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Tag: Chemistry

Robert Bunsen: More Than The Inventor of Bunsen Burner

If you had googled today, you must have already seen the above Google doodle. This was Google’s way of celebrating 200th birth anniversary of Robert Bunsen who is known as the inventor of ubiquitous Bunsen burner. Anyone who has been to high school has used his namesake invention. It was not like burners didn’t exist before he invented his own version, but for his studies and experiments, he needed a hot, clean and colorless flame which other burners couldn’t provide. So he designed his own. The reason he wanted a colorless flame was because he wanted to study how different elements emit different colors of light when heated in a flame, in short he wanted to perform atomic emission spectroscopy, one of the first systematic spectroscopic studies. He along with Gustav Kirchhoff invented the first spectrograph in which they used prism to split the light emitted from the flame into different wavelengths and thus were able to identify the element present in the flame. He was able to detect Sodium, Lithium and Potassium. He also discovered new elements– Caesium  in 1860 and Rubidium in 1861. For studying cesium, he carefully and laboriously distilled 40 tons of mineral water to get 17 grams of cesium! He named these elements based on the color of light they emitted– Caesium after caesius in Latin which means “light blue” and Rubidium after rubidus which means “red.” Caesium today is used in atomic clocks while Rubidium gives the purple color in your fireworks.

Besides pioneering contributions to spectroscopy, he also developed gas- analytical techniques to analyze gases coming out of furnaces, volcanoes etc. He also invented jet pumps, ice and vapor calorimeters and Bunsen battery (predecessor to dry cells we use). He also found antidote to Arsenic poisoning which is still used till day– Iron oxide hydrate. Later in his life he focused mainly to study the problems in the field of geology and mineralogy. Thanks to Google Doodle for making us think about contributions Robert Bunsen made to the field of science and our daily lives in general.

Leave a Comment March 31, 2011

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. If delay exists, does the delay also depend on the energy level from which electron is being emitted? Until now, it was assumed that the photo-emission process is instantaneous. Recent study by researchers at Max Planck Institute of Quantum Optics in Munich, Germany and group of other collaborators , has been able to precisely measure the delay time in photoemission process using ultra-short time measurement technology. They used Neon atoms to study the phenomena. Neon  is more complex than Helium, but it was chosen because Neon is simpler to model theoretically and it also has higher photo-ionization cross-section resulting higher Signal-to-Noise ratio. They found out that that electrons leave 2P level subshell   Formula attoseconds after the electrons have left 2S subshell.  The delaytime of 21 attoseconds between electron emission from 2S and 2P seem to be very small, but it’s an important result as it shows that the process is not instantaneous, as it was assumed until now, and there is certain delay involved possibly due to electron-electron interactions. Scientists also performed complex theoretical computations to calculate the delay time and they came with a delay time 0f 5 attoseconds. The discrepancy can be attributed to multi-electron Neon atom system which makes it very difficult to make accurate theoretical computations. For experiments, two ultrafast laser pulses were used: extreme UV pulse (<200 attosecond duration) was used to eject electrons from 2S and 2P subshells while near infra-red pulse was used for time resolved measurements.

“These to-date poorly understood interactions have a fundamental influence on electron movements in tiniest dimensions, which determine the course of all biological and chemical processes, not to mention the speed of microprocessors, which lie at the heart of computers”, explains Ferenc Krausz, co-author of the study from MPQ. “Our investigations shed light on the electrons’ interactions with one another on atomic scale“. [ Press Release]

The results of the study was published in Science (June 2010, Vol 328, pp 1658) and abstract is as follows:

Delay in Photoemission

Schultze et al.

Vol. 328. no. 5986, pp. 1658 – 1662
DOI: 10.1126/science.1189401

Photoemission from atoms is assumed to occur instantly in response to incident radiation and provides the basis for setting the zero of time in clocking atomic-scale electron motion. We used attosecond metrology to reveal a delay of Formula attoseconds in the emission of electrons liberated from the 2p orbitals of neon atoms with respect to those released from the 2s orbital by the same 100–electron volt light pulse. Small differences in the timing of photoemission from different quantum states provide a probe for modeling many-electron dynamics. Theoretical models refined with the help of attosecond timing metrology may provide insight into electron correlations and allow the setting of the zero of time in atomic-scale chronoscopy with a precision of a few attoseconds.

