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Devangshu Datta: Nobel causes

The great physicist Richard Feynman was once asked to explain his work in non-technical language. He pointed out: “If I could explain it to the average person, it wouldn’t have been worth the Nobel”.

In the absence of easy explanations, the press tries to find human interest angles. That was easy this year. Half of the physiology award went to the Norwegian couple, May-Britt and Edvard Moser. This is the fifth husband-wife pair to win Nobels – a sign that birds of a feather do flock together.

The Mosers did some fascinating work on the brain’s “GPS”. They improved upon a breakthrough by the pioneer John O’Keefe in the 1970s. O’Keefe received the other half of the award. The trio have explained how the brain uses nerve cells to form grids and maps for spatial orientation.

O’Keefe saw that a certain type of nerve cell in a part of the brain called the hippocampus activated when a rat was in one part of a room. Other nerve cells activated when the rat moved to other parts. He guessed that these “place cells” represented a map of the room.

In 2005, the Mosers added key details. They found another type of position-related nerve cell in another part of the brain, the entorhinal cortex. These “grid cells” generated a coordinate system, enabling precise positioning and pathfinding.

Higher cognition about spatial positioning is built on top of this “cellular GPS”. It probable that similar cell-based processes enable other higher cognitive processes such as memory, thinking and planning.

The Chemistry Nobel was awarded to Eric Betzig, Stefan W Hell and William E Moerner “for the development of super-resolved fluorescence microscopy”. Hell is German, Betzig and Moerner are Americans.

The trio found ways to get past a physical barrier – the wavelength of light – in building optical microscopes. Two different principles are required to breach this barrier, called the Abbe Diffraction Limit.

Hell developed stimulated emission depletion (STED). A wave is cancelled out when it interacts with another wave, which has the same amplitude and inverted phase. This is how noise cancellation works. Light may be cancelled the same way, by using lasers to pulse inverted phase radiation to darken a given spot.

In a STED microscope, fluorescent molecules are pushed into cells. One light pulse excites all fluorescent molecules, while an anti-phase pulse nullifies all fluorescence, except in a very small area which stays illuminated. That area can be shifted nanometre by nanometre for very high-resolution images.

Moerner meanwhile, was working on the green fluorescent protein (GFP), used by jellyfish for fluorescence. He found a way to switch a single GFP cell on and off, by hitting it with light of exact frequencies. Betzig had tried to bypass the Abbe Limit by using dispersed molecules of different colours. In 2005, he realised that Moerner’s work could be used to illuminate molecules at different times, and by superimposing time-lapsed images, the Abbe limit could be bypassed. By combining these differing insights, the nanoscope was created.

The physics prize also involves light and is the easiest to explain in lay terms. It was awarded jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura “for the invention of efficient blue light-emitting diodes (LEDs)”.

An LED uses semiconductors, which emit light when an electric current is passed between layers. The colour depends on semiconductor wavelength. LED save energy by directly converting electricity into light particles (photons), while filaments and neon tubes have to be heated to glow.

But in order to produce white light, a combination of reds (long wavelength), greens (mid) and blues (short) is required. Efficient red and green LEDs were developed in the 1950s. It was only in the 1990s that Akasaki and Amano found ways to create high-quality gallium nitride crystal semiconductors, which emitted blue. Nakamura found a different, more efficient way to create gallium nitride crystals.

The trio also contributed to the invention of the Blu-ray, which uses the short-wavelength property to pack more information into less space. Given that a fourth of all electricity is used to provide light, the LED has a huge impact.

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