|SCIENCE TRIBUNE||Thursday, January 10, 2002, Chandigarh, India|
Combating blockage of TV signal
NEW PRODUCTS & DISCOVERIES
Electronics in the service of medicine
ON September 19, 2001, surgeons sitting in New York used a tiny robot to remove the gall-bladder of a woman patient in France. This was the world’s first long-distance surgical operation — made possible by a marriage of robotics, video technology and telecommunications. It marked yet another advance in medical imaging — looking into the inner organs of the body.
It all began with William Roentgen who on November 8, 1895, noticed that a lump of radioactive material placed on a photographic plate had fogged it. Some unknown radiation was penetrating the material and fogging the photographic plate in the same way as visible light did. In the same way, Roentgen was able to obtain the image of a hand on a photographic plate. We now know that this radiation, which was called X-rays because of its unknown nature, is similar to visible light but of much shorter wavelength [in the range of 5 x 10-7 cm to 6 x 10-10 cm].
Doctors began to use X-ray images of bone fractures. Today, radiology, or the use of X-rays in medical imaging, has made possible advanced surgery of the central nervous system, the lungs, the stomach, the duodenum and the large intestine, the kidney and particularly the heart. X-rays penetrate through the body to cast an image either on a film or a fluoroscopic screen. The image is formed by the difference in the density of the various tissues through which the X-rays pass, particularly bone and air spaces. The drawback with radiology is that the shadow cast by three-dimensional objects like body organs are formed on a two-dimensional surface like film.
This drawback is eliminated in the technique called "computerised axial tomography" [CT], in which a machine passes X-rays through the patient’s body from various angles. This yields a picture of the patient as if he had been cut right through. The CT scan is a digital image produced by the computer from a large number of direct transmission measurements at different angles through the patient’s body. The computer reconstructs the image and displays it on a monitor, from which a hard copy can be taken. CT scanning is now used for examination of the vertebral column, the middle and inner ears, the eyes, the pancreas and the lung.
Since different types of tissue absorb different amounts of X-rays, a physician can make out a solid tumour from a fluid-filled cyst. CT-scanning gives a much higher resolution than radiology. However, the patient is exposed to a higher dosage of radiation than in conventional X-radiographs; hence it is not used unless really needed.
In nuclear medicine, radioactive materials are used for imaging. Not only can masses of relatively uniform tissues be differentiated, but the technique can be also used in determining the turnover rate of a certain substance in the body. For instance, to measure the activity of the thyroid gland [an endocrine gland] the patient is given "labelled" or radioactive iodine; when this is converted into thyroid hormones by the thyroid gland, the radioactive iodine is measured with a scintillation counter. For imaging moving structures inside the body, a gamma camera is used.
Magnetic resonance imaging
Unlike radiology, magnetic resonance imaging [MRI] uses magnetism, thus protecting the patient from ionising radiation in the form of X-rays, which could be harmful to health. MRI employs the phenomenon of nuclear magnetism, a prominent quality possessed by hydrogen nuclei [protons]. Hydrogen is an element abundantly present in the human body. The technique uses a series of powerful electromagnets in the shape of a large tube, which surrounds the patient and envelopes him in a powerful magnetic field. The MRI scanner excites the protons in the hydrogen atoms in such a way that they emit faint radio signals which are read by the computer and converted into a very detailed image.
In MRI, the varying intensities of the signals indicate the distribution of water in the tissues. Three-dimensional images of any section of the body can be obtained in a manner of minutes. With its capacity to detect diseases of the brain and spinal cord, as well as of the bones and the heart and blood vessels, MRI has found a place in most modern hospitals.
Telling by the sound
Information concerning the structures within the body can also be obtained through high-frequency sound pulses, with frequencies in the range of 3.5 to 20 MHz [1 MHz or megahertz = 1 million oscillations per second]. The time taken by the sound pulses to travel to a reflecting surface within the body and return to a detector gives the depth of that surface. Ultrasound images are composed of thousands of echoes collected within the span of about 1/25 second. Nowadays, automated mechanical and electronic devices produce 15 to 25 images per second.
The main user of ultrasound is the
gynaecologist, to whom it is of prime importance to know the position
of the placenta [the layer of the uterus through which the embryo is
nourished.] He can estimate the maturity of the embryo by measuring
the diameter of circumference of the skull, the chest or abdominal
area. Ultrasound or sonography has more or less replaced X-ray methods
for imaging abdominal organs, since it does not use ionising
radiation, which X-ray diagnosis does. However, since ultrasound is
totally reflected by gas in the stomach and almost totally by bone, it
is not of much use in imaging the lungs and in seeing through bones or
Combating blockage of TV signal
DURING the times of hostilities, the warring nations try to block the radio and television signals coming in from the rival countries. During World War II Germany tried to block the signal of the BBC. During the cold war the Russians tried to block the signal of the Voice of America. More recently after the crackdown in Tiannenmen Square, the Chinese tried to block the signals from the BBC and the Voice of America. Cuba, during the eighties, tried to do it against the Voice of America. These measures have met with limited success in the past.
Just a few days back, the Government of Pakistan issued an order banning all Indian television channels within Pakistan. This means an effective end to all the satellite channels including "Aaj Tak", "Star News" "Zee News" and "DD News". All these channels were carried by the cable operators. This is the easier part. Now I am talking about the difficult part.
