RC 004
Is our planet the sole habitat of life? In a universe that contains billions of galaxies, each galaxy containing the order of hundred billion stars like Sun, is there any possibility of the existence of extra-terrestrial intelligence? This latter question, of course, presumes that we humans on the Earth are intelligent. Our ancient mythologies, as indeed those of most ancient cultures, routinely talk of the extra-terrestrials, like the yakshas, kinnaras, and gandharvas. So, does modern science fiction with its high profile versions in Star Trek or Star Wars. What are the ground (or, rather, space) realities for modern technology to carry out a Star Trek type interstellar exploration? Till the late fifties scientists were cautious about talking of SETI, that is the search for extra-terrestrial intelligence. But today it is a respectable discipline attracting support even from a conservative funding agency like NASA. What has been the key factor in bringing about this change of perception?
In the mid-fifties the astrophysicist Fred Hoyle proposed that gigantic clouds containing molecules might exist in space. But his ideas were considered so radical that he could not get his paper published. So he put it all as part of a science fiction novel called The Black Cloud that was a great success.
Within a few years, however, special dish antennas equipped to receive radiation of a few millimeters wavelength began to detect molecules in space. What is more, these molecules were organic as well as inorganic, with the organic ones being not only large and complex but also recognizable as sub-structures of the DNA molecule known to be basic to all living systems on the Earth. Today we know of gigantic molecular clouds filling the vast spaces between stars, and extending to several tens to hundreds of light years. So, circumstantial evidence suggests that if the basic building blocks of life are seen scattered in space, why not life itself?
Thus in the sixties there started inter-disciplinary discussions about extra-terrestrial life. The astronomers can tell what are the likely sites for life and how many of them are there in our Milky Way Galaxy of stars. Biologists have to decide what is it that triggers the life-mechanism and where among the various astronomical sites it is likely to occur. Then the evolutionists have to say how a simple living system can develop over what time span into a complex intelligent species. Experts in artificial intelligence, communications and information transfer are needed to resolve the problem of contacting such species if they exist. And the social scientists need to assess the lifetime of an advanced civilization.
In the sixties, Frank Drake, an astronomer from Cornell University, quantified these issues into what has come to be known as the Drake's equation. Simply put, it is a series of factors which, when multiplied together, would give us the total number, N, of extraterrestrial civilizations in our Milky Way, which have progressed beyond us on the technological ladder.
The assumptions behind Drake's equation are fairly conservative. They suppose that such a civilization would exist on a planet moving around a star from which it gets energy for survival. The planet would have to be at an optimum distance from the star, not too near or it will be too hot for survival, and not too far, otherwise, there will be hardly any energy available for sustaining life. The nature of life is also assumed to be not very radically different from the way we perceive it here. It is for the experts from the various disciplines to estimate these factors and thereby arrive at a realistic value of N. If calculations give N = 1 then we are the only advanced civilization in our Galaxy enjoying a unique, lonely status. If N turns out to be large, say, a million or so, then we do lose our uniqueness but can aspire to a social intercourse in the Galaxy.
The current state of our knowledge is such that we cannot estimate this number. But when you start asking experts, their guesses are many. There are the pessimists who think that we are alone. These are largely the biologists who think that the appearance of life on Earth is a combination of such rare events that not even the astronomical numbers quoted in the beginning can compensate for it. The optimists, and among these are the astronomers who are impressed by the vastness of the Universe, think otherwise. For them, it is the belief that once we know how life originates we will find it not such a rare phenomenon. One argument the pessimists put forward is: If life is so common, why has no one visited us from an alien habitat? At this stage, a UFO-buff will say that we have visited that we are being- visited. There is, however no scientifically valid evidence for this assumption. Visiting even the nearby planetary systems is not so simple. With our present technology, let us suppose we can reach the Moon in 50 hours. How far is the Moon? Rather than quote a distance in kilometers, left me say that light would take approximately a second and a quarter to cover the distance. How long will it take for such a spaceship to come from the nearest star Proxima Centauri to the Earth? Light takes four and a quarter years to make the journey.
Well, I will spare you the arithmetic and give the answer; it will take about six lakh years! No doubt, aliens will have better technology and can reduce the travel time but it shows the enormity of the problem. Many optimists answer the above question in a different way. They invoke the so-called "zoo-hypothesis". We humans have zoos and sanctuaries in which wild animals enjoy a protected life. Animals or birds are remotely observed and their behavioural patterns studied, but there is no interference with their life. Likewise, we on the Earth are being remotely observed and studied by the extra terrestrials and on purpose they do not interfere with our life-system, which they want to study!
Leaving speculations aside how can we look for alien ETs? As seen earlier, with our present technology space explorations with humans or without them are out. The only practical way is the one proposed by two scientists Giuseppe Cocconi and Philip Morrison in 1959. The method involves using the radio wavelength of 21 centimeters for interstellar communications. The atom of hydrogen, the most common element in the Galaxy, naturally emits radiation of this wavelength. Thus it will be known to the ET as it is to per quantum to send out and is less likely to be absorbed en route, compared to other waves. Our atmosphere is also relatively less noisy at this wavelength.
