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| SCIENCE TRIBUNE | Thursday, July 6, 2000, Chandigarh, India |
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The digital revolution Fingers reveal sex orientation Science Quiz |
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Preventing cracks in buildings CRACKS in buildings are very common and give an impression of faulty work. Penetration of moisture through them spoils the external as well as internal finish of the building. Though it may not be possible to eliminate cracks altogether these can be minimised by careful planning and construction. Certain number of cracks always occur in RCC and brick work whenever stresses in structure exceed its strength, which can be caused due to wind pressure, foundation settlement, moisture changes and increase in load etc. Cracks are generally of two types. First are non-structural cracks (shrinkage cracks) not damaging the structure directly, but with the passage of time and seepage of water, rusting of steel reinforcement takes place making the structure unsafe. Second are structural cracks which take place due to incorrect design, overloading and faulty construction and can cause major damage to the structure. Latest buildings with thin walls comparatively tall and slender constructed on a war footing are more cracks prone as compared to old short buildings with thick walls built at a slow speed. Therefore measures for control of cracks in buildings have assumed much significance these days. The cracks up to 1 mm in width even though closely spaced and greater in number are less damaging then a fewer number of wide cracks (more than 2 mm width). Horizontal cracks at the base of a brick parapet wall over an RCC/RBC cantilevered (projected) slab are very common and we find almost in maximum buildings as shown in photograph and
fig. 1. Such cracks occur due to differential expansion and contraction of RCC and brick work. By having RCC parapet instead of brick parapet such cracks can be avoided completely. However, these can be minimised by delaying the construction of brick parapet over the slab for a period of minimum one month and simultaneously plastering on parapet and slab should also be deferred for another one month. Moreover, plaster should be discontinued by V-groove at the joint of slab and brick parapet to conceal the crack if any takes place later on. Dislodging or cracking of glazed, marble and granite tiles from walls can be checked by allowing about one month’s time to new brick walls to undergo excessive shear stress likely to develop between wall and the tiles before fixing the same. Cracks in external walls along the roof level usually occur when a roof slab undergoes thermal movement due to variation in temperature. Such shear cracks can be prevented by providing a slip joint bearing as shown in
fig.2. between slab and supporting wall with a smooth bearing for RCC slab/beam with 1/4 inch thick (1.3) cement plaster finished with a floating coat of neat cement followed by a thick coat of limewash.
Moreover, the bearing of the slab shall not be extended to full thickness of external wall. Roof slab must be provided with adequate insulation in the shape of earth filling/tile terracing. Ceiling plaster and wall plaster should be made discontinuous by a 10mm wide groove. This joint will also check the horizontal cracks at window sill and lintel level in the topmost storey of the building. Cracks in partition wall supported on RCC beam and slab can be avoided by having horizontal expansion joint/gap between the top of the wall and soffit of beam/slab, filled with some mastic compound and by delaying the construction of partition wall as well as plaster work as much as possible. Vertical cracks occur when two RCC beams with expansion joints rest over one masonary pillar. Such cracks can be checked by providing RCC bed plate over the masonary pillar for its full size finished with a coat of neat cement. Vertical cracks along the junction of RCC column and brick walls generally appear after a few months of construction due to differential strain between RCC and brick work. Cracks, if thin in size, can be filled in at the time of finishing coat and by removing 10cm. wide strip of plaster around the crack and then filling the crack after enlarging and cleaning the same with mortar in case of wide cracks. Cracks in RCC sun shades, projections and louvers generally occur due to inadequate cover, more water cement ratio and insufficient cover to reinforcement. To prevent such cracking and premature deterioration, it is required to construct these components with (1:1½:3) concrete of M-20 mix, with proper cover to steel reinforcement, lesser water cement ratio, proper compaction and curing of concrete for 10 days, the minimum required time. Expansion joints
should also be provided at required intervals to check transverse cracks. Freshly laid cement concrete pavements and slabs some times also develops cracks before concrete has hardened due to plastic shrinkage, specially during hot weather. In order to prevent such cracks use of warm aggregates (bajri and sand) and water should be avoided by storing the same