Photocredit: Press Release/ MPQ/ LMU/ T. Naeser/ C. Hackenberger

Leave a Comment August 23, 2010

ICORS 2010

I will be traveling to Boston to attend International Conference on Raman Spectroscopy (ICORS 2010) from 7th Aug to 12th Aug. This is after 14 years ICORS is coming back to US and there are some very interesting talks and sessions in the program. Laser co-inventor and Nobel prize winner, Charles Townes, will be giving a talk on Thursday which unfortunately I wont be able to attend as I have to be back in Cincinnati by Thursday. There is a wide range of topics which will be covered- Raman Spectroscopy for biological systems and biomedical applications, analysis and characterization of Carbon nanotubes and other carbonaceous materials, Semiconductors and nanoparticles, femtosecond and attosecond spectroscopy and much more. Depending on available time, I will be posting some updates about interesting talks from time to time. And ofcourse about Boston as well !! I am excited about it, time to learn some new stuff.

Leave a Comment August 5, 2010

Auroras, Why Are They Green?

What you see here is the amazing image of Aurora (aurora australis to be specific or southern lights) taken by astronauts onboard International Space Center.  Isnt’t it beautiful! Auroras are result of the interaction between ions and electrons from the solar wind with Earth’s magnetic field and upper atmosphere. During Coronal Mass Ejections from the sun, high energetic ions are bombarded towards the earth. These ions migrate towards poles due to Earth’s magnetic fields, that’s why this phenomenon is seen mostly at Northern and Southern poles of the earth. These high energetic ions interact with Oxygen and Nitrogen of the upper atmosphere and excite them to higher energy levels. When the atoms fallback to ground state it emits light typical to particular atom. Oxygen emits at a wavelength of 558 nm (green) and at 630 nm (red ). Emission at 558 nm is more prominent and that’s how Aurora gets it’s greenish color. A slight tinge of red color can also be seen at lower left corner of the image.  Auroras in other colors have also been seen such as blue and purple but green ones are most prominent. Also, seen in the image is earth’s horizon, the limb, and the upper atmosphere (shown in blue).

This particular Aurora image is a result of a recent  coronal mass ejection activity in the sun which occurred during May 24, 2010. Our Sun has been surprisingly low in activity this year and scientists are puzzled as to what is happening to Sun. But there was some activity this month when four such mass coronal ejections occurred during May 22-May 24, 2010.  Here is the image of one such activity recorded during this period by NASA’s SOHO mission.  In the image, you can see the loop which is the mass of charged particles coming out of the sun’s surface; a disc has been used to cover the sun so that to get better image of the corona. The size and location of the sun’s surface  is indicated by the white circle. Truly amazing images and amazing phenomena. I will try to write in detail more about sun’s activity and it’s impact on earth sometime next week.

