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For years, the contents of a child’s sandbox have confounded some of the nation’s top physicists. Sand and other granular materials, such as powders, seeds, nuts, soils, and detergent, behave in ways that seem to undermine natural laws and cost industries ranging from pharmaceuticals to agribusiness and mining, billions of dollars.
Just shaking a can of mixed nuts can show you how problematic granular material can be. The nuts do not ‘mix’; they ‘unmix’ and sort themselves out, with the larger Brazil nuts on top and the smaller peanuts at the bottom. In this activity and others, granular matter’s behaviour apparently goes counter to the second law of thermodynamics, which states that entropy, or disorder, tends to increase in any natural system.
Mimicking the mixed-nut conundrum with a jar containing many small beads and one large bead, one group of physicists claimed that vibrations causing the beads to percolate open up small gaps rather than larger ones. Thus, when a Brazil nut becomes slightly airborne, the peanuts rush in underneath and gradually nudge it to the top. Another group of physicists colour coded layers of beads to track their circulation in a container and achieved a different result. Vibrations, they found, drive the beads in circles up the centre and down the sides of the container. Yet downward currents, similar to convection currents in air or water, are too narrow to accommodate the larger bead, stranding it on top.
One industrial engineer who has studied the problem says that both the ‘percolation’ and ‘convection current’ theories can be right, depending upon the material, and that percolation is the major factor with nuts. Given the inability of scientists to come up with a single equation explaining unmixing, you can see why industrial engineers who must manage granular materials go a little, well, ‘nuts’! Take Pharmaceuticals, for instance. There may be six types of powders with different sized grains in a single medicine tablet. Mixing them at some speeds might sort them, while mixing at other speeds will make them thoroughly amalgamated. One aspirin company still relies on an experienced employee wearing a latex glove who pinches some powder in the giant mixing drum to see if it ‘feels right’.
Granular material at rest can be equally frustrating to physicists and engineers. Take a tall cylinder of sand. Unlike a liquid, in which pressure exerted at the bottom increases in direct proportion to the liquid’s height, pressure at the base of the sand cylinder doesn’t increase indefinitely. Instead, it reaches a maximum value and stays there. This “quality allows sand to trickle at a nearly constant rate through the narrow opening separating the two glass bulbs of an hourglass, thus measuring the passage of time.
Physicists have also found that forces are not distributed evenly throughout granular material. It is this characteristic that may account for the frequent rupturing of silos in which grain is stored. In a silo, for instance, the column’s weight is carried from grain to grain along jagged chains. As a result the container’s walls carry more of the weight than its base, and the force is significantly larger at some points of contact than at others. Coming up with equations to explain, much loss, predict the distribution of these force chains” is extremely difficult.
Again, using beads, physicists developed a simple theoretical model in which they assume that a given bead transmits the load it bears unequally and randomly onto the three beads on which it rests. While the model agrees well with experimental results, it does not take into account all of the mechanisms of force transmission between grains of sand or wheat.
In the struggle to understand granular materials, sand-studying physicists have at least one thing in their favour. Unlike particle physicists who must secure billions of dollars in government funding for the building of super-colliders in which to accelerate and view infinitesimal particles, they can conduct experiments using such low-cost, low-tech materials as sand, beads, marbles, and seeds. It is hoped that more low-tech experiments and computer simulations will lead to equations that explain the unwieldy stuff and reduce some of the wastage, guesswork, and accidents that occur in the various industries that handle it.[1] The percolation theory of unmixing is bout illustrated by which of the following examples?
(a) Contents settling in a bag of potato chips so that the package appears less full after handling.
(b) Currents of small beads blocking the upward movement of large beads in a shaken container.
(c) Larger rocks rising to the surface in a garden after a period of frost.
(d) Largo nuts blocking the upward movement of small nuts in a shaken container.[2] In saying that the percolation and convection current theories may both be right, the industrial engineer means that.
(a) though the theories have different names, they describe same physical mechanism.
(b) both theories are still unproven, as they have not been tested on a variety of materials.
(c) neither theory is supported by an adequate mathematical basis.
(d) the mechanism causing unmixing varies depending upon the type of granular material.[3] Which of the following appears to be the best solution for combating the ‘unmixing’ problem faced by pharmaceutical manufacturers that must prepare large quantities of powders?
(a) To mix all the powders together at the same speed.
(b) To craft powders in which every grain weighs the same amount.
(c) To craft powders so that all the grains have similar sizes and shapes.
(d) To hire engineers who have years of experience in powder mixing.[4] The passage implies that if the top bulb of an hourglass were filled with water instead of sand the pressure pushing the water through the opening would
(a) remain constant as water trickles through the opening.
(b) decrease as water trickles through the opening.
(c) increase as water trickles through the opening.
(d) be directed at the walls of the container rather than the base.asked in MAT
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There are a few instances of diseases that have laid waste huge tracts of forests throughout India. Caused mainly by pathogens and pests, these diseases are deadly and are capable of wiping out entire forests and plantations, causing immense economic as well as ecological loss.
