Ancient Egypt :


INTRODUCTION Ancient Egypt, homeland of the Egyptian civilization, one of the earliest and greatest civilizations, which began in about 3100 BC, flourished for over 2,000 years up until 1070 BC, and ended in about 30 BC. Ancient Egyptian civilization was remarkable for its richness and sophistication, seen not only in the great monuments that to this day bear witness to the power of pharaohs and the skill of engineers, but also in its evolved system of government, the invention of irrigation and picture-writing, the beginnings of astronomy, mathematics, and medicine, and in its pantheon of deities and concepts of life after death, and great artistic skill. So much is this true that the Greek historian Herodotus, writing in the early 5th century BC, observed that “there is no country that possesses so many wonders, nor any that has such a number of works which defy description”.
Modern knowledge about life in ancient Egypt is derived in large measure from the great monuments and tombs that still exist today and from the findings of archaeology, which have revealed a wealth of objects, preserved in the arid climate. A significant facet of Egyptology is the information provided by writings in hieroglyphic script; covering the walls of tombs and temples, obelisks, and columns, and found on clay tablets and in contemporary manuscripts, these writings describe various aspects of life in ancient Egypt, from the greatness of kings to medicinal cures and the minutiae of tax revenue. However, were it not for the Rosetta Stone, this hieroglyphic script might still be indecipherable today. Ancient Egyptian civilization began around 3,100 BC, when the kingdoms of Lower Egypt (on the Nile delta) and Upper Egypt (south of the delta) were unified by the legendary king, Menes, who ruled from the capital, Memphis. The period known as the Old Kingdom was established in 2686 BC: it was during the Old Kingdom that hieroglyphic writing developed and the great pyramids were built. The Middle Kingdom (1991-1786 BC) was a period of prosperity, when Nubia, taken by conquest, became part of the kingdom of Egypt and trade links in Asia were established. During the New Kingdom (1554-1196 BC), when the capital was moved to Thebes, the Egyptian Empire was at its greatest and Egyptian civilization reached its zenith ... .

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Telephone II :



IV TRANSOCEANIC TELEPHONY
Overseas radio-telephone service was introduced commercially in 1927, but the problem of amplification prevented the laying of telephone cables until 1956, when the world’s first transoceanic submarine telephone cable, extending between Newfoundland and Scotland, was placed in service.



V CARRIER-CURRENT TELEPHONY
Through the use of frequencies above the voice range, extending from about 4,000 to several million cycles per second, or hertz, as many as 13,200 telephone messages can be carried simultaneously over a single conducting medium. Carrier-current telephony techniques are also being used to send telephone messages over the normal distribution lines without interfering with regular service. With the growth in size and complexity of systems, solid-state amplifiers, called repeaters, are used to amplify the messages at regular intervals.



VI COAXIAL CABLE
Developed in 1936, the coaxial cable uses cable conductors to carry a large number of circuits. The modern coaxial cable consists of copper tubes 0.95 cm (0.375 in) in diameter. Each has a thin copper wire held exactly in the centre of the tube by plastic disc insulators about 2.5 cm (1 in) apart. The tube and the wire have the same centre; that is, they are coaxial. The copper tubes shield the transmitted signal from electrical interference and prevent energy losses by radiation. A cable, consisting of up to 22 coaxial tubes arranged in tight rings sheathed in polyethylene and lead, can carry 132,000 messages simultaneously.



VII OPTICAL FIBRES
Coaxial cables are increasingly being replaced by optical glass fibres. Messages are digitally coded into pulses of light and transmitted over great distances by these slender fibres. A fibre cable may contain up to 50 fibre pairs, each pair carrying up to 4,000 voice circuits. The basis of the new fibre optics technology, the laser, exploits the visible region of the electromagnetic spectrum, where frequencies are thousands of times higher than in radio and thus able to carry much larger volumes of information. The light-emitting diode (LED), a simpler device, is adequate for most transmission purposes.
One fibre-optic cable, TAT 8, carries more than twice the number of transatlantic circuits that were available in the 1980s. Used in a system that stretches from New Jersey to Britain and France, it can transmit up to 50,000 conversations at once. Such cables also provide channels for high-speed transmission of computer data that are more secure than those offered by communications satellites. Another major advance in telecommunications, TAT 9, which is an even higher capacity fibre cable, came into operation in 1992 and can carry 75,000 calls simultaneously... .

