This section was edited by Associate Editor Jeffrey Winters.

TAILGATER'S FAIL SAFE

For some people, there's no more heinous kind of motorist than the tailgater: a driver who keeps his vehicle close to the car ahead of him. Particularly at highway speeds, the experience of being tailgated is especially nerve-wracking. But according to police records, the greatest danger for accidents is in normal city driving—some 75 percent of rear-end collisions occur between vehicles traveling at less than 20 miles per hour.

To guard against such collisions, Continental, the automotive parts supplier based in Hanover, Germany, in March started production of a sensor system aimed at monitoring the distance between vehicles.

Too close for comfort? The infrared ranging system attached to this car's rearview mirror measures the distance between vehicles and can trigger the brakes if a collision is imminent.

The sensor, which is mounted on the rearview mirror, emits three infrared beams that sweep an area some 20 feet in front of the car. If the car begins to close in on a vehicle in that area, a signal is sent to the brakes, slowing or stopping the car automatically.

The company says that if the relative difference in speed between the vehicles is 10 mph or less, a rear-end collision can be avoided by cars using their new system. At higher speed differentials, the collision will likely still occur, but it will be less severe. What's more, the system, which will be included in a suite of electronics called "City Safety" for upcoming Volvo models, will send data to airbag and restraint systems, triggering them earlier.

The system will be standard on 2009 Volvo XC60 sport utility vehicles.

THE NAG NECKLACE

One of the signs of getting older is the growing size of the daily pill intake. Sometimes it seems that the daily regimen runs against human nature. Indeed, medical researchers find that as many as one in three adults fails to take medicines as prescribed.

For that forgetful third, engineers at Georgia Tech have developed a necklace that records the exact time and date when specially designed pills are swallowed. And if the patient forgets, the necklace can send a message to him—or to his doctor.

The necklace, called MagneTrace by its developers, has an array of magnetic sensors clustered near the esophagus. When a pill containing an embedded signaling device is swallowed, it passes close enough to the sensors to be detected. The necklace sends the time, date, and other information to a wireless phone or personal digital assistant that keeps track of the dosage.

The research team has yet to try the necklace on a human subject. Instead, they've built an artificial neck out of PVC pipe to see how well the system can detect a microscale magnet passing through it.

As important as taking medicine on schedule is for treatment, it can be critically important in clinical drug trials. Participants often miss doses or take two pills to make up for ones they have skipped. Either tactic can alter the effect of a medicine and influence the results of a clinical trial.

Currently, participants in drug trials record their intake in diaries, which aren't always reliable. By creating an exact record of pill taking, researchers hope that drug companies can get better results over a shorter amount of time and with fewer participants.

MOLECULE SPOTTER

Seeking a metaphor for something impossibly hard to find? "Needle in a haystack" fits the bill. But researchers at Rice University in Houston have come up with something new, which might be even more difficult: They have made simultaneous optical and electronic measurements of a single molecule. If work continues apace, says one of the project leaders, the research could lead to the ability to watch individual chemical reactions as they unfold.

Researchers led by Douglas Natelson of Rice's quantum magnetics laboratory created their sensor using two nanoscale gold electrodes separated by a molecule-size space. When a molecule settled across that gap, tiny amounts of electric current flowed from one electrode to the other. At the same time, infrared light passing through the gap was focused to help researchers identify the molecule being measured.

The result is expected to help researchers better understand what goes on in nanotech electronics. The way electricity is conducted at the nano-scale depends not only on the bulk properties of materials, but on such hard-to-measure factors as how a molecule is oriented in respect to the contact points.

DETAILED TAILLIGHTS

Brake lights are an essential piece of auto equipment, but they don't relay much information. When the light flashes on the car ahead of you, you don't know whether a sudden stop is imminent—or if the driver is tapping his toe to the music.

That insight, which followed being part of a multicar chain-reaction pile-up some years back, led a businessman to contact Virginia Polytechnic Institute in Blacksburg. After some research and a couple of iterations, a Virginia Tech research team recently unveiled their results at a trade show in Kentucky: an extra brake light for commercial trucks that warns trailing motorists of a quick deceleration.

