WHY DO WE GET FEVER?

FEVER -

Fever is one of the most common health disorders that afflict humans. Have you given a thought to why this ailment is so common? The normal body temperature of a healthy person is 98.4F (37 deg.C). Fever is a condition in which the body temperature rises above the normal. It is a common symptom of some diseases.

The heat energy produced by the chemical reactions taking place inside the body is controlled by brain and skin. As long as there is no disease or malfunctioning in the body, the temperature remains at 98.4 deg. F. When germs of any specific disease attack the body, certain reactions take place in the body cells. As a result, the centers controlling the body temperature are affected and, the body temperature starts rising. This rise in temperature is called 'fever'. The first signs of fever are chills, loss of appetite and a feeling of weakness. The body temperature is measured with the help of a clinical thermometer.

Fever is a body mechanism that helps us in destroying the germs of diseases. During fever, some of the body organs start working fast and some physiological processes get accelerated.  The rate of production of hormones, enzymes, and blood cells increases considerably. These hormones, enzymes and blood cells start fighting the germs, causing the body temperature to rise. During fever, blood circulation and respiration become faster. Both these processes help the body in getting rid of the poisonous germs present inside. Fever is often the symptom of infection.

Persistence of any fever for a long period is not good. During fever, the internal parts get heated and there is a deficiency of water causing the contraction of the capillaries of blood and urinary tract. Protein accumulated in the body gets depleted. Disorder sets in, in the brain due to high temperature. It is, therefore, a big mistake to ignore fever and wait for it to pass. Though fever is a physiological activity aimed at fighting any disease, it is absolutely essential to seek immediate medical help once you get it.

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WHY ARE HEAD INJURIES DANGEROUS?

HEAD INJURIES -

In times of war, soldiers use special helmets to protect their heads. While driving a scooter, the riders often wear helmets to protect heads against any injury. In many cities, the government has made the helmets compulsory for riders. Do you know why the protection of the head is necessary?

The most important part of our body, the brain, is located in the cranium under the protection of bones. The human brain is divided into three main parts - the cerebrum, the cerebellum, and medulla oblongata. It controls all the important functions of the body - sight, taste, smell, hearing, touch, movements, memory, speech, etc. Any damage to the brain can disturb the proper body functioning.

Our brain is protected by the thick bone of the skull. Further, a shock absorbing fluid cushions it against the blows bumps. But if the blow is sharp or hard enough, it can injure the skull. Thus to protect the brain from injuries, it is essential to first protect the head.

Now the question arises, what may be the consequences of head injuries?
A severe head injury due to an accident may cause brain hemorrhage which eventually may lead to death. The injury may damage the memory unit of the brain by which a man can lose memory, temporarily or permanently. It has been often seen that after having a severe injury of head, people remain in the coma for long periods.

If the brain tissues are damaged, it may give rise to multiple sclerosis. Parkinson's disease is caused by a disorder of brain chemistry which may result due to a head injury. Brain injury may cause aphasia, a serious disorder of thought and communication. Apart from these effects, many other disabling conditions can be generated by head injuries.

It is, therefore, essential to protect the head against injuries.

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WHEN DID PEOPLE FIRST USE MONEY?

MONEY -

Money has always fascinated man ever since ancient times. Money has come to become the most important thing in the world. Aristotle observed that man is a social being who establishes certain norms and regulations for his social interaction. The man employed money as a mode of exchange to facilitate such social dealings for his economical aspect.

In primitive societies, when people wanted to buy anything, they had to give something else in return for it. For example, if a potter wanted to buy rice from a farmer, he offered him earthenware in exchange for rice. The farmer would accept them because he needed pots. This was called the barter system, which involved goods in exchange for goods.

During those times goods served the purpose of money. But with the development of trade, the barter system could not meet the growing demands of a convenient exchange system for buying and selling. People started using the token or symbolic goods in exchange all over the world. American Indians used beads of shells, Fijians used whale's teeth and North Americans used tobacco in their exchange system. The Roman army men were provided salt for their services. But when was the coin first used as currency?

The precise origin of money in the form of coins is not clearly known. According to the available sources, the earliest coins were minted in about 800 B.C. when Indians who lived in Asia used stamped pieces of metal as a medium of exchange. Some believe that the Chinese used coins even earlier. Coins were preferred because they were easy-to-carry and durable. The early coins were of irregular shape and were stamped with rough designs. The money value of coins depended on the value of the metal that the coins were made of. Coins were mostly made of gold, silver or copper because they were precious and durable metals.

The use of paper currency was known to China as early as in the 9th century but it did not develop in Europe until the 17th century. The governments of different countries favored the use of paper currencies and coins to simplify the monetary dealings. It helped because what mattered was the money value printed or stamped on them and not their real value. This is because the printed value on the currencies denoted their purchasing power as assured by the government. People accept a coin or currency in payment not because they value the coin itself but because they have confidence in the authority that issued it.

As coins are heavy and bulky, larger payments are made in paper money issued by the paper legal authority.

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WHY DOES THE BLOOD GROUP VARY FROM PERSON TO PERSON?

BLOOD GROUP -

Even though the blood of all the human beings looks alike, in reality, it is not so. Our blood is mainly composed of red blood corpuscles, white blood corpuscles, platelets, and plasma. It has been observed from microscopic investigations that molecules of antigens found on the surface of red blood corpuscles are different in different people. Antigen molecules are a kind of proteins that stimulate the production of antibodies. It is this difference in the antigen molecules that give rise to different groups of blood.

In the year 1900, Dr. Karl Landsteiner discovered two kinds of antigen - `A' and `B' type. He was awarded the Nobel Prize for medicine in 1930 for this discovery. Blood containing 'A' type antigen was classified as A group, while that containing 'B' type as B group. Subsequently, it was discovered that the blood of some people contains both A and B type antigens. This type was classified as AB group. The blood that contained neither A nor B type antigens was called O group. Thus the blood of all human beings has been divided into four groups. Studies made till now have revealed the existence of more than 200 groups of human blood.

However, as far as the transfusion of blood to any patient is concerned, only the aforesaid four groups of blood are important. Before transfusing blood to any patient, it is essential to get his blood group tested. It is very essential to match the blood of the patient with that of the donor before transfusion. It has been found that the blood of even real brothers and sisters may not be of the same group. On the other hand, the blood of two individuals belonging to two different states may be of the same group.

If the wrong blood transfused to the patient, he can die, because antigens of different classes cannot combine with each other. However, the blood plasma of one individual can be given to another because it is the same in everybody. Landsteiner and Alexander S. Wiener discovered another important blood antigen in 1940. This additional factor is called the Rhesus antigen or Rh factor.

Rhesus antibodies do not occur in naturally blood groups - both for recipients and donors. 'AB' group is called the universal recipients whereas `O' is the 'universal donor.

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WHEN DID THE FIRST ALPHABET APPEAR?

ALPHABET -

The origin and development of any language can be traced back to the rudimentary symbols the primitive people used in their verbal interaction. These symbols, when used over a long period, take an established pattern thus giving rise to a new language, But the growth of a language does not stop at oral communication a script for writing is also to be developed. But when did the first alphabet that enabled man to express himself in writing?