Given these advantages, the best strategy is to erect huge antennas and try to intercept any communication that may be going on between two ET groups. If we can detect and decode intelligent messages, we will be able to locate the sender and the receiver. This wire-tapping on a cosmic scale may have doubtful morality, but the success of the experiment will justify the means. SETI enthusiasts are trying this out as well as the more hone method of sending our own messages to likely sites of ETs and hoping for a reply. But enormous patience needed in carrying out any conversation of this kind. For, if you say "hi" to your ET neighbor going around Proxima Centauri, you will have to wait for eight and a half years for a reply!.
1)The success of 'The Black Cloud' suggests that _______.
a)Fred Hoyle was indeed right
b)the universe does not inhibit life
c)radical ideas are not always unsuccessful
d)conservative astronomers can be totally wrong
2)The author firmly believes that we are being visited by the UFOs. This statement is _______.
a)true
b)false
c)indeterminate
d)none of these
3)Drake's equation can best be described as ______.
a)a radical hypothesis
b)a run-of-the mill postulate
c)a rigorous science
d)a careful estimate
4)The enormous distances in our galaxy prove that __________.
a)it is impossible for humans to travel across solar systems
b)radio astronomy has limited usefulness
c)SETI is more difficult than earlier imagined
d)life is abundant
5)Which of these is false?
a)The author is not ready to believe that humans can travel to stars with their present technology.
b)The author has discounted the possibility of aliens visiting us, basically due to the enormous galactic dimensions.
c)Even radio conversations can be extremely time consuming.
d)NASA has not rejected the theory of ET life.
RC004:
1. c
2. b
3. b
4. c
5. b
RC 004:
1- C
2- B
3- C
4- A
5- B
explanations bhi post kar dena...
1- D
2 - C
3 - B
4 - C
5 - B
2 - C
3 - B
4 - C
5 - B
RC 004 OA
@ankitpurohit991 @RDN @bvdhananjay @nikemen @joyjitpal
@ankitpurohit991 @RDN @bvdhananjay @nikemen @joyjitpal
1)Correct answer is (C).
When we look at the options, we can simply strike off (2) and (4) as the answer choices because they do not relate to the question that is asked. (1) is a choice which can be the one where one could get confused. But we can' t deduce (1) as the commercial success of a book as it doesn't prove its technical correctness. (3) actually states the idea which is inherent in the 3rd para of the passage2)Correct answer is (b).
Be careful with the words firmly believes which are very strong. Also read the 7th statement onwards in para 8. Here, the author says that there is no scientific validity of UFOs. So, we can safely say that (2) should be the answer.
3)Correct answer is (d).
The Drake's equation finds a mention in para 7. Read the very first line which says, The assumptions behind Drake's equation are fairly conservative. This means that the equation has some solid ground on which it stands. This inference directly eliminates the choices (1) and (2). Coming to the choice (3), the equation isn't a science and that too a rigorous one. So, even (3) can't be the answer leaving the choice (4) that seems to be the most appropriate answer.
4)Correct answer is (c).
The passage tells us that the galaxy in which we are living is a huge one. Now, looking at the options, we can directly eliminate (4) because it is immaterial to life being abundant whether the galaxy is big or not. (1) again is a far-fetched statement. It uses the word 'impossible' that is too strong to use, especially, when not given explicitly in the passage. (2) can be the only confusing choice as it may be right. But the passage is not talking about it at all. So, we eliminate it. When we read the 2nd paragraph of the passage, (3) seems to be the best possible answer choice.
5)Correct answer is (b).
The author has talked about the statement (1) especially along with the discussion of the Drake's equation. (3) and (4) also find a mention in the passage. So, (2) is the answer as the author has not outrightly rejected the proposition that aliens have been visiting our planet.
When we look at the options, we can simply strike off (2) and (4) as the answer choices because they do not relate to the question that is asked. (1) is a choice which can be the one where one could get confused. But we can' t deduce (1) as the commercial success of a book as it doesn't prove its technical correctness. (3) actually states the idea which is inherent in the 3rd para of the passage2)Correct answer is (b).
Be careful with the words firmly believes which are very strong. Also read the 7th statement onwards in para 8. Here, the author says that there is no scientific validity of UFOs. So, we can safely say that (2) should be the answer.
3)Correct answer is (d).
The Drake's equation finds a mention in para 7. Read the very first line which says, The assumptions behind Drake's equation are fairly conservative. This means that the equation has some solid ground on which it stands. This inference directly eliminates the choices (1) and (2). Coming to the choice (3), the equation isn't a science and that too a rigorous one. So, even (3) can't be the answer leaving the choice (4) that seems to be the most appropriate answer.
4)Correct answer is (c).