in shaded portion instead of direct sun, wherever possible. Concreting should be done during early hours of the day when bajri and mixing water are comparatively cool. Corner cracks in concrete floor panels can be minimised by using less water while mixing the concrete and avoiding excessive trowelling during finishing. Upheaving of concrete floor which usually happens due to sulphate attacks can also be avoided by using the brick ballast not containing more than 1% of soluble sulphates in the base course. Settlement of all types of floors can be checked by filling the earth in 9 inches layers and then watering and compacting the same before the floor is laid. Cracks in roof terracing results in leakage of roof during rains. Such cracking occurs along the parapet at the junction of the terrace and parapet. Such cracks should be repaired by enlarging, cleaning the cracks and filling with some mastic compound instead of cement mortar. Cracks around door chowkets occur mainly due to shrinkage of unseasoned wooden frames. Such cracks can only be avoided by using properly seasoned wooden frames having 10x10 mm size recess at the outer side of the chowket. These cracks can also be minimised by allowing RCC lintel to dry and
shrink as much as possible before plastering of wall. In general, to overcome cracks, masonary work should be proceeded systematically and uniformly at all levels. The plaster work on wall should be deferred as much as possible (minimum one month) so as to let shrinkage in RCC and masonary work take place before plastering. Cracks more than 1.5 mm width generally need repairing. Carrying out repairs to cracks should only be started when these have been stabilised. No useful purpose is served in repairing the cracks when these are still developing. Large number of cracks can be avoided if vibrated concrete with less water is used in all the construction work. Minor cracks repaired with the special putties (adhesives) like Feviseal/M seal available in the market have shown very good results. |
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The digital revolution The limitless potentials held out by the digital revolution that accompanied the evolution of computers and information technology have brought about a sea change in areas such as entertainment, photography, medicare, education and communications. Perhaps the digital cameras that have opened up the frontiers of
hassle-free photography are the most visible symbols of ongoing digital revolution. In fact, over the last two years digital photography has emerged as the “sunrise sector” of information technology (IT). Digital photography allows those owning personal computers to do away with the rough and tumble loading and unloading films and getting the films printed in the neighbourhood photoshops. Digital photography is a simple procedure involving clicking downloading and editing and printing it right inside one’s home. A recent study by the American outfit IDC (International Data Corporation) reveals that digital photography will emerge as a $ 5billion plus business within the next couple of years. Clearly and apparently, digitisation results in replacement of dots by smaller number of pixels — the smallest component of a picture. In digital photography, individual elements are represented by digits in the form of 0 and 1. The heart and brain of a digital camera is the charge coupled device (CCD) which is highly light sensitive. The digital data obtained from CCD is fed into a digital signal processor which adjusts the contrast and compresses the data with the result that it occupies much less space than it could have otherwise. Digitisation has also provided a new dimension to cinema industry by enhancing the visual impact of each scene by a substantial extent. The digitised audio discs not only retain the fidelity of the original sound but also are not corrupted with the passage of time as is the case with the conventional audio discs. Bits in the form of digits are perfect. Thanks to the advances in digitisation, pictures can be altered, sound can be processed and information can be manipulated without let or hindrance. Here the imagination is the only limiting factor. As pointed out by digital technology gurus, nature sets the perfect example of digitisation in the life process itself — the instruction for replication are transmitted in the four letter digital code by the DNA, the master molecule and blueprint of life. Indeed at this micro level, we clearly discern the indestructibility and immortality of digits without which life process would have remained incomplete. Significantly, the seeds of the digital revolution had been laid even before the emergence of microelectronics as the handmaiden of computer revolution. The first digital computer, ENIAC, was built out of the massive vacuum tubes way back in 1946 by a team of researchers at the University of Pennsylvania. However, it was the invention of transistors and emergence of integrated circuits that gave a real push to the march of digitisation. And with rapid shrinking of the size of chips and microprocessor, sky alone seems to be the limit for the growth of digitisation. No wonder researchers have been driving home the point that the digital technology having escaped the barriers of physical laws can continue to expand in unforeseen directions. Perhaps the best bet for giving digitisation a totally new dimension is the evolution of material systems other than silicon. For that could lead to circuits of unimaginably small size. But surprisingly in areas such as image compression, mathematical modelling has brought about a higher level of sophistication than the application of computer technology. |