The earliest people used pictures for writing which we call pictograph. The stone age people used this form in their writing. In pictograph, a particular sign represents an object such as a tree or a bird which in turn communicates a specific meaning or idea. Ideas could be communicated through picture writing in the sense that the picture of a bird might mean flying.

The ancient Egyptians also used picture writing. But this form had its limitations. It required thousands of pictures, which were also called characters, to symbolize a few things. This drawback of pictograph led to the discovery of signs that represented sounds used in verbal communication. These signs representing different sounds were grouped differently to form new words. But when did the sound-signs first appear which we now call alphabet?

About 3500 years ago, the Phoenicians in the eastern Mediterranean, invented the first alphabet. Later the Greeks and Romans developed their own alphabet which were improvements of the Phoenician script. In fact, the word 'alphabet' is derived from two words alpha (a) and beta (b) which were the first two letters in the Greek alphabet. The appearance of the alphabet made it easier to create thousands of words using a few alphabets. For example, there are only 26 letters in English alphabet but just imagine how many words we make out of these 26 letters. Pictograph lacked this advantage since one picture represented only one meaning or idea.

Now, most of the languages in the civilized world have their own alphabet but the number of letters in the alphabet and their pronunciation differ from language to language.

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WHY IS CUTTING OF NAILS AND HAIR PAINLESS?

NAILS AND HAIR -

You may have noticed that whenever any part of our body is cut, we experience tremendous pain but when we cut out our hair or nails, we do not feel any pain. Do you know why is it so?

We have, in all, twenty nails on our hands and feet. We do not experience any pain in cutting them because they are composed of dead cells. Nails are special structures of the body formes from the outer layer of the skin. They are made up of a hard material called keratin. Keratin is a kind of dead protein. The base of the nails is located inside the skin of the fingers. The skin beneath the nails is similar to that in other parts of the body, but it has flexible fibers. These fibers are attached to the nails and keep them in a fixed position. Generally, nails are thick but their roots in the skin are very thin. The portion near their roots is white and semi-circular. It is known as lunule. The fingernails grow at the rate of about 2 inches per year. Nails are very useful for our body. They help us in picking up things as well as in doing artistic work. They protect the fingertips too. For ladies, nails are an object of beauty.

Similarly, hair is also a filamentous structure made of keratin - a dead protein. The hair grows on our head about 13 millimeters each month. We have about 100,000 hairs on our head. the base of the hair - the root, as it is often called, is in the form of a round Bulb. About 50 to 100 hairs fall every day. Each hair usually lasts for about 3 years and then it falls. New hairs grow to replace the fallen ones. They grow out of pits in the skin and are called foliates. And, it is the shape of these follicles that make our hair straight, wavy or curly.

Men and women from very ancient times have practiced the custom of cutting and styling the hair. Hairdressing occupies a very important position in grooming and beautification in the present time.

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WHY DO SOME PEOPLE SNORE DURING SLEEP?

SNORING -

You must have definitely come across people who snore during sleep. Their mouth remains open and a peculiar sound comes out while breathing. Do you know why this happens?

Normally, people breath through the nose. But some people's nose remains blocked due to some reason. And thus they breathe through the mouth. Sleeping on the back can also make a person snore. When we are asleep and breath through the mouth, the air coming out causes our soft palate (tissue at the back and top of our mouth) to flutter back and forth. Thus, a strange sound of snoring is produced. Often this vibrations also causes cheeks, lips, and nostrils to vibrate which produces an even louder sound. When we are awake, the palate remains tight and, therefore, no such sound is produced.

If we clean our nose and mouth before sleeping, snoring can be controlled to some extent. This increases the possibility of breathing through the nose rather than through the mouth. If one develops the habit of breathing through nose, the possibility of snoring is greatly reduced.

Breathing through the mouth is harmful to health. The germs of many diseases can enter directly into the mouth and causes disease. If we breathe through the nose, the hairs present in the nose do not allow these germs to enter into the body. It is, therefore, advisable to develop the habit of breathing through the nose.

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WHO WAS MICHAEL FARADAY?

MICHAEL FARADAY -

The great scientist Sir Humphry Davy was once asked by a friend to name his greatest discovery to which he replied ' Michael Faraday'. Faraday was then working as his assistant. Later his contributions in the field of electromagnetism and electrochemistry led to the invention of many things including dynamo and motor.

Born in 1791 in a poor blacksmith family, Faraday began his career at the age of 13 as an errand boy in a bookshop and moved along the pavements of London carrying and delivering newspapers. But his curious and inquisitive mind accompanied by hard work enabled him to reach great heights. His considerate employer in the bookshop taught him the art of book production. Thus Farady found an access to books and devoted his spare time to reading. He had always the inherent desire to achieve something great.

One day, Faraday got the opportunity to attend a lecture by Sir Humphry Davy. Faraday noted down his lectures and sent them to Sir Humphry along with suitable diagrams,. In return, Sir Humphry offered him the post of a laboratory assistant and Faraday served him for a long time. When Faraday got the opportunity to work on his own, his genius flourished. Chemistry was his first love and he invented stainless steel, liquid chlorine, new kinds of optical glasses, benzene etc. He also propounded the laws of electrolysis. He got instant fame when he ventured into the field of electricity. Oersted had earlier discovered that electricity could produce magnetic effects but Faraday started thinking of the reverse phenomenon. He thought if electricity could produce magnetic effects then there must be a way for magnetism to produce electricity. Later he invented the 'magneto-electric machine' that had a spinning disk became the forerunner of a dynamo. A dynamo converts mechanical energy into electrical energy. It consists of a powerful magnet and in between the poles of it, a suitable conductor (a coil) is rotated. The mechanical energy generated by rotation is thus converted into an electric current in the coil.

Faraday could not make money out of his inventions as he never bothered for money. Though at some stage of his life he earned a lot of money, he remained poor in his later days. He was generous, charitable and deeply religious. He died in 1867.

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DOES A BLACK CAT BRING BAD LUCK?

BLACK CAT  -

Have you heard someone telling you that a black cat crossing the road is a bad omen and you should not walk on the road if the cat has just passed by? Do you know why a cat in general and a black cat, in particular, is considered inauspicious?

Superstitions have taken various forms over the centuries but one of the most common superstitions that still prevails is that of the 'black cat'. Many people all over the world regard the site of a black cat as inauspicious.

The thought that a black cat is inauspicious in a mere superstition. This superstition goes back to a belief of thousands of years. The ancient Egyptians worshipped cats. They had a goddess called PASHT whose head resembled that of a cat. They believed that this goddess had nine lives. Whenever a black cat died in Egypt, its dead body was preserved as a mummy (the preserved corpse of a human being or animal). Remains of thousands of black cats have been recovered from a cemetery of Egypt. Killing a cat was then considered an offense, punishable with a death sentence. Thus people had a great fear of the sight of a black cat.

During the middle ages, witches and witch doctors always used the skull of a black cat to prepare mysterious medicines. As a result, people started thinking that a black cat brought bad luck and was a bad omen. People have believed in this superstition for many centuries. The truth is that no cat is inauspicious. The cat is a pet animal being domesticated from past 5,000 years.

