17 December 2007

Balene ucigase vanand in grup

Trei orca colaboreaza pentru a face un val suficient de mare incat sa dea o foca jos de pe un iceberg (2min40s):
The behaviour was first seen in 1979, but at the time it was considered a one-time moment of orca ingenuity. Now, Ingrid Visser of the Orca Research Trust in New Zealand and her colleagues report on six further observations of the animals using group hunting behaviour to divide ice floes, push them into open water, and create waves to wash animals off them into their waiting jaws. The behaviour has been seen only along the Antarctic Peninsula and nowhere else in the world, they note, including other icy orca habitats in the Arctic and Antarctic. [Visser, I. N. et al. Mar. Mamm. Sci. doi: 10.1111/j.1748-7692.2007.00163.x (2007).]
Ceea ce e cel mai spectaculos la comportamentul asta e faptul ca arata ca orcile sunt capabile sa separe actiunile in termeni de mijloace si scopuri si ca sunt in stare sa se vada unele pe altele ca agenti (sa inteleaga ce scopuri are altcineva). Pana acum nu era confirmat decat ca cimpanzeii mai sunt in stare sa faca asa ceva (in afara de oameni). De asemenea, balenele ucigase se recunosc in oglinda (chiar si o oglinda extrem de mica fata de dimensiunile lor): Tehnicile de vanatoare sunt probabil invatate si fac parte din cultura lor. Se pare ca diferite grupuri de orca au culturi diferite. De pilda tehnica prin care orcile prind foci de pe uscat sarind pe plaja e invatata:
Hunting school Both the beaching and the wave hunting seem to be techniques that pod elders teach to younger animals. The Argentinean orcas have been seen nudging youngsters onto the shore, encouraging them to try the tactic, often coming up alongside to demonstrate. In the group at the Antarctic Peninsula, young orcas are often present during the hunt, and adults sometimes put living seals back on the ice after catching them, seemingly so that the young can have another try. “This is orca culture,” says Visser. [...] Orcas (Orcinus orca) are not considered an endangered or threatened species; they are found in all the world's oceans. Some local populations, however, are threatened by changes to their habitat. Whether subsets of orcas with unique cultures should be considered separately is a matter that has not really been dealt with, he says. “Distinct social populations with specialized traditions are far more at risk than the genetic population, and our conservation policies need to reflect that,” says Astrid van Ginneken at the Center for Whale Research in Friday Harbor, Washington.
Fact about orcas:
Orcas have been known to feed on over 25 different species of whales and dolphins, including some that are much bigger than themselves (sperm whales, gray whales and even blue whales). Not all orcas eat other mammals though. The resident population off Vancouver Island, for example, eat fish, and their favourite food is salmon. Male orcas generally don't live as long as females. In the wild, males average 35 years or so, maximum 50-60 years, females average 50 years, maximum 80-90 years. However, one male, known as ‘Old Tom’ was reportedly spotted every winter between 1843 and 1932 off New South Wales, Australia. This would have made him at least 89 years old! Once in captivity, an orca's lifespan is drastically reduced to an average of only 5 or 6 years.

06 December 2007

Auto-organizare in fluide feromagnetice

Al doilea experiment e chiar tare.
A fluorocarbon-based ferrofluid, with about 400-G saturation magnetization and low field magnetic susceptibility of 3, is placed within a glass Hele-Shaw cell of 1.1-mm gap. Magnetic fields are applied that have in-plane clockwise rotating and dc axial magnetic fields. The ferrofluid is surrounded by a 50/50 mixture of isopropyl alcohol and deionized water, which prevents ferrofluid wetting of the glass plates. In all cases, the rotational field strength is 20 G rms, and the frequency is 25 Hz. The dc magnetic field will be increased from 0 to 100 to 200 G. The first experiment uses a 50-µl drop of ferrofluid. The dc axial field is first increased to 100 G, and then the clockwise rotating field is turned on. The ferrofluid drop is circular before the magnetic field is applied. When the dc magnetic field is applied, the ferrofluid drop forms a spiking labyrinth pattern. Then the clockwise rotating field is applied, and the spikes begin to curl in on themselves, forming a smooth spiral pattern after some of the spikes are absorbed into the larger structure. The smooth spirals form from viscous shear as the clockwise rotating magnetic field causes counterclockwise flow on the outside ferrofluid surfaces, which return on the inside surfaces. The second experiment uses a 200-µl drop of ferrofluid. First, the clockwise rotating field is applied, which causes a counterclockwise flow that holds the circular fluid drop together without spikes. Then a 100-G dc axial field is gradually applied. This results in the ferrofluid drop appearing to expand before a phaselike transition at a critical dc magnetic field strength around 100 G. Careful observations show that the pattern forms at slightly less than 100-G dc field under a thin ferrofluid coating on the top glass plate, which then abruptly peels away at slightly increased dc axial magnetic field. The magnetic field is then increased from 100 to 200 G to form an intricate internal pattern surrounded by a circle of ferrofluid with spiraled arms. The second experiment is repeated again three more times under essentially identical conditions, with common features but it appears that the fine features are different each time.

Care-i faza cu mecanica cuantica

04 December 2007

"Nu religiile sunt violente sau pasnice, ci oamenii"

Lewis Black - Anticipation

Chimpanzeii au memoria mai buna decat oamenii

Link
Dr. Matsuzawa and a colleague, Sana Inoue, first trained chimps to recognize the numerals 1 through 9 in sequence. Ai, the first chimp trained, an adult female was found with a memory capability equal to that of adult humans. When the researchers went to see if there was a difference with chimps younger than 6, the animals had a touch screen where scattered numerals appeared for up to two-thirds of a second and were then masked by white squares. With the shortest exposure time, about a fifth of a second, the chimps had an 80 percent accuracy rate, compared with adult humans’ 40 percent. Dr. Matsuzawa said the ability reminded him of the phenomenon called eidetic imagery, in which a person memorizes details of a complex scene at a glance. This so-called photographic memory is present in a very small number of children, and is often associated with autism. Dr. Matsuzawa speculated that perhaps somewhere back in common evolution, humans and chimps had this ability. But humans lost it because they gained something else, communicating through a complex language. As Ai demonstrates, adult chimps lose the ability, too. Dr. Matsuzawa suggested that as the chimps age, their memory capability is otherwise occupied.
BBC Video