A team of student engineers under the guidance of mechanical engineering professor Mehdi Ahmadian originally sought to develop a high-tech brake light for passenger vehicles. That team came up with a horizontal array of amber and red light-emitting diodes. The display would communicate exactly what the car was doing: When the car slowed, the amber lights would flick on. A more rapid stop would engage a set of flashing red lights on either side of the amber ones. Slamming on the brakes would make the whole bar glow red.

While the design was clever, it ran afoul of two laws. One was a statute forbidding tampering with original brake equipment in passenger vehicles, according to school officials. The other was economic—at $50 apiece, the lights were too expensive to produce.

The Virginia Tech team then redesigned the system to take these limitations into account. It targeted the commercial truck market, since those vehicles often have extra lights. The new system would incorporate data from an accelerometer to modify the signal from the brake system. Under heavy braking, some of the lights would flash.

Eventually, such a system could incorporate data from other sensors, such as the ones that trigger automatic traction control or a collision avoidance system, to provide warnings to other motorists.

PEROXIDE BOMB 

While security experts scramble to detect potential nuclear and radiological weapons wielded by terrorists, homemade bombs haven't received as much attention. But while their impact wouldn't be as widespread, a homemade bomb detonated in a crowded public area can be devastating; in 2005, such weapons killed more than 50 people during a coordinated attack on the London transit system.

Now a penny-size sensor may be able to sniff out a bomb like the ones used in the London attacks by looking for one of its basic ingredients.

It's been known for years that terrorists could make explosives from an unstable mixture of common chemicals, including hydrogen peroxide. Such explosives can elude conventional detectors, which are geared toward finding nitrate-based chemicals. But chemists and physicists at the University of California, San Diego, working with funds provided by the Air Force Office of Scientific Research, realized that peroxide fumes could betray the presence of the explosives.

The sensor uses thin films of metal phthalocyanines, which normally show increased electrical conductivity when exposed to an oxidizing chemical. But electrical current through a film of cobalt phthalocyanine decreases when exposed to peroxide vapors. The detector created by the UCSD team uses two films, one of cobalt phthalocyanine and another of copper phthalocyanine; if the conductivity in the two films trends in opposite directions, that's a sign of peroxide in the vicinity.

Because the devices are small and simple, they could be built cheaply enough to deploy in many public places, the developers say. In addition, they can be used in industrial settings, such as paper mills, where overexposure to peroxide vapors might be a problem. 

ASTHMA AIR ANALYZER

In spite of the millions of people, particularly children, who suffer from it, doctors still don't fully understand why people get asthma. But they do know that the attacks, which can be potentially life-threatening, can sometimes be triggered by such common gases as ozone, nitrogen oxide, and volatile organic compounds, or VOCs.

With an eye toward better treating the disease, researchers have developed a sensor system that continuously monitors the air around research subjects who are prone to asthma attacks. The battery-powered sensor system fits in a vest that volunteers wear while they're part of a study.

A vest pocket holds an air-monitoring device used to study the causes of asthma attacks.

The monitor was built from commercially available sensors that were integrated by engineers at Keehi Technologies, a company in Decatur, Ga. The sensors measure temperature, relative humidity and airborne concentrations of formaldehyde, VOCs, and other compounds. The device takes readings every two minutes, records the data, and then goes into a power-conserving sleep mode.

After an asthma attack, the volunteer will note the time and date, and researchers will later match that to the air quality.

The system also incorporates an air filter to trap particles. Although minute-by-minute data on particle exposure won't be possible, the filters are analyzed at the end of the study periods to look for environmental clues about what might trigger attacks.

Six volunteers have worn the sensor system so far to test for comfort and effectiveness. Those trials, conducted by the Georgia Tech Research Institute in Atlanta, unexpectedly helped one volunteer: The sensors detected a high concentration of VOCs in his home, the result of automobile exhaust and gasoline fumes migrating in from an attached garage.

