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The body electronics
Cosmic mountains of creation
Making ice at room temperature
Prof Yash
Pal |
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The body electronics
In all living organisms, from tiny single-celled protozoans to huge whales and sequoia trees, electricity plays vital roles in the normal functioning of the human body. Our nervous system is a highly sophisticated internal information network composed of different types of neurons (nerve cells). Sensory neurons provide input to the brain, associative neurons process information in the brain, and motor neurons carry signals from the brain to muscles and some glands.
There are approximately 12 billion nerve cells in the human body, some up to a metre long. Electricity in the cells, though not nearly as strong, is the same as the electricity that lights our house but it is produced a little differently. The electric current that lights our house is the flow of electrons whereas the electricity in our cells comes from the flow of “ions.” Ions are atoms or molecules that have an electric charge because they have either lost or gained electrons. The cells generate “potential energy” by separating electrical changes. That means the energy used to separate them will be released if they come back together. That released energy is called “voltage.” The cells separate the charges by pumping one kind of ion through a “channel,” basically a hole, in their membranes that will only let one kind of ion through. So we get two opposite charges separated by the cell membrane. But these opposite charges long to get back together. So when the cell needs electricity, all it needs to do is open one of these channels to complete the electrical circuit. The amount of electricity generated by the cells depends on what the cells do and what they use the electricity for. Nerve cells and heart cells generate a lot of electricity. Nerve cells use it to transmit messages over long distances. The specialised sensory cells associated with touch, taste, sight and the other senses produce electrical signals when the outside environment stimulates them. These signals are passed on from neuron to neuron, through the spinal cord, and into various regions of the brain. Command signals from the brain are transmitted by motor neurons in the opposite direction to muscles, which contracts after the electrical signal is received. Developments in using electrical signals of body i)
Recently researchers have developed ways to control computers using electrical signals associated with muscle contraction. One goal is to provide physically disabled individuals full use of computer without the need of keyboards and pointing devices. ii)
An electroencephalogram (EEG) is a record of the periodic voltage changes associated with brain activity; they are made by monitoring the minute voltages that appear on the scalp near different parts of the brain. EEGs show characteristic patterns for different levels of mental activity and can indicate certain disorders such as epilepsy. iii)
A small group of cells in the heart produces electrical impulses spontaneously at a rate of around 70/minute which help the heart to pump blood by coordinated muscle contraction and relaxation process. The heart rate is regulated by the brain and autonomic nervous system. An electrocardiogram (ECG or EKG) is similar to an EEG in that it is a record of voltages produced by various parts of the heart as it beats. EKGs are routinely used to detect irregularities in the heart’s operation such as heart murmur. iv)
Pacemaker: With age, the intrinsic ability of the heart to control its beating diminishes. A common problem is that different parts of the heart start to beat at different rates because the controlling signal is too weak. A pacemaker can often be implanted near the heart to remedy this problem. This device supplies a small electrical shock to the heart at regular intervals to reestablish coordinated heart contraction. v)
Defibrillators: A current of 100mA or more through the heart can induce uncoordinated contractions, called fibrillation. For over 50 years, defibrillators have been used to save lives by sending a momentary current through fibrillating hearts, thereby restoring normal heartbeat. Some individuals with high risk of fibrillation can have a miniature, automatic defibrillator surgically implanted. vi) Over the past decade another implanted device has been developed that controls tremors by sending electrical pulses into part of the brain. —
The writer is currently with the Department of Physics, |
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Homi and his Bhai
In many informal letters, Bhabha addressed Nehru, 21 years his senior, “My dear Bhai”. Nehru reciprocated. He addressed Bhabha, “My dear Homi”. But the issues discussed were seldom anything personal. These letters brought out as a special issue of NUCLEAR INDIA in 1989 reveal several interesting facets of their personal relationship. On April 26, 1948, Dr Homi Bhabha, Chairman, Board of Research on Atomic Energy reminded Pandit Jawaharlal Nehru, then Prime Minister of India, about his immediate plans in the field of atomic energy. Brief and to the point, the letter touched every aspect. Nehru received the proposals enthusiastically. He knew his protégé. On January 4, 1947, after laying the foundation stone of the National Physical Laboratories at New Delhi he said: “I do not see how we can lag behind in this very important matter, because atomic energy is going to play a vast and dominating part, I suppose in the future shape of things”… Bhabha and Nehru dreamt of India, breaking away from the shackles of poverty and disease, surging forward as a great nation. On April 3, 1950, Bhabha wrote thus to his dear Bhai, “I am writing to bring to your notice a rather serious situation, which has been developing for some time in our system. It has been observed by several people — and I have observed it myself — that the quality of the men and women who are being turned out by the universities has been gradually deteriorating since 1940…. The universities are admitting far more people than they are capable of teaching adequately with their limitations of staff and equipment…” It is true even today. Two years later, “Homi” came back to his “Bhai” with certain general proposals regarding the administration of higher technical education and research. There are many occasions on which Nehru addressed Bhabha “My dear Homi” in response to his formal letters. —
Dr K. S. Parthasarathy is former Secretary, Atomic Energy Regulatory Board |
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A dazzling photo taken by NASA’s Spitzer Space Telescope shows colossal pillars of cool gas and dust, giving scientists an intimate look at the star-forming process. The image released yesterday shows the columns stretching out like fingers similar to an iconic photo taken of the Eagle Nebula by the Hubble Space Telescope in 1995. While the Hubble visible-light image was dubbed ``Pillars of Creation,’’ NASA describes the Spitzer infrared image as ``cosmic mountains of creation.’’ The image reflects a region in space known as W5, in the constellation Cassiopeia 7,000 light years away, which is dominated by a single massive star. The largest pillars — formed by radiation and winds from hot, massive stars — contains hundreds of newborn stars. “We believe that the star clusters lighting up the tips of the pillars are essentially the offspring of the region’s single, massive star,” Lori Allen of the Harvard-Smithsonian Center for Astrophysics said in a statement. Spitzer was able to spy the stars being born inside the pillars because of its infrared capability. A visible light telescope would see the same region as dark columns outlined by specks of light. Scientists believe the pillars eventually become dense enough to give rise to a second generation of stars, which may in turn, trigger successive generations. — AP
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Making ice at room temperature
Researchers in Korea have shown that water can be frozen into ice at room temperature under certain
conditions.
