Atomic magnetometers

Miniaturized atomic magnetometers the size of a grain of rice require little power and are sensitive to very weak magnetic fields. Impact: Tiny, inexpensive magnetometers could lead to portable MRI machines, tools for detecting buried explosive devices, and ways to evaluate mineral deposits remotely.

Much of modern life depends on forecasts: where the next hurricane will make landfall, how the stock market will react to falling home prices, who will win the next primary. While existing computer models predict many things fairly accurately, surprises still crop up, and we probably can't eliminate them. But Eric Horvitz, head of the Adaptive Systems and Interaction group at Microsoft Research, thinks we can at least minimize them, using a technique he calls "surprise modeling."

Horvitz stresses that surprise modeling is not about building a technological crystal ball to predict what the stock market will do tomorrow, or what al-Qaeda might do next month. But, he says, "We think we can apply these methodologies to look at the kinds of things that have surprised us in the past and then model the kinds of things that may surprise us in the future." The result could be enormously useful for decision makers in fields that range from health care to military strategy, politics to financial markets.

Granted, says Horvitz, it's a far-out vision. But it's given rise to a real-world application: SmartPhlow, a traffic-forecasting service that Horvitz's group has been developing and testing at Microsoft since 2003.

Displayed on Jeff Lichtman's computer screen in his office at Harvard University is what appears to be an elegant drawing of a tree. Thin multicolored lines snake upward in parallel, then branch out in twos and threes, their tips capped by tiny leaves. Lichtman is a neuroscientist, and the image is the first comprehensive wiring diagram of part of the mammalian nervous system. The lines denote axons, the long, hairlike extensions of nerve cells that transmit signals from one neuron to the next; the leaves are synapses, the connections that the axons make with other neurons or muscle cells.

The diagram is the fruit of an emerging field called "connectomics," which attempts to physically map the ­tangle of neural circuits that collect, process, and archive information in the nervous system. Such maps could ultimately shed light on the early development of the human brain and on diseases that may be linked to faulty wiring, such as autism and schizophrenia. "The brain is ­essentially a computer that wires itself up during development and can rewire itself," says Sebastian Seung, a computational neuroscientist at MIT, who is working with Lichtman. "If we have a wiring diagram of the brain, that could help us understand how it works."

Although researchers have been studying neural connectivity for decades, existing tools don't offer the resolution needed to reveal how the brain works. In particular, scientists haven't been able to generate a detailed picture of the hundreds of millions of neurons in the brain, or of the connections between them.

Krishna Palem is a heretic. In the world of microchips, precision and perfection have always been imperative. Every step of the fabrication process involves testing and retesting and is aimed at ensuring that every chip calculates the exact answer every time. But Palem, a professor of computing at Rice University, believes that a little error can be a good thing.

Palem has developed a way for chips to use significantly less power in exchange for a small loss of precision. His concept carries the daunting moniker "probabilistic complementary metal-oxide semiconductor technology"--PCMOS for short. Palem's premise is that for many applications--in particular those like audio or video processing, where the final result isn't a number--maximum precision is unnecessary. Instead, chips could be designed to produce the correct answer sometimes, but only come close the rest of the time. Because the errors would be small, so would their effects: in essence, Palem believes that in computing, close enough is often good enough.

Every calculation done by a microchip depends on its transistors' registering either a 1 or a 0 as electrons flow through them in response to an applied voltage. But electrons move constantly, producing electrical "noise." In order to overcome noise and ensure that their transistors register the correct values, most chips run at a relatively high voltage. Palem's idea is to lower the operating voltage of parts of a chip--specifically, the logic circuits that calculate the least significant bits, such as the 3 in the number 21,693. The resulting decrease in signal-to-noise ratio means those circuits would occasionally arrive at the wrong answer, but engineers can calculate the probability of getting the right answer for any specific voltage. "Relaxing the probability of correctness even a little bit can produce significant savings in energy," Palem says.

Every time you use your cell phone, you leave behind a few bits of information. The phone pings the nearest cell-phone towers, revealing its location. Your service provider records the duration of your call and the number dialed.

Some people are nervous about trailing digital bread crumbs behind them. Sandy Pentland, however, revels in it. In fact, the MIT professor of media arts and sciences would like to see phones collect even more information about their users, recording everything from their physical activity to their conversational cadences. With the aid of some algorithms, he posits, that information could help us identify things to do or new people to meet. It could also make devices easier to use--for instance, by automatically determining security settings. More significant, cell-phone data could shed light on workplace dynamics and on the well-being of communities. It could even help project the course of disease outbreaks and provide clues about individuals' health. Pentland, who has been sifting data gleaned from mobile devices for a decade, calls the practice "reality mining."