The passage tells us that the galaxy in which we are living is a huge one. Now, looking at the options, we can directly eliminate (4) because it is immaterial to life being abundant whether the galaxy is big or not. (1) again is a far-fetched statement. It uses the word 'impossible' that is too strong to use, especially, when not given explicitly in the passage. (2) can be the only confusing choice as it may be right. But the passage is not talking about it at all. So, we eliminate it. When we read the 2nd paragraph of the passage, (3) seems to be the best possible answer choice.
5)Correct answer is (b).
The author has talked about the statement (1) especially along with the discussion of the Drake's equation. (3) and (4) also find a mention in the passage. So, (2) is the answer as the author has not outrightly rejected the proposition that aliens have been visiting our planet.
RC 05
One of the criteria by which we judge the vitality of a style of painting is its ability to renew itself — its
responsiveness to the changing nature and quality of experience, the degree of conceptual and formal
innovation that it exhibits. By this criterion, it would appear that the practice of abstractionism has failed to
engage creatively with the radical change in human experience in recent decades. It has, seemingly, been
unwilling to re-invent itself in relation to the systems of artistic expression and viewers' expectations that
have developed under the impact of the mass media.
The judgement that abstractionism has slipped into 'inter gear' is gaining endorsement, not only among
discerning viewers and practitioners of other art forms, but also among abstract painters themselves. Like
their companions elsewhere in the world, abstractionists in India are asking themselves an overwhelming
question today: Does abstractionism have a future? The major crisis that abstractionists face is that of
revitalising their picture surface; few have improvised any solutions beyond the ones that were exhausted
by the 1970s. Like all revolutions, whether in policies or in art, abstractionism must now confront its
moment of truth: having begun life as a new and radical pictorial approach to experience, it has become an
entrenched orthodoxy itself. Indeed, when viewed against a historical situation in which a variety of subversive,
interactive and richly hybrid forms are available to the art practitioner, abstractionism assumes the remote
and defiant air of an aristocracy that has outlived its age; trammelled by formulaic conventions yet buttressed
by a rhetoric of sacred mystery, it seems condemned to being the last citadel of the self-regarding 'fine art'
tradition, the last hurrah of painting for painting's sake.
The situation is further complicated in India by the circumstances in which an indigenous abstractionism
came into prominence here during the 1960s. From the beginning it was propelled by the dialectic between
two motives, one revolutionary and the other conservative — it was inaugurated as an act of emancipation
from the dogmas of the nascent Indian nation state, when art was officially viewed as an indulgence at
worst, and at best, as an instrument for the celebration of the republic's hopes and aspirations. Having
rejected these dogmas, the pioneering abstractionists also went on to reject the various figurative styles
associated with the Santiniketan circle and others. In such a situation, abstractionism was a revolutionary
move. It led art towards the exploration of the subconscious mind, the spiritual quest and the possible
expansion of consciousness. Indian painting entered into a phase of self-inquiry, a meditative inner space
where cosmic symbols and non-representational images ruled. Often, the transition from figurative idioms
to abstractionist ones took place within the same artist.
At the same time, Indian abstractionists have rarely committed themselves wholeheartedly to a nonrepresentational
idiom. They have been preoccupied with the fundamentally metaphysical project of aspiring
to the mystical-holy without altogether renouncing the symbolic. This has been sustained by a hereditary
reluctance to give up the murti, the inviolable iconic form, which explains why abstractionism is marked by
the conservative tendency to operate with images from the sacred repertoire of the past. Abstractionism
thus entered India as a double-edged device in a complex cultural transaction. Ideologically, it served as an
internationalist legitimisation of the emerging revolutionary local trends. However, on entry, it was conscripted
to serve local artistic preoccupations — a survey of indigenous abstractionism will show that its most
obvious points of affinity with European and American abstract art were with the more mystically oriented
of the major sources of abstractionist philosophy and practice, for instance, the Kandinsky-Klee School.
There have been no takers for Malevich's Suprematism, which militantly rejected both the artistic forms of
the past and the world of appearances, privileging the new-minted geometric symbol as an autonomous
sign of the desire for infinity.
Against this backdrop, we can identify three major abstractionist idioms in Indian art. The first develops
from a love of the earth, and assumes the form of a celebration of the self's dissolution in the cosmic
panorama; the landscape is no longer a realistic transcription of the scene, but is transformed into a
visionary occasion for contemplating the cycles of decay and regeneration. The second idiom phrases its
departures from symbolic and archetypal devices as invitations to heightened planes of awareness.
Abstractionism begins with the establishment or dissolution of the motif, which can be drawn from diverse
sources, including the hieroglyphic tablet, the Sufi meditation dance or the Tantric diagram. The third idiom
is based on the lyric play of forms guided by gesture or allied with formal improvisations like the assemblage.
Here, sometimes, the line dividing abstract image from patterned design or quasi-random expressive
marking may blur. The flux of forms can also be regimented through the policies of pure colour arrangements,
vector-diagrammatic spaces and gestural design.