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WHY DOESN'T FROZEN FOOD GET SPOILED?

FROZEN FOOD -

Have you ever wondered why we store perishable foodstuff in the freezer compartment of our fridge? It is because frozen food does not decompose for a long time and can be preserved for many months. There is an interesting fact about the discovery of the method of preserving food through low temperatures. In 1798, some explorers from Norway camped at the mouth of the river Lena in Northern Siberia. All of a sudden their dogs started barking aloud. When the explorers came out, they found the dogs digging in the snow. As they dug deeper they found the huge body of a dead mammoth. The flesh was dry. The explorers then hacked off a piece and cooked it. They found that it tasted like fresh meat. The last mammoths had died out about 30,000 years ago. This was a dramatic discovery. It meant that food could be preserved over such long periods. Since then, the man started preserving food at low temperatures.

What keeps food from getting spoiled at low temperatures? Food materials decompose because of the microscopic organisms called bacteria. At normal temperatures, bacteria flourish and multiply very fast and decompose the food. But at low temperatures, especially when the water present in the food material is frozen, the bacteria become inactive and stop growing. And thus, the frozen food can be preserved for a long time.

Nowadays, several techniques are being employed to preserve food materials. Among the important ones are the cold storage and freezing of foodstuffs. For the cold storage, many factors are to be kept in the mind. The type of food, the storage temperature and the amount of moisture in the storage room have to be taken into consideration. Cold storage temperatures range from 1Deg.C to 10 Deg.C. Freezing, however, is accomplished with dry ice (solid carbon dioxide), liquid air or nitrogen. Although freezing does not destroy the nutritive value of foods, some vitamins may be lost.

Domestic refrigerators are now widely used for food preservation. But, in a refrigerator, we can't preserve food for a long period. By using low-temperature techniques, great quantities of ice cream, frozen meat, fish, fruit, and vegetables are imported and exported throughout the world every year.

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WHAT IS THE BLACK MAGIC OF WITCH DOCTORS?

BLACK MAGIC -

In the recent times, witches and magic have become very popular due to the books of Harry Potter
. The phenomenon of magic and witch doctors is a very old one. In primitive societies, people had little control over supernatural forces, diseases, or natural calamities, etc. due to limited knowledge and lack of a scientific temper. They were afraid of natural elements because they could not control them. Occultism and mysticism dominated their lives due to ignorance.

The gradual development of science empowered men to deal with events and occurrences that were beyond their control earlier. In the primitive era, people were made to believe in them to resolve their problems. These practices gave rise to a class of people known as witch doctors, black magicians, tantriks, etc. who claimed to have mystical powers to control and influence the supernatural forces. Even today are found in certain primitive societies and villages. Among the practitioners of mysticism, the witch doctor was considered to be an important community member in a tribe. He was able to predict the weather, spot out a thief or a killer. He could treat illness by his magical powers and communicate with the dead.

Witch doctors were supposedly armed with black magic. He used it to frighten people with his power and make them follow his wishes. If he wished he could bring a curse on others, could make the crops fail, cause illness to children, or make people die. He used a variety of methods to curse people to death. Sometimes he made a small figure of the man and stuck pins in it or wound the rope around it. At times, he would get some man's hair or nail cuttings and bury them. As they decayed, the man died a slow death. People believed that he could extract blood and organs with his supernatural powers.

Witch doctors often used herbs and plants for curing illness and purifying water for curing the infection. Sometimes he would sprinkle water on a magic stone. He would chant magical songs, prayers, and dance in a weird manner to impress people. He would even dress up in bright-colored clothes and wear masks or paint his face. Some witch doctors wore hides of the animals. He hypnotized people to make them believe that he was responsible for their good luck. However, most witch doctors are quacks, they have no real power. Unfortunately, many innocent people are still victimized because of their belief in witchcraft.

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WHO WAS MOZART?

MOZART -

Mozart is one of the greatest musicians ever born in the world. Whenever the word music is mentioned, his name is the first to come up. Music has been the main component of our culture since times immemorial. Generation after generation, people have enjoyed and experienced different forms and varieties of music. As a result, every period of history has produced its own breed of musicians, but only a few have been able to make a lasting impact in the minds and hearts of people. Mozart was one such product of the 18th century who went on to become one of the most brilliant composers in the history of music. His great genius was his ability to compose every form of music that included operas, choral, orchestral, and chamber music.

Wolfgang Amadeus Mozart was born in Salzburg, Austria in 1756. His father was a musician at the court of the Archbishop and his sister was also a talented musician. Even as a very young child, Mozart could play violin and harpsichord so well that his father took him on a tour to Europe to play before the Royalty. The trio consisting of Mozart, his father, and sister, were acclaimed wherever they performed. The young Mozart began to compose at the young age of 5. Later he studied music in Italy. Did you know that Mozart composed the poem "'Twinkle, twinkle, little star" when he was just 5 and it is longer than the four lines most of us know?

During his brief life of 35 years, Mozart was able to usher in a change in the trend of music that was prevalent during that time. The symphonies, sonatas and other instrumental works created by him were full of emotional energy. In the pre-Mozart era, music mostly lacked any kind of emotional expression. He is, generally, considered as a classical composer because his symphonies, concerts, and sonatas follow the rules of the musical forms of the classical period. What is not classical about some of Mozart's music is his intense personal touch. Some of his finest compositions sound as if he was pouring his heart out in his music.

Mozart composed some of the finest operas that include The Marriage of Figaro, Don Giovanni, The Magic Flute and Cosi Fantulte. He was one of those 18th-century musicians who is bracketed with Beethoven and Hayden for evolving and perfecting the orchestral music. His operas reflected every change of mood and twist of plot. The characters were presented as real people rather than theatrical puppets.

Although Mozart captured great attention as a child artist, his popularity waned with his growing age. As a result, he had to earn his living as a humble musician. He spent a greater part of his life in poverty and his health suffered consequently. He died very suddenly after a short illness. He died in 1791 at the young age of 35. The great composer died so poorly that only the gravedigger attended his funeral.

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WHO WAS COLUMBUS?

COLUMBUS -

A man has always had a burning desire to explore the world around him. This natural urge within him to discover and see what lies beyond his limited horizon has always led him to explore outside his own land. The explorers of ancient times often undertook perilous journeys across the seas as well as by land for trading, conquest and other purposes.

But events were somewhat different in the 14th and 15th centuries. It was the period of Renaissance when after a long gap, people again became interested in every aspect of art, science, architecture, and literature. New ideas and outlooks were emerging in all fields and the field of exploration was no exception. New lands and sea-routes were being discovered by European explorers. Columbus, a very brave and determined seaman, probably has earned the highest recognition in the history of exploration for his adventures. The most famous among his voyages was the one when he discovered the first sea-route to America, thereby opening it to the rest of the world.