Reality mining, he says, "is all about paying attention to patterns in life and using that information to help [with] things like setting privacy patterns, sharing things with people, notifying people--basically, to help you live your life."

Researchers have been mining data from the physical world for years, says Alex Kass, a researcher who leads reality-mining projects at Accenture, a consulting and technology services firm. Sensors in manufacturing plants tell operators when equipment is faulty, and cameras on highways monitor traffic flow. But now, he says, "reality mining is getting personal."

Within the next few years, Pentland predicts, reality mining will become more common, thanks in part to the proliferation and increasing sophistication of cell phones. Many handheld devices now have the processing power of low-end desktop computers, and they can also collect more varied data, thanks to devices such as GPS chips that track location. And researchers such as Pentland are getting better at making sense of all that information.

Solar Broadband Radio Spectrometer

A new radio spectrometer, Solar Broadband Radio Spectrometer (SBRS) with characteristics of high time resolution, high-frequency resolution, high sensitivity, and wide frequency coverage in the microwave region is described. Its function is to monitor solar radio bursts in the frequency range of 0.7–7.6 GHz with time resolution of 1–10 ms. SBRS consists of five `component spectrometers' which work in five different wave bands (0.7–1.5 GHz, 1.0–2.0 GHz, 2.6–3.8 GHz, 4.5–7.5 GHz, and 5.2–7.6 GHz, respectively). A combination of multi-channel and scanning techniques is adopted. The component spectrometers are attached to different antennas which are separately located at Beijing, Kunming, and Nanjing. Close attention was paid to solve the problems of sensitivity, dynamic range, interference-resistance, data acquisition, and handling a large amount of data. The SBRS was put into operation in the 23th solar maximum activity period, and has proved itself to be a valuable instrument for the study of solar bursts in microwaves.

A researcher at Stanford University has provided strong experimental evidence that ribbons of carbon atoms can be used for future generations of ultrafast processors.

Hongjie Dai, a professor of chemistry at Stanford, and his colleagues have demonstrated a new chemical process that produces extremely thin ribbons of a carbon-based material called graphene. He has demonstrated that these ribbons, once incorporated into transistors, show excellent electronic properties. Such properties have been predicted theoretically, Dai says, but not demonstrated in practice. These properties make graphene ribbons attractive for use in logic transistors in processors.

The discovery could lead to even greater interest in the experimental material, which has already attracted the attention of researchers at IBM, HP, and Intel. Graphene, which consists of carbon atoms arranged in a one-atom-thick sheet, is a component of graphite. Its structure is related to carbon nanotubes, another carbon-based material that's being studied for use in future generations of electronics. Both graphene and carbon nanotubes can transport electrons extremely quickly, which could allow very fast switching speeds in electronics. Graphene-based transistors, for example, could run at speeds a hundred to a thousand times faster than today's silicon transistors.

But graphene sheets have one significant disadvantage compared with the silicon used in today's chips. Although graphene can be switched between different states of electrical conductivity--the basic characteristic of semiconductor transistors--the difference between these states, called the on/off ratio, isn't very high. That means that unlike silicon, which can be switched off, graphene continues to conduct a lot of electrons even in its "off" state. A chip made of billions of such transistors would waste an enormous amount of energy and therefore be impractical.

Researchers had theorized, however, that it might be possible to dramatically improve these on/off ratios by carving graphene sheets into very narrow ribbons just a few nanometers wide. There had been early evidence supporting these theories from researchers at IBM and Columbia University, but the ratios produced were still much lower than those in silicon.

Robot-assisted brain surgery a reality

Despite advances in technology and technique, there will always be one limiting factor in the operating room: the surgeon. Hours of exacting work can tire anybody, especially someone navigating the delicate intricacies of the human brain.

The solution is as old as science fiction, but the technology has only recently caught up to the concept. The Robot-Assisted Microsurgery (RAMS) prototype is a robotic surgical tool first developed for space use and later refined as a precision instrument for microsurgery. Peter D. LeRoux, MD, a neurosurgeon at the University of Pennsylvania Medical Center, reports on the feasibility of RAMS in brain surgery in the March issue of Neurosurgery.

"The RAMS system works like an extension of the surgeon's hands," said LeRoux. In essence, the system consists of a set of robotic arms: a master arm, which functions like a joystick; and an operating arm, which actually performs the surgery. The surgeon manipulates the master arm just as they would hold a surgical instrument, and the operating arms mimic the surgeon's movements on the patient. "Robotic surgery is not about replacing surgeons, but enhancing their abilities in the operating room," explained LeRoux.

Wireless power

In the late 19th century, the realization that electricity could be coaxed to light up a bulb prompted a mad dash to determine the best way to distribute it. At the head of the pack was inventor Nikola Tesla, who had a grand scheme to beam electricity around the world. Having difficulty imagining a vast infrastructure of wires extending into every city, building, and room, Tesla figured that wireless was the way to go. He drew up plans for a tower, about 57 meters tall, that he claimed would transmit power to points kilometers away, and even started to build one on Long Island. Though his team did some tests, funding ran out before the tower was completed. The promise of airborne power faded rapidly as the industrial world proved willing to wire up.

Then, a few years ago, Marin Soljačić, an assistant professor of physics at MIT, was dragged out of bed by the insistent beeping of a cell phone. "This one didn't want to stop until you plugged it in for charging," says Soljačić. In his exhausted state, he wished the phone would just begin charging itself as soon as it was brought into the house.

So Soljačić started searching for ways to transmit power wirelessly. Instead of pursuing a long-distance scheme like Tesla's, he decided to look for midrange power transmission methods that could charge--or even power--portable devices such as cell phones, PDAs, and laptops. He considered using radio waves, which effectively send information through the air, but found that most of their energy would be lost in space. More-targeted methods like lasers require a clear line of sight--and could have harmful effects on anything in their way. So Soljačić sought a method that was both efficient--able to directly power receivers without dissipating energy to the surroundings--and safe.

He eventually landed on the phenomenon of resonant coupling, in which two objects tuned to the same frequency exchange energy strongly but interact only weakly with other objects. A classic example is a set of wine glasses, each filled to a different level so that it vibrates at a different sound frequency. If a singer hits a pitch that matches the frequency of one glass, the glass might absorb so much acoustic energy that it will shatter; the other glasses remain unaffected.

Soljačić found magnetic resonance a promising means of electricity transfer because magnetic fields travel freely through air yet have little effect on the environment or, at the appropriate frequencies, on living beings. Working with MIT physics professors John Joannopoulos and Peter Fisher and three students, he devised a simple setup that wirelessly powered a 60-watt light bulb.

The researchers built two resonant copper coils and hung them from the ceiling, about two meters apart. When they plugged one coil into the wall, alternating current flowed through it, creating a magnetic field. The second coil, tuned to the same frequency and hooked to a light bulb, resonated with the magnetic field, generating an electric current that lit up the bulb--even with a thin wall between the coils.

A Record-Breaking Optical Chip

The road to a faster Internet, data center, and personal computer is paved with silicon. Or so believe researchers at Intel who have unveiled a test chip--made entirely from silicon--that can encode 200 gigabits of data per second on a beam of light. In contrast, the most advanced chips used in today's fastest optical networks operate at speeds of 100 gigabits per second. And these 100-gigabit chips, which are made from nonsilicon materials, have limitations that Intel's chip doesn't: they can't scale to faster speeds as inexpensively as can those made from silicon.

While silicon is the material of choice in the electronics industry, it has been overlooked in the photonics industry because its optical properties are inferior to those of other semiconductors. Silicon doesn't produce, detect, and manipulate photons as well as materials such as indium phosphide and gallium arsenide. But within the past few years, optical engineers have been giving silicon a second look and cleverly engineering around some of its natural limitations.

The new Intel test chip splits an incoming beam of light into eight channels. Within each channel is a modulator, a device that encodes data onto light. After the beams are encoded with data, they are recombined. In the tests, each modulator ran at a rate of 25 gigabits per second, and each performed nearly identically, says Mario Paniccia, director of the company's silicon-photonics lab. He notes that only one modulator was tested at a time but says that in a future paper his team will publish the results from running multiple channels simultaneously. The multiple channels could produce cross talk, electrical or optical activity that could hinder performance. However, preliminary results, Paniccia says, show that due to the design, cross talk is limited.

In 2004, Intel researchers, led by Paniccia, proved that silicon could be used to build a one-gigabit-per-second modulator; in 2005, the team boosted the speed to 10 gigabits per second. Also in 2005, the researchers built a remarkably good all-silicon laser, and in 2006, they introduced a hybrid laser that combines indium phosphide with silicon, allowing a practical telecom laser to be fabricated on a silicon wafer. Most recently, they have sped up the modulator to 40 gigabits and built a silicon detector.