Photo credit: NASA Earth Observatory

2 Comments June 25, 2010

The Mortal Life Of Cells

I came across an interesting fact about how our cells grow and function, so thought of writing a quick post. Our body has close to 40-50 trillions of cells (most of which are Red Blood cells, while solid tissue cells consists of roughly 10% of the total cells). On an average we lose 2-3 million cells every second (a very crude estimate). But these cells are replenished by mitosis process where chromosome is replicated and cell divides into two and that’s how we keep growing and maintain the balance of cells. But the question comes how many times a particular type of cell can divide? Are they immortal and will they keep dividing for ever or is there an upper limit to it? The answer lies in something called Hayflick Limit , named after scientist Leonard Hayflick. According to this limit, a cell can divide only up to a certain number of times, after which it stops dividing. How many times a cell can divide depends on “telomeres” length which is a region of DNA  towards the end of chromosome. Every time a cell divides, telomeres gets shortened and the new cell has shorter length of telomeres. As the process continues, daughter cells have even smaller length of telemeres and eventually when telomeres is completely gone, cell division stops and that particular cell starts dying in our body. That’s how we age, and that’s how our body controls any malfunction or malignant growth too. Cancer cells have enzymes called  telomerase which is able to restore the telemeres length and thats how the cancer cells keep growing for ever. So, if scientists are somehow able to control the enzyme action in cancer cells, probably we will have cure for cancer someday. So, Hayflick limit is a good thing for us. Researchers who work in field of anti aging, are working on developing some chemicals or enzymes which can slow down the telomere depletion rate or in other words increase the Hayflick limit. But if asked to me, I will prefer to keep my natural Hayflick limit rather than induce some changes in my body by these chemicals or enzymes whichmight alter the Hayflick limit in such a way that my cells can become immortal.

People who work in field of cells must have sure heard the name of HeLa cells, the first line of immortal cells which have been extensively used in research. These are the cancer cells taken from a poor tobacco farmer Henrietta Lacks, without her knowledge, and has been used in research all over the world since 1951. These cells are still alive, even after Henrietta died in 1951, and recently a book was published by Rebecca Skloot- The Immortal Life of Henrietta Lacks. You can watch Rebecca’s interview talking about the book in the video below. Interestingly, one of the recent episodes of Law and Order titled “Immortal” ripped off the story of Henrietta Lacks, call it immortal or immoral? HeLa cells have been used for past 60 years for so many scientific discoveries including polio vaccines and many cancer related studies, without properly acknowledging Henrietta or her family, forget about any monetary benefits. More than 60,000 research papers have been published based on HeLa cells research. If you want to take a look in various scientific fields where HeLa cells have been used, click this image showing the flow chart of various research based on HeLa cells since 1951.

The Colbert Report Mon – Thurs 11:30pm / 10:30c
Rebecca Skloot

Photo Credit: Flickr user pong; used under Creative Commons License

1 Comment May 24, 2010

Laser Induced Healing

The title might be little deceptive, but maybe not. These days lasers can be seen in use everywhere, some examples being: laser pointers, laser shows, analyzing aerosols, eye treatments, inducing rains, cooling down the atoms and so on. If lasers can do everything, they can also stitch your wounds as well, right, without leaving any scars, no pain, no damage to surrounding tissues. Sounds excellent. Well, scientists have been working on a technique called Photochemical Tissue Bonding (PTB) where they use a photo-reactive dye which is applied to the tissue surface and then it’s illuminated with a laser for few minutes. The dye absorbs the laser energy, the energy is not very high to cause any thermal damage to the tissue, and it induces collagen molecules in the tissue to cross-link by formation of reactive intermediates. The dye which has been typically studied and used for this process is Rose Bengal which is a FDA approved dye and has been extensively used for liver treatments and also being studied for liver and eye cancer studies. Rose Bengal absorbs the light strongly around 530-550 nm (maximum at 550 nm) and hence a visible 532 nm laser can be used to induce the bonding process. The mechanism of bonding is not still understood clearly and that provides a good opportunity to study the process and optimize the process so that it can be applied for healing people.

Photo Credit: KOCHEVAR LAB At Wellman center

References: Microvascular anastomosis using a photochemical tissue bonding technique: Lasers in Surgery and Medicine  Volume 39 Issue 9, Pages 716 – 722
Electron Transfer Quenching of the Rose Bengal Triplet State: Photochemistry and Photobiology, 1997, 66(1): 15-25