Meanwhile, forest pathologists and entomologists are grappling with new maladies that are surfacing almost every year. But with meagre resources and just a few experts working on the issue, things are heading virtually towards a culde-sac.
Moreover, no assessment has been made so far to quantify the devastation. While large chunks of forests fall prey to maladies, it is also an opportunity for some politician and timber merchants to cash in on it. Research and documentation on forest disease, particularly on forest pathology, began in India way back in 1929, by pioneering pathologists KD Bagchi and BK Bagchi. Although it has been eight decades since then, not much headway has been made in this; direction. The forestry sector today is ailing due to its misplaced priorities, resource crunch, and mismanagement. “Forest management lacks scientific approach,” says Surendra Kumar, director of the Himalayan Forest Research Institute (HFRI), Shimla.
The scientific community involved with forest diseases is today a dispirited lot. With only a few stalwarts left in this field, forest disease is a neglected area of research. Moreover, bureaucracy is increasingly taking over the scientific institutions and scientists in most of these institute arc a marginalised group.
To top it all, there are no institutions dedicated to forest diseases. Although the ministry of environment and forests is the facilitator for such research, it is not paying enough attention to promote scientific research of forest diseases;. In fact, the government’s lackadaisical approach came to the fore with the Sal borer epidemic in Madhya Pradesh in 1998. While forest bureaucracy slept, the beetles merrily continued to wipe out entire tracts of precious Sal forests. Eventually, with no solution in sight, thousands of valuable trees were hacked. There were also allegations that the Sal tragedy was a chance for the timber mafia in the state to cash in on timber through the legal loophole, with the nexus of politicians.
Today, things haven’t changed one bit. India’, forest department and research institutes have yet to formulate contingency plans to face any assault of similar dimensions.
Forest diseases are elusive. Although experts claim that they know quite a lot about forest diseases, there are still aspects of the maladies that are not completely understood. Says RS Bhandari, entomologist in the Forest Research Institute (FRI), Dehradun, “We know about all the important pests and insects, their life cycles and their development. But there are a few diseases which remain an enigma.” According to Jamaluddin, head of the pathology department in the Tropical Forest Research Institute (TERI), Jabalpur, “Due to micro climatic changes, we are discovering new aspects of the same disease every year. Diseases have also increased manifold.” Another FRI scientist points out that although forest diseases are increasing, there is no study to estimate the economic and ecological damage caused by these pests and pathogens.
Varying with different geophysical regions and climatic conditions, pathogens and pests are essentially responsible for the tree maladies and their mortality. When the pristine, natural and mixed forests existed, forest diseases acted as a natural control measure to check the proliferation of a particular species that could threaten the balance of the ecosystem. Perhaps, this is why forest diseases paled into insignificance in the past. But today, with shrinking forests and increasing monoculture plantations, any outbreak of disease takes on a virulent form.
To top this, changed climatic and forest patterns and environmental pollution have given rise to newer forms of forest diseases. While trees are forced to take an additional load of human-induced environmental changes, the introduction of mono culture has substantially increased the problems. Whatever little we know about forest diseases today comes primarily through mycology, the study of forest pathogens. Mycology explains that the prime pathological reasons for forest disease are fungi, bacteria and viruses. “Among these, fungi playa major role, while the other two are relatively less significant. There are 150 to 200 major pathological infections in central India. Out of these, only five per cent are bacterial. The rest are fungal,” says Jamaluddin.
Most of these pathogens stay close to a tree, waiting for a chance to infiltrate. Their entry points are small openings or wounds in the tree. However, invasion is not always easy. Like human beings, trees also have antibodies that fight anything alien. In case of invasion from the trunk of a tree, the sapwood acts as a shield and secretes enzymes to fight pathogens. But when attacked and conquered, there are tell-tale signs in the form of knotty growths of fruit bodies that are extensions of the fungi in the tree.[1] Which of the following is the author most likely to agree with?
(a) The ministry responsible should take a more serious view towards research in forest diseases.
(b) There is a likelihood of another forest disease epidemic, similar to the Sal Borer epidemic, spreading the country.
(c) There needs to be a more coordinated effort to wards dealing with forest diseases in India.
(d) All of these[2] Which of these incidents discourages the government to formulate any kind of concrete plans?
(a) India lacks specialists in this area of forestry.
(b) The government is not able to work in concomitance with specialists, like entomologists and pathogenists.
(c) The prevalence of malpractices, such as the alleged nexus of politicians with some of the forest officials.
(d) None of these[3] Which of these statements cannot be inferred from the passage?
(a) With the variation of different climatic conditions, pests responsible for forest tree degradation, disappear.
(b) There are hardly any committed institutions in India, for the promotion of research in forest diseases in India.
(c) It is possible that the timber mafias could spread their network with help from vested interest in the political and bureaucratic brass.
(d) None of these.
[4] The discussion on the present condition of forest diseases proves that
(a) there must be a cooperative endeavour by scientists, government officials and politicians to weed out the possibilities of forest diseases.
(b) a lot more needs to be done by the government for sustaining the ecological balance.
(c) hitherto forestry has been a neglected area of research.
(d) None of theseasked in MAT
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