Transmission Control Protocol, or TCP, is an algorithm that manages data congestion on the Internet, and as such was integral in allowing the early web to scale up from a few dozen nodes to the billions in use today. Here’s how it works: As a source, A, transfers a file to a destination, B, the file is broken into numbered packets. When B receives each packet, it sends an acknowledgment, or an ack, to A, that the packet arrived.
This feedback loop allows TCP to run congestion avoidance: If acks return at a slower rate than the data was sent out, that indicates that there is little bandwidth available, and the source throttles data transmission down accordingly. If acks return quickly, the source boosts its transmission speed. The process determines how much bandwidth is available and throttles data transmission accordingly.
It turns out that harvester ants (Pogonomyrmex barbatus) behave nearly the same way when searching for food. Gordon has found that the rate at which harvester ants – which forage for seeds as individuals – leave the nest to search for food corresponds to food availability.
A forager won’t return to the nest until it finds food. If seeds are plentiful, foragers return faster, and more ants leave the nest to forage. If, however, ants begin returning empty handed, the search is slowed, and perhaps called off.
Prabhakar wrote an ant algorithm to predict foraging behavior depending on the amount of food – i.e., bandwidth – available. Gordon’s experiments manipulate the rate of forager return. Working with Stanford student Katie Dektar, they found that the TCP-influenced algorithm almost exactly matched the ant behavior found in Gordon’s experiments.
From the “22 Strange Animals You Probably Didn’t Know Exist” post.
Today, two white doves, a symbol of the hope for peace, were released from a window in the Lateran Palace by children standing next to the Pope… and immediately attacked by other birds. It happened, not just in front of the Pope, but before a large crowd that had gathered in St. Peter’s Square to hear him give the Angelus Prayer.
Slashdot lets us know that we finally know where’s the most freezing place on Earth:
What is the coldest place on Earth? It is a high ridge in Antarctica on the East Antarctic Plateau where temperatures in several hollows can dip below minus 133.6 degrees Fahrenheit (minus 92 degrees Celsius) on a clear winter night. Scientists made the discovery while analyzing the most detailed global surface temperature maps to date, developed with data from remote sensing satellites including the new Landsat 8, a joint project of NASA and the U.S. Geological Survey (USGS). Ted Scambos, lead scientist at the National Snow and Ice Data Center in Boulder, Colo., joined a team of researchers reporting the findings Monday at the American Geophysical Union meeting in San Francisco. Researchers analyzed 32 years’ worth of data from several satellite instruments. They found temperatures plummeted to record lows dozens of times in clusters of pockets near a high ridge between Dome Argus and Dome Fuji, two summits on the ice sheet known as the East Antarctic Plateau. The new record of minus 93.2 C was set Aug. 10, 2010.
One thing that is not so obvious about this research is the problem with tools – most thermometers that we are using elsewhere will simply stop working at these temperatures.
And just in case you were wondering how cold is it in space, here is a very nice explanation:
Snake traps, snake-sniffing dogs and snake-hunting inspectors have all helped control the population, but the snakes have proved especially hardy and now infest the entire island. Guam is home to an estimated 2 million of the reptiles, which in some areas reach a density of 13,000 per square mile — more concentrated than even in the Amazonian rainforests, the government says.
But brown tree snakes have an Achilles’ heel: Tylenol.
For some reason, the snakes are almost uniquely sensitive to acetaminophen, the active ingredient in the ubiquitous over-the-counter painkiller. If you can get a tree snake to eat just 80 milligrams, you can kill it. That’s only about one-sixth of a standard pill — pigs, dogs and other similarly sized animals would have to eat about 500 of them to get into any trouble.
A few years ago I posted the link to SnowCrystals.com, which had a whole lot of photographs of snowflakes. It’s time to have a fresher look at the beauty of those ice crystals up-close. Via kottke.org, I came across this Flickr collection of close-up images of snowflakes done by photographer Alexey Kljatov.
Some are extremely simplistic in structure. The others are the opposite – incredibly complicated. Some are by alone, all by themselves. Yet others are in groups. But all of them amazingly unique and beautiful. And available in larger image sizes too.