Saturday, August 11, 2007

Is Glass Solid Or Liquid?

When most people look at a window, they see solid panes of glass. But for decades, physicists, who view window glass at the molecular level, have pondered the question of whether or not glass is a solid or merely an extremely slow-moving liquid. An Emory University research team led by physicist Eric Weeks has yielded another clue in the glass puzzle, demonstrating that, unlike liquids, glasses aren’t comfortable in confined spaces.


The Emory team's findings are reported in the paper "Colloidal glass transition observed in confinement," published in the Physical Review Letters July 13. The Emory research adds to the evidence that some kind of underlying structure is involved in glass transition, Weeks says. "This provides a simple framework for looking at other questions about what is really changing during the transition."


Weeks has devoted his career to probing the mysteries of "squishy" substances that cannot be pinned down as a solid or liquid. Referred to as "soft condensed materials," they include everyday substances such as toothpaste, peanut butter, shaving cream, plastic and glass.


Scientists fully understand the process of water turning to ice. As the temperature cools, the movement of the water molecules slows. At 32 F, the molecules form crystal lattices, solidifying into ice. In contrast, the molecules of glasses do not crystallize. The movement of the glass molecules slows as temperature cools, but they never lock into crystal patterns. Instead, they jumble up and gradually become glassier, or more viscous. No one understands exactly why.


"One idea for why glass gets so viscous is that there might be some hidden structure," says Weeks, associate professor of physics. "If so, one question is what size is that structure?"


The Emory Physics lab began zeroing in on this question two years ago when Hetal Patel, an undergraduate who was majoring in chemistry and history, designed a wedge-shaped chamber, using glue and glass microscope slides that allowed observation of single samples of glassy materials confined at decreasing diameters.


For samples, the Emory lab used mixtures of water and tiny plastic balls – each about the size of the nucleus of a cell. This model system acts like a glass when the particle concentration is increased.


The samples were packed into the wedge-shaped chambers, then placed in a confocal microscope, which digitally scanned cross-sections of the samples, creating up to 480 images per second. The result was three-dimensional digital movies, showing the movement and behavior of the particles over time, within different regions of the chamber.


"The ability to take microscopy movies has greatly improved during the past five to 10 years," Weeks says. "Back in the mid-90s, the raw data from one two-hour data set would be four gigabytes. It would have completely filled up your hard drive. Now, it's just a tiny part of your hard drive, like a single DVD."


The data showed that the narrower the sample chamber, the slower the particles moved and the closer they came to being glass-like. When the researchers increased the particle concentration in the samples, the confinement-induced slowing occurred at larger plate separations. The dimension between the plates at which the particles consistently slowed their movement was 20 particles across.


"It's like cars and traffic jams," Weeks says. "If you're on the highway and a few more cars get on, you don't really care because you can still move at the same speed. At 3 p.m., traffic gets worse and you may slow down a little bit. But at some point, your speed has to go from 40 mph to 5 mph. That's kind of what's happening with glass."


Previous research has shown groups of particles in dense suspensions move cooperatively. "Our work suggests glasses are solid-like because these groups can't move when the sample chamber is thinner than the typical size of these groups," Weeks says. "These experiments help us understand earlier work done with thin polymer films and other glassy materials, but as we use particles rather than atoms, we get to directly see how confinement influences the glass transition."


Nanotechnology is one example of a field that can benefit from research into the behavior of colloidal glass and plastics in tight spaces. 




"When making machines as small as a cell, people have found that they're even more fragile than you might expect," Weeks said. "One interesting thing is that small plastic structures become more fragile because, when they are really tiny, they're less glassy."



###

Emory University is one of the nation's leading private research universities and a member of the Association of American Universities. Known for its demanding academics, outstanding undergraduate college of arts and sciences, highly ranked professional schools and state-of-the-art research facilities, Emory is ranked as one of the country's top 20 national universities by U.S. News & World Report. In addition to its nine schools, the university encompasses The Carter Center, Yerkes National Primate Research Center and Emory Healthcare, the state's largest and most comprehensive health care system.
Posted by Ajay :: 12:11 PM :: 0 comments

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---------------oOo--------------- Hilarious

The Nigeria scams riled up one person enough to write a parody spam.

