Why HOT water freezes quicker than COLD water

HOT water sometimes freezes faster than cold water - but why? This peculiar phenomenon has baffled scientists for generations, but now there is evidence that the effect may depend on random impurities in the water.

Fast-freezing of hot water is known as the Mpemba effect, after a Tanzanian schoolboy called Erasto Mpemba (see "How the Mpemba effect got its name"). Physicists have come up with several possible explanations, including faster evaporation reducing the volume of hot water, a layer of frost insulating the cooler water, and differing concentration of solutes. But the answer has been very hard to pin down because the effect is unreliable - cold water is just as likely to freeze faster.

James Brownridge, who is radiation safety officer for the State University of New York at Binghamton, believes that this randomness is crucial. Over the past 10 years he has carried out hundreds of experiments on the Mpemba effect in his spare time, and has evidence that the effect is based on the shifty phenomenon of supercooling.

"Water hardly ever freezes at 0 °C," says Brownridge. "It usually supercools, and only begins freezing at a lower temperature." The freezing point depends on impurities in the water which seed the formation of ice crystals. Typically, water may contain several types of impurity, from dust particles to dissolved salts and bacteria, each of which triggers freezing at a characteristic temperature. The impurity with the highest nucleation temperature determines the temperature at which the water freezes.

Brownridge starts with two samples of water at the same temperature - say, tap water at 20 °C - in covered test tubes and cools them in a freezer. One will freeze first, presumably because its random mix of impurities give it a higher freezing point.

If the difference is large enough, the Mpemba effect will appear. Brownridge selects the sample with the higher natural freezing temperature to heat to 80 °C, warming the other to only room temperature, then puts the test tubes back in the freezer. The hot water will always freeze faster than the cold water if its freezing point is at least 5 °C higher, Brownridge says.

It may seem surprising that moving the finish line by only 5 °C makes enough of a difference, when the hotter sample starts out 60 °C behind in the race. But the bigger the temperature difference between an object and its surroundings - in this case, the freezer - the faster it cools. So the hot sample will do most of its cooling very quickly, helping it to reach its own freezing point of -2 °C, say, before the cooler water gets to its freezing point of -7 °C.

You can now smell a terrorist a mile away

A new intelligent system has been developed to help identify terrorists carrying explosives. Sensitive electronic noses capture the smell of the explosives; the system processes the acquired data, correlates it with individuals' movements... and ultimately tracks down the suspects.

Literally hundreds of people are hurrying through the long airport corridor between Terminals A and B. Among them are two terrorists, who've hidden themselves in the crowd. They're carrying small containers of chemicals in their jacket pockets, individual components for an explosive. But there's something the criminals don't know. As well as being observed by security cameras, they're also being "sniffed out" by chemical noses hidden in the corridor wall.

The smell sensors sound the alarm when the terrorists walk past, alerting an airport security guard who notes the problem on his monitoring equipment. At this point in time, he can't tell precisely who is carrying hazardous chemicals - but he knows the sensor network will continue to "sniff out" and track down the suspects.

Researchers at the Fraunhofer Institute for Communication, Information Processing and Ergonomics FKIE in Wachtberg have built a prototype security system to replicate just such a scenario. They've named it HAMLeT, which stands for Hazardous Material Localization and Person Tracking. "HAMLeT will alert security personnel to suspicious individuals," says head of department Dr. Wolfgang Koch from the FKIE. The system involves a network of highly-sensitive smell sensors which follow an explosive's trail. There are oscillating crystals on the sensor chips, and whenever the electronic noses capture chemical molecules, their oscillation frequency changes. The precise nature of the change is different for different substances.

A further component in the system - the sensor's data fusion function - traces the explosive's path and ferrets out the carrier. A second sensor network is needed to track the route the individual takes; for this, the researchers have used laser scanners. "HAMLeT's real achievement is its ability to collate all the data and convert it into a clear and accurate overall picture," says Koch. The sensor data fusion process employs complex algorithms which allow HAMLeT to build up a precise image of pedestrian flows and connect a particular smell with a specific individual.

In a trial involving the German Armed Forces, researchers at the FKIE proved the system's ability to track down five "terrorists" carrying hidden explosives. The scientists are now working to refine the prototype's algorithms in order to reduce the false alarm rate.