MAKING CO₂ VISIBLE

If greenhouse gas emissions are a lot like the weather-you know, lots of talk, little action-then researchers at Purdue University in West Lafayette, Ind., have come up with a carbon dioxide weather map. But unlike conventional weather maps, which might clue in an observer as to whether he ought to put on a jacket or leave it home, this weather map might actually help people do something about the climate.

The map is a product of a data system known as Vulcan. It's not a direct measure of CO₂, however. Instead, researchers rely on the monitoring of conventional air pollution, such as carbon monoxide and nitrogen oxides, that is performed by the Environmental Protection Agency, the Department of Energy, and other government agencies. Agencies track those emissions with a network of air monitors in order to assess air quality in major cities and provide alerts when it deteriorates.

Carbon emissions are greatest in urban and suburban areas and along interstate corridors.

In order to get information on CO₂ emissions from the data on pollutants, researchers from Purdue, Colorado State University in Fort Collins, and the Lawrence Berkeley National Laboratory in California developed a model that related carbon dioxide emissions to conventional pollution for various sources, such as coal-fired power plants and automobile tail-pipes. Once the CO₂ data were extracted, they were combined with geographic information to create regional and national maps.

The Vulcan maps can provide researchers and others not only with the geographic distribution of CO₂ emissions—because cells on the map can be as small as six miles on a side—but also on variations from hour to hour and season to season. For instance, data from Vulcan indicate that emissions from the southeastern United States are greater than previously realized.

The Vulcan system is expected to complement a satellite that NASA plans to launch later this year. The Orbiting Carbon Observatory will carry three high-resolution grating spectrometers developed by Hamilton Sundstrand Sensor Systems and will provide some of the most fine-grained measurements of the Earth's atmosphere ever obtained from space.
 

DISTRIBUTED SEISMOLOGY 

The more data points you have, the more finely detailed analysis you can make. Geologists tracking hidden seismic faults know that the earthquakes they study may have millions of eyewitnesses, but quality information is limited to the number of dedicated seismographs they have available.

That number could increase substantially if a project from the San Diego Supercomputer Center in California takes off. The project hopes to take advantage of millions of motion detectors already deployed in laptop computers.

In recent years, all Macintosh laptops have featured built-in accelerometers; these motion sensors are part of a system designed to protect the hard drive if the machine is dropped. In addition, every new Mac has built-in wireless communications hardware and a video camera.

The researchers have found a way to link these tools into what they call the iSeismograph. During an earthquake, software created by the SDSC's Network for Earthquake Engineering Simulation Cyberinfrastructure Center records the motion experienced by the laptop and sends the data via a wireless network to a central information center. There, the data can be accessed by researchers in real time. Presumably, the computer center will also be able to keep track of how often Mac users drop their expensive machines.

DEWDROP MRIs

Most people encounter magnetic resonance imaging when they sprain a knee. But for researchers, a similar technology called nuclear magnetic resonance imaging is an extraordinarily powerful tool for studying materials. For instance, subjecting a rock sample to an NMR scan could help petroleum geologists better understand how much oil a field might contain.

Unfortunately, typical NMR machines are enormous, limiting their usefulness. But a supersensitive sensor developed by the National Institute of Standards and Technology promises to change that. Its NMR can fit on a microchip.

This microchip holds a fully functional, room temperature nuclear magnetic resonance detector.

In a recent experiment conducted at the University of California, Berkeley, the NMR chip detected magnetic signals in tap water flowing through minuscule channels etched in silicon. Such magnetic signals can reveal physical, chemical, or structural details about a material. Due to the small sample, however, the NMR detector had to be both powerful and about the same size as the material. That last constraint ruled out superconducting quantum interference devices, the large, cryogenically cooled machines most often used for NMR.

The NIST sensor, conversely, works at room temperature and is sensitive enough to pick up normal brain waves. The sensor uses a milliwatt laser shone through a small container of rubidium gas. As the magnetic field fluctuates through the container—in response to, say, the motion of nearby fluids—the rubidium atoms change the amount of laser light they absorb. Those fluctuations can be measured by a sensitive optical sensor.

The micro-NMR is being considered for use in medical applications, as well. The device could be used, for example, to measure small electrical currents in the muscles of a fetus's heart.