such an event would surely impoverish the suburban lower middle-class that lives in what D'Hooghe refers to as "the Grey Goo"--the massive tarmac between our cities' centers and their leafier exurbs--and create "a new underclass eager to consume the rhetoric of fascist populism, thriving on anti-intellectualism, sectarianism, conquest abroad and repression at home."
If such a crisis were to occur, he asked his students, and if the government then stepped in to restart the economy artificially--as it did during FDR's New Deal--what buildings and infrastructures would represent the best investments? What should the nation do first to build a new suburban future?

The studio focused on New Jersey's Passaic County, an area emblematic of many American suburbs, as well as the focus of Robert Smithson's seminal 1967 article, "Tour of the Monuments of Passaic, NJ." The result was a set of building proposals for the sprawl around New York that would, among other things, curb dependence on the car and offer additional alternative modes of organization.

The results are presented as an "official report" to the fictional Federal Organization for the Reactivation and Modernization of Mankind as a set of program briefs, compiled by D'Hooghe and his students, for federal construction projects to "employ, educate, house and emancipate the proletariat." The report includes proposals for neighborhood development, shopping centers, logistics complexes, housing and education.

The 97-page "white paper" appears in Volume, a bimonthly publishing project of Archis, the national architecture magazine of the Netherlands. Previous issues of Volume have dealt with such topics as the architecture of power, ubiquitous China and broadcasting architecture.

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MIT Ethanol Analysis Confirms Benefits of Biofuels

Controversy over the benefits of using corn-based ethanol in vehicles has been fueled by studies showing that converting corn into ethanol may use more fossil energy than the energy contained in the ethanol produced. Now a new MIT analysis shows that the energy balance is actually so close that several factors can easily change whether ethanol ends up a net energy winner or loser.

Regardless of the energy balance, replacing gasoline with corn-based ethanol does significantly reduce oil consumption because the biomass production and conversion process requires little petroleum. And further MIT analyses show that making ethanol from cellulosic sources such as switchgrass has far greater potential to reduce fossil energy use and greenhouse gas emissions.
The Bush administration is pushing the use of ethanol as a domestically available, non-petroleum alternative to gasoline. But most U.S. ethanol is now made from corn, and growing corn and converting the kernels into ethanol consume a lot of energy--comparable to what is contained in the ethanol produced. Making ethanol from corn stalks, other agricultural wastes and wild grasses would consume less energy, but the technology for converting them to ethanol may not be economically viable for another five or so years.

Does using corn-based ethanol in place of gasoline actually make energy consumption and emissions go up, as some researchers claim? Why do others reach the opposite conclusion? And how much better would ethanol from "cellulosic" feedstocks such as switchgrass be?
To answer those questions, Tiffany Groode, a graduate student in MIT's Department of Mechanical Engineering, performed her own study, supervised by John B. Heywood, Sun Jae Professor of Mechanical Engineering.

Using a technique called life cycle analysis, she looked at energy consumption and greenhouse gas emissions associated with all the steps in making and using ethanol, from growing the crop to converting it into ethanol. She limited energy sources to fossil fuels. Finally, she accounted for the different energy contents of gasoline and ethanol. Pure ethanol carries 30 percent less energy per gallon, so more is needed to travel a given distance.

While most studies follow those guidelines, Groode added one more feature: She incorporated the uncertainty associated with the values of many of the inputs. Following a methodology developed by recent MIT graduate Jeremy Johnson, she used not just one value for each key variable (such as the amount of fertilizer required), but rather a range of values along with the probability that each of those values would occur. In a single analysis, her model runs thousands of times with varying input values, generating a range of results, some more probable than others.

Based on her "most likely" outcomes, she concluded that traveling a kilometer using ethanol does indeed consume more energy than traveling the same distance using gasoline. However, further analyses showed that several factors can easily change the outcome, rendering corn-based ethanol a "greener" fuel.

One such factor is the much-debated co-product credit. When corn is converted into ethanol, the material that remains is a high-protein animal feed. One assumption is that the availability of that feed will enable traditional feed manufacturers to produce less, saving energy; ethanol producers should therefore get to subtract those energy savings from their energy consumption. When Groode put co-product credits into her calculations, ethanol's life-cycle energy use became lower than gasoline's.

Another factor that influences the outcome is which energy-using factors of production are included and excluded--the so-called system boundary. A study performed by Professor David Pimentel of Cornell University in 2003 includes energy-consuming inputs that other studies do not, one example being the manufacture of farm machinery. His analysis concludes that using corn-based ethanol yields a significant net energy loss. Other studies conclude the opposite.
To determine the importance of the system boundary, Groode compared her own analysis, the study by Pimentel and three other reputable studies, considering the same energy-consuming inputs and no co-product credits in each case.

"The results show that everybody is basically correct," she says. "The energy balance is so close that the outcome depends on exactly how you define the problem." The results also serve to validate her methodology: Results from the other studies fall within the range of her more probable results.

Growing more corn may not be the best route to expanding ethanol production. Other options include using corn stover (the plants and husks that are left on the field), or growing an "energy crop" such as switchgrass. While corn kernels are mostly starch, corn stover and switchgrass are primarily cellulose. Commercial technologies to make ethanol from cellulose are not yet available, but laboratory and pilot-scale tests are generating useful data on processing techniques. So how do cellulosic sources measure up in terms of saving energy and reducing greenhouse gas emissions?

Using her methodology, Groode performed an initial analysis of switchgrass and, drawing again on Johnson's work, corn stover. She found that fossil energy consumption is far lower with these two cellulosic sources than for the corn kernels.

Farming corn stover requires energy only for harvesting and transporting the material. (Fertilizer and other inputs are assumed to be associated with growing the kernels.) Growing switchgrass is even less energy intensive. It requires minimal fertilizer, its life cycle is about 10 years, so it need not be replanted each year, and it can be grown almost anywhere, so transport costs can be minimized.

Groode and Heywood now view the three ethanol sources as a continuum. In the future, cellulosic sources such as corn stover and ultimately switchgrass can provide large quantities of ethanol for widespread use as a transportation fuel. In the meantime, ethanol made from corn can provide some immediate benefits.

"I view corn-based ethanol as a stepping-stone," says Groode. "People can buy flexible-fuel vehicles right now and get used to the idea that ethanol or E85 works in their car. If ethanol is produced from a more environmentally friendly source in the future, we'll be ready for it."

The research was supported by BP America.


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