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
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
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.
Till now, 283 posts have been posted in this blog– some of them good, some not so good, some got numerous hits wile some were lost in the crowd. I will be recycling some of these posts in coming days. In today’s post, I will be re-posting 7 posts which, according to me, were good ones but were lost in the crowd and didn’t get as many hits as they should have. So here they are:
The Courageous Life of Sophie Scholl-Now, who is Sophie Scholl? Sohpie Scholl was a member of non-violent student resistance movement against Nazi rule in Germany. The group called itself “White Rose” which was mostly based in University of Munich campus and its main activity was printing and distributing leaflets denouncing Hitler’s rule, which was equivalent to asking for death sentence in Hitler’s regime.
Invictus: The Unconquered Ones-Gandhi, Mandela, Martin Luther King were all Invictus, the unconquered ones, and they were the masters of their souls. The poem “Invictus”by William Henley probably describes very well the struggles of such souls amongst all the obstacles, still emerging victorious.
Hole-Punch Clouds: Mystery Solved- Any guesses what punched that hole in the cloud? Well, researchers have been looking for the answer for a while and airplanes have been the main suspect for this phenomenon.New research studyconfirms that planes, both propellers and jet planes , can cause formation of these shapes in the clouds named as “hole-punched clouds ” or “punched hole clouds” as a result of enhanced precipitation effect. These clouds have also been linked to UFO sightings in past, most famous one being inMoscow during October 2009.
Wait For It…Wait For It- Patience pays, Don’t give in to temptations, Have Self-control: we have been told since our childhood. Well, depending on how much self control or patience we have, determines our success in life. To study these effects and what mental processes lead to self control or delayed gratification, psychologist Walter Mischel conducted a very famous Marshmallow experiment with a group of few 4 year old kids in Stanford in 1960.
Time To Tickle You-Tickling is a very interesting sensation, it can burst you into laughter and on the other hand it can make you agitated as well. We all have tickled someone or have been tickled either by parents or siblings or friends. It’s also interesting to note that you can not tickle yourself implying that an element of surprise is very important.
Prime is in Nature-Magicicadais one of the genus of cicada species and are primarily found in eastern US and they have a very interesting periodic life cycle pattern. They follow either a 13 or 17 year life cycle pattern where after hatching from the eggs, and lying under the ground for 13 or 17 years, all of them emerge at once on the surface. Emergence of all the adult cicadas after 13/17 years is well synchronized.
Photoemission Delay Time-Photoelectric effect has been known to us for a long time. Heinrich Hertz first observed this phenomena in 1887 where a material absorbs electromagnetic radiation and emits electrons. While most of details are clearly understood, one aspect which has been missing is the delay time in emission of electrons after the matter absorbs photon.
Image credit: Flickr user Missbng | Used under Creative Commons License
After exploring surface of Mars for about 7 years, Spirit has been officially declared dead for all scientific purposes. Spirit started it’s Martian journey on Jan 2004 to carry out it’s scientific mission which was supposed to last for 90 days. But Spirit surpassed all the expectations and continued exploring Mars for another seven years. It stopped communicating on Mar 2010 and attempts were being made by NASA to communicate with the rover. Finally,NASA concluded it’s attempts of contacting Spirit today.
“We’re now transitioning assets to support the November launch of our next generation Mars rover, Curiosity,” said Dave Lavery, NASA’s program executive for solar system exploration. “However, while we no longer believe there is a realistic probability of hearing from Spirit, the Deep Space Network may occasionally listen for any faint signals when the schedule permits.” [NASA]
Great job Spirit! Here is xkcd’s take on spirited Martian journey of our beloved scientific instrument:
Image credit: 1) Artist concept of Mars rover| NASA/JPL/Cornell Univ 2)Xkcd
In order to make up for the reduced number of posts during the last month, here are some bonus videos for this weekend. The vidoes are so amazing that I couldn’t wait for the next weekend to post them. The first video is an amazing time-lapse video of the full moon (supermoon event), beautifully shot by Frédéric Lagléra in Tignes France. Great work Fredric and thanks for submitting the video to “science is beautiful” vimeo blog. Second video was shot by Norwegian photographer Terje Sorgjerd. He shot about 22,000 mesmerizing pictures of Aurora Borealis event (Northern Lights) and put together the pictures to create a breathtaking time-lapse video for us to enjoy and cherish. You can read my earlier posts (here and here) to understand the science behind the origin of green and violet colors as seen in Aurora Borealis. As the Sun is now entering into a more active phase after a period of lull, more such beautiful events will occur owing to strong solar storms.