Christopher Columbus (1451-1506) was a gifted voyager who had a dream to discover the sea-route to Indies (Asia) by sailing westwards. Sailors of those days used to sail east to reach China, Japan, and India and managed to bring plenty of gold, spices, and treasure. Columbus was convinced that Earth was not flat but round and thought he could reach Indies quicker by sailing west as this could be the shortest route. To translate his ideas into action, he approached the kings of Portugal and England for help who turned him down. Finally, Queen Isabella of Spain agreed to sponsor his voyage and provided him with ships, manpower, and money, required for the voyage.

Columbus sailed with 90 men in three small ships - Santa Maria, Nina, and Pinta. After sailing for three weeks without the sight of any land, his crews became restive, afraid and rebellious. Finally, on October 12, 1492, they reached an island in America which Columbus named as San Salvador which was an island in the Bahamas. He was convinced that it was the Indies and he was very near Japan. When he sailed around one island to another, he saw the inhabitants of those islands whom he thought were 'Indians'. That is why they are still called American Indians and the islands he first reached are called the West Indies. During the journey, the Santa Maria was wrecked off one island which he named Hispaniola. He left 40 of his men there to form a colony and then returned to Spain where he was given a hero's welcome.

Consequently, Columbus made another voyage and arrived at Hispaniola where he found that all 40 men he left had been murdered. This time ha also visited Jamaica. Some fellow sailors complained about his wild behavior and harsh rule as a viceroy. But he was permitted a third expedition in 1498 and this time he landed on Trinidad and also stepped on the mainland America.

Though Columbus excelled as an explorer yet he failed as a governor. When complaints about his misrule were made against him and his brother, he was replaced by a new governor who promptly arrested him and sent him back to Spain. He was later pardoned and given an opportunity to make one more voyage. This time he was sure that he had reached near the mouth of the Ganges in India. He returned to Spain as a sick man, died in poverty still with the belief that he had in fact reached 'Indies'.

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WHO WAS PICASSO?

PICASSO -

Every art lover in the world has heard of the name Picasso. The famous Spanish painter and sculptor, Pablo Picasso, holds the honor of being one of the greatest and the most celebrated and the most celebrated artist of the 20th century as well as one of the most productive artists in the world history. During his 78 years of continuous artistic work, Pablo Picasso produced 13,500 paintings, 1,00,000 prints and engravings, 34,000 book illustrations, and 300 pieces of sculpture. These works are valued at over $690,000,000.

Picasso was born in Malaga, Spain, on October 25, 1881. His father was an art teacher in Malaga. It is said that Picasso as a child had already learned drawing before he could speak. At the age of 14, he could cover the lessons from an art school on a day that most people needed a month to take. By the age of 16, he had passed all the tests that Spain's art schools could offer. In 1904, he settled down in Paris and married Fernande Olive. He became famous only after his marriage.

Picasso disliked paintings that looked like photographs and admired the curving shapes of African sculpture. During the period between 1899 and 1905, he dealt with subjects like cabarets, race-courses, prostitutes, and drunkards. Later, however, he turned to the varied facets of life. After 1925, Picasso began to produce emotionally charged pictorial formulations of bodies and heads. In 1947, he took to pottery in a factory, and in 1948, he exhibited 150 pieces of painted pottery. Picasso may very well be called the 'Father of the modern art'. After the age of 85, till he was 90, he produced mythological scenes. He became more deeply involved with politics during the Spanish civil war. One of the most famous paintings of Picasso is 'Guernico', which shows the destruction of a Spanish town. His work was suppressed by the Nazis during the Second World War.

Picasso died in France on April 8, 1973.

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WHO WAS PLATO?

PLATO -

Plato was a great philosopher of ancient Greece whose writings and teachings still carry great importance. The works of this great thinker are read all over the world even now. He was a student of a Socrates and teacher of Aristotle. In fact, the ideas of Socrates were translated into writing by his great disciple Plato. He is also credited with implanting the seeds of Aristotle's thought and intellect.

Plato was born in 427 B.C. in Athens. He belonged to a wealthy aristocratic family and joined Socrates as his pupil at the age of 20. When Socrates was poisoned to death in 399 B.C., Plato left Athens in disgust and spent a few years traveling. But he returned soon to establish his famous Academy in Athens in 388 B.C. which is considered as the first university in the world.

Plato's teaching covered a wide range of subjects. But his views and thoughts on education, justice, ideal state, and ideal rulers are still hotly debated and discussed among the intellectuals. For him, 'philosophy' was the supreme thing and no learning is complete without it. He advocated the rule of philosophers, he said, "Either philosophers should be kings or kings should be philosophers". Justice for him was the performance of one's duties. His model code for ideal rulers suggested that rulers should neither get married nor own property. He said that there is an ideal world beyond the real world which can be experienced only in one's mind and man should always strive to bring the real world closer to the ideal one.

There is another interesting aspect of Plato's method of teaching. He did not permit his lectures at the Academy to be circulated in written form as he was afraid that readers outside the Academy might not understand his ideas correctly. His logic was that a man gets the opportunity to defend himself in a debate but can't do so in his writings. So when he started writing his ideas, he did so in the form of dialogues that provided the mention of different viewpoints along with his own.

Among his books, the most famous is The Republic which is a political dialogue providing
the requirements for an ideal state. This great philosopher died in Athens at the age of 80.

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WHO WAS CHARLES DARWIN?

CHARLES DARWIN -

For a long time, people believed that each form of life on the Earth appeared separately and that these forms of life have remained unchanged. Charles Darwin was the first scientist who condemned this belief and laid the foundation of the modern theory of evolution. According to his theory, evolution is the process by which all living things on Earth today descended from common ancestors that lived millions of years ago. All plants and animals have evolved in an orderly way and continue to change even now.

Charles Darwin was born in 1809. He received his education at Edinburgh University. He was fascinated by biology since his early days. When he was only 22, he got an opportunity to go around the world on a voyage, on the Beagle ship of England. The voyage lasted for 5 years and during this period Darwin saw many new countries and got the opportunity to study different creatures. It was on this voyage that Darwin formed many ideas on evolution and adaptation. After his return to England, Darwin received a letter from the naturalist Alfred Russell Wallace, who had formed a similar conclusion about evolution. A joint paper by Darwin and Wallace was read in 1858. Darwin then wrote an account of his voyage and published it in the form of a book. The title of the book was The Origin of Species by Natural selection. Its first edition was published in 1859. Setting a record, it was sold out on the very first day it appeared in the market. Darwin spent more than 20 years studying evolution.

The Origin of Species attempted to prove on the basis of Darwin's study that the living creatures had acquired their present shape and form after generations of evolution, and all of them had a common ancestry. In addition to this, his theory of natural selection explains that in the struggle for life only the fittest creature survives. Each organism differs slightly from its predecessor and in the course of time, they acquired their present form. The book caused an uproar when it was the first published.  Today, Darwin's theories are widely accepted. Darwin devoted his entire life to the study of complex problems of biological science. He avoided entering the controversies surrounding his work and left it to others to debate the supposed consequences of 'Darwinism'. The great naturalist died in 1882.

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HOW DOES MICROPHONE WORK?

MICROPHONE -

Radio and television stations make use of microphones. They are also used in public address systems and in motion pictures and phonograph records. The mouthpiece of a telephone is the simple type of microphone. Let us see what exactly a microphone is.

