Thursday, July 9, 1998
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Thursday, July 9, 1998 |
| Waterlogged
soil: Can trees act as bio-drains? by G.S. Dhillon Bio-technology is making rapid advances and it is finding numerous applications in the field of agriculture, such as use of bio-fertilisers to replace chemical fertilisers, biological control for pests and insects. All these are regarded as eco-friendly. Mystery of black holes by Dr Nataraja Sarma STARS are thermonuclear reactors where lighter elements like hydrogen, helium and lithium fuse into heavier elements up to iron. The energy that is created during the fusion process is converted to light, X-rays and gamma rays.This radiation exerts an outward pressure that exactly balances the inward pull of gravity and stabilises the star. |
| Waterlogged
soil: Can
trees act as bio-drains? by G.S. Dhillon Bio-technology is making rapid advances and it is finding numerous applications in the field of agriculture, such as use of bio-fertilisers to replace chemical fertilisers, biological control for pests and insects. All these are regarded as eco-friendly. Now experts are suggesting the use of bio-drains for cure of the waterlogged and salinised soils.The conventional modes for cure of waterlogged soils is to drain the excess water by using vertical drainage through working of pumps or the horizontal drainage through installing of sub-soil tile drainage systems. These modes create a gradient to “force” excess water present in the soil towards the created “sink”. The water so collected in the sinks is taken for disposal to a nearby natural drain. The provisions of the conventional modes not only require initial capital investment but funds for operation and maintenance.The evapo-transpiration capacity of vegetation (mostly tree species) to remove the excess soil water, is made use of in this mode. To put it in simple words: to let the vegetation drink out the waterlogging problem.The above mode of water removal is considered to be a low-cost alternative as it does not require the installation of the field facilities for creation of sinks or means for disposal of water. The O&M expenses are not there and on the other hand some useful produce, namely fibre, wood, fodder may be obtained instead. The use of eucalyptus plantations, as bio-drains is most favoured because of the voracious thirst of this species. But whether this mode would work in the severely waterlogged soils is debatable.“The concept of the bio-drainage is an inherently dubious concept,” says Dr Bert Samedema of IPTRID (International Programme for Technology Research in Irrigation and Drainage) Washington (USA).  He reported in a recent issue of the GRID, that
“it is well known that plants generally do not grow
well in the waterlogged soils because the root-zone lacks
air needed by the plant roots.So according to the above expert, the bio-drainage will not be a realistic option when common crops fail to grow due to waterlogged conditions. He concludes that in such situations, there is no real alternative to the conventional physical drainage.However, it may be said that the bio-drainage system, under certain conditions does have its merits. The conditions confine to growing of tolerant species in the area not under extreme waterlogging condition, but in the areas where the crops can get air for roots occasionally when the watertable drops to levels below the root-zone, after the rainy season is over. The tolerant species will have a capability of surviving short periods of air deficiency. Such species are physiologically more active than the normal species under the marginal conditions, as they are capable of creating their own favourable drainage regime.Experts claim that bio-drains can also cope with salinity of soils. However, such claims are not based or backed by authentic field data. But the observed data from Australia and California indicate that bio-drainage without any physical drainage leads to accumulation of salts to a harmful level in the root-zone resulting in toxic conditions. Eucalyptus is an Australian genus comprising more than 140 species, mostly found in Australia only. It is an ever-green, fast growing species, whose leaves contain oil-glands which yield eucalyptus oil having medicinal properties, which is obtained through distillation of eucalyptus leaves. The eucalyptus trees are the dominate feature of vegetation of Australia and range from the sandy desert shrubs to the giant luxurious trees. The advent of the eucalyptus species in India dates back to the year 1790, when it made an appearance in the Palace Gardens — Nandi Hills (Mysore). As a source of fuel-wood, it came to be adopted around the year 1843 and large plantations took place on the Nilgiri Hills. After adaptability trials of the different species, the species known as the E-Hybrid (termed Mysore Gum) was cleared for growing in the moist to sub-tropic climates.Its selerophyte character imparts the eucalyptus “high evapo-transpiration
rate”. It has been found that the water demand of
fully grown large eucalyptus trees (with spacing of 2m x
2m), during the keen demand season, may be around 80
gallons per day (which is equivalent to 8 cm delta of