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Fingers reveal sex orientation The forefinger on the right hand can indicate whether a person is homosexual, lesbian or heterosexual, AFP reports quoting a study published in Nature.Researchers at the University of California at Berkeley say the difference in length between the forefinger and the fourth finger of the hand is a pointer to sexual orientation. They base their work on a previous study, published in the journal Human Reproduction in 1998, which says finger lengths are determined by exposure in the womb to male hormones called androgens. In women, the index finger is almost the same length as the fourth finger. But in men, the index finger is more often shorter than the fourth as a result of greater exposure to androgens in the uterus, according to the theory. In, both sexes, the index-finger to fourth finger ratio is more pronounced on the right hand which seems to be more sensitive to foetal androgens than the ratio on the left hand. The Californian team found that the ratio was “significantly” smaller — that is, there was less distance between the two fingers — among homosexuals and lesbians. Among heterosexuals, the ratio was bigger. The finger measurement concurred with another finding: men who had several older brothers were more likely to be homosexuals. This backs previous research which says that, for some still unknown reason, the uterus “remembers” its previous male occupants. The higher dose of androgens also accounts for “hyper-masculine characteristics” among some gays, such as greater promiscuity and larger genitalia, the researchers contended. — PTI |
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Science Quiz 1. This British chemist turned industrialist developed an industrial process (known after his name now) for extracting pure nickel from its ore. He also produced what is popularly called producer gas, using a mixture of two common gases. Who was this industrialist ? Which two gases constitute producer gas ? 2. Some US scientists have recently made a controversial claim that particles of light (usually called photons) can be accelerated to up to 300 times their normal velocity of 3 lakh km per second. Which basic theory does this claim violate and how? 3. What is common between “trigger guard”, “trail-breaker”, “carabiner”, “crampon” and “bong-bong”? 4. Although these fresh water animals are a protected species under the Wildlife Protection Act, 1972, hundreds of these animals are being killed every year in Assam’s lakes and rivers for their meat and eggs. Which is this species that faces destruction of its breeding grounds and thus extinction? 5. A tissue or organ which is transplanted from one individual to another of the same species is called homograft or isograft. What is a tissue or organ called which is transplanted to another animal of a different species? 6. SONAR is a system that transmits and receives ultrasonic waves to locate objects under water and to measure the depth of these objects or that of water. What is the full form of SONAR? 7. Cigarette smoking contributes substantially to air pollution, especially in big cities. It has been found that a minimum air velocity of 8 km per hour is required to disperse cigarette smoke. In case the wind velocity is less than this, the smoke does not get dispersed. What is this effect called? 8. This summer fruit contains the chemicals called carotenoids which check the growth of tumours in the body and help fight cancer. When taken preferably with milk, this fruit cleans the stomach and kidneys and rejuvenates the intestines. But those suffering from skin diseases and stomach ulcers should avoid taking it. Which fruit are we talking about? 9. In organic chemistry, what general name is given to those compounds in which the carbon atoms are bonded to one another by single covalent bonds only, due to which such compounds tend to be unreactive? 10. There have been conflicting reports about the monsoon forecast in the regions of Gujarat, Rajasthan and parts of Andhra Pradesh prepared by two leading organisations of India — IMD and CMMACS. What are the full names of these two
organisations? Answers 1. Ludwig Mond; carbon monoxide and nitrogen 2. Albert Einstein’s theory of relativity, according to which no particle can move with a velocity greater than that of light 3. These are devices/mechanical aids used in rock climbing 4. Ganges softshell turtles, scientifically called Trionyx Gangeticus 5. Heterograft 6. Sound Navigation And Ranging 7. Concrete canyon effect 8. Mango 9. Saturated compounds 10. Indian Metrological Department and Centre for Mathematical Modelling and Computer Stimulation.
