Wednesday, June 19, 2013

Light breaks up to cloak gaps in time

Method could hide messages without sender's knowledge

A device that manipulates light to open up small gaps in time has crept toward implementation outside the lab. Detailed June 5 in Nature, it could soon improve security over fiber-optic lines or improve data streaming rates.

“It’s exciting to see this exotic manipulation of light and its applications for communications and data processing,” says Alexander Gaeta, a Cornell University physicist who demonstrated the first time cloak two years ago (SN: 8/13/11, p. 12).

The term “cloak” can bring to mind Harry Potter-esque materials that hide an object at a specific point in space. These cloaks, a hot area of research since they were proposed in 2006, manipulate light so that an observer cannot see a stationary object.

Often in physics, what goes for space also holds for time. Last year Gaeta’s team showcased that truism by developing a cloak that hides events during a fixed time interval. A specially designed lens split light beams passing through a fiber into two segments. The trailing segment of light lagged behind the leading one by up to 50 trillionths of a second, creating a gap of total darkness between them. When Gaeta fired a laser at the fiber, the laser shot was undetectable because it had passed through the 50-picosecond interval of invisibility. Finally, Gaeta set up another lens to stitch the light segments back together, ensuring that the light beam emerged from the fiber looking exactly as it did at the start.

After reading Gaeta’s study, Joseph Lukens at Purdue University realized he could improve the technique. He designed an apparatus using off-the-shelf equipment that forced light to interfere and create repeating gaps of darkness at fixed temporal intervals. Each 40-picosecond gap was sandwiched between about 40 picoseconds of light, meaning that the time cloak was on roughly half the time.
Lukens’ study demonstrates how a time-cloaking device could eventually allow law enforcement or the military to prevent a nefarious person from communicating without the person’s realizing it. Just as the time gap in Gaeta’s experiment made the laser undetectable, the gaps created by Lukens’ cloak can conceal digital data. Lukens’ team tried to inject an electrical signal of 1s and 0s into the fiber, a task that would be no problem without a cloak, but the message never got encoded into the light beam. The receiver would assume that no message had been sent.

 Source: http://www.sciencenews.org/view/generic/id/350852/description/Light_breaks_up_to_cloak_gaps_in_time

Tuesday, June 18, 2013

The blog reopens!

Oh my! A year already?
After a very long and busy year between faculty books and work i found myself bored to death and with nothing more to do... So i decided to reopen the blog!  I'm sorry about having left you for SO long!

This I promise to you all:


Friday, January 13, 2012

Dunbar's number

The Dunbar's number is, according to the anthropologist Robin Dunbar, the theoretical cognitive number of individuals that can develop fully in a given system. He theorizes that this value (of approximately 150 individuals), its related to the size of the brain neocortex, and his processing capacity.
The primatologists noted that because of their highly sociable nature the non-human primates have to maintain personal contact with the other members of his social group. The number of members with who a primate can maintain said contact seems to be restricted by the size of the neocortex, and that suggests that there is an index of group size relative to the specie. So in 1992 Dunbar used the correlation observed in primates to predict the size of the social group in humans. He predicted a size of 147.8 group members, usually represented as 150.
Dunbar compared this prediction with observable human groups and noted that the groups fall in three categories, of 30-50, 100-200, and 500-2500.The research of Dunbar on the size of tribes and villages seemed to corroborate his prediction: 150 was the estimated size of a village farmer of the Neolithic; 150, as the point of break and separation of a hutterite settlement and 150 as the basic size of a military unit in ancient Rome and in modern times since the 16th century.
Dunbar theorized that a group with a size of 150 persons needs to have a very high incentive to stay together, thus 150 members groups only occur due to an absolute necessity, for example, aggressive economic pressure. For a group this size to maintain such cohesion, he speculated was needed to dedicate a 42% of the time to socialization; a dispersed group would have fewer ties, meeting less frequently.
Dunbar proposed also that the language may have generated as an easy way to socialize, because without language the humans would have had to occupy almost half their time socializing; the language may have allowed societies to remain cohesive, reducing the need for physical and social intimacy.
It's considered that -according to Dunbar's theory- in small-scale (less tan 150 individuals) most social orders could function properly, but due to population growth, problems arise due to the difficulty of maintaining properly controlled relations between individuals. This theory also applies to problems of overpopulation, because the further away a group moves of the hypothetical limit of 150 in any delimited system, its more likely for conflict to grow.

Wednesday, January 11, 2012

Pandora's box

In greek mythology, Pandora (Πανδώρα) was the first woman, made by order of Zeus to introduce evil in human life after the titan Prometheus stole the fire that the sun god carried on his chariot and gave it to the humans.
The first two appearances of Pandora in Greek literature occur in "Theogony" and "Works and Days" both works of Hesiod. When mortals and Immortals separated, Prometheus hatched a deceit so that in the future, in the making of sacrifices to the gods, they could keep the meat and viscera for themselves. Zeus, angered by the scheme, denied fire to men, but Prometheus stole it for them.
Zeus ordered Hephaestus to model a clay image with the figure of a lovely maiden, similar in beauty to the immortal, and to give life to her. But while he sent Aphrodite to give her grace and sensuality and Athena along with the Graces and the Hours to give her domain of the arts related to the loom and garnish, Hermes job was to sow lies, seduction and a voluble character in her. This all in order to set up a "beautiful evil", a gift that men are glad to receive, actually accepting countless misfortunes. Then Zeus sent her to the home of Prometheus and his brother Epimetheus, who despite having been warned of the impending vengeance of Zeus accepted his gift and married her.
Hesiod states that mankind have lived free of fatigue and disease, but Pandora opened a jar that contained all the evils (the expression "Pandora's box" is a deformation Renaissance) releasing all human misfortunes. The amphora was closed just before that hope was liberated.
There are other versions of the myth which tell the jar contained goods and not evils. The opening of the jar caused the goods to fly back to the mansions of the gods, removing themselves from the life of men, who live on only afflicted by evil... and who could only keep hope.


Monday, January 9, 2012

Changes

Im changing the whole look, url and topic of this blog; I realized that it was limiting me and that it would be difficult to write always about the same topic. I can now write whatever i want!.

Okay, to the matter at hands: I'm not a very good designer (Heh!, thats funny, i studied design to some degree) so im asking for your help. What do you think of the new look of the blog?, what do you think i can change for better?. What subject do you think i should write about in the next post?. Im waiting your comments!

Tuesday, January 3, 2012

Pavarotti Masterclasses

Today i bring to you the vids of a masterclass Pavarotti gave in 1979 at Juilliard , where he coaches top young singers, guiding the students through the elements of breath control, phrasing and interpretation.








Thursday, December 29, 2011

Opera Boston will cease operations on January 1 because of deficit.

Opera Boston's board chair and president announced that the city's second-largest opera company intends to permanently cease operations on January 1, 2012.

In a press release the company declared that in the face of an “Insurmountable budget deficit” and insufficient fundraising amid a difficult economic climate, informed the staff on December 22 that the opera would cease to function. The board claims to have taken the responsible decision, being it to work with their creditors. The company hasn’t announced whether ticket holders to February and April performances will receive refunds.

This is a great loss to Boston arts community: the company was greatly known for its performances of modern operas and presentations of lesser-known works…