Leave a Comment May 5, 2010

The Rain Maker: Laser-induced Water Condensation

No, I am not talking about John Grisham novel, rather I am talking about a new study published today in Nature Photonics which uses laser energy to induce rain! Researchers at Freie Universität Berlin, Université de Genève and CNRS France have developed a technique called Laser-induced Water Condensation where they use a high energy pulsed femtosecond laser to form a guided filament which can be used to induce water-cloud condensation in free sub-saturated atmosphere . They conducted laboratory as well as field experiments to test the technique and the researchers are very optimistic that with further optimization of various parameters, it can be used to seed the clouds and form rain in parched dryer parts of the world without any danger of any side effects to the environment. Usually, conventional techniques for seeding the cloud include adding silver iodide molecules to upper atmosphere or sodium, potassium, lithium based salts in lower atmosphere to induce cloud condensation. But theses techniques have issues due to side-effects it can cause to the environment. This new technique described in the current study has no such side effects. The pulsed femtosecond laser can form a long filament shaped plasma by altering the refractive index of the air and self focusing nature of such laser beams. These plasma filaments when interact with air molecules ionize the Nitrogen and Oxygen molecule and provide the seeding material for condensation process. In their lab experiments , the researchers were able to increase the volume of condensed water droplets by 50% by laser-induced process. You can see in the video here showing the effect of plasma filament on the number and size of condensed particles in the saturated chamber (230% saturation). The flashes you see are the result of increase in the scattering of probe laser due to increased size and number concentration of water droplets in the chamber due to laser-induced water condensation process.

Even though the researchers feel that with proper optimization and further study, this method can be used in real world, but  some researchers are not too optimistic about it due to certain issues. The major issue being the relative humidity condition, the lab experiments were performed at relative humidity of about 230% which is never the case in atmosphere ( maximum ~ 101 %). So, the lab results can not be expected to be achieved in the atmospheric conditions. To counter that, the researchers in current study also performed experiments in open atmosphere in Berlin and LIDAR data showed the enhancement in condensation process using laser. Another issue can be the laser span, in order to increase the laser-induced effect to larger volumes of the cloud, an effective laser spanning technique will be needed. Nonetheless, it’s an interesting study, atleast from the proof of concept point of view.
Source: Nature Photonics : 2 May 2010 | doi:10.1038/nphoton.2010.115

Picture Credit: Jean-Pierre Wolf/University of Geneva  and New Scientist

1 Comment May 3, 2010

Source of Water on Earth– Icy Asteroids?

It’s still not clear what led to formation of huge reservoirs of water on the earth’s surface. But recent discovery of ice on asteroid might be able to provide few answers or lead us to think in different direction about how our solar system was formed. Asteroids are basically failed planets and these huge chunks are remainants or you can say building blocks of our solar system. Asteroid belt lies in between Mars and Jupiter and these celestial bodies have largely remained unchanged all these past 4 billion years, unlike the planets, and so studying asteroids might provide clues to how our solar system evolved including the answer to the question “Why our Earth is blue?”. Scientists until recently thought that these asteroids are too close to the sun (orbiting at 297 million miles from sun) for them to retain any water on their surface, but these ideas have been debunked by few recent discoveries including the present one where scientists have found presence of water and organic materials on the asteroids surface. Recent study, published in latest edition of Nature, shows the presence of thin coating of ice and other organic compounds on asteriod 24 Themis by using absorption spectroscopy. This leads us to speculate that maybe these asteroids were the first source of water on earth’s surface when they smashed our dry earth and left huge reservoirs of water during the Late Heavy Bombardment period (LHB). Recently NASA’s instrument onboard India’s Chandrayan-1 spacecraft  discovered ice caps on the North pole of the moon as well by measuring OH species using combination of near IR and UV-Vis spectroscopic data. Here are some absorption spectra from the recent asteroid study by Rivkin showing the detection of water at 3.1 µm (0.4µm wide), C-H stretching at 3.4-3.5 µm, and aromatic compound stretch bands at 3.3 µm. (The spectra images have been linked to the article in Nature and so if you are not able to see the images, probably you might need Nature subscription to view it).

Reference: Detection of ice and organics on an asteroidal surface, Andrew S. Rivkin& Joshua P. Emery, Nature Volume: 464, Pages: 1322–1323 Date published: (29 April 2010) DOI: doi:10.1038/nature09028

Picture Source:Asteroid Illustration- NASA; Absorption Spectra- Nature©

Leave a Comment April 29, 2010

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