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Satellites as guides Molecular
walker
THIS UNIVERSE
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Satellites as guides Like the Internet, Global Positioning System (GPS) has military origins, though now it is extensively used in civilian applications. If you are lost in Delhi, and who doesn't need a bit of help in the nation's Capital, you just have to seek assistance from your latest mobile phone and you will find out not only where you are but also how to get to your destination! Thus, satellite navigation is a force multiplier that gives distinct advantages to those who use it. Since it was developed by the US military, they did not want to share it with anyone else. In time, civilians were allowed to use GPS, but the system has a called "selective availability" feature through which, if the US military wants, it can introduce errors in the publicly available navigation signals, while allowing selected military receivers to get accurate information. This feature is currently disabled. While many countries have tried to set up GPS systems, the only fully functional and available global navigation satellite system belongs to the USA which has put up a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails) in six different orbital planes. Each of these 3,000 to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits panned such that at any time, anywhere on the Earth, there are at least four satellites "visible" in the sky. A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on the mathematical principle of trilateration. Basically, your GPS receiver draws a sphere around each of three satellites it can locate. These three spheres intersect in two points — one is in space and other is on the ground. The point on the ground at which the three spheres intersect is your location. As you can imagine, other nations have tried to put similar systems. Russia's competing system GLONASS is the most complete one, but it is not widely used. The European Union's Galileo positioning system is in a stage of initial deployment. Recently, India and China have announced widening of their own navigational systems, however, as of now, most of the world depends on the US system. GPS has been in operation since 1978. Civilian use of GPS was allowed following a tragedy. In 1983, a Korean Airlines plane was shot down after it strayed into Soviet airspace. Soon thereafter, President Ronald Reagan made the GPS freely available for civilians the following year. With ever-decreasing cost and increasing portability of GPS devices, the system has found widespread civilian use, not just as an aid to navigation, but also for making maps, surveying land, and as we noted before, even helping drivers get to their destination. We must remember, however, that a GPS receiver has to have a clear line of sight to the satellite to operate, so dense tree cover and buildings can keep it from getting a fix on your location. Many applications have been developed around the information that GPS provides and only recently Nokia has introduced phones in India with GPS capability, and support in the shape of Nokia Maps, along with various features, like the nearest petrol pump, hospital, shopping center, etc., all this with voice-guided navigation. MapmyIndia provides the maps which are used by various mobile phone vendors. Microsoft India recently launched Live Search Maps for India which has been developed by the company's India Development Centre (IDC) in Hyderabad. Microsoft's map services offers detailed listings and street maps for nine cities, business listings across 29 cities and access to highway networks to 20,000 cities and towns. The nine cities include the four metros along with Bangalore, Hyderabad, Pune, Ahmedabad and Jaipur. We have seen how a system evolves far more than the limited purposes that start its development. With the opening up of GPS, millions are finding uses far beyond what the system was originally intended for. What was designed to make smart bombs more accurate is today being used to make shore that children can find their way home. That's human ingenuity. |
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Molecular
walker Nature has exhibited all around us the controlled motion from molecular levels (i.e. functioning of life) to large levels (i.e., the functioning of the universe). Man is always on progress to mimic these miracles scientifically. It was a great achievement of mankind to have controlled motion of machines at macro-level and could design successfully sizable, efficient and controlled transport vehicles. But with the development of nanotechnology he (Man) is trying for controlled manipulation of transport properties of matter at molecular and atomic scales.