The picture above is an X-ray image of supernova remnant, Tycho, produced from the explosion of a white dwarf star in our galaxy. The image has been taken by Chandra X-ray observatory. The supernova remnant is about 13,000 light years away from earth and is located in Cassiopeia constellation in the Northern hemisphere. If you ask, how big is the explosion, it’s roughly 55 light years across (1 light year= 9.5 x 10^15 m). This supernova remnant was first observed by Danish astronomer Tycho Brahe, in 1572 and that’s how it got it’s name.
Now let’s get to some science behind the image. The blue color seen on the rim of the circular blob is from high energy X-rays (blast wave which contains high energetic electrons), while the interior red color is from the low energy X-rays (which contain expanding debris from the supernova). The interesting phenomenon observed in this image is the presence of stripes in the outer regions of the exploding star. Such “X-ray” stripes have never been observed in any other supernova remnant.
These X-ray stripes are beleived to form due to high turbulence and magnetic field entglements as compared to surrounding regions. In these regions, the electrons get trapped and get energized and emit X-rays as they sprial along the magnetic lines. In the image below, the black lines are the magnetic field lines, while the red lines show the path of the electrion. The spacing between these stripes is determined by the radius of the spiralling high energy proton (path shown in yellow), the energy of which can be over 100 times larger than what can be gerenrated in Large Hadron collider! These high energy particles are believed to be the source of cosmic rays on earth. So that’s for the science behind this beautiful image!
In the wake of looming nuclear crisis, we keep hearing or reading about the units Sievert or Sv for the amount of radiation exposure. So what is Sievert and what to make of it when media reports that 0.6 μSv radiation per hour has been detected (as seen in the picture above).
Scientists use different terms to report the radiation measurement depending upon the context. For eg, unit Curie (Ci) or Becquerel (Bq) is used to measure the amount of radiation which is being released or emitted by a radioactive material, while unit rad or Gray (Gy) is used to measure the amount of radiations absorbed and deposited in the human tissue. A person’s biological risk which means the risk that person will suffer health effects due to radiation exposure is measured and reported in units rem (roentgen equivalent man) or Seivert (Sv). Biological risk depends upon the type of ionizing particles emitted (alpha, beta, gamma, X-rays) and their ability to transfer energy to the cells. Based on this energy transfer function, each particle has been assigned a Quality factor (Q). In order to asses the biological risk this factor is multiplied by the radiation dose measured.
So, 1 Sv = 100 rem = Q x rad
Are these nuclear disasters the only source of radiation dose to humans? No. we constantly get slight dosage of radiation from variety of sources including cosmic rays (more when we are flying), naturally occurring radioactive minerals in soil, medical X-rays etc. In order to get some sense of what these numbers mean, here are few typical numbers from various sources (CDC):
Hopefully these numbers will give us some idea the radiation exposures being reported in the media. So on average, we receive about 300-350 mrems (3-3.5 mSv) of radiation dose per year, sometimes even higher if we are undergoing medical treatments. International law permits exposure of about 2000 mrems per year for those who work with or around radioactive materials. Here is an excellent chart by XKCD and another by BoingBoing which can be helpful in understanding radiation exposure and health effects.
So how much are the radiations from the failed Japanese plants. It was reported that radiation level shot to about 0.8 rem per hour on March 15th. There have been conflicting reports on the correctness of amount of radiation exposure reported by various media as well as by Govt agencies. According to NRC, if a person is exposed to 500 rems of radiation at once, person will likely die without any medical treatment. Single dose of 100 rem will cause nausea and skin reddening and 25 rem of single dose can cause temporary sterility in men. However, NRC also says that if the radiation is spread out over time instead of being delivered at once, the affects are less severe.
More about how radiations are measured and the current status in Japan in later post.
Image credit: Boston.com/Bigpicture| AP photos|Kyodo News: A radiation detector measures 0.6µSv, exceeding normal day data on Mar 15 near Tokyo station.
May 20, 2012 1799 Honore De Balzac 1851 Emile Berliner 1908 James Stewart 1920 Betty Driver 1942 Lynn Davies 1944 Joe Cocker 1946 Cher 1961 Nick Heyward