In this genealogy, some pure lines of descent follow their logic to the inevitable point of extinction, others
engage in cross-fertilization, and yet others undergo mutation to maintain their energy. However, this
genealogical survey demonstrates the wave at its crests, those points where the metaphysical and the
painterly have been fused in images of abiding potency, ideas sensuously ordained rather than fabricated
programmatically to a concept. It is equally possible to enumerate the troughs where the two principles do
not come together, thus arriving at a very different account. Uncharitable as it may sound, the history of
Indian abstractionism records a series of attempts to avoid the risks of abstraction by resorting to an overt
and near-generic symbolism, which many Indian abstractionists embrace when they find themselves bereft
of the imaginative energy to negotiate the union of metaphysics and painterliness.
Such symbolism falls into a dual trap: it succumbs to the pompous vacuity of pure metaphysics when the
burden of intention is passed off as justification; or then it is desiccated by the arid formalism of pure
painterliness, with delight in the measure of chance or pattern guiding the execution of a painting. The
ensuing conflict of purpose stalls the progress of abstractionism in an impasse. The remarkable Indian
abstractionists are precisely those who have overcome this and addressed themselves to the basic elements
of their art with a decisive sense of independence from prior models. In their recent work, we see the logic
of Indian abstractionism pushed almost to the furthest it can be taken. Beyond such artists stands a lost
generation of abstractionists whose work invokes a wistful, delicate beauty but stops there.
Abstractionism is not a universal language; it is an art that points up the loss of a shared language of signs in
society. And yet, it affirms the possibility of its recovery through the effort of awareness. While its rheotoric has
always emphasised a call for new forms of attention, abstractionist practice has tended to fall into a complacent
pride in its own incomprehensibility; a complacency fatal in an ethos where vibrant new idioms compete for the
viewers' attention. Indian abstractionists ought to really return to basics, to reformulate and replenish their
understanding of the nature of the relationship between the painted image and the world around it. But will they
abandon their favourite conceptual habits and formal conventions, if this becomes necessary?
1. Which one of the following is not stated by the author as a reason for abstractionism losing its
vitality?
a. Abstractionism has failed to reorient itself in the context of changing human experience.
b. Abstractionism has not considered the developments in artistic expression that have taken place
in recent times.
c. Abstractionism has not followed the path taken by all revolutions, whether in politics or art.
d. The impact of mass media on viewers' expectations has not been assessed, and responded to,
by abstractionism.
2. Which of the following, according to the author, is the role that abstractionism plays in a society?
a. It provides an idiom that can be understood by most members in a society.
b. It highlights the absence of a shared language of meaningful symbols which can be recreated
through greater awareness.
c. It highlights the contradictory artistic trends of revolution and conservatism that any society
needs to move forward.
d. It helps abstractionists invoke the wistful, delicate beauty that may exist in society.
3. According to the author, which one of the following characterises the crisis faced by abstractionism?
a. Abstractionists appear to be unable to transcend the solutions tried out earlier.
b. Abstractionism has allowed itself to be confined by set forms and practices.
c. Abstractionists have been unable to use the multiplicity of forms now becoming available to an
artist.
d. All of the above
4. According to the author, the introduction of abstractionism was revolutionary because it
a. celebrated the hopes and aspirants of a newly independent nation.
b. provided a new direction to Indian art, towards self-inquiry and non-representational images.
c. managed to obtain internationalist support for the abstractionist agenda.
d. was an emancipation from the dogmas of the nascent nation state.
5. Which one of the following is not part of the author's characterization of the conservative trend in
Indian abstractionism?
a. An exploration of the subconscious mind.
b. A lack of full commitment to non-representational symbols.
c. An adherence to the symbolic while aspiring to the mystical.
d. Usage of the images of gods or similar symbols.
6. Given the author's delineation of the three abstractionist idioms in Indian art, the third idiom can be
best distinguished from the other two idioms through its
a. depiction of nature's cyclical renewal.
b. use of non-representational images.
c. emphasis on arrangement of forms.
d. limited reliance on original models.
7. According to the author, the attraction of the Kandinsky-Klee School for Indian abstractionists can
be explained by which one of the following?
a. The conservative tendency to aspire to the mystical without a complete renunciation of the symbolic.
b. The discomfort of Indian abstractionists with Malevich's Suprematism.
c. The easy identification of obvious points of affinity with European and American abstract art, of
which the Kandinsky-Klee School is an example.
d. The double-edged nature of abstractionism which enabled identification with mystically-oriented
schools.
8. Which one of the following, according to the author, is the most important reason for the stalling of
abstractionism's progress in an impasse?
a. Some artists have followed their abstractionist logic to the point of extinction.
b. Some artists have allowed chance or pattern to dominate the execution of their paintings.
c. Many artists have avoided the trap of a near-generic and an open symbolism.
d. Many artists have found it difficult to fuse the twin principles of the metaphysical and the painterly.