Heon and his-workers at Seoul National University confined water in a
nano-sized gap and showed that it froze when an electric field was applied. They trapped the water in a nanometer wide gap between the gold-plated tip of a scanning tunneling microscope
(STM) and a gold surface. Earlier, it was predicted that water would freeze above its normal freezing point if an electric field of 109 volts per meter was applied. In Seoul, they found that the water froze in a much weaker electric field of just 106 volts per meter. The team also detected the ice through this effect on the vibrating tip of the
STM. The tip was made to oscillate with a small amplitude and high-frequency as it was moved slowly toward the surface. The ice resists the motion of the tip much more than liquid water. Ice has been observed at room temperature before, but only under extremely high pressures. Kang claimed that its discovery may affect our understanding of ice formation phenomena in diverse natural environments, such as within crevices in rocks and at biological and electrochemical interfaces. Interfacial water freezing might also affect
nano-sized electrical devices. He is now thinking about further experiments to freezing at such high temperatures. The result cold have implications for the formation of ice in a number of wide varieties of natural environments.
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This Universe
What is the “diamond ring” observed during a solar eclipse? Is it normally present? Is it a part of the sun or the moon?
Adjacent to the spectacle of the diamond ring, we sometimes also see a number of bright “beads”. This latter spectacle would occur when there happen to be several valleys or depressions, approximately in the same direction, roughly pointing towards us. These bright spots are usually referred to as Bailey’s beads. It should be clear that these beads as also the diamond ring might not appear equally spectacular in all eclipse events. The earth attracts the moon, and attracts objects such as meteors. Why is it then that meteors crash into the earth while the moon does not? How does the moon stay in perpetual orbit despite the earth’s attraction? Let me take the last part of your question first. Everything that has mass, or energy, is subject to the force of gravitation. Every particle in the universe attracts every other particle. The force is proportional to the product of their masses and inversely proportional to the square of the distance between them. When you simply drop a ball from the top of a building, it drops straight down to the ground. If you throw it outward with some force, it still drops to the ground but only after going some distance in the horizontal direction. Imagine now that you are Superman and the earth has no atmosphere (and so, offers no friction). You could then throw the ball horizontally with such high speed that, even though it keeps falling towards the earth, it never actually hits it. It could keep going round and round and become a satellite, much like the moon. If you had not imparted any horizontal (parallel to the surface of the earth) velocity to it, it would fall on to earth. Now take the case of a meteorite. Meteorites are primarily residents of the asteroid belt between the orbits of Mars and Jupiter. In this belt, thousands — or more — of objects, big and small, keep going around the sun, much like the earth and other planets. But these asteroids also have random motions, which get affected by interaction with each other as well as by the force of the planets near which they might happen to pass. Sometimes these stones are perturbed into orbits that might pass close to the earth. Most of the time they just pass by but, sometimes, gravitational attraction may pull them into a collision course with the earth. Thus, meteorites do not fall on the earth only due to their mutual force of attraction but also due to opportune velocity and direction of the stone itself. |
We celebrated the 95th birth anniversary of Dr Homi Bhabha on October 30, 2005. Pandit Jawaharlal Nehru’s 116th birth anniversary falls on November 14, 20005. These outstanding sons of India are the architects of nuclear India.
During a total solar eclipse, the moon completely covers the sun. Now think of the moment the sun is beginning to emerge from behind the moon. The sun is round and so is the moon, but not quite. The moon has ridges and valleys.
There always will be one valley in the line of sight that is deeper than the others. It is natural, therefore, that the sun will shine through that lunar indentation before it emerges out of the lunar edge, suddenly appearing like a bright diamond in the middle of a thin a streak of light along the lunar edge. Such a diamond ring can be seen either just before, or just after totality.