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Tag: Research

First LIBS Spectra From Mars!

Publishing a post after long long time, busy times! But couldn’t resist posting first LIBS (Laser Induced Breakdown Spectroscopy) Spectra from Mars! It is interesting to see Hydrogen lines at 656 nm (possibly from ice on Mars or water condensation from Mars atmosphere). Carbon line adjacent to it is doubtful and needs further analysis. I can try to write more details about it later when I get time. If anyone is interested how LIBS plasma looks in Mars environment as compared to earth, you can see it here.

Leave a Comment August 24, 2012

Science Is Beautiful: Season 2- From New Location

Time to restart my blog now! Time to analyze and discuss numerous scientific stories, share some pictures, videos. While the web address of this blog remains same, my physical location has changed. I have moved to Purdue University at West Lafayette, Indiana where I will be  be doing ultra-fast spectroscopy to understand laser and matter interaction. This week, for the first time I operated femtosecond laser and was able to create a  plasma 🙂 Now just thinking of creative ways to use  this new scientific tool I am learning. So, Science Is Beautiful-Season 2 starts from today with pictures from Purdue University after weekend snowfall.

 

Leave a Comment January 21, 2012

‘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

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:

DOI: 10.1126/science.1136091

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

Lost In The Crowd

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:

  1. 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.
  2. 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.
  3. 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.
  4. Wait For It…Wait For ItPatience 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.
  5. 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.
  6. Prime is in Nature Magicicada is 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.
  7. 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

1 Comment June 3, 2011

Global Warming Trend

Global Warming deniers should look at this plot depicting warming trends measured by four different institutes. Different agencies, independent measurements but the result remains the same– our earth is warming. 2010 has been declared to be the hottest year on record tied with 2005 by NASA GISS and NOAA. Japanese Meteorological Agency’s preliminary data shows that 2010 is the second hottest year. Absolute surface temperature is difficult to calculate, instead relative temperature is measured which is here referred to as temperature anomaly. Average temperature of a particular location is compared with average long term temperature (base temp) and the difference is termed as temperature anomaly. Different agencies use different base temperature, e.g. NASA GISS uses average temperature from 1951-1980 as the base temperature while Japanese Agency uses 1971-2000 as the base temperature. This may lead to some differences in the measurement by different agencies. Also, the way data is processed can lead to some differences in the temperature reported. This sometimes canlead to confusion in public as why the temperatures reported by different agencies are different and can give an impression that the temperatures reported are not accurate. If you look at the plot closely, you can see slight differences in the values, but the overall trend remains the same. Global temperatures are meaningful only when observed over a span of time rather than just for an year or two and you can clearly see the trend– the earth is warming.

Image and info credit: NASA Earth Observatory/Robert Simmon

1 Comment January 13, 2011

Kepler Mission Finds A Hot And Rocky Expolanet

Kepler Space Mission has found it’s first exoplanet, Kepler-10b. The announcement was made today in Seattle at the meeting of American Astronomical Society. It’s one of the smallest exoplanet discovered outside our solar system  and unlike other exoplanets found, this one is dense and rocky (or molten). It’s density is about 8.8 g/cc. The planet is 560 light years away, size is about 1.4 times that of earth and mass is about 4.6 times that of earth. It rotates very close to it’s sun, almost 20 times as close as Mercury is to our Sun, making it extremely hot and thereby makes it un-habitable (surface temperature is more than 2,500 F on the side which faces sun). I will try to write in more detail as to how the measurements of such planets are done (size, density, orbit radius etc.), probably tomorrow, meanwhile the  video below will give you a good idea about this new discovery. Looks like it’s going to be an exciting year in discovery of more exoplanets and maybe few of them will be in habitable zones.


1 Comment January 11, 2011

98.6 Degrees F, It’s The Perfect Temperature

98.6 degrees Fahrenheit (37 degree Celsius), that’s the number we all have learnt right since our childhood as the normal human body temperature, and anything above or below indicates that something is wrong with our body. This particular temperature (with slight fluctuations) is our normal temperature set point which our body tries to maintain. Fahrenheit initially designed the temperature scale with human body temperature as reference point and defined it to be 100°F, but later the reference point was changed to boiling point of water (100°C). Later in 1861, Carl Reinhold measured mean temperature of a healthy human body to be 98.6°F (or 37°C). Currently, most accurate number is 98.2°F (or 36.8°C) . Our brain regulates temperature of our body and keeps it regulated at the set point, which is very important for various chemical reactions to occur inside our body. Fever is defined as that state of body when the temperature set point is raised due to different causes while hyperthermia is defined as the state of body when temperature of the body increases without any increase in set point temperature (heat-stroke).

But why 98.6 degrees, why such a high temperature which is an energy intensive and costly affair. The answer lies in the cost and benefits of having high body temperature. Recent study by researchers at Albert Einstein College of Medicine have shown that per degree increase in body temperature reduces the number of fungi species which can infect the animal by about 6%. Thus by having high body temperatures, mammals have minimized the chances of getting infected and increased the survival rate at the cost of more energy intake. In a recent study, Dr. Casadevall  and Aviv Bergman have developed a simplistic first order mathematical model to estimate the optimum temperature considering the trade-off between metabolic costs incurred and benefits obtained in the form of increased resistance. The metabolic rate function is defined as B which is a function of body mass (m), while the benefit function is defined as F which is a function of rate of reduction in number of fungal species capable of infecting the animal (s~ 6% per degree rise in temperature based on earlier study).

Using these two functions, the fitness curve was plotted against body temperature and optimum T was found to be 36.7 °C or 98.06 °F!

You can access the full paper here.

Image credit: Flickr user Josh md | Used under creative commons license

Article and plot credit: Aviv Bergman and Arturo Casadevall: Mammalian Endothermy Optimally Restricts Fungi and Metabolic Costs, mBio 2010. doi:10.1128/mBio.00212-10

Leave a Comment December 29, 2010

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