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The Network Effect

Why is social networking via web so effective as compared to snail-mail, email, TV or phone? The reason lies in the structure of network and connections it allows to form (see the plot below). Take for example television network , it’s a one-to-many type of network and the number of possible connections such a network allows depends on how many people own/watch TV. Such networks are like one-way traffic where users don’t have any capability to interact with other users in the network system. So basically it’s networking capacity scales as a function of N, where N is the number of people (Sarnoff’s Law). Emails and phones allow multiple connection possibilities between people in the network which scales as N^2-N (Metcalfe’s Law). Social networking is just completely another beast which expands exponentially with the size of people in the network as 2^N-N-1 (Reed’s Law). Social networking allows formation of groups and sub-groups and there lies the immensely powerful network effect. In a group of N people, you can from 2^N such groups and thereby the potential networking capacity increases exponentially. That’s what Facebook and other social networking websites are trying to capitalize on. How strong are these networks and connections, that’s a different story and will be subject of my other post sometime later.

Top image credit: Facebook | Paul Butler

Leave a Comment June 17, 2011

Doubly-True Anagram

Here is one of the coolest anagram I have ever seen. Anagram is basically a play of words where by re-arranging the words or phrases you create another words or phrases, only catch is that you have to use each alphabet just once. Mike Kieth used names of sixty elements from the periodic table to create this magic, 30 elements on each side of the equality. But the anagrammy didn’t end just with the words.  If you replace each element with its atomic number, the equality still persists in terms of the sum of the numbers. He won the best Anagrammy award in 1999 for the same. Doubly-true Anagram!

Leave a Comment June 16, 2011

Endeavour Lift-off: Up And Close

Here is a beautiful Endeavour lift-off video compiled by Chase Heavener. He used videos released by NASA which were taken by 4 cameras attached to the twin-rocket boosters of the space shuttle which made it’s last journey to space on May 16th. He put all the videos side by side so that we can take a look at all the action simultaneously. It’s fun to watch when rocket boosters detach at 2:26 and shuttle just flys off into the space. It’s simply beautiful to watch sunlight glistening off the surface of the shuttle in camera 1 (from 2:05-2:25). You can watch all the videos separately here.

Leave a Comment June 15, 2011

Motion And Phases of Moon

While people are enjoying today one of the longest lasting lunar eclipse since 2000 (about 100 minutes long), let’s watch this beautiful video created by folks at NASA Goddard Space Flight Center (see below) using data collected by Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter (LRO). In the video you can see various phases and movement of moon during the course of one year; one month of movement has been compressed into 12 seconds. As we know, we are able to see only one face of the moon from earth (moon and earth are phase-locked– rotation time of moon is same as it’s revolution time around the earth- about 27 days), in the video it is clearly evident that only one side is visible to us. Since we get to see the moon from different angles owing to it’s tilt and elliptical shape of the orbit, in the video it appears to us as if moon is wobbling. In technical terms we call that wobbling as “liberation”. Because of liberation, we are able to see little bit more than half of the moon’s surface, close to 60%. Due to elliptical orbit, moon also appears to rock back and forth from us (perigee- nearest position, apogee- farthest position). You can also observe different phases of moon such as new moon and full moon and their variations in different months. Enjoy the video, I will be uploading some cool videos or pictures from today’s lunar eclipse event later on.

Video/Image credit: NASA/Goddard Space Flight Center Scientific Visualization Studio

Leave a Comment June 15, 2011

Weekday Video: 3-Way Street@NYC

Traffic in big cities are a mess. People who have traveled to Rome or Mumbai or Miami know what crazy traffic means. New York traffic is not that crazy as compared to some other cities in the world, but this video by Ron gives a bird-eye view of one of the NYC intersection and shows how bikes, pedestrians, cars, trucks juggle their way out, sometimes getting too close. The video is a creative approach of educating people about how little changes in habits while on streets could reduce traffic accidents and congestion and make everyone’s life a bit easier. Good job Ron.

Leave a Comment June 15, 2011

How Do Scientists See The World?