For several reasons Pakistan is quite unprepared to block the terrestrial signal of Doordarshan. First, Pakistan does not possess strategic geographical locations to effectively block signals coming out of India’s border stations. There are certain rural areas in Lahore and Kasur districts, where Amritsar’s recently strengthened DD signal cannot be effectively blocked even with matching power of jamming transmitters. Second Pakistan does not have the ability to block signals from hitherto unutilised Dalhousie peak in Himachal Pradesh. Doordarshan, I do not understand why, is not yet using this hilltop location for beaming Doordarshan to Pakistan as well as vast areas in Jammu and Kashmir, Himachal Pradesh and Punjab. But if worst comes to worst, India needs to use this location. We can use it very effectively. Pakistan even after installing jammer transmitters cannot block the signals from this naturally elevated location. The signal will overshoot the radius of blockage and shall be available more than 100 miles away in remote areas. For achieving optimum utility, India can also use as much power as possible up to 100 kilowatts. If Pakistan has to do the same to India, they simply do not have close enough hill locations to beam high powered transmissions into the hinterlands in India.
To start with Pakistan does not have enough number of spare transmitters to act as jamming transmitters. If they place the orders today, it will take months to receive the parcels in Pakistan. The only exception can be if China could dismantle some of its own serving transmitters and make those available to Pakistan. Such a scenario is not impossible, but it is difficult to achieve. But that sort of arrangement may also take months to materialise.
As far as radio is concerned, India’s
Urdu, Pushto, Sindhi and Dari services have adequate reach in
Pakistan. Both Urdu and Sindhi services are available in medium wave
and shortwave both. The Pushto and Dari services are available on
shortwave. Only the Punjabi and Saraiki (a dialect of Punjabi spoken
in Multan Division of West Punjab) services are unavailable on
shortwave. The range of India’s mediumwave transmitters does not
reach the whole of West Punjab. This shortcoming can be ovrercome by
offering the spare time on Delhi and Aligarh based shortwave
transmitters or as an alternative, locally manufactured 50 kilowatt
transmitters can be installed close to the border. This is certainly
not a short time measure.
NEW PRODUCTS & DISCOVERIES
Infra-Red massage chair
There are plenty of massage chairs that will vibrate energetically up and down your weary body, but the new H.9 Inada Chair from Japan puts some brains behind the brawn.
When you sit in it. infrared sensors scan your body to detect some 350 acupressure points. Once oriented, the leather chair begins a customised, Shiatsu-style massage accompanied by synchronised music meant to melt your tension away. If the synthesiser music drives you nuts, you can always pop in a CD of your own. Cost: about $3,500.
"Self-heal" method for materials
Researchers have come up with an ingenious system that allows composite materials to "self-heal" making them, in the process, as good as new.
Polymer composites are advanced material that consist of two components — a reinforcing fibre (such as carbon, glass, kevlar, flax, hemp or jute) and a liquid moulding resin. These composite materials find wide applications in fields such as civil engineering, aerospace, defence related projects electronics and biomedine.
In contrast to minor scratches or abrasions which heal making the damaged skin as good as new, people have got so used to products of all sorts breaking or wearing out that they fully accept the phenomenon. Designing of a self-repairing composite thus seemed to be stuff of fantasy.
The damage to a material may involve bond rupture, formation of microvolts or various other events at the molecular and microscopic levels that collectively weaken the material and perhaps put its user at risk, a report in Nature said.
The most common route to failure is fatigue — the formation of microvoids incurred by mechanical stress through repeated usage. The microvoids coalesce to form microcracks in the material which can grow to catastrophic proportions and cause total failure of the product.
The system developed by White and coworkers, involves adding several low-volume components to the composite. PTI
Elephant grass to make car parts
Scientists are developing car parts made of elephant grass that are biodegradable, thus ensuring an environmentally acceptable way of disposal after the end of their life.
Researchers at Warwick University, English Midlands, have produced structural filler for car wheel trims and strengthened biodegrdable plastics for other automobile uses by using short lengths of elephant grass mixed with polymers.
The hardy, perennial grass which producers high yields of bamboo-like cane upto three metres tall has the advantage of being environmentally friendly, requires no pesticide and yields 15 tonnes a hectare in southern England.
The parts made out of the grass do not degrade during the lifetime of the vehicle but can be encouraged to biodegrade if they are composed at the end of the vehicle’s life, a report in British Commercial News said.
The grass shows a remarkable combination of light water and nitrogen use efficiencies. Its photosynthetic mechanism appears to be better adapted to low temperatures than of many other C4 crops equipping it for high productivity under relatively cool temperatures.
Although water efficiency is high, the crop may require substantial amounts of water for maximal growth because of its high productivily.
United Kingdom farmers are already growing it for use as animal bedding, thatching and to create biomass fuel for power generation, the report said.
Science & Technology crossword — I
1. Excavation done to deepen a lake.
8. An important feature of traffic engineering.
9. Strength of concrete increases with it.
11. Pits for it are provided in locomotive yards.
12. A simple chart used in planning a work.
14. Used in drills.
15. International system of allotting numbers to books.
17. Used to measure canal lengths.
18. A conductor made from aluminium alloy rods.
19. A coat applied just before spreading premix on road.
22. Calculated while designing concrete mix.
23. Prepared to keep record of bore-hole findings.
1. An important parameter in concrete.
2. Soft silvery metallic element.
3. This density is important.
4. A public sector fertiliser corporation.
5. A line joining all places of same declination on a map.
6. A type of track in which one track superimposes other.
7. Used in bored cast in situ piles.
10. A special junction used in sidings.
13. An economical bridge.
16. Used to counter wind loads.
20. A name for a computer.
21. Reduced level.