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Alzheimer's Disease :



I INTRODUCTION Alzheimer's Disease, progressive degenerative disease of the brain and the leading cause of dementia in the elderly. Symptoms of sufferers include loss of recent memory, disorientation for place and time, and a progressive loss of capacity for thought, learning, planning tasks, and maintaining attention to what is going on around them.


II OCCURRENCE It was first described by the German neuropathologist Alois Alzheimer in 1906. It is estimated that 20 per cent of people over 80 in the United Kingdom will develop dementia and that Alzheimer's disease is by far the main contributing cause. The number of individuals with this condition is estimated to rise to over 1 million by the year 2010. Percentage rates (cases per 100 individuals of 65 years and over) worldwide vary considerably between 0.6 in China to 10.3 in Massachusetts in the United States. The prevalence of the disease increases with advancing age, but there is no evidence that it is caused by the ageing process.


III CAUSES AND DIAGNOSIS The cause of this disease has not been discovered. However, the ability of doctors to diagnose Alzheimer's disease has improved in recent years, but remains a process of elimination. Final diagnosis can still only be positively confirmed by post-mortem examination. Computerized tomography and magnetic resonance imaging scanning can show the brain shrinkage characteristic of the disease.
During a post-mortem, Alzheimer's patients show massive nerve cell loss in all parts of the brain. The hallmark lesions of Alzheimer's disease include abnormal proteins known as neurofibrillary tangles and neuritic plaques. The nature of these abnormal proteins and the location of the gene for producing the precursor protein have been identified; and excess amounts of amyloid protein have been discovered in pathological examinations of the brains of Alzheimer's patients. Alzheimer's disease is also characterized by profound deficits in the brain's neurotransmitters (chemicals that transmit nerve impulses, particularly acetylcholine), which have been linked with memory function.
The important scientific issue concerning the disease revolves around the question of why particular classes of nerve cells are vulnerable and subject to cell death. Many researchers are actively pursuing an answer to this question in studies examining the potential effects of genetic factors, toxins, infectious agents, metabolic abnormalities, and a combination of these factors. Recent findings indicate that a percentage of Alzheimer's cases are inherited. The average life expectancy of people with the disease is between 5 and 10 years, although many patients now survive 15 years or more because of improvements in care and medical treatment. Palliative therapy (relief of symptoms) is still the only treatment available.

Telephone І :


Telephone, communication instrument designed to transmit speech and other sounds to a distant point by means of electricity, and to reproduce them. The telephone contains a diaphragm, which vibrates when struck by sound waves. The vibrations (wave motion) are converted into electrical impulses and transmitted to a receiver, which converts the impulses back into sound.
In common usage, the term “telephone” is also applied in a much broader sense to the entire system to which an individual telephone set is connected; a system which allows the sending of not only a user’s voice but also data, pictures, or any other information which can somehow be encoded and converted into electrical energy. This information is exchanged between points connected to the network. The telephone network consists of all of the transmission paths between subscriber’s sets and of the switching machinery used to select a particular path or group of paths between subscribers.


II DEVELOPMENT In 1854 the French inventor Charles Bourseul suggested that vibrations caused by speaking into a flexible disc or diaphragm might be used to connect and disconnect an electric circuit, thereby producing similar vibrations in a diaphragm at another location, where the original sound would be reproduced. A few years later, the German physicist Johann Philip Reis invented an instrument that transmitted musical tones but could not reproduce speech. In 1877, having discovered that only a steady electric current could be used to transmit speech, the American inventor Alexander Graham Bell produced the first telephone capable of transmitting and receiving human speech with its quality and timbre.


III BELL’S MAGNETIC TELEPHONE The basic unit of Bell’s invention consisted of a transmitter, a receiver, and a single connecting wire. The transmitter and receiver were identical; each contained a flexible metallic diaphragm and a horseshoe magnet with a wire coil. Sound waves striking the diaphragm caused it to vibrate in the field of the magnet. This vibration generated an electric current in the coil that varied in proportion to the vibrations of the diaphragm. The current travelled through a wire to the receiving station, where it produced changes in the strength of the magnetic field of the receiver, causing its diaphragm to vibrate and reproducing the original sound.
In the receiver of the modern telephone the magnet has been flattened into the form of a watch, and the magnetic field acting on the ferrotype iron diaphragm has been made more intense and uniform. The modern transmitter consists of a thin diaphragm mounted behind a perforated grill. At the centre of the diaphragm is a small dome forming an enclosure filled with carbon granules. Sound waves passing through the grill cause the dome to move in and out. When the diaphragm presses in, the granules become densely packed, allowing an increase in the flow of current through the transmitter ... .