Image credit: Abstruse Goose A Web comic | Used under Creative Commons License

1 Comment June 13, 2011

‘Living Laser’ Created Using Jellyfish Protein And Human Cell

In a new study published today in Nature Photonics, scientists from Wellman Center for Photomedicine and Harvard Medical school have developed a “living laser” by using biological materials- human cell and jellyfish fluorescent protein. In order to get coherent beam of light from a lasing device, three things are required- a pump source (typically flash lamp,  electric current or other laser source), a ‘gain media’ for amplifying the source (optical gain) and an ‘optical cavity’ for concentration and alignment of the laser beam. Typically, crystals, dyes, gas mixtures and even alcohol have been used as gain media to amplify the light. Pumping source produces population inversion in the gain media  wherein majority of the atoms and molecules are in excited state. When a photon of appropriate wavelength interacts with such a system of atoms/molecules, stimulated emission occurs. In a very novel approach, researcher Malte Gather has used Green Fluorescent Protein (GFP) and inserted the protein in living human embryonic kidney cell. Bioluminiscent GFP was  first isolated from jellyfish in 1962 which ultimately resulted in Noble prizes for it’s discoverers. The kidney cell-GFP combo (gain medium) was then  kept in between an optical cavity made of mirrors kept 20 microns apart. The dimension of single cell gain media was also about the same. When researchers hit the cell with low energy pulses of blue light using a microscope, typical diffused ordinary fluorescence was observed. But after reaching a certain threshold of input energy (~0.9 nJ), the light output from the cell changed drastically and resulted in bright, directional and narrowband emission of green light, which are the characteristics of a laser beam. Certain regions of cell showed intense lasing action (as shown in picture above) which occurred at different but close range of wavelengths (~514-519 nm). Researchers also reported that even after prolonged lasing action, the cell was still alive. The lasing action lasted for few nanonseconds and was easily detectable. The cell was able to lase about 100 pulses at excitation pulse energy of 50 nJ after which photobleaching occurred and depleted the GFP. But an interesting aspect of GFP infused cell is that the cell is able to heal itself and replenish GFP with time.

Here is an output emission spectra of the laser filled with purified GFP solution when pumped using different wavelengths of light. As can be seen that the output spectra is independent of the pump wavelength. This spectra tells two things i) independence of excitation wavelength on the emission rules out any stimulated scattering process as an explanation for lasing action by GFP, ii) FWHM ( Full Width at Half Maximum) of about 12 nm signifies the presence of  simultaneous oscillations of various longitudinal modes.

Next figure shows that replacing the GFP solution with GFP-transfused cell resulted in much narrow output spectra. At energy threshold of 0.9 nJ, single emission peak was observed at 516 nm (FWHM <0.04 nm). As the energy was increased, multiple emission peaks were observed which can be attributed to multiple longitudinal oscillation modes. The spectral spacing between these emission line was in the range of 5 nm.

Researchers speculate that the resulting light could be used to study various intercellular processes. Before producing output light, the light travels several times through the cell placed inside the optical cavity and the resulting lasing light should contain information regarding the intercellular processes. Another possible use could be to produce such lasing beams inside the body itself to kill certain cancerous cells .

Creators of living laser, Yun and Gather,  have some broad and speculative ideas about how the technology might be used.

They suggest that biologists could turn cells of interest into lasers to study them. The light produced has a unique emission spectrum related to both the structure of the cell and the proteins inside it. “By analysing the pattern you can get some idea of what is happening inside the cell,” says Yun.

The researchers also suggest possible medical applications. Doctors today shine lasers into the body to gather images or to treat disease by attacking cells. Yun thinks that lasers could instead be generated or amplified inside the body, where they could penetrate the relevant tissues more deeply. [Nature News]

Image credit: 1) Malte Gather | Nature Photonics | Wired 2) From the supplement files of the article provided on Nature website 3) Snapshot of the plots as seen at Nature website

Reference: Single-cell biological lasers: Nature PhotonicsYear (2011) DOI: 10.1038/nphoton.2011.99

Leave a Comment June 13, 2011

Origin of Word Photon

When do you think was the word “photon” first coined? Your first guess might be somewhere around 1900-1910, when Einstein and Planck introduced the idea of light quantum or das Lichtquantas as Einstein called them. But interestingly, neither Enistein nor Planck coined the word photon. The word photon was introduced by chemist Gilbert Lewis in 1926 when he wrote a letter to Nature magazine titled ” The conservation of Photons”. The letter was published in December 1926 issue of Nature magazine. In the letter he introduced his hypothesis “we are dealing here with a new type of atom, an identifiable entity, uncreatable and indestructible, which acts as the carrier of radiant energy and, after absorption, persists as an essential constituent of the absorbing atom until it is later sent out…… I therefore take the liberty of proposing for this hypothetical new atom, which is not light but plays an essential part in every process of radiation, the name photonYou can read the complete letter here. His theory and explanation about light failed but the word ‘photon’ he introduced, survived.

The word photon can be broken down to Greek word phōs, which means light. Phōs can also be related to Sanskrit word bhā or ābhā which means light. Other words originating from phōs were already in use by that time (photo, photograph, photometer). I plotted frequency of occurrence of words –photon and photograph– in books during the years 1800-2000 using Google ngram which gives us an idea of the evolution of both the words. As you can clearly see, photon became popular after 1926 while the word photography was already in vogue by that time. But it’s interesting to see a hump in photon curve during 1900-1910, same time period during which Planck and Einstein presented their idea of light quantum. I don’t have an explanation for that, whether it’s an artifact from Google ngram data sampling or whether the word photon was used sometime even earlier than 1926, but it would be interesting to investigate.

1 Comment June 9, 2011


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