Electronic Nose

Onboard the space station, astronauts are surrounded by ammonia. It flows through pipes, carrying heat generated inside the station (by people and electronics) outside to space. Ammonia helps keep the station habitable.

But it's also a poison. And if it leaks, the astronauts will need to know quickly. Ammonia becomes dangerous at a concentration of a few parts per million (ppm). Humans, though, can't sense it until it reaches about 50 ppm.

Ammonia is just one of about forty or fifty compounds necessary on the shuttle and space station, which cannot be allowed to accumulate in a closed environment.

And then there's fire. Before an electrical fire breaks out, increasing heat releases a variety of signature molecules. Humans can't sense them either until concentrations become high.

Astronauts need better noses!


That's why NASA is developing the Electronic Nose, or ENose for short. It's a device that can learn to recognize almost any compound or combination of compounds. It can even be trained to distinguish between Pepsi and Coke. Like a human nose, the ENose is amazingly versatile, yet it's much more sensitive.


Here's how it works: ENose uses a collection of 16 different polymer films. These films are specially designed to conduct electricity. When a substance -- such as the stray molecules from a glass of soda -- is absorbed into these films, the films expand slightly, and that changes how much electricity they conduct







 


Because each film is made of a different polymer, each one reacts to each substance, or analyte, in a slightly different way. And, while the changes in conductivity in a single polymer film wouldn't be enough to identify an analyte, the varied changes in 16 films produce a distinctive, identifiable pattern.

Electronic Noses are already being used on Earth. In the food industry, for example, they can be used to detect spoilage. There's even an Electronic Tongue, which identifies compounds in liquids. NASA's ENose needs to be able to detect lower concentrations than these devices.


As a safety device, the ENose has a lot to offer here on Earth, too. With some modifications, an ENose could be used to check for gas buildups in offshore oil rigs. "The workers have to go down into the legs of the rigs, and they want to make sure it's not going to blow up while they're in there." Sanitation workers would benefit by knowing if any poisonous gases have collected down in the sewers.

Amazon's Improved eBook Plot Stumbles on Resolution

Amazon.com hopes its new Kindle tablet will make buying and reading electronic books as easy as buying the paper kind. But while Kindle avoids some flaws of such earlier attempts as 1998's NuvoMedia Rocket eBook and last year's Sony Reader -- thanks in part to a free wireless connection that downloads books off the air -- it can't quite close the deal.

The $399 Kindle (sold out through Christmas) is a slim, white tablet about the size and shape of a paperback, weighing just over 10 ounces. Its front consists of a 6-inch screen and a miniaturize keyboard.

The device's gray-scale screen doesn't look anything like other computer displays. It uses the same "E Ink" technology as the Sony Reader, which keeps the screen readable even in direct sunlight but can't duplicate other qualities of the printed word.

The Kindle's screen, for example, doesn't include a backlight and displays only a few shades of gray. Between the dark-gray text and the light-gray background, its contrast falls short of a newspaper's and is inferior to that of a book.

The Kindle's screen, for example, doesn't include a backlight and displays only a few shades of gray. Between the dark-gray text and the light-gray background, its contrast falls short of a newspaper's and is inferior to that of a book.

Worse, the Kindle's sluggish screen needs about 1 1/2 seconds to draw a new page, during which time the next page distractingly appears as a photo-negative image of itself before settling into place.

That delay seems short next to most waits on a computer but feels like infinity compared with turning a paper page. The Kindle screen's lag ensures there can be no such thing as flipping through a book on this device.

The design of the rest of the Kindle can get in the way, too. Two-thirds of each side is taken up by buttons to skip to the previous and next page, so you must remember where you can safely grab the thing without losing your place.

To navigate through the Kindle's on-screen menus and links -- say, to bookmark a page, search the book's contents, view a footnote or add a comment -- you spin a small scroll wheel to move a tiny indicator up and down a thermometer-like column to the right of the screen. You're supposed to line up this indicator with the item you want to select, an awkward task when a chapter list hugs the left side of the screen.

The reward for mastering this often-awkward interface is a small library you can read on the go. Amazon stocks 90,000 titles for the Kindle, a fraction of its print inventory, and makes them available through a wireless connection that comes free with the device.

Once you set up a Kindle with your Amazon account, everything downloads directly and almost instantly -- no computer or special software required.