RC 05:
1)c
2)b
3)d
4)b
5)a
6)c
7)c
8)d
Tough one 
1 - D
2 - B
3 - C
4 - B
5 - D
6 - B
7 - A
8 - D
@vivekrajarshi @busybrains7
1. d All the reasons are cited in the first paragraph itself.
Choice (a) is mentioned in the 2nd line, (b) in the
second last line, (c) in the last line and (d) is not
mentioned. Instead mass media창€™s impact is also stated
in the para. This makes choice (d) correct.
2. b The opening lines of the final paragraph are represented
suitably in (b). (a), (c) and (d) are doubtful choices.
3. d (a), (b) and (c) are stated vividly in the second
paragraph, hence (d) is the answer.
4. b The author mentions this aspect in the third and fourth
last lines of the third para. This makes choice (b)
correct.
5. a (a) has been described as revolutionary in the third
paragraph. (b), (c) and (d) are given in the fourth
paragraph as the conservative tendency.
6. c The latter part of the fifth paragraph makes it clear that
(c) is the answer. (a), (b) and (d) are not mentioned.
7. a (a) is stated in the opening lines of the fourth
paragraph. (b), (c) and (d) are thus peripheral
observations.
8. d The first line of the seventh paragraph begins with
considering a 창€œdual trap창€? and this till the fifth line tells
us about the details of the same. This makes choice
(d) correct.
1. d All the reasons are cited in the first paragraph itself.
Choice (a) is mentioned in the 2nd line, (b) in the
second last line, (c) in the last line and (d) is not
mentioned. Instead mass media창€™s impact is also stated
in the para. This makes choice (d) correct.
2. b The opening lines of the final paragraph are represented
suitably in (b). (a), (c) and (d) are doubtful choices.
3. d (a), (b) and (c) are stated vividly in the second
paragraph, hence (d) is the answer.
4. b The author mentions this aspect in the third and fourth
last lines of the third para. This makes choice (b)
correct.
5. a (a) has been described as revolutionary in the third
paragraph. (b), (c) and (d) are given in the fourth
paragraph as the conservative tendency.
6. c The latter part of the fifth paragraph makes it clear that
(c) is the answer. (a), (b) and (d) are not mentioned.
7. a (a) is stated in the opening lines of the fourth
paragraph. (b), (c) and (d) are thus peripheral
observations.
8. d The first line of the seventh paragraph begins with
considering a 창€œdual trap창€? and this till the fifth line tells
us about the details of the same. This makes choice
(d) correct.
RC006
In a modern computer, electronic and magnetic storage technologies play complementary roles. Electronic
memory chips are fast but volatile (their contents are lost when the computer is unplugged). Magnetic
tapes and hard disks are slower, but have the advantage that they are non-volatile, so that they can be
used to store software and documents even when the power is off.
In laboratories around the world, however, researchers are hoping to achieve the best of both worlds. They
are trying to build magnetic memory chips that could be used in place of today's electronic ones. These
magnetic memories would be non-volatile; but they would also be faster, would consume less power, and
would be able to stand up to hazardous environments more easily. Such chips would have obvious applications
in storage cards for digital cameras and music players; they would enable handheld and laptop computers
to boot up more quickly and to operate for longer; they would allow desktop computers to run faster; they
would doubtless have military and space-faring advantages too. But although the theory behind them looks
solid, there are tricky practical problems that need to be overcome.
Two different approaches, based on different magnetic phenomena, are being pursued. The first, being
investigated by Gary Prinz and his colleagues at the Naval Research Laboratory (NRL) in Washington DC,
exploits the fact that the electrical resistance of some materials changes in the presence of a magnetic
field — a phenomenon known as magneto-resistance. For some multi-layered materials, this effect is
particularly powerful and is, accordingly, called 'giant' magneto-resistance (GMR). Since 1997, the
exploitation of GMR has made cheap multi-gigabyte hard disks commonplace. The magnetic orientations
of the magnetised spots on the surface of a spinning disk are detected by measuring the changes they
induce in the resistance of a tiny sensor. This technique is so sensitive that it means the spots can be
made smaller and packed closer together than was previously possible, thus increasing the capacity and
reducing the size and cost of a disk drive.
Dr. Prinz and his colleagues are now exploiting the same phenomenon on the surface of memory chips,
rather than spinning disks. In a conventional memory chip, each binary digit (bit) of data is represented
using a capacitor reservoir of electrical charge that is either empty of full — to represent a zero or a one. In
the NRL's magnetic design, by contrast, each bit is stored in a magnetic element in the form of a vertical
pillar of magnetisable material. A matrix of wires passing above and below the elements allows each to be
magnetised, either clockwise or anticlockwise, to represent zero or one. Another set of wires allows
current to pass through any particular element. By measuring an element's resistance you can determine
its magnetic orientation, and hence whether it is storing a zero or a one. Since the elements retain their
magnetic orientation even when the power is off, the result is non-volatile memory. Unlike the elements of
an electronic memory, a magnetic memory's elements are not easily disrupted by radiation. And compared
with electronic memories, whose capacitors need constant topping up, magnetic memories are simpler
and consume less power. The NRL researchers plan to commercialize their device through a company
called Non-volatile Electronics, which recently began work on the necessary processing and fabrication
techniques. But it will be some years before the first chips roll off the production line.