Crazy Girl on Train Remix

Girl terroizes old lady on an Atlanta Bus

The 10 Most Outrageous Military Experiments

From this choice list of Experiments performed by the U.S. Military here are 2 of my favourites:

GET YOUR PLUTONIUM SHOT

As the United States raced to build its first atomic bombs near the end of World War II, scientists wanted to know more about the hazards of plutonium. Testing began on April 10, 1945 with the injection of plutonium into the victim of a car accident in Oak Ridge, Tenn., to see how quickly the human body rid itself of the radioactive substance. That was just the first of over 400 human radiation experiments. Common studies included seeing the biological effects of radiation with various doses, and testing experimental treatments for cancer. Records of this research became public in 1995, after the U.S. Department of Energy published them.

NERVE GAS SPRAY

Threats of chemical and biological warfare led the U.S. Department of Defense to start "Project 112" from 1963 to the early 1970s. Part of the effort involved spraying different ships and hundreds of Navy sailors with nerve agents such as sarin and VX, in order to test the effectiveness of decontamination procedures and safety measures at the time. The Pentagon revealed the details of the Project Shipboard Hazard and Defense (SHAD) project in 2002, and the Veterans Administration began studying possible health effects among sailors who participated in SHAD. This was just one of many chemical warfare experiments conducted by the U.S. military, starting with volunteer tests involving mustard gas in World War II.

Lickable Wallpaper

Willy Wonka would be proud. When Adnan Aziz saw people licking orange-flavoured wallpaper in the movie Willy Wonka and the Chocolate Factory, it gave him the idea for a novel form of advertising.

Together with Jay Minkoff, a "serial entrepreneur," he set up First Flavor, a company that makes edible film strips that allow consumers to sample the flavours of foods, drinks and other products.

So far First Flavor has distributed strips that taste of grape juice, acai-berry juice, lime-spiked rum, and baking-soda toothpaste in shops and magazines and via direct-mail campaigns.

Just as retailers stuff newspapers with coupons and sales promotions, First Flavor wants to get food and drink companies to attach a sealed pouch, containing a flavour sample, to front-page newspaper advertisements for their products. Consumers can then take them for a "taste drive," puns Minkoff.

First Flavor has already run magazine-based campaigns, so edible ads in newspapers are an obvious next step.

First Flavor and US Ink think the decline in newspaper advertising revenue, as a result of the recession and the rise of the Internet, provides an opportunity.

While Internet advertisements can do all sorts of things, so far there is no way to transmit tastes electronically.

Edible ads would allow newspapers to offer something the Internet cannot match.

And who said guys were useless!

So here's our softball fan left holding the Baby - but that doesn't stop him! Watch the Ball, watch the ball....................................

CRAZY FLYING MAN

The theme for today is flying! And on that note - Kids don't try this at home, without the correct supervision.....

Dude if you're gonna grow Weed at home don't have a burgular alarm that calls the police!

Police seized more than 40 marijuana plants, two pounds of cultivated marijuana, $10,000 in cash, handguns and rifles when they responded to a burglar alarm at the waterfront home of a local dentist.

Dr. Raymond Pacholec, 61, was charged with possession of more than 50 grams of marijuana, possession with intent to distribute and operating a marijuana growing facility, police said. Pacholec was released after posting $50,000 bail.

According to Detective Sgt. James J. Smith, at 8:27 a.m. police responded a burglar alarm at Pacholec's home at Bayview Avenue and Magnolia Drive. Officers John Sperber and Don Rowley walked through the house with Pacholec, but did not find a burglar. They did, however, notice a strong odor of raw marijuana, Smith said.

The officers also saw other indications of illegal drug use and took the doctor into custody. Police left and obtained a search warrant, Smith said. The Ocean County sheriff's canine unit and Criminalistics Investigations Unit assisted. The State Police Marijuana Eradication Unit assisted in taking the evidence into custody.

The subsequent search turned up additional evidence, Smith said.

Pacholec has a practice on Route 9 in the Bayville section.

"I don't think it had anything to do with medicinal purposes," Smith said. Detectives are investigating. "This was really the result of good heads-up police work by the two officers who responded there for the burglar alarm," Smith said. "Without their keen observations, we never would have got involved with it."

Crazy Christian Bale!

Think Christian has finally crossed over to THE DARK SIDE!