A microphone is a device which converts sound waves into electrical signals. These signals can then be broadcast through the air or sent over to distant points, where they can again be converted back into sound.

Microphones can be divided into two groups depending upon how they respond to sound waves. These are - the pressure type and the velocity type. The pressure type microphones contain a thin metal plate called a diaphragm. This is stretch like a drumhead inside a rigid frame. The diaphragm is a part of the electrical circuit. When the sound waves strike the diaphragm, it starts vibrations at the rate a same as the sound waves. These vibrations produce corresponding electric signals by changing the electric current that flows through the circuit.

The pressure microphones are of several types, such as a condenser microphone, a moving coil or a dynamic microphone, the crystal microphone and the carbon microphone. In the condenser microphone, the vibrating diaphragm changes the capacitance of a condenser. A moving coil microphone consists of a coil of wire attached to the diaphragm. As the diaphragm vibrates in response to the sound., the coil slides up and down the centerpiece of an M-shaped permanent magnet. The coil thus cuts through the magnetic lines of force which induce a fluctuating voltage in it. This fluctuating voltage represents the variations in sound pressure.

Crystal microphones make use of the piezoelectric effect. Whenever certain crystals, such as quartz, are bent or twisted, they generate an electric voltage. Such crystals are called piezoelectric crystals. In a crystal microphone, a piezoelectric crystal is firmly clamped at one end and attached at the other to a flexible diaphragm. When someone speaks before it, the sound waves make the diaphragm vibrate. Due to this, a pressure acts on the crystal, and as a result, an oscillating voltage is produced. This is picked up by the heads attached to the crystal surface. This is how sound waves are converted into electric signals and transmitted. A carbon microphone works like a telephone transmitter. In this, carbon granules vary the current to create a signal. Ribbon microphones have a metal ribbon instead of coils.

The velocity microphone has a light ribbon of aluminum foil loosely held in a strong magnetic field. The sound waves vibrate the ribbon. The movement of the ribbon in the magnetic field induces a current along its length which is picked up by the connecting leads. Several people including the American inventor Thomas Alva Edison have been credited with the invention of the microphone. The first practical microphone, however, was invented in 1878 by David Edward Hughes of United States. Other inventors who have contributed to the invention of the microphone are Emile Berliner, Philip Reis, Franus Blake and Henry Hunnings.

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HOW DO TRAFFIC LIGHTS WORK?

TRAFFIC LIGHTS -

The growing urbanization is a direct outcome of rapid industrialization owing to which a large population gest concentrated in the cities. This consequently, results in a heavy rush of vehicular traffic, which necessitates effective control and efficient management to avoid chaos and accidents.

Regulation of traffic is done either by uniformed men who use different hand gestures to send different signals to the drivers or by the use of traffic lights which indicate the desired signals to the drivers.

Traffic lights are found at most of the important crossings and junctions of the city. These lights are arranged one above the other on a pole and covered by glasses of three different colors, viz. green, orange and red. Red light indicates to stop, and green gives the 'go ahead' signal. Orange signals are used in between to prepare or get ready for the red signal - that it to slow down the vehicle. These lights either change at a preset time or in some cities sets of timed lights are connected together so that traffic can proceed along the main road-route at a certain controlled speed without stopping. But the modern day traffic lights are computerized and time intervals are not fixed but vary in tune with vehicular presence. But what is the working mechanism of all these types of traffic lights?

The lights with fixed timing run according to a preset timed cycle. If a vehicle pulls up just as the signals changes from green to red, then it has to wait for the cycle to be completed till the light changes to green again even if no other vehicle is present in other directions of the crossing.

But in the modern style, timings of signals are not preset but respond to the presence of the vehicles. The technique used in this case is the setting up of a weak magnetic field through an electric wire buried under the road which is sensitive to the metal parts of the vehicle of the road. A computer- operated control box  senses this through the wire and if there are no other vehicles waiting to move in other directions then it flashes the green signal to the waiting vehicle, The computers also change the lights, and in the case of a centrally computerized traffic system, it is possible to operate sets of lights simultaneously to allow an easy and smooth flow of traffic.

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WHY DOES A SHIP FLOAT ON WATER?

SHIP FLOAT ON WATER -

It is a well-known fact that a solid block of iron which may be as small as needle readily sinks in the water but something as big as a ship floats on water. It is interesting to know how it happens.

According to Archimedes principle, the apparent loss in weight of a body totally or partially immersed in a liquid is equal to the weight of liquid displaced. The center of gravity of the body and that of the displaced liquid (center of buoyancy) must lie in the same vertical line which is called the center line of the body. In the case of solid iron block, the weight of the liquid displaced is less than the weight of the block - so it sinks.

The case is different in case of an iron ship due to its special construction. Its body is shaped in such a manner that it displaces a large quantity of water, and therefore, experiences an upward thrust greater than its weight. Therefore when it floats on water, its weight is equal to the weight of water displaced by its immersed portion. In other words,  when the ship enters the water, the volume of the water displaced is much greater than the volume of actual iron immersed, and as a solid, it can't displace more than its own weight of liquid. The ship sinks only when the extent of the weight of the displaced water is equal to the weight of the ship. Thus, the remaining portion of the ship stays out of the water.

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HOW WAS WHEEL INVENTED?

WHEEL INVENTED -

One of the greatest inventions of man was the invention of wheels. Imagine the world without wheels; There would be no cars, buses, motorcycles, and trucks, literally no means of transport other than by foot or horseback.

Today we have different kinds of wheels made from different material. Wheels are used in almost all modes of transportation - trains, buses, trucks, cars, aeroplanes, scooters, cycles, rickshaws, bullock carts, etc. The invention of the wheel has enabled us to cover long distances in a short time.

How was the wonder invention made?
During the stone ages before the invention of the wheel, the man carried all loads himself. Later, animals like oxen, donkeys, horses, and camels were tamed and used for carrying the load. This was done by dragging loaded wooden planks with the help of animals. Later Stone Age man learnt to roll the loads on logs, usually downhill. The oldest known wheels were nothing but rounded slices of wood cut across a log with a hole in the center. Soon after the primitive wheel was made, two wheels were joined by an axle and fastened to a platform of wood. This could be considered as the first crude cart made in the world. In this cart, both the wheel and the axle moved.

Later, with the passage of time, more advanced versions of the wheel were developed. Recorded history says that wheels were very much used in ancient Mesopotamia (Modern Iraq) between 3500-3000 B.C. The picture of a cartwheel appears on some clay tablets from Mesopotamia dating to this era. Studies reveal that wheels were in use in Indus valley during 2500 B.C.

The next innovation in the use of wheel was the fixed axle. The axle was fastened to the vehicle and the wheels were allowed to spin freely which enabled faster movement. The first wheeled vehicles were the bullock, horse and camel carts, chariots, two and four-wheeled carts for goods and other similar vehicles. Later around 2000 B.C. Asians invented the spoke wheel that reduced the weight of the wheel to a great extent.