Most attention in the field is focused on an alternative approach based on magnetic tunnel-junctions
(MTJs), which are being investigated by researchers at chip makers, such as IBM, Motorola, Siemens and
Hewlett-Packard. IBM's research team, led by Stuart Parkin, has already created a 500 element working
prototype that operates at 20 times the speed of conventional memory chips and consumes one per cent
of the power. Each element consists of a sandwich of two layers of magnetisable material separated by a
barrier of aluminium oxide just four or five atoms thick. The polarisation of lower magnetisable layer is fixed
in one direction, but that of the upper layer can be set (again, by passing a current through a matrix of
control wires) either to the left or to the right, to store a zero or a one. The polarisations of the two layers are
then in either the same or opposite directions.
Although the aluminium-oxide barrier is an electrical insulator, it is so thin that electrons are able to jump
across it via a quantum-mechanical effect called tunnelling. It turns out that such tunnelling is easier when
the two magnetic layers are polarised in the same direction than when they are polarised in opposite
directions. So by measuring the current that flows through the sandwich, it is possible to determine the
alignment of the topmost layer, and hence whether it is storing a zero or a one.
To build a full-scale memory chip based on MTJs is, however, no easy matter. According to Paulo Freitas,
an expert on chip manufacturing at the Technical University of Lisbon, magnetic memory elements will
have to become far smaller and more reliable than current prototypes if they are to compete with electronic
memory. At the same time, they will have to be sensitive enough to respond when the appropriate wires in
the control matrix are switched on, but not so sensitive that they respond when a neighbouring element is
changed. Despite these difficulties, the general consensus is that MTJs are the more promising ideas.
Dr Parkin says his group evaluated the GMR approach and decided not to pursue it, despite the fact that
IBM pioneered GMR in hard disks. Dr. Prinz, however, contends that his plan will eventually offer higher
storage densities and lower production costs.
Not content with shaking up the multi-billion-dollar market for computer memory, some researchers have
even more ambitious plans for magnetic computing. In a paper published last month in Science, Russell
Cowburn and Mark Welland of Cambridge University outlined research that could form the basis of a
magnetic microprocessor a chip capable of manipulating (rather than merely storing) information magnetically.
In place of conducting wires, a magnetic processor would have rows of magnetic dots, each of which could
be polarised in one of two directions. Individual bits of information would travel down the rows as magnetic
pulses, changing the orientation of the dots as they went. Dr. Cowburn and Dr. Welland have demonstrated
how a logic gate (the basic element of a microprocessor) could work in such a scheme. In their experiment,
they fed a signal in at one end of the chain of dots and used a second signal to control whether it
propagated along the chain.
It is admittedly, a long way from a single logic gate to a full microprocessor, but this was true also when the
transistor was first invented. Dr. Cowburn, who is now searching for backers to help commercialize the
technology, says he believes it will be at least 10 years before the first magnetic microprocessor is
constructed. But other researchers in the field agree that such a chip is the next logical step. Dr. Prinz
says that once magnetic memory is sorted out 'the target is to go after the logic circuits'. Whether all magnetic
computers will ever be able to compete with other contenders that are jostling to knock electronics
off its perch — such as optical, biological and quantum computing — remains to be seen. Dr Cowburn
suggests that the future lies with hybrid machines that use different technologies. But computing with
magnetism evidently has an attraction all its own.
1. In developing magnetic memory chips to replace the electronic ones, two alternative research paths
are being pursued. These are approaches based on
a. volatile and non-volatile memories.
b. magneto-resistance and magnetic tunnel-junctions.
c. radiation disruption and radiation neutral effects.
d. orientation of magnetized spots on the surface of a spinning disk and alignment of magnetic dots
on the surface of a conventional memory chip.
2. A binary digit or bit is represented in the magneto-resistance based magnetic chip using
a. a layer of aluminium oxide.
b. a capacitor.
c. a vertical pillar of magnetized material.
d. a matrix of wires.
3. In the magnetic tunnel-junctions (MTJs) tunnelling is easier when
a. two magnetic layers are polarised in the same direction.
b. two magnetic layers are polarised in the opposite directions.
c. two aluminium-oxide barriers are polarised in the same direction.
d. two aluminium-oxide barriers are polarised in the opposite directions.
4. A major barrier on the way to build a full-scale memory chip based on MTJs is
a. the low sensitivity of the magnetic memory elements.
b. the thickness of aluminium oxide barriers.
c. the need to develop more reliable and far smaller magnetic memory chips.
d. All of the above
5. In the MTJs approach, it is possible to identify whether the top most layer of the magnetized
memory element is storing a zero or one by
a. measuring an element's resistance and thus determining its magnetic orientation.
b. measuring the degree of disruption caused by radiation in the elements of the magnetic memory.
c. magnetizing the elements either clockwise or anticlockwise.
d. measuring the current that flows through the sandwich.
