My Science School

One day I noticed that I was ready breathing through the left nostril. Some hours later, I observed that I was breathing through the right nostril but not the left one!

I wondered if anything was wrong with me.

Most of the time we use only one nostril while breathing. This happens because of alternate swelling and decongestion of some valve-like structures called turbinates in each nostril.

When one nostril swells the other one diminishes in swelling and allows passage of air. This gives a resting period to each nostril.

When we exercise or do brisk work we need more oxygen than usual. In such circumstances both nostrils open and we breathe through both of them simultaneously.

 

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The cells of the raw fruit or vegetable are tightly packed and are held rigidly together by a carbohydrate called pectin which forms a strong bond with the walls of the cells and cements the cell together. As the fruit ripens, enzymes in the cells dissolve the pectin. When this happens the cells are no longer tightly bound to each other and the fruit becomes soft to the touch. Heating also dissolves the pectin. That is why vegetables and fruit become soft when cooked.

Rather than focusing on the ripeness of fruit to try and manipulate your diet into being healthier, consider the many other factors that can affect the quality and nutritive value of your food, such as whether a fruit is in season, or if it has been frozen. Some other factors to think about include the fruit’s time to market, as well as the temperature and humidity it has been exposed to during the shipping process. Eating ripe fruit is almost always more enjoyable, from a taste perspective, and it should have the same or a greater effect on your health as eating an under ripe fruit.

 

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Mountaineers find it time-consuming and difficult to brew a good cup of tea or cook food, especially as they climb higher. You just can’t make your usual cup that cheers on the top of Mount Everest.

Water normally starts boiling when it reaches a temperature of 100  (or 212 ). But this is true only if you are at sea level. As you go higher, due to a fall in the atmospheric pressure, water starts boiling at a lower temperature. (70  or 158  on the summit of Mount Everest!)

This heat is not enough to extract the best flavour from the tea leaves. Cooking in a saucepan or pressure cooker also takes much longer on mountain tops.

 

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Basic radar equipment consists of a transmitter to generate the radio signals, a revolving scanner – the aerial or antenna that sends out and receives the signals – and a video screen on which the returning signals are displayed. The radio signals are transmitted as pulses (short bursts) at microwave frequencies, which are between 1000 and 35,000 million cycles per second. By comparison., the sound waves from a bar’s signals have frequencies of 30-120 thousand cycles per second.

Radar pulses are timed to allow one signal to hit its target and bounce back before the next one is emitted. Because radio waves travel at the speed of light, about 186,300 miles (300,000km) a second, pulse timing is measured in micro-seconds – millionths of a second. By measuring the time a signal takes to return, the distance to the target can be calculated.

If the object is moving, the returning signal has a slightly different frequency from the outgoing one. This is known as the Dolpher shift, and is caused by the radio waves bunching up if the objects approaching, or stretching out if it is going away. From this shift, radar operators can distinguish a moving object from a stationary one (such as a mountain) and can work out the direction in which it is travelling. From the size of the shift,m they can also calculate the speed. Radar microwave beams from orbiting spacecraft or satellites respond differently to the conditions they encounter – dense forests or cultivated fields, for example. Computers analyse the differing strengths of the return signals and build up picture of the surface.

 

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Bats navigate by emitting shrill squeaks that are reflected back to their ears from insect prey or obstacles in their path. Radar works in a similar way, but uses reflected radio signals to detect object up to 2000 miles (over 3200 km) away. Without radar, complex air-traffic control and missile early warning systems would be impossible to operate, and ships at sea would risk collision in the dark or in fog.

Radar devices its name from the term ‘Radio detection and ranging’. It was first developed in Europe and America in the 1930s, after the Italian engineer Guglielmo Marconi (the pioneer of radio) suggested the idea in 1922.

The French liner Normandie – which in 1935 set the Atlantic crossing record in just over four days – was fitted with radar in 1936, for detecting icebergs. By 1939 Britain, thanks to the work of physicist Sir Robert Watson-Watt, had a radar network on its south and south-east coast for detecting aircraft. The system proved invaluable to the country’s defences during the Battle of Britain in 1940. It had a range of about 40 miles (64 km), and operated day and night, passing the range, bearing and height of German planes to the RAF defence network.

Modern radar is sensitive enough to locate all the aircraft coming into a busy airport and allow air-traffic controllers to stack them at different heights in the sky while they organise a landing rota. Airliners are fitted with a radar beacon or transponder (transmitter-responder) on the underside. This sends their radar signals to the ground and back to give the pilot his altitude, and reflects signals from the airport’s two radar systems. The primary system gives warning of the aircraft’s approach and distance, and the secondary system sends coded signals to the transponder, which gives back the aircraft’s identity and height.

Radar signals can also be reflected from raindrops. Weather forecasters use radar networks to locate rain and snow clouds. Airliners have nose-mounted radar scanners that give the pilot a map of the weather up to 200 miles (320 km) ahead, so that he can avoid storms. In case of necessity, the pilot can tilt the scanner to get a rough map of the ground below.

Spacecraft and satellites orbiting the Earth use radar beams to gather information about the Earth’s surface for map-makers, geologists and oceanographers. Radar is also used to find out about the surfaces of other planets.

 

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Some toothpastes have the fluoride or mouthwash incorporated as a stripe.

The standard cleaning mixture is usually chalky white, while the fluoride or mouthwash is often a clear blue or red gel. The two pastes are mixed separately. As with all toothpastes, the empty tubes, called blanks, are filled from the wide end, which is then crimped and sealed. The two pastes contain colours that will not mix, so the pastes so not flow into one another. When the toothpaste is squeezed out of its tube, white and coloured stripes emerge.

 

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People who cleaned their teeth in the 1840s probably used one of various brands of toothpowder which contained ground-up coral, cuttlefish bone, burnt eggshells or porcelain. The powder might have been coloured purple with cochineal, derived from the bodies of tropical scale insects.

Today’s toothpastes – white, coloured or striped – contain ten or more ingredients. Some play a part in cleaning or protecting the teeth; some make the paste tastier; some bind the paste together; other help it a flow out of the tube.

The main ingredient in the white part of toothpaste is finely powdered chalk (calcium carbonate), or another mineral powder such as aluminium oxide, which is an slightly abrasive and help to remove the dulling film which is deposited by food and drink and contains decay-causing plaque.

Some titanium oxide, a white powder, is sometimes also added to whiten the toothpaste.

Clear gel toothpastes get their abrasive quality from transplant compounds of silica, often with a colouring added.

The cleaning and polishing ingredients are combined with water into a thick paste by the addition of a binding and thickening agent such as alginate, which is derived from seaweed.

A trace of detergent is added to create foam and help the cleaning process. to make the paste palatable, it is usually sweetened with peppermint oil and menthol.

A moisturizer such as glycerin is also added to prevent the paste from drying out. In addition most toothpastes now contain fluoride which helps to strengthen tooth enamel. Disinfectant such as formalin may also be included to kill bacteria.

 

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In 1861 the firm of Bryant & May produced their first safety match at a factory at Bow, East London. By the end of its first year the factory was turning out 1,800,000 matches a week. They were so much in demand that in 1871 the Chancellor of the Exchequer proposed a ‘match tax’ of a penny a box. The proposal caused an outcry in Parliament and the Press – and thousands of match workers protested at what they saw as a threat to their livelihood. Riots resulted, and so Parliament abolished the levy.

Throughout the world matchmaking techniques became more streamlined until today more than 800 boxes of matches can be made every minute.

 

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To make