With the passage of time, numerous improvements have been made in the design of wheels. Today, we have the rims and spokes of wheels made of metals such as iron, steel, aluminum alloy etc. Rubber tyres and tubes are put around them to facilitate smoother movement. Different types of tyres have also been designed for comfort and stable driving. Now the wheel has become lighter, more efficient and long-lasting, and almost one of the essentials of life.

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HOW WAS GEOMETRY INVENTED?

GEOMETRY INVENTED -

Geometry, the supreme branch of mathematics, studies different kinds of figures and their properties, and also how shapes, angles, and distances are related. Elementary geometry is divided into two parts - plane geometry and solid geometry. Plain geometry deals with two-dimensional figures whereas, solid geometry deals with three-dimensional figures.

The word 'geometry' comes from two Greek words - geo meaning 'Earth' and metry meaning 'measurement'. Thus geometry simply means, measurement of the Earth. The ancient Egyptians needed geometry for remeasuring the pieces of their land, which had been washed away by the floods in the Nile. They devised a method of marking the land with the help of poles and ropes. A pole was dug into the ground at a suitable place. A second pole was placed at another place and then the two poles were connected by a rope, which marked the boundary. With two more posts, the area would be marked as a site for cultivation or building. And since their religion required them to build tombs for their dead, such as pyramids, so they needed geometry for construction purposes as well.

In the beginning, all geometry was intuitive. But in 600 B.C., a Greek teacher named Thales set about proving geometrical principles scientifically. In geometry, a truth is called a 'theorem'. Thales discovered the proofs of some theorems and marked the beginning of demonstrative geometry.

However, it was Euclid of Alexandria, Egypt, who gave geometry the status of a science. Around 300 B.C., he collected all geometric results known till then and set them in a systematic form in a series of thirteen books. These books were called 'Elements' and were used by the whole world for nearly 2,000 years. Based on these rules, Euclidean geometry was developed. As time passed by, other branches of geometry were developed that are: analytic, trigonometric, projective, Minkowskian, Non-Euclidean, and Riemannian geometry.

It is an important subject of engineering. Many instruments such as compass, sextant and the transit, used by surveyors are directly related to principles of geometry.

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HOW DID LIFE BEGIN ON EARTH

LIFE -

Today we see innumerable varieties of insects., birds and animals besides human beings on Earth.; there are various kinds of trees, plants, and bushes, too. All of them come under the category of living beings. Do you know how life started on the Earth?

To study the origin of life on the Earth, the scientists study the fossils of those animals, trees, and plants, which lived millions of years ago. Excavations carried out at various places on the Earth have made available fossils, rocks, and bones that throw a significant light on the existence of living beings of ancient times.

There are many theories about how life began on Earth. Almost all religions teach that all forms of life were created by some divine or supernatural power or force. Another theory states that life originally came to Earth from outer space through micro-organisms. Many biologists and biochemists believe that life developed from non-living matter.

However, scientific studies have revealed that life on Earth started with a unicellular organism called amoeba. This happened some 570 million years ago. From this unicellular amoeba evolved the multicellular life on earth. The first 345 million years saw the development of the marine life, the subsequent 160 million years saw the development of reptiles, and in the last 65 million years, the evolution of mammals took place. Man's birth is approximately one million years old. After a lot of research, scientists found that the cells of plants and animals are made of proteins, carbohydrates, fats and many other substances. All these substances must have existed on the earth much before the origin of the unicellular life. This perplexed the researchers. They wondered how did these substances, which are so essential for life come on earth? Then they found that these were formed by electric discharged.

Around 3500 million years ago, the Earth's atmosphere was full of ammonia, methane, hydrogen, water vapor, etc. At that time, the Earth was very hot and the sky was overcast with clouds. Lightning and thunder were common occurrences. The electric discharge during the lightning led to the chemical combination of molecules of these gases, resulting in the formation of proteins, carbohydrates, etc., which finally gave birth to the unicellular amoeba.

Even though we have been able to solve many mysterious relating to the origin of life on the Earth, there are many more aspects, which we still need to look into. For example, atoms and molecules have no life, then how come their combination creates life? What is that enables a unicellular amoeba to produce multicellular creatures? Scientists are still studying to find answers to many such complex questions.

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HOW DO ICE COLUMNS GROW INSIDE CAVES?

ICE COLUMNS -

Ice columns appear in many caves or caverns. They are called stalactites and stalagmites. Stalactites are stony deposits hanging like icicles from roofs of the caves. Stalagmites are similar deposits rising in columns and cones from floors of the caves. Do you know how are they formed?

Most of the caves occur chiefly in limestone and chalk formations. Limestone is a fairly soft rock mainly made of calcium carbonate that can be dissolved by a weak acid. The acid that dissolves limestone comes from rainwater. Falling drops of rain pick up carbon dioxide from the air. This carbon dioxide changes the rainwater into carbonic acid that dissolves the limestone. The seepage of water down the cave walls and through the roof produces constant dripping and evaporation. Stone icicles formed on the cave roof, slowly grow with the addition of successive layers of calcium carbonate. The word 'stalactite' has Greek origin and means 'drop by drop'. This is why these stone icicles are also known as 'dripstone'.

At the initial stage, the stalactite remains hollow due to faster carbonate deposit at the outer ring of the water drops. However, it slowly turns to solid when the cavity fills up in the process of evaporating the water particles from the mineral substances.

If the seepage of water is quick the drop might fall on the floor of the cave. It deposits its calcium carbonate there and cones and domes of stone are formed. These are called stalagmites. They may grow up to join the stalactites above and form single columns. They may grow up to join the stalactites above and form single columns. They may even grow as high as to block the entrance of the cave. Each stalactite or stalagmite grows at a different rate, depending on the wetness of the cave, the inside temperature of the cave and the thickness of the limestone bed above it. Some stalactite might grow an inch a year while others would take one hundred years or so to grow that much. When water stops reaching the underground caves, the stalactites stop growing and the cave is considered 'dead'.

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WHY DOES THUNDER FOLLOW LIGHTNINJG?

THUNDER FOLLOW LIGHTNING?

During the rainy season, we often see lightning in the sky. It is almost always followed by the sound of thunder. Do you know, what this lightning is and why does thunder follow it?

In ancient times, whenever man saw lightning in the sky and heard thunder he believed that gods were angry and punishing him for some sin. Benjamin Franklin was the first person who, in 1872, scientifically explained the occurrence of lightning. In fact, whenever the sky gets overcast with clouds, the small particles of water present in them get charged due to air friction. In the process, some clouds become positively charged, while some others are negatively charged. When a positively charged cloud approaches negatively charged one, there develops a potential difference of millions of volts between them. Because of this high voltage, there is sudden electric discharge through the air between the two clouds and a streak of light is seen. This is called 'lightning'.

The electric discharge through the air produces a large amount of heat due to which the atmospheric air suddenly expands. With this sudden expansion, the innumerable molecules of the air collide with one another and produce sound. This is known as 'thunder'. In other words, the thunder is the acoustic shock waves, which may be a sudden clap depending upon the lightning path. Although lightning and thunder are produced simultaneously, we always see the flash of lightning first. It is so because the speed of light is very high that is 300,000 kilometers per second. On the other hand, the speed of sound is only 332 meters per second. Thus, because of high velocity, the light immediately reaches our eyes, but the sound takes some time to reach our eyes.