6. A line of research which is trying to build a magnetic chip that can both store and manipulate
information, is being pursued by
a. Paul Freitas.
b. Stuart Parkin.
c. Gray Prinz.
d. None of them
7. Experimental research currently underway, using rows of magnetic dots, each of which could be
polarised in one of the two directions, has led to the demonstration of
a. working of a microprocessor.
b. working of a logic gate.
c. working of a magneto-resistance based chip.
d. working of a magneto tunnelling-junction (MTJ) based chip.
8. From the passage, which of the following cannot be inferred?
a. Electronic memory chips are faster and non-volatile.
b. Electronic and magnetic storage technologies play a complementary role.
c. MTJs are the more promising idea, compared to the magneto-resistance approach.
d. Non-volatile Electronics is the company set up to commercialize the GMR chips.
RC 007
6. The author quotes Snyder et al in lines 38-43 most probably in order to
(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory
Caffeine, the stimulant in coffee, has been called
“the most widely used psychoactive substance on Earth .”
Synder, Daly and Bruns have recently proposed that
caffeine affects behavior by countering the activity in
the human brain of a naturally occurring chemical called
adenosine. Adenosine normally depresses neuron firing
in many areas of the brain. It apparently does this by
inhibiting the release of neurotransmitters, chemicals
that carry nerve impulses from one neuron to the next.
Like many other agents that affect neuron firing,
adenosine must first bind to specific receptors on
neuronal membranes. There are at least two classes
of these receptors, which have been designated A1 and
A2. Snyder et al propose that caffeine, which is struc-
turally similar to adenosine, is able to bind to both types
of receptors, which prevents adenosine from attaching
there and allows the neurons to fire more readily than
they otherwise would.
For many years, caffeine's effects have been attri-
buted to its inhibition of the production of phosphodiesterase,
an enzyme that breaks down the chemical
called cyclic AMP.A number of neurotransmitters exert
their effects by first increasing cyclic AMP concentrations
in target neurons. Therefore, prolonged periods at
the elevated concentrations, as might be brought about
by a phosphodiesterase inhibitor, could lead to a greater
amount of neuron firing and, consequently, to behavioral
stimulation. But Snyder et al point out that the
caffeine concentrations needed to inhibit the production
of phosphodiesterase in the brain are much higher than
those that produce stimulation. Moreover, other compounds
that block phosphodiesterase's activity are not
stimulants.
To buttress their case that caffeine acts instead by pre-
venting adenosine binding, Snyder et al compared the
stimulatory effects of a series of caffeine derivatives with
their ability to dislodge adenosine from its receptors in
the brains of mice. “In general,” they reported, “the
ability of the compounds to compete at the receptors
“the most widely used psychoactive substance on Earth .”
Synder, Daly and Bruns have recently proposed that
caffeine affects behavior by countering the activity in
the human brain of a naturally occurring chemical called
adenosine. Adenosine normally depresses neuron firing
in many areas of the brain. It apparently does this by
inhibiting the release of neurotransmitters, chemicals
that carry nerve impulses from one neuron to the next.
Like many other agents that affect neuron firing,
adenosine must first bind to specific receptors on
neuronal membranes. There are at least two classes
of these receptors, which have been designated A1 and
A2. Snyder et al propose that caffeine, which is struc-
turally similar to adenosine, is able to bind to both types
of receptors, which prevents adenosine from attaching
there and allows the neurons to fire more readily than
they otherwise would.
For many years, caffeine's effects have been attri-
buted to its inhibition of the production of phosphodiesterase,
an enzyme that breaks down the chemical
called cyclic AMP.A number of neurotransmitters exert
their effects by first increasing cyclic AMP concentrations
in target neurons. Therefore, prolonged periods at
the elevated concentrations, as might be brought about
by a phosphodiesterase inhibitor, could lead to a greater
amount of neuron firing and, consequently, to behavioral
stimulation. But Snyder et al point out that the
caffeine concentrations needed to inhibit the production
of phosphodiesterase in the brain are much higher than
those that produce stimulation. Moreover, other compounds
that block phosphodiesterase's activity are not
stimulants.
To buttress their case that caffeine acts instead by pre-
venting adenosine binding, Snyder et al compared the
stimulatory effects of a series of caffeine derivatives with
their ability to dislodge adenosine from its receptors in
the brains of mice. “In general,” they reported, “the
ability of the compounds to compete at the receptors
correlates with their ability to stimulate locomotion in
the mouse; i.e., the higher their capacity to bind at the
receptors, the higher their ability to stimulate locomotion.”
Theophylline, a close structural relative of caffeine
and the major stimulant in tea, was one of the most
effective compounds in both regards.