irrigation water).ADOPTION AS BIO-DRAINS:The eucalyptus trees were planted near Rome, around 19th century, for draining of the swamps. During the 20th century, Israel, Australia and Uganda assigned the task of water pumps to eucalyptus trees, for the deliberate lowering of water-table. The CSSRI (Central Soil Salinity Research Institute) Karnal (Haryana) has reported that eucalyptus plantation has successfully managed waste (sewage) waters. It is also clained that such species also remove heavy and toxic matter from the sewage waters used for irrigation of such plantation.Trials by the Forests Research Institute, Dehra Dun (UP), have indicated that eucalyptus plantation need good, fertile, well drained soils for good growth. On poor soils, the trees stagnate after showing early growth in the height. PUNJAB’S SCENARIO:Large tracts of Punjab are facing threat of waterlogging. More than 2.5 lakhs of land of the South-Western districts of Punjab have been reported to be facing waterlogging and salinity. Crop production has fallen and in some areas the agricultural operation is no longer possible. Some areas in the districts of Gurdaspur, Hoshiarpur and Ropar are facing the problem of waterlogging and salinity. Last year, production in the cotton growing belt declined by 9 lakh bales which constituted about 45 per cent of total production.Looking back, it is seen that after October 1955, floods, the watertable rose in the most of the areas of Punjab state and near waterlogging conditions developed in three-forth part of the state. As a part of strategy for fighting waterlogging, the plantations of eucalyptus was adopted in a ‘big way’. Very soon one could see such plantations along road, rail tracks, canal banks etc. and during 1965-66, nearly 60 per cent of the total annual plantation by the state was of eucalyptus. In a decade or so, severe water-table decline came to be reported from the central districts having sweet water zone. The decline could not be entirely apportioned to the eucalyptus plantations, as the same time, in the sweet water zone, the farmers pumped excessive amount of water (greater than the recharge to the ground water table) through lakhs of shallow tubewells owned and operated by them.But the above phenomenon, led to the change in the policy of plantations in Punjab, the eucalyptus came to be allocated a very low priority and during the year 1992-93, the annual plantation of eucalyptus hardly amounted to 1.6 per cent of the annual plantation by the state.The scope of bio-drainage for cure of badly waterlogged soils, where normal crops growth is not possible, has not yet been established.The writer is a Water Resources Consultant. |
| Mystery of black holes by Dr Nataraja Sarma STARS are thermonuclear reactors where lighter elements like hydrogen, helium and lithium fuse into heavier elements up to iron. The energy that is created during the fusion process is converted to light, X-rays and gamma rays.This radiation exerts an outward pressure that exactly balances the inward pull of gravity and stabilises the star. As the fuel for the fusion reaction is exhausted, the outward forces of radiation diminish, allowing the gravitation to compress the star inward. This contraction of the star causes its temperature to rise and allows remaining nuclear material to be used as fuel. Eventually, all the nuclear fuel is exhausted and the star collapses, shedding much of its mass in a dramatic supernova explosion. Such a dramatic event was seen 11 years ago, when a neighbouring star weighing 20 times the mass of the sun blew up in a spectacular supernova explosion.The enormous and dense mass of the residue after the supernova explosion presses down on itself under the pull of gravity and the entire mass implodes into the centre. Opposing this
implosion is the electrostatic repulsion between the
nuclei of the elements. How far it collapses, into what kind of object, and at what rate, is determined by the star’s final mass and the remaining outward pressure from the burnt-up nuclear residue. The more massive it was, the smaller it becomes up to a limit. Small stars are left with a core that eventually cools and contracts to about the size of the earth to form a white dwarf. Our galaxy houses many white dwarfs but most are invisible. One of the first to be seen was Sirius B, a companion of Sirius, the dog star. Its very strong gravitational field causes its light to be shifted towards the red as predicted by Einstein’s General Theory of Relativity. Still larger red shifts have more recently been detected in studies of collapsed stars that are even denser.In 1930, the late S. Chandrasekhar calculated that when the burnt out star weighed more than 1.4 times the mass of our sun, it would collapse under its own weight and turn into a dense and exotic object. The electrons flying around the atoms would depart, like rats leaving a sinking ship, and under further
compression, the positive charge on the protons would
leak out leaving an electrically neutral neutron star. In
1967, the first evidence was obtained for such a neutron
star, exotic beings billions of times denser than
ordinary stars, so dense that a teaspoonful would weigh
100 million tons! Heavier stars would collapse further,
the neutrons disintegrating into quarks and gluons, the
constituents of nucleons.Beyond two solar masses, gravity
would predominate and the collapse forms a black hole, an
object whose density is infinite and termed as a
singularity in mathematical language.In this singularity, matter is crushed to infinite density. A long time ago, Einstein suggested that such extremely large gravitational forces lead to an “event horizon” through which nothing, not even light goes. Such objects generate gravitational fields so strong that only Einstein’s General Theory of Relativity can describe their behaviour. Curvature of space-time is so high that space and time cease to exist, as we know them. All the laws of physics break down, gravity gets quantized and randomness reigns. The star melts into a black hole, an event horizon forms at the centre and expands through the star’s surface. In other words, the strong gravitational field shifts so far towards longer wavelengths that it is never seen! Nothing, not even light, can escape. It is as if the star has totally disappeared from the universe. A ball shaped black hole, known as a Schwarzschild black hole has an even horizon