Thunder is the acoustic shock wave, and its sound takes more time than the flash of lightning to reach us because of its low velocity. Whenever a charged cloud passes by some tall tree or high building, it produces the opposite charge that tree or building due to induction. When the amount of charge so produced is very high, a giant electric spark travels between the cloud and the ground. It is then said that lightning has struck the tree or building.

To protect high buildings from such mishaps, pointed rods of copper or some other metal are fixed on the top of buildings, which run to the bottom and are buried deep in the Earth. These are called 'lightning conductors'. Whenever some charged cloud passes by such a building and produces opposite charge on it, the charge passes to the Earth through the metal rod and does not damage the building. Most tall structures have these lightning conductors installed in them, to protect against any damage caused by lightning.

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HOW IS ATMOSPHERIC PRESSURE MEASURED?

ATMOSPHERIC PRESSURE -

The blanket of air, dust, and moisture that surrounds our planet is called the 'atmosphere'. The air has weight and it exerts pressure. The instrument used to measure the atmospheric pressure is called a 'barometer'. The various changes in the atmospheric pressure are used to forecast the weather. For example, a sudden fall in the pressure indicates a storm. It is also used to measure the altitude or height of objects above sea level.

In 1643, an Italian, Evangelista Torricelli, demonstrated that air exerts pressure. He was able to prove that air pressure at sea level is normally, 76 centimeters of mercury barometer for measuring the atmospheric pressure.

A simple barometer consists of a glass tube, open at one end and closed at the other. It is filled with mercury. When turned upside down and immersed in a container of mercury, there is a drop in its level in the tube. The rest of the mercury is held up in the tube due to the air pressure. The height of the mercury column, in the tube, indicates, the atmospheric pressure. This simple barometer was later improved upon by a scientist called 'Fortin'.

Nowadays, two types of barometer are used to measure the atmospheric pressure: mercury barometers and aneroid barometers. In a mercury barometer, a printed scale, besides the tube containing mercury, indicates the pressure. They are heavy and are difficult to move from place to another. Aneroid barometer does not use any liquid. It consists of a cylindrical box, which is evacuated and closed with a thin elastic diaphragm. The variations in atmospheric pressure cause the diaphragm to move in and out. The change is indicated by a pointer, which moves on a scale by a system of levers. Aneroid barometers are smaller in size, and thus, easier to carry. Scientists now measure air pressure in a unit called 'millibar'. The millibar is equal to the column of mercury - 0.08 centimeter high in a tube of 1-centimeter diameter. Previously, it was being measured in the unit 'torr'. One torr is equal to 1 millimeters column of mercury. The atmospheric pressure equals 6.7 kilograms per square inch or 14.7 pounds per square inch.

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HOW DO WE MEASURE THE MASS OF THE EARTH?

MASS OF THE EARTH -

When we wish to know the mass of an object, we weigh it in a balance. The size of the balance varies with the size of the object to be weighed. The earth is a giant body and to think of a balance for weighing it, is almost impossible. Then, what is the way of measuring the mass of the Earth?

Scientists use Newton's law of gravitation to determine earth's mass. According to this law, there exists a force of attraction between any two bodies in the Universe and this is dependent on the masses of the two bodies as well as on the distance between them. The force of attraction is directly proportional to the product of the masses of the two bodies and inversely proportional to the square of the distance between them.

An experiment is performed to determine Earth's mass with the help of the above-mentioned law. In this experiment, a small metallic ball is suspended with the help of thin thread. The position of this ball is accurately determined. Now a big lead ball weighing a ton is brought near this ball. The small ball is attracted towards the big ball due to the gravitational pull and as such, it is slightly displaced from its initial position with respect to the big ball. The change in the position of the small ball is even less than one-tenth of an inch. This displacement is very accurately measured with the help of the precision instrument. Using the value of displacement in a formula of physics, the mass of the earth is calculated. The mass of the earth has been found to be  598x10 (5980,000,000,000,000,000,000) tonnes.

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HOW DOSE THE INTAKE OF SALT HELP OUR BODY?

INTAKE OF SALT -

The human body contains about 65% of water. Some body parts have very high water content, for instance, muscles contain 75% water, while liver 70%, brain 79%, and kidneys have 83% water content. The water present in the body has common salt dissolved in it. To maintain the required level of salt in the body, we eat salt. Now the question arises-why should we maintain a certain level of salt in our body?

According to one scientific theory, all land animals including man, are the descendants of organisms that came from the sea. The body fluid of these creatures had a high content of seawater. Since they were born in the seas, they were not able to survive without salt water. When these creatures shifted to dry land, they retained seawater as their body fluids, as the organs of the body were accustomed to it. Once out of the sea they still needed salt, and as they could not get it from the sea, to make up the deficiency of salt, they started consuming salt.

Carnivorous animals do not need extra salt since their salt requirements are fulfilled by the amount of salt present in the meat they consume. This is true of human beings also. Non-vegetarians need only small quantities of salt. Eskimos who are mainly non-vegetarians take very little salt.

Those who live on land need more salt. In ancient Mexico, common salt was treated so precious that people used to worship it as God. The word 'salary' comes from the word salt because in Roman times 'salarium' or allowance of money for salt was given to officers and men in the Roman Army. Most of the salt in our body is stored in the skin. The excretions from our body deplete the amount of salt in our body. If we consume food without salt, the amount of salt in the blood reduces, in which case the salt stored in the skin gets used up. The excretion of salt from the body is mainly done by the kidneys and skin as sweat.

Salt is essential for effective functioning of our body. Today, iodized salt is consumed to meet the iodine requirements in our body. Iodine deficiency causes ailments like goiter and congenital disease like cretinism. Some medical authorities opine that excess of salt intake increases the risk of high blood pressure and hence leads to heart attack.

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HOW DO URINE TESTS HELP IN DIAGNOSIS OF DISEASES?

URINE TESTS - 

Diagnosis of different diseases by urine examination has been a common practice for a long time. But the traditional methods were not very scientific as the modern methods. Although special urine tests in the laboratory can reveal many diseases, even a casual examination can indicate certain diseases. Let us see how different urine tests help in diagnosing some diseases.

Normal urine is straw yellow in colour due to the presence of the pigment 'urochrome'. If a person has a fever, it becomes deep yellow. In case of jaundice, it becomes still deeper in colour. Consumption of vitamin B-complex also makes the urine deep yellow. This is because of the presence of riboflavin in the tablets. If the colour of urine changes to brown or black due to atmospheric pressure, it indicates congenital disease called alcaptonuria. If its colour is brown or black, it suggests derangement of hemoglobin metabolism.

If the urine of a diabetic patient is left in the open for some time, it would attract ants. This is due to the presence of glucose in it. Its taste is also sweetish. To test the presence of sugar in urine, it is boiled with Benedict solution. If a red precipitate is formed, it indicates the presence of glucose. To test albumin in the urine, dilute acetic acid is added to it and heated. If a white precipitate is formed, it indicates the presence of albumin. Normal urine should not contain albumin.