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How do you know Edison ?


Edison, Thomas Alva (1847-1931), American inventor, whose development of a practical electric light bulb, electric generating system, sound-recording device, and film projector had profound effects on the shaping of modern society.
Edison was born in Milan, Ohio, on February 11, 1847. He attended school for only three months, in Port Huron, Michigan. When he was 12 years old he began selling newspapers on the Grand Trunk Railway, devoting his spare time mainly to experimentation with printing presses and with electrical and mechanical apparatus. In 1862 he published a weekly, known as the Grand Trunk Herald, printing it in a freight car that also served as his laboratory. For saving the life of a station official's child, he was rewarded by being taught telegraphy. While working as a telegraph operator, he made his first important invention, a telegraphic repeating instrument that enabled messages to be transmitted automatically over a second line without the presence of an operator.
Edison next secured employment in Boston, Massachusetts, and devoted all his spare time there to research. He invented a vote recorder that, although possessing many merits, was not sufficiently practical to warrant its adoption. He also devised and partly completed a stock-quotation printer. Later, while employed by the Gold and Stock Telegraph Company of New York, he greatly improved the company's apparatus and service. By the sale of telegraphic appliances, Edison earned US$40,000, and with this money he established his own laboratory in 1876. Afterwards he devised an automatic telegraph system that made possible a greater speed and range of transmission. Edison's crowning achievement in telegraphy was his invention of machines that made possible simultaneous transmission of several messages on one line and thus greatly increased the usefulness of existing telegraph lines. Important in the development of the telephone, which had recently been invented by the American physicist and inventor Alexander Graham Bell, was Edison's invention of the carbon telephone transmitter.
In 1877 Edison announced his invention of a gramophone by which sound could be recorded mechanically on a tinfoil cylinder. Two years later he exhibited publicly his incandescent electric light bulb, his most important invention and the one requiring the most careful research and experimentation to perfect (see Electric Lighting). This new light was a remarkable success; Edison promptly occupied himself with the improvement of the bulbs and of the dynamos for generating the necessary electric current. In 1882 he developed and installed the world's first large central electric-power station, located in New York. His use of direct current, however, later lost out to the alternating-current system developed by the American inventors Nikola Tesla and George Westinghouse.
In 1887 Edison moved his laboratory from Menlo Park, New Jersey, to West Orange, New Jersey, where he constructed a large laboratory for experimentation and research. (His home and laboratory were established as the Edison National Historic Site in 1955). In 1888 he invented the kinetoscope, the first machine to produce films by a rapid succession of individual views. Among his later noteworthy inventions was the Edison storage battery (an alkaline, nickel-iron storage battery), the result of many thousands of experiments. The battery was extremely rugged and had a high electrical capacity per unit of weight. He also developed a gramophone in which the sound was impressed on a disc instead of a cylinder. This gramophone had a diamond needle and other improved features. By synchronizing his gramophone and kinetoscope, he produced, in 1913, the first sound film (see Cinema, History of). His other discoveries include the mimeograph, the microtasimeter (used for the detection of minute changes in temperature), and a wireless telegraphic method for communicating with moving trains. At the outbreak of World War I Edison designed, built, and operated plants for the manufacture of benzene, carbolic acid, and aniline derivatives. In 1915 he was appointed president of the United States Navy Consulting Board and in that capacity made many valuable discoveries. His later work consisted mainly of improving and perfecting previous inventions. Altogether, Edison patented more than 1,000 inventions. He was a technologist rather than a scientist, adding little to original scientific knowledge. In 1883, however, he did observe the flow of electrons from a heated filament—the so-called Edison effect—whose profound implications for modern electronics were not understood until several years later.
In 1878 Edison was appointed Chevalier of the Légion d'honneur of France and in 1889 was made Commander of the Légion d'honneur. In 1892 he was awarded the Albert Medal of the Royal Society of Arts of Great Britain and in 1928 received the Congressional Gold Medal “for development and application of inventions that have revolutionized civilization in the last century”. Edison died in West Orange on October 18, 1931.