on its surface. Kerr black holes are also spherical but they spin at high velocities. A black hole whose mass equals 10 suns has a radius of about 30 kilometres. The collapse need not be uniform, any more than water would go straight through a hole in a basin. Simulations done by large supercomputers indicate that spiral patterns or a certain clustering of matter could lead to a doughnut shaped black hole. By emitting gravitational waves, these black holes lose energy, eventually become stationary black holes, namely holes that are perfectly spherical or whose rotation is perfectly uniform. All this is not mere speculation. Einstein’s theory predicted that disturbances in space-time should generate gravitational waves. Since black holes are by definition virtually “invisible,” the only way to confirm they exist is to measure the gravitational waves emitted as they form or interact with other massive objects. However, a black hole seems to have a natural mode of vibration that tells how big the black hole is and how fast it’s spinning. Astronomers can detect black holes by their effect on other stars. Gas sucked towards the black hole from a nearby star would heat up to millions of degrees and emit X-rays, gas dust, or even stars may orbit the black hole and this could be seen as pulsars.Astrophysicists have also seen the event horizon around the black hole. They have shown that black holes may spin around each other and spray out gravitaitonal waves and when they collide their event horizons would merge. Theories have been proposed to predict what happens under such extreme conditions. In much the same way that entropy increases when two gases are mixed, the event horizon increases when two black holes collide. But black holes, Hawking showed, have a temperature because they could radiate particles with a thermal spectrum of energies. The stronger the gravity of a black hole at the event horizon, the hotter it is. By emitting particles, the black hole disappears slowly, perhaps violating several laws of conservation in physics.The most convincing observation of black hole is from microwave measurements on a gaseous disc less than 0.5 light years across at the centre of a galaxy, NGC4258, 20 million light years away. The gas of the disc whirls around a compact dark object weighing around 36 million suns. There is also evidence for black holes in the heart of other galaxies, including one not so very heavy in the centre of our Milky Way. In this case, 39 stars seem to circle a dark mass of several million suns and of volume one cubic light year. The Hubble space telescope has mapped 15 galaxies that appear to have black holes in them. (PTI) |
| New
products
& discoveries Virtual journey to Mars SPACE exploration gets more exciting as virtual reality makes it possible to travel virtually to Mars. Using a Morphis simulator with authentic data from NASA, travellers can experience the sights and sounds as on Mars. Join an exciting deep-space mission to Mars and experience what future astronauts orbiting the planet and landing there will see, feel and hear – and be back in time for lunch.Experts from a UK group have used authentic data from NASA in the US, to produce a state-of-the-art, stimulated exploratory journey to the Red Planet for a space museum and other venues worldwide.The Morphis ride system is a premier attraction and part of a social extension at the US Astronaut Hall of Fame near the Kennedy Space Station at Titusville, Florida. Morphis represents a new design concept in the full-motion, entertainment simulator market.Besides the Mars Mission ride, there are more than 40 other
virtual experiences covering action, education and
sports, available for use on the Morphis system.A
spokesperson for the Astronaut Hall of Fame said the
company chose the Morphis machine because it was the best
system to create the Mars virtual reality experience and
it would be making the ride the centrepiece attraction of
the Astronaut Adventure area of the new Apollo Extension,
a multi-million dollar investment.The Morphis Movie Ride
Theatre experience, made by Camber Entertainment of
Crawley, Sussex, southern England, allows visitors to fly
a mission over Martian mountains, valleys and ravines
– and even encounter dust storms.The mission
involves carrying out a geological expedition on Mars,
some 20 or 30 years in the future. The base station and
vehicles are all based in genuine NASA concepts and the
terrain is based on scientifically known data. (Newscribe)Ever-glowing pen NEED to write in the dark? The Power-Glow pen uses a green, blue, or red LED to light the way. Unlike other pens with conventional lights, there’s no flament to burn out, so the light lasts for the life of the pen. The top half of the pen can be removed for use as a flashlight. Price: $ 15. DNA test to detect malaria Mosquito species that carry malaria can now be swiftly identified with a DNA test kit developed by researchers in Australia, that will aid eradication of disease-carrying species quickly and cheaply, reports New Scientist.Though DNA probes are a more reliable way of identifying species than morphology, but until now samples had to be taken to laboratories away from an outbreak of malaria.The Australian scientists have developed DNA probes for each of the 10 species that carry the disease. To do this, the team used a technique called the “mosquito squash blot”.In this procedure, the abdomen of the mosquito is squashed on a nylon membrane dampened with detergent. The detergent ruptures the insect’s tissue, releasing the DNA that binds to the membrane.At any one time, the researchers can check the DNA of thousands of squashed mosquitos against DNA probes — radioactively tagged DNA from the 10 species that carry the disease. |
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