Defence

Sodium carbonate is an alkaline powder familiar to many generations of laundry workers as washing soda. However, this is a versatile substance with myriad other uses. Most notably, in this age of the skyscraper, it forms glass when heated then rapidly, cooled with sand and calcium carbonate. On a more grisly note, sodium carbonate is used in taxidermy to strip away flesh from bone. It is also a common food additive. Traditionally, sodium carbonate was sourced from mining and from the ashes of plant matter (hence its other name, soda ash). Throughout the industrial era, efforts were made to find a synthetic process to produce the compound, which was in great demand for textiles and glass. The first attempt was made in 1790 by Frenchman Nicolas Leblanc (1742-1806), who found a way to convert salt into sodium carbonate using sulfuric acid, limestone, and coal. The method worked, and was used more...

After the futuristic-looking compact disc (CD) took the audio market by storm—consigning the humble cassette tape to the back of a billion cupboards—it was only a matter of time before technological wizards set their sights on abolishing the VHS tape. Although the technology for LaserDisc already existed, it never really took off in the way that CD technology did, and so the market for a compact digital video disc was still very much open. The first proposals for a high-density CD were put forward in 1993, leading to the creation of two competing formats. Electronic powerhouses Sony and Philips led their collected investors forward with the MMCD format, going head to head with industry giants Toshiba, Masushita, and Time Warner's effort, the SD. Then, in 1995, a combined effort—known as the DVD—was officially announced and consequently developed by a consortium of ten companies. The DVD was capable of storing two more...

"To only a few chemicals does man owe as great a debt as to DDT…” National Academy of Sciences, 1970 In 1874 Austrian chemist Othmar Zeicfler made one of the more famous chemicals of all time— dichlorodiphenyltrichloroethane(DDT). Zeidler was more interested in making chemicals then determining their possible uses. It was not until 1935 that another chemist, Paul Hermann Muller (1899-1965) began a hunt for insecticides while working at the J. R. Geigy Corporation in Switzerland. By 1939 Muller had independently synthesized DDT, studied it for use as,-:an insecticide, and found it was lethal for mosquitoes, potato beetles, body lice, and other pests. Muller's studies also revealed that in small doses DDT was safe for humans. In 1940, he was granted a Swiss patent and by 1942 DDT products were commercially available. Almost immediately, the power of DDT was recognized as unparalleled in combating infectious diseases such as yellow fever, more...

It is a common misunderstanding that radio waves are sound waves. In fact, they are part of the electromagnetic spectrum—just another type of light, with a long wavelength. The clever bit is that if the waves are varied in height or length, they can carry information. Of course the most common example of this is to carry audio information, which is then deciphered by your radio and turned back into sound. There are two ways of varying radio waves and these are called AM (amplitude modulation) and FM (frequency modulation), which are the two most common modes on radio. The first changes the intensity of the transmission—or if you think in terms of waves, it changes their height—and it was this method that Canadian inventor Reginald Fessenden (1866-1932) came up with in 1906. Fessenden's set-up used a microphone to convert sound into an electric signal that was then combined with more...

Samuel Alderson developed the first working model of an electrically powered artificial arm, which appeared in 1949. Designed for factory workers who had suffered amputation, the device was very bulky and was plugged into an external power source. Reinhold Reiter, a physics student at Munich University, patented the first myoelectric prosthetic arm. Also requiring an external power source, it used muscle-contraction signals from the remaining biceps to control the opening and closing of the hand. It was bulky and used vacuum tubes. The transistor would have made the technology more feasible, but this was not invented until 1948. By then the German currency was revalued, and the project lost its funding. In 1958 a Russian team led by A. E. Kobrinski had developed a myoelectric hand controlled by signals from surviving wrist muscles. Both Otto Bock Orthopaedic Industry in Germany and Viennatone in Austria marketed versions of the "Russian hand." more...

"[Scientists] should return to the plainness... of Observations on material and obvious things." Robert Hooke, Micrographia (1664) In a mercury thermometer, mercury in a small glass bulb expands into an evacuated, linear, uniform cross- section glass tube; the amount of expansion is used to measure the temperature of the bulb. Dante Gabriel Fahrenheit (1686-1736) left Gdansk, Poland, and eventually became a glassblower and scientific instrument maker in the Netherlands. His first glass thermometer (1709) used alcohol as the expanding fluid, but this has a limited temperature difference between its freezing and boiling points. In 1714 Fahrenheit turned to mercury, a liquid metal that expands uniformly over normal temperature ranges. Fahrenheit insisted that thermometer results should be universally reproducible, and similar temperatures should be represented by the same number. To this end he introduced, in 1724, three "fixed" points and eight graduations on his thermometer tube. Zero degrees was the lowest more...

Her voice was once described as sounding like two robot tobacco auctioneers fighting over a cigar butt. However, Audrey's synthesized speech was state-of- the-art back in 1952. A clumsy acronym for Automatic Digit Recognition, Audrey was an analog computer at Bell Laboratories. But it was not her primitive voice that she was renowned for. Scientists at Bell Laboratories had tried for many years to devise a technology that could recognize human speech and Audrey was their first working solution. The potential applications for a computer that could convert words spoken by humans directly into digital text were obvious. However, the sheer number of variations in the qualities of people's voices, along with their different intonations and pronunciations, means that foolproof speech recognition is a huge task. Audrey could only recognize spoken numbers from one to ten, and used flashing lights to illustrate what she had heard—or thought she had heard. more...

"A table, a chair, a bowl of fruit, and a violin; what else does a man need to be happy?" Albert Einstein In 2006 Microsoft announced a new way in which a human can interact with a computer. The mouse and keyboard are thrown away and replaced with a tabletop containing an embedded rear-projection touch screen. Behind the screen, inside the table, are five cameras with overlapping fields of view. These can look through the screen and be programmed to recognize or read items that are placed on the screen. These cameras can also recognize physical objects, track hand gestures and the movement of pens and brushes, and read credit cards and "loyalty" cards. The software supports a multitude of touch points so many people can use the computer at once. A single user can also multitask. For example, if a digital camera is placed on the computer table, the more...

"Zillah bore Tubal-Cain; he was the forger of all instruments of bronze and iron." Genesis 4:22 Metallurgy is one of the most ancient fields of technology and also one of the most important. The use of metals has been so essential to humankind that long periods of history—the Bronze Age and the Iron Age—have been named after the metals that were used most predominantly in those times. Being able to join pieces of metal together has always been essential in making metal artifacts. The joining can be done in a number of different ways, including welding, brazing, and soldering. Metal items to be joined by welding must themselves be partly melted before the joining can take place. Brazing or soldering—which are sometimes called "hard" and "soft" soldering respectively, with brazing carried out at a higher temperature—are processes whereby pieces of metal are joined together by the introduction of a metal more...

The birthday of first Prime Minister Sh. Jawahar Lal Nehru, 14th November, is celebrated as Children's Day throughout the country. He was reciprocated as "Chacha Nehru" by the children for his immense love towards children. This year also the Children's Day was celebrated in our school with great zeal and enthusiasm. The children themselves organized the whole function. The compound of the school was beautifully decorated with multicolored buntings. Balloons were also hanging in large number. A good seating arrangement was made for the teachers and the students. The Principal was the honourable guest at the function. After the arrival of the Principal a well organized programme started. The first item was 'Vande Matram' the National Song. Then there was an item of the "Mangal Gaan". A girl student was in leading role of "Bharat Mata". She was looking very pretty in her white dress and crown on her head. more...