With the development of nanocars (based on molecular motion), chemists two years ago could move a molecule straight on a flat surface and now are able to force this walking molecule to carry packages like two CO2 molecules. It resembles the way nature does it as in the human body; the molecule hemoglobin carries oxygen from and carbon dioxide to the lungs, thereby allowing us to breathe — and to live. Just like human, this nano-worker is slower when it carries other molecules. The researchers think their discovery will lead to many fruitful applications for mankind in near future. We all know that ordinarily, molecules move in every unpredictable direction when supplied with thermal energy. Researchers are working on a project which would convert such random thermal oscillation into directed motion and in 2005 the molecular walker was invented. Prof. L Bartels and his colleagues at the University of California (USA), guided by theorist Prof. (Ms)Talat Rahman of Kansas State University, for the first time, created a organic molecule — anthraquinone or 9,10-dithioanthracene (DTA) (chemical formula: C14H8O2) containing a chain of three benzene rings, with two oxygen atoms attached to the central ring, one on each side called linkers that act as feet configured in such a way that only one foot at a time can rest on the substrate (Figure 1). DTA is a derivative of anthracene with an appearance of yellow or light gray to gray-green solid crystalline powder. It is insoluble in water or alcohol, but dissolves in nitrobenzene and aniline and is chemically fairly stable under normal conditions. DTA only moves along one line, however, and retains this property even if pushed or pulled aside with a fine probe. Similar to a human walking, where one foot is kept on the ground while the other moves forward and propels the body, the molecule always has one linker on a flat surface, which prevents the molecule from stumbling to the side or veering off course. During testing, the molecule took about 10,000 unassisted steps. Alternating the motions of its two "feet," DTA is able to walk in a straight line without the assistance of nano-rails or nano-grooves for guidance. The work proves that molecules can be designed deliberately to perform certain dynamic tasks on surfaces. The UCR research team is now trying to build a molecular ratchet, which would convert random thermal oscillation into directed motion. Applications This is really an elegant study and key to understanding transport at a molecular scale which will lead to various uses. l The fact that the motion is fully controllable might lead to applications in molecular computing, for example for storing large amounts of information on nanoscale chips. An abacus-like molecular memory using DTA would be more than 1000 times more compact than current silicon devices. l The experiments show a means to transport molecules reliably which is an unprecedented step forward towards the realisation of molecular-scale machinery of the future as trucks and conveyor belts are for factories of today. l Work in this area could have "real technological implications in the next three to five years" in terms of developing catalysts. An automobile's catalytic converter, for example, uses platinum as a catalyst: carbon monoxide and oxygen attach to the platinum surface and react when they get close to each other. But moving the two closer with the help of another molecule would speed up the process and use less of the expensive platinum. l Experts say the work could also have implications for building molecular electronics, a fledging research area in which organic molecules, rather than silicon, serve as transistors and other electronic devices. By understanding how the energy barrier changes, we can learn how to control it, which would be crucial for assembling molecular circuits. l A research team has created a molecule that can function as an ultra-miniaturised version of a keypad locking mechanism. Keypad locks allow an action to take place only when the right password is entered. It will lead to inventions in other areas such as information security and even medicine. Faster and more powerful molecular locks could serve as the smallest ID tags, providing the ultimate defense against forgery. l In the future, molecular keypads might prove valuable, as well, in designing "smart" diagnostic equipment to detect the release of biological molecules or changes in conditions that indicate disease. The writer is from Department of Physics, S.L.I.E.T., Longowal |
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THIS UNIVERSE You must have found that white light can be split up into colours when passed through a prism. Not only the prism that school children have in their school laboratory, but also many other materials, including dew drops and cut diamonds. We also see these colours in rainbows. Physically colour is a rough indicator of the wavelength of light. Red light has about twice the wavelength of deep blue. It is experimentally found and theoretically established in scattering with air molecules the blue part of the sunlight scatters about eight times more than the red light. When we turn our face to the sky what we see is this scattered light, which is dominated by blue. Indeed what we call the sky is nothing but this blue scatter. If there were no scattered light the sky would be black - as it is in space. In fact we would also see the stars during the day! I might mention two other things you must have noticed. Around sunset the sun looks orange coloured. At that time the light of the sun has to travel through a long path through the atmosphere. There is a lot of scattering in the atmosphere and the component of light scattered out is mostly short wave lengths, namely the blue colour. Robbed of the blue, and some green, the remaining light is only orange or red. Is it true that gravitation force is only attraction force? If it is true then if we considered Earth as an object and Moon as another object then why do they not coincide with each other? The Earth and the Moon do attract each other, but they do not fall on to each other because of their motion with respect to each other. You know that the Moon goes around the earth. This motion produces an outward force which balances the attraction. The same argument can be given to explain why the Earth does not fall into the Sun; this is because the earth is going around the Sun. Another way of understanding this is to say that the Moon is continuously falling towards the earth but because of its circular motion it keeps on missing it! |
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The system that allows you to do so originated in the USA. It was planned as means of satellite navigation for military purposes. Such navigation would enable unheard-of precision in delivering weapons like smart bombs to targets. It would also help in tackling the problem of troops that get lost and don't know their location during war.