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 photon” You 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.
Leave a Comment June 9, 2011
Volcanoes And Lightning
This is an image from recent volcaninc eruption in Chile. On June 4th, Puyehue volcano started erupting sending plumes of volcanic ash as high as six miles leading to evacuation of more than 3,500 people and shutting down of the airports in the area. The ash has majorly affected nearby cities in chile and Argentina. The volcano which was dormant since 1960 also produced some spectacular and mighty lightning bolts (few miles long) as seen in the picture above. Such lightning shows have been also documented in other volcanic eruptions including Mt Vesuvius, Eyjafjallajökul, Mt St Augustine volcano in Alaska, Chaiten volcano in Chile and many more. But not all volcanoes lead to lightning display. Volcanic lightning can be roughly divided into three types depending on the length of lightning bolt and how and where they are formed: i) Large volcanoes which spew out large amount of ash deep into the sky can lead to formation of lightning bolts many miles long. ii) Mid range lightning bolts can sometimes come directly from the volcanic vents. iii) Small range sparks (few meters long ) can occur in the plume which are short lived (few milliseconds). But what is the main mechanism of volcanic lightning. The answer is not clear yet.
For lightning to occur, a potential difference need to developed and then an ionization channel need to be created for the charges to flow from highe potential to lower potential. But how do you create a potential difference in the volcanic cloud or ash plume? Charge separation is the answer according to one theory. Volcanic plume is extremely hot and energetic and collision causes particles to get charged. Positive and negative charged particles have different aerodynamic properties which lead to their separation in different zones in the volcanic cloud. Probably, positive charged particles settle down in the lower cloud while negative particles move in the upper regions of the cloud. This charge separation keeps on occurring until enough voltage difference has been created to form an ionization channel (streamer, leader head formation) and boom- lightning bolt occurs! Since the potential difference is between different regions in the clouds , you can see the bolts originating as well as ending up within the cloud itself. But again, this is just one of the explanations and the process is still not clearly understood. This doesn’t explain how lightning sometimes start from the vents, during the beginning of eruption itself, as in this short time it’s not possible for charge separation to occur. Interestingly, there has not been many scientific studies explaining the phenomenon. It was not until 2007, when scientific observations were documented in a Science paper where the authors studied Mt St Augustine eruption. Here is an abstract of the article:
Electrical Activity During the 2006 Mount St. Augustine Volcanic Eruptions
Thomas et al | Science 23 February 2007:
Abstract
By using a combination of radio frequency time-of-arrival and interferometer measurements, we observed a sequence of lightning and electrical activity during one of Mount St. Augustine’s eruptions. The observations indicate that the electrical activity had two modes or phases. First, there was an explosive phase in which the ejecta from the explosion appeared to be highly charged upon exiting the volcano, resulting in numerous apparently disorganized discharges and some simple lightning. The net charge exiting the volcano appears to have been positive. The second phase, which followed the most energetic explosion, produced conventional-type discharges that occurred within plume. Although the plume cloud was undoubtedly charged as a result of the explosion itself, the fact that the lightning onset was delayed and continued after and well downwind of the eruption indicates that in situ charging of some kind was occurring, presumably similar in some respects to that which occurs in normal thunderstorms.
I will try to find more details about the process and would add more information in my later posts. For now, here is one more picture from the Puyehue volcano.
Inage credit: 1) Boston.com/Bigpicture|Carlos Gutierrez/Reuters 2) Boston.com/Bigpicture|Claudio Santana/AFP/Getty Images
Leave a Comment June 9, 2011
Potrait of Endeavour And International Space Station
Here is an amazing picture of space shuttle endeavour parked at the International Space Station. The image was taken on May 23rd by ESA astronaut Paolo Nespoli while he was leaving the space station aboard on Russian spacecraft Soyuz. His spacecraft was at a distance of about 600 feet when this picture was taken. Endeavour helped in building up the station over the past decade and this was the last space trip of Endeavour. Truly an amazing image. By the way if you ever wondered how parking your vehicle in space would look like, now you got the idea! If you want more of this, here is a high quality video taken by Nespoli.