Another test is performed to detect the derangement of fat metabolism in the body. In this test, urine is treated with ammonium sulfate, sodium nitroprusside, and alkali. If red colour develops, it indicates the abnormality. Normal urine should have no such colour. Urine culture test also provides valuable information regarding the bacterial infections in the body. It is done only when the doctor advises it. Nowadays, many more complicated urine tests like urine culture are done to detect the diseases and sensitivity to antibiotics.

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HOW LONG CAN MAN SURVIVE WITHOUT FOOD?

WITHOUT FOOD -

Like air and water, food is also an essential part for all leaving beings. From the smallest insects to the biggest animals-all need food for their survival. So much so that even plants cannot live for long without food. Each person requires a certain amount of food daily, depending on his size, weight, age and amount of activity. Most of us feel uncomfortable if we skip just one meal. Also, if we go without food for 12 hours or more we feel all the more lethargic.

The energy required to do work obtained from the food we eat. Our cells and tissues suffer damage every day while doing work and need to be repaired and replaced. Food is thus needed for the growth, maintenance, and development of our body. In short, we need carbohydrates, proteins, fats, vitamins, minerals and water as food for the proper functioning of our body.

Have you ever given a thought to how long we can survive without food? There are some animals that can store food in their bodies and live on stored food for a long time. It has been observed that smaller and more active animals consume more food than others, in proportion to their body weight. Warm-blooded animals use up the food stored in their body more quickly. A dog can survive without food for 20 days at the most. However, some bugs can survive without food for one full year.

Man canto store food in his stomach. If he misses one meal, he feels weak. Food is required to maintain the flow of blood. All constituents of blood are obtained from food. The moment blood runs low on nutritional materials, a signal goes to the brain and we start feeling hungry.

There are a few examples of people who survived for a year-long time without food. Angus Warviern of Scotland survived without food for 382 days, i.e. from June 1965 to July 1966. During this period,  he took only coffee, tea water, and soda water. One South African woman survived for 102 days on water and soda water. Stefan Taylor of New Zealand survived for 40 days in 1970 on a daily intake of just one glass of water. There are many such examples. Such people are endowed with exceptional power. A common man can, at the most, survive without food for a week.

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WHICH FISH KEEPS ITS EGGS IN ITS MOUTH?

EGGS IN ITS MOUTH -

Eggs in the mouth? Sounds quite strange! But there is a fish known as the catfish, which is found in the Atlantic Ocean off the east coast of America. It is quite different from other fish as it keeps its eggs in its mouth. The interesting fact about it is that instead of the female, the male takes the responsibility of looking after the young ones. After the eggs are laid and fertilized, the male quickly puts them into his mouth. The young ones completely fill its mouth and prevent it from eating. The male fish carries them around for a month. During this period it is unable to take its food and lives off the food reserves built up before the spawning. Moreover, his motherly role does not end even after hatching of eggs. For two more weeks, the youngsters swim into his mouth to hide when any danger threatens them. There are seven kinds of fishes, which are called catfish and are found in eastern and central North America.

Some species, like the flathead catfish and blue catfish, can weigh more than 45 kilograms. The catfishes live near the bottom of slow-moving rivers and lakes. They have four pairs of barbels around their mouth. These barbels look like the whiskers of a cat and hence they are called catfishes. The barbels are quite sensitive and help the catfish feel its way around and find its food.

The male catfish plays the role of a mother immediately after the fertilization of eggs. The electric catfish is a variety which uses electrical discharges to stun and capture other fishes. Its electric organs lie just under the skin and cover its body and part of the tail. A large catfish may even produce a voltage of 350 volts.

Another kind of catfish, the wels catfish, grows to huge sizes in muddy-bottomed lakes in central Europe. Some specimens grow up to 9 feet in length and weigh 600 pounds; some other compete with Arapaima, which is claimed to be the largest freshwater fish in the world.

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WHAT ARE HARMONES?

HORMONES -

Hormones have been called the 'chemical messengers' of the body. They are substances that regulate certain bodily functions such as, growth, development, reproduction, and metabolism. There are eight well-defined endocrine (or ductless) glands in the body. The main endocrine glands are the pituitary, thyroid, parathyroids, pancreas, adrenals, testes and ovaries. In all, they secrete at least 25 hormones into the bloodstream. The absence or excess of hormones causes certain bodily malfunctions such as diabetes, goiter, dwarfism, and gigantism. What are these different endocrine glands and what are the hormones they produce?

An endocrine gland is groups of cells., which take away certain raw materials from the blood and convert them into hormones. The hormones are then released directly into the bloodstream. The pituitary gland is situated near the base of the brain. This gland produces a number of hormones, which control most of the functioning of other glands. One of these hormones controls the growth of the body. If it is overactive, it causes an abnormal growth or gigantism. Similarly, if it is underactive it leads to dwarfism.

The thyroid gland secretes a hormone called 'thyroxin', which is rich in iodine. An abnormality in its secretion can cause serious disorders in the body. If the secretion is insufficient in children then they do not grow in a normal way, either physically or mentally. It controls the oxidation of food in the body. If too little thyroxin is produced, people become very fat. This is because their food is changed into fat instead of being oxidized to produce energy. If the diet lacks iodine, the thyroid gland can get enlarged. This is called 'goitre'. Consuming iodized salt may help to prevent goitre. Our body has four parathyroid glands. Each is about the size of a rice grain. Their hormones enable the teeth and bones to make use of calcium. It is also necessary for proper functioning of the nervous system.

The thymus gland is located in the chest region. To begin with, it is large but becomes progressively smaller as the child grows up. The thymus produces thymosin. Although its function is not clearly understood the hormone apparently protects babies from disease. The adrenal glands are located just above the kidneys. These glands produce a hormone called 'adrenaline' in times of a anger, fear or tension. This increases heartbeat and the amount of energy available to the muscles. The pancreas produces two hormones - pancreatic juice and insulin. Pancreatic juice is used in the digestion of food while insulin controls the amount of sugar in the blood. Insufficiency of insulin results in a disease called 'Diabetes Mellitus'. Its excess, however, can cause hypoglycemia, which is characterized by low blood sugar.

Testes and ovaries are male and female sex glands, respectively. Testes produce testosterone, a male sex hormone. The ovaries produce three hormones-estrogen, progesterone (which controls menstrual cycle) and relaxing. Progesterone plays an important role during pregnancy. Relaxin helps widen the birth canal (vagina) just before the birth of a baby. Hormones control the amounts of various chemical constituents in the body; they regulate the rate of chemical reaction inside the body cells during normal and stressful activities and they control the chemical process involved in growth. One of their most important functions is to maintain functions is to maintain the body's internal environment in a steady state. Specific hormones control the balance of water, important minerals such as, sodium, potassium, calcium, and glucose, which is the main source of energy.

Scientists have now developed synthetic methods for producing hormones. These are used to treat hormonal deficiencies. Synthetic sex hormones are used in birth control pills. Cortisone hormone is often used to treat arthritis and allergies.

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