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New products & discoveries — IT Digest Plane for paraplegics
The idea struck the research and development wing of the University when Yataro Kasai of Vamaguchi west of Tokyo, a former pilot who has been in a wheelchair since a traffic accident in 1977, wished someone could develop the controls of a plane in such a way as to suit the needs of the handicapped. Members of the Nippon University developed exactly the kind of plane he was hoping for. Yataro Kasai has tested the plane. But he would have to wait a few more months before actually taking control. But he can fly his plane in the USA as he is not allowed to fly in Japan. However, the Japanese authorities recently granted him permission to a test flight of his own paraplane in the grounds of Nippon University in Funagashi, Chiba, near Tokyo.
Quantum hard disk drive
Network Associates
programmes
Quantum drive
interface Ultra ATA/100 is the third generation of advanced hard drive interface technology developed and introduced by Quantum. The interface is supported by Intel Corp. and other leading chip manufacturers.
IBM storage
systems CA/s solutions add superior management, monitoring, and automated data storage capabilities to the SystemPac programme and can be leveraged in both
distributed and centralised environments. For e-Business applications to run successfully, the uninterrupted availability of storage system is essential. CA’s Enterprise Storage solutions are designed to ensure continuous 24x7 storage system availability, anytime, anywhere-enterprise-wide.
SAS tie-up with
Satyam Satyam will be setting up a SAS Competency Centre in Chennai. The centre will assist corporates, especially telecom segment, in the implementation of SAS solutions and therefore benefit the end user by contributing to a speedier
wrap-up of data warehousing projects.
PictureTel
service
The service options include continuous presence layout option, audio add-on ports, meet me/Dial In service and data rates
up to 384 KBPS.
IDT integrated
processor The RC32334 extends IDT’s broad communications microprocessor family with a low cost, high-performance embedded solution for network equipment such as SOHO routers, LAN switches and xDSl residential gateways. At the heart of the integrated processor is the IDT Peripheral Bus. Transparent to designers, the IPBus functions as the “glue” that enables a simplified design methodology for integrating intellectual property modules around the high performance 32-bit CPU core.
Bright future for microchips The new chip uses magnetic fields to represent and process information. Versions currently being tested are up to 40,000 times more efficient than the electronic chips being used today. Russell Cowburn reported in Science that the chips, which he and colleague Mark Welland have developed at Cambridge University’s Department of Engineering, may revolutionise manufacture of microchips. A major advantage of the new chip is its size. Existing electronics chips can fit up to 6.6 million transistors (the basic building blocks of all microchips) into one square centimetre of space. “But we have demonstrated a device that can fit 5,500 million transistors into a similar area. We estimate in future years this could increase to 250,000 million transistors, per square centimetre,” the scientists report. The other advantage is energy consumption. Electronic chips use energy during operation, whereas a magnet does not, which means computers developed using magnetic microchips will need much less power to work. The days of carrying around heavy batteries for laptop computers and mobile phones are numbered they say. However, it will be several years before the new technology can be exploited commercially.
Cycab — the robotic vehicle The highly compact and light vehicle, called Cycab reaches speeds of
up to 30 kilometres per hour and carries two adults and luggage. It weighs three quintals. Operating like a mobile robot, it can be driven manually using a joystick, remotely controlled, assisted by automatic on-board systems for obstacle detection and guided by Global Positioning System (GPS), according to a report from Agency for Promotion of French technologies. — R. Suryamurthy and Gaurav Chaudhary. |
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