There were some apparent exceptions to the general
correlation observed between adenosine-receptor binding
and stimulation. One of these was a compound called
3-isobuty1-1-methylxanthine(IBMX), which bound very
well but actually depressed mouse locomotion. Snyder
et al suggest that this is not a major stumbling block to
their hypothesis. The problem is that the compound has
mixed effects in the brain, a not unusual occurrence with
psychoactive drugs. Even caffeine, which is generally
known only for its stimulatory effects, displays this
property, depressing mouse locomotion at very low
concentrations and stimulating it at higher ones.
the mouse; i.e., the higher their capacity to bind at the
receptors, the higher their ability to stimulate locomotion.”
Theophylline, a close structural relative of caffeine
and the major stimulant in tea, was one of the most
effective compounds in both regards.
There were some apparent exceptions to the general
correlation observed between adenosine-receptor binding
and stimulation. One of these was a compound called
3-isobuty1-1-methylxanthine(IBMX), which bound very
well but actually depressed mouse locomotion. Snyder
et al suggest that this is not a major stumbling block to
their hypothesis. The problem is that the compound has
mixed effects in the brain, a not unusual occurrence with
psychoactive drugs. Even caffeine, which is generally
known only for its stimulatory effects, displays this
property, depressing mouse locomotion at very low
concentrations and stimulating it at higher ones.
1. The primary purpose of the passage is to
(A) discuss a plan for investigation of a phenomenon that is not yet fully understood
(B) present two explanations of a phenomenon and reconcile the differences between them
(C) summarize two theories and suggest a third theory that overcomes the problems encountered in the first two
(D) describe an alternative hypothesis and provide evidence and arguments that support it
(E) challenge the validity of a theory by exposing the inconsistencies and contradictions in it
(A) discuss a plan for investigation of a phenomenon that is not yet fully understood
(B) present two explanations of a phenomenon and reconcile the differences between them
(C) summarize two theories and suggest a third theory that overcomes the problems encountered in the first two
(D) describe an alternative hypothesis and provide evidence and arguments that support it
(E) challenge the validity of a theory by exposing the inconsistencies and contradictions in it
2. According so Snyder et al, caffeine differs from adenosine in that caffeine
(A) stimulates behavior in the mouse and in humans, whereas adenosine stimulates behavior in humans only
(B) has mixed effects in the brain, whereas adenosine has only a stimulatory effect
(C) increases cyclic AMP concentrations in target neurons, whereas adenosine decreases such concentrations
(D) permits release of neurotransmitters when it is bound to adenosine receptors, whereas adenosine inhibits such
release
(E) inhibits both neuron firing and the production of phosphodiesterase when there is a sufficient concentration in
the brain, whereas adenosine inhibits only neuron firing
(A) stimulates behavior in the mouse and in humans, whereas adenosine stimulates behavior in humans only
(B) has mixed effects in the brain, whereas adenosine has only a stimulatory effect
(C) increases cyclic AMP concentrations in target neurons, whereas adenosine decreases such concentrations
(D) permits release of neurotransmitters when it is bound to adenosine receptors, whereas adenosine inhibits such
release
(E) inhibits both neuron firing and the production of phosphodiesterase when there is a sufficient concentration in
the brain, whereas adenosine inhibits only neuron firing
3. In response to experimental results concerning IBMX, Snyder et al contended that it is not uncommon for
psychoactive drugs to have
(A) mixed effects in the brain
(B) inhibitory effects on enzymes in the brain
(C) close structural relationships with caffeine
(D) depressive effects on mouse locomotion
(E) the ability to dislodge caffeine from receptors in the brain
psychoactive drugs to have
(A) mixed effects in the brain
(B) inhibitory effects on enzymes in the brain
(C) close structural relationships with caffeine
(D) depressive effects on mouse locomotion
(E) the ability to dislodge caffeine from receptors in the brain
4. According to Snyder et al, all of the following compounds can bind to specific receptors in the brain EXCEPT
(A) IBMX
(B) caffeine
(C) adenosine
(D) theophylline
(E) phosphodiesterase
(A) IBMX
(B) caffeine
(C) adenosine
(D) theophylline
(E) phosphodiesterase
5. Snyder et al suggest that caffeine's ability to bind to A1 and A2 receptors can be at least partially attributed to
which of the following?
(A) The chemical relationship between caffeine and phosphodiesterase
(B) The structural relationship between caffeine and adenosine
(C) The structural similarity between caffeine and neurotransmitters
(D) The ability of caffeine to stimulate behavior
(E) The natural occurrence of caffeine and adenosine in the brain
which of the following?
(A) The chemical relationship between caffeine and phosphodiesterase
(B) The structural relationship between caffeine and adenosine
(C) The structural similarity between caffeine and neurotransmitters
(D) The ability of caffeine to stimulate behavior
(E) The natural occurrence of caffeine and adenosine in the brain
6. The author quotes Snyder et al in lines 38-43 most probably in order to
(A) reveal some of the assumptions underlying their theory
(B) summarize a major finding of their experiments
(C) point out that their experiments were limited to the mouse
(D) indicate that their experiments resulted only in general correlations
(E) refute the objections made by supporters of the older theory