System Bits: June 23

Amplifying movements; grinding nanotubes.

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Magnifying motions indiscernible to the naked eye
For several years now, the research groups of MIT professors of computer science and engineering William Freeman and Frédo Durand have been investigating techniques for amplifying movements captured by video but indiscernible to the human eye. Versions of their algorithms can make the human pulse visible and even recover intelligible speech from the vibrations of objects filmed through soundproof glass.

They recently presented a new version of their algorithm that can amplify small motions even when they’re contained within objects executing large motions. This could make visible the precise sequence of muscle contractions in the arms of a baseball player swinging the bat, or in the legs of a soccer player taking a corner kick.

They explained that the previous version of the algorithm assumed everything was small in the video, and now they want to be able to magnify small motions that are hidden within large motions. The basic idea is to try to cancel the large motion and go back to the previous situation.

Canceling the large motion means determining which pixels of successive frames of video belong to a moving object and which belong to the background — this is a particularly acute problem at the object’s boundaries.

A key to the new motion-magnification algorithm is a technique for very precisely extracting foreground objects from their backgrounds. (Source: MIT)

A key to the new motion-magnification algorithm is a technique for very precisely extracting foreground objects from their backgrounds.
(Source: MIT)

Ordinarily, an algorithm separating foreground from background could probably get away with keeping those borderline pixels but the purpose of the MIT researchers’ motion amplification algorithm is precisely to detect variations invisible to the naked eye. Changes of color at an object’s boundaries could be interpreted as motions requiring magnification.

Grinding nanotubes to get nanoribbons
Rice University researchers have discovered a simple way to turn carbon nanotubes into valuable graphene nanoribbons may be to grind them up.

Rice materials scientist Pulickel Ajayan said the trick is to mix two types of chemically modified nanotubes because when they come into contact during grinding, they react and unzip — a process that until now has depended largely on reactions in harsh chemical solutions.

The researchers stressed that the new process is still a chemical reaction that depends on molecules purposely attached to the nanotubes in a process called functionalization. They said the most interesting part of this is that a process as simple as grinding could deliver strong chemical coupling between solid nanostructures and produce novel forms of nanostructured products with specific properties.

Chemical reactions can easily be done in solutions, but this work is entirely solid state, and they wonder if nanotubes can be used as templates, then functionalize them and get reactions under the right conditions. If possible, what kinds of things can we make with a large number of possible nanostructures and chemical functional groups?

Researchers led by materials scientists at Rice University discovered that altering carbon nanotubes with carboxyl (COOH) and hydroxyl (OH) groups and grinding them together produces nanoribbons. The find could lead to novel nanostructured products with specific properties. (Source: Mohamad Kabbani/Rice University)

Researchers led by materials scientists at Rice University discovered that altering carbon nanotubes with carboxyl (COOH) and hydroxyl (OH) groups and grinding them together produces nanoribbons. The find could lead to novel nanostructured products with specific properties. (Source: Mohamad Kabbani/Rice University)

They expect the process should enable many new chemical reactions and products: by using different functionalities in different nanoscale systems, this could revolutionize nanomaterials development.

For more research and application, check out the Mobile Technology Lab’s projects at MIT. Very interesting!