X-Spam-Status: No, hits=4.3 required=5.0
tests=BILLION_DOLLARS,DEAR_SOMETHING,IN_REP_TO,ITS_LEGAL,
LINES_OF_YELLING,LINES_OF_YELLING_2,LINES_OF_YELLING_3,
NIGERIAN_TRANSACTION_1,NIGERIAN_TRANSACTION_2,REFERENCES,
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UPPERCASE_75_100,USER_AGENT,USER_AGENT_MUTT,US_DOLLARS_3
version=2.43
X-Spam-Level: ****

HIGHLY CONFIDENTIAL

FROM: GEORGE WALKER BUSH
DEAR SIR / MADAM,

I AM GEORGE WALKER BUSH, SON OF THE FORMER PRESIDENT OF THE UNITED STATES OF
AMERICA GEORGE HERBERT WALKER BUSH, AND CURRENTLY SERVING AS PRESIDENT OF THE
UNITED STATES OF AMERICA. THIS LETTER MIGHT SURPRISE YOU BECAUSE WE HAVE NOT
MET NEITHER IN PERSON NOR BY CORRESPONDENCE. I CAME TO KNOW OF YOU IN MY SEARCH
FOR A RELIABLE AND REPUTABLE PERSON TO HANDLE A VERY CONFIDENTIAL BUSINESS
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THE UNITED STATES OF AMERICA, AND BRAVELY SERVED HIS COUNTRY AS DIRECTOR OF THE
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IN THE DECADE OF THE NINETEEN-EIGHTIES, MY FATHER, THEN VICE-PRESIDENT OF THE
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MY FATHER RE-SECURED THE PETROLEUM ASSETS OF KUWAIT IN 1991 AT A COST OF
SIXTY-ONE BILLION U.S. DOLLARS ($61,000,000,000). OUT OF THAT COST,
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BILLION DOLLARS ($16,000,000,000) BY GERMAN AND JAPANESE PARTNERS.

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FUNCTION AS OUR TRUSTED INTERMEDIARY. I PROPOSE THAT YOU MAKE THIS TRANSFER
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I KNOW THAT A TRANSACTION OF THIS MAGNITUDE WOULD MAKE ANYONE APPREHENSIVE AND
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I PRAY THAT YOU UNDERSTAND OUR PLIGHT. MY FAMILY AND OUR COLLEAGUES WILL BE
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BELOW.

SINCERELY WITH WARM REGARDS,
GEORGE WALKER BUSH


--------------------------------------------------------------------------------

Happy Linuxing!

Posted by Ajay :: 12:09 PM :: 0 comments

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---------------oOo--------------- How Women Use To Dominate Men

9 WORDS WOMEN USE

1. Fine: This is the word women use to end an argument when they are right and you need to shut up.

2. Five Minutes: If she is getting dressed, this means a half an hour. Five minutes is only five minutes if you have just been given five more minutes to watch the game before helping around the house.

3. Nothing: This is the calm before the storm. This means something, and you should be on your toes. Arguments that begin with nothing usually end in fine.

4. Go Ahead: This is a dare, not permission. Don’t Do It!

5. Loud Sigh: This is not actually a word, but is a non-verbal statement often misunderstood by men A loud sigh means she thinks you are an idiot and wonders why she is wasting her time standing here and arguing with you about nothing. (Refer back to #3 for the meaning of nothing.)

6. That’s Okay: This is one of the most dangerous statements a women can make to a man. That’s okay means she wants to think long and hard before deciding how and when you will pay for your mistake.

7. Thanks: A woman is thanking you, do not question, or Faint. Just say you’re welcome.

8. Whatever: Is a woman’s way of saying F@!K YOU!

9. Don’t worry about it, I got it: Another dangerous statement, meaning this is something that a woman has told a man to do several times, but is now doing it herself. This will later result in a man asking “What’s wrong?” For the woman’s response, refer to #3.

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