Image and video credit: NASA
Leave a Comment June 8, 2011
What Do People Search To Reach My Blog?
I dont know what algorithm Google uses to send people to my blog when people search for certain keywords, but Google analytics has been very generous to me in directing people especially those who are looking for Demetri Martin or Tim Tebow or Paul the Octopus.I have written just one post on each of them but it seems like people want more of them! People have also been searching Gliese 581g, ununseptium, Gandhi, India, Nobel prize winners and Lammert de Jong (my only blog interview) quite a bit as well. I just created the word cloud (shown above) of recent search words which people have used to reach my blog. Just for fun, I also created another word cloud of the phrases and words I used in my last 10 posts (shown below). It’s fun, you too can create your own word cloud at wordle.net!
Leave a Comment June 6, 2011
Green Nobel Prize Winners For 2011
Every year on April 22nd we celebrate the Earth Day and on the same day Goldman Environmental prizes are awarded to grass root environmental activists in order to recognize their efforts as well as to highlight the importance of protecting our environment, endangered ecosystems, species, and to promote sustainability and influence environmental policies. These awards are also called as Green Nobel prizes. On the occasion of World Environment day, let’s take a look at this year’s award winners and their stories (video playlist showcasing the work of all the winners is embedded at the end of the post).
Africa
RAOUL DU TOIT, Zimbabwe
Raoul du Toit coordinated conservation initiatives that have helped to develop and maintain the largest remaining black rhino populations in Zimbabwe. “Conserving rhinos saves much more than the rhino themselves – they are flagships for biodiversity and for national development based upon sustainable wildlife management in Africa.”
Asia
DMITRY LISITSYN, Russia
Dmitry Lisitsyn fought to protect Sakhalin Island’s critical endangered ecosystems while also demanding safety measures from one of the world’s largest petroleum development projects. “The last wild, untouched salmon rivers, which we are trying to save on our island, are the embodiment of beauty, power and freedom of wild nature. I’m convinced – if we would lose them, all our planet would be poorer, because we will never be able to get them back”
Europe
URSULA SLADEK, Germany
In response to Germany’s expanded reliance on nuclear energy, Ursula Sladek created her country’s first cooperatively-owned renewable power company. “A renewable energy supply helps reduce nuclear dangers as well as climate change and therefore is central for the future of mankind.”
Islands
PRIGI ARISANDI, Indonesia
Biologist Prigi Arisandi initiated a local movement to stop industrial pollution from flowing into a river that provides water to three million people. “Protecting our water quality is important work to do, but it is more important to guarantee that water resources will be available for the next generations, because we do not want to be called a greedy water robber generation by our grandchildren”
North America
HILTON KELLEY, USA
Now leading the battle for environmental justice on the Texas Gulf Coast, Hilton Kelley fights for communities living in the shadow of polluting industries. “I speak up for the disadvantaged because it is my duty, it is the duty of all mankind to help those in need, those who have no voice, no way of helping themselves. Having compassion for others in adverse situations is the very thread that creates a civilized and just nation, a just society.”
South & Central America
FRANCISCO PINEDA, El Salvador
Living under the constant threat of assassination, Francisco Pineda led a citizens’ movement that stopped a gold mine from destroying El Salvador’s dwindling water resources. “My work is as an environmentalist; this is the principle for my life. When I began to understand the impact of the mining exploration, I couldn’t stay quiet.”
Image credit: Inhabitat.com
Leave a Comment June 6, 2011
Weekend Video: A Love Story… In Milk Cartons
On the occasion of World Environment Day (June 5th), this edition of “weekend video” showcases a beautiful and thought-provoking love story, but here the characters are a bit unusual- two milk cartons. In 2 min and 11 sec, the animators deliver a beautiful story with strong message of recycling and reducing garbage. The movie has a sad ending but if you want to see a happy ending you can take certain steps – first by informing yourself and then by taking appropriate steps of reducing waste and your carbon footprint . The movie was commissioned by Friends of Earth, UK and beautifully conceptualized and created by folks at Catsnake.com.
Leave a Comment June 5, 2011
