washingtonpost.com  > Nation > Science

SCIENCE

Notebook

Monday, April 18, 2005; Page A07

Hulls to Blame for 'Old Maids'

So why is it that whenever you make popcorn there are always unpopped kernels left at the bottom of the bowl or the bag at the movies -- the ones that stick in your throat, plug up your teeth and pop your fillings?

"It's a matter of scientific curiosity, and we are in the food business, " said Purdue University's Rengaswami Chandrasekaran. "So we decided to find out."


Popcorn popability is tied to a kernel's cellulose hull. (Julia Ewan -- The Washington Post)

In research scheduled to appear in the July 11 edition of the journal BioMacromolecules, scientists led by food chemist Bruce Hamaker, of Purdue's Whistler Center for Carbohydrate Research, analyzed 14 varieties of microwaveable popcorn to determine what causes the bb-hard leftovers known as "old maids."

Popcorn makers for years have used trial-and-error breeding to make popcorn pop more thoroughly, but the team found that the results were mixed. In analyzing 14 microwave varieties, the number of unpopped kernels ranged from 4 to 47 percent.

The key popability factor, it turned out, is the kernel's cellulose hull, known as the pericarp. Chandrasekaran, a crystallographer, found that the pericarp in the better performers had a stronger crystalline structure than the pericarp in the losers.

"With a better organized crystal structure, the kernel retains moisture better," Chandrasekaran said in a telephone interview. The kernel swells as it heats up, until it finally explodes, creating popcorn. If the moisture leaks out prematurely, or the pericarp collapses, the pressure will not build, and the frustrated consumer is left with old maids.

-- Guy Gugliotta

Brain's Grasp of Acceleration

Humans are very good at predicting how long it will take for something to fall. On some level, even people who never took physics know that objects speed up 9.8 meters per second every second.

It is a fine adaptive trait, useful whether swinging from trees or catching pop flies. Yet tests have shown that the human visual system by itself is notoriously poor at detecting such a subtle degree of acceleration, raising questions as to how the brain does it.

Now a team led by Francesco Lacquaniti of the Scientific Research Foundation in Rome has proposed an answer. They knew that astronauts in Spacelab -- the European Space Agency's low-gravity science lab that was carried in the cargo hold of a U.S. space shuttle -- had trouble catching objects during the first few days in space. Only after a few days of accommodation did their brains catch on to the lowered acceleration, suggesting that some aspect of the gravity-detecting vestibular system in the inner ear might be involved.

On Earth, the team presented volunteers with video games featuring images of falling balls that they were asked to "catch" by pressing a button. In some cases the game mimicked actual gravitational forces, and in other cases it substituted false ones. At the same time, the volunteers underwent a kind of brain scan called functional magnetic resonance imaging, which measures localized regions of brain activity.

As described in the April 15 issue of the journal Science, they concluded that a part of the brain called the cortical vestibular network, long believed to be involved in the processing of gravitational information, plays a previously unknown role: It integrates information from the eyes with gravitational information from the vestibular system to create a virtual representation of the physical laws of motion that allows a person to accurately predict the actual arrival time of a falling object.

-- Rick Weiss

New Dinosaur Species Identified

Paleontologists have identified a new dinosaur species, an early relative of Tyrannosaurus rex that probably roamed what is now the southeastern United States about 77 million years ago.

The scientists made the identification from hundreds of fossilized fragments collected mostly in Montgomery County, Ala., and southwestern Georgia.

They named the new dinosaur Appalachiosaurus montgomeriensis, which means "the Appalachian lizard from Montgomery County." The 25-foot-long creature roamed Earth 10 million years before T. rex and was smaller and more primitive, with a narrower snout.

David R. Schwimmer of Columbus State University; Thomas Carr of Carthage College of Kenosha, Wis.; and Thomas Williamson of the New Mexico Museum of Natural History and Science were credited with the discovery when the dinosaur's name was recognized by the Journal of Vertebrate Paleontology.

The researchers said Appalachiosaurus montgomeriensis was buried in mud at the bottom of a shallow sea about 77.8 million years ago, after currents carried it away from shore.

-- Associated Press


© 2005 The Washington Post Company