Really Big Chill

A group of MIT physicists has achieved the lowest temperature ever in a lab, and possibly in the universe. The new record is 500 picokelvin — a half- billionth of a degree above absolute zero. That’s six times lower than the prior record, and the first time scientists have gotten lower than the billionth- of-a-degree mark. Setting such a record takes more than the world’s most powerful refrigerator. In fact, you can’t use any kind of structure or container because atoms at super low temperatures tend to cling tenaciously to surfaces. Instead, the researchers isolated a small quantity of sodium gas in a vacuum using high-powered magnets and laser beams. They then used a combination of evaporative cooling and laser cooling to chill the sodium atoms to the point where their roomtemperature speed of about 1,000 miles per hour dropped to less than .002 mph. The accomplishment may have payoffs in such areas as extremely precise clocks and gravity sensors but it’s also a key basic science achievement, says Wolfgang Ketterle, who co-led the team with fellow MIT physicist David Pritchard. Getting below one-billionth of a degree kelvin “is a little like running the first four-minute mile,” says Ketterle, who won a physics Nobel Prize for work involving earlier low-temperature experiments.

Saving Synapses

The places where brain cells connect, called synapses, though completely invisible to the naked eye, have everything to do with who we are and what we do. For example, our ability to form memories depends heavily on the brain’s ability to strengthen synapses — or, in the case of memories that fade, to let beefed-up synapses return to a weaker state. Synapses can even go away completely, and an MIT group’s findings about this disappearing act may set the stage for new strategies to combat Alzheimer’s, among other conditions. The job of dismantling synapses falls to a specialized set of proteins in neurons that can act as enzymes. A group headed by MIT neuroscientist Morgan Sheng showed that one such enzyme, serum-inducible kinase (SNK), degrades elements of brain synapses by chemically modifying specific proteins within the synapse. This suggests that if you could block or slow SNK, you might be able to impede the progression of ailments like Alzheimer’s that involve synapse loss. The group has in fact shown that by interfering with SNK you can promote extra synapse growth — but so far only in brain cells in culture. “Whether it’s doable in the brain itself, we don’t know yet,” says Sheng.

Disarming Pathogens

Not unlike humans, bacteria bunch together when endangered. In work that could set the stage for new tactics against infectious disease, an MIT-Harvard research group has found what may be a widespread mechanism behind bacterial clumping behavior. The group, led by MIT biophysicist Alexander van Oudenaarden, studied the microbes called E. coli. ( E. coli are widely present in our bodies, and are generally harmless but in certain circumstances can cause serious disease and even death.) When the bacteria are exposed to a biological agent they emit under stress, the microbes individually start maneuvers that bring them together. The researchers also discovered that the bacteria have a “memory” for this agent: if they sense that the agent’s concentration is higher than four seconds earlier, they know they’re headed into the cluster and keep on going. If weaker, in effect they head elsewhere. Van Oudenaarden, whose group included Harvard biological engineer Michael Brenner, says that if we could stretch out the bacteria’s memories to say, 40 seconds, it could lead to new disease-fighting tactics. “Their clusters would be about 10 times bigger,” he notes. “This would make it much tougher for the whole group to stay in contact, making the individual bacteria more vulnerable.”

Manipulating the Miniscule

With scientists and engineers at MIT and elsewhere increasingly building devices with parts measured in nanometers (billionths of a meter), there’s a need for machines that can manipulate those near-infinitesimal items. MIT’s Martin Culpepper, an assistant professor in mechanical engineering, has now come up with such an instrument. Called the HexFlex, it’s the first-ever flexure-based nanopositioning instrument that can move or rotate in any direction. It’s also the smallest and least expensive of all the nanomanipulators. The instrument’s main structure is a flat, sixpointed “star” made from titanium with elements that can be slightly, and very precisely, bent. That flexing capability sets it apart from other manipulators, which are basically small, multi-piece robots that move nano-items around. And it lets HexFlex users manipulate such items with more precision than they could achieve using the robot-style manipulators. “With other machines, you can ‘step’ in increments of ten nanometers,” says Culpepper. “We can do better than three nanometers.” The device received an R&D magazine R&D 100 Award as one of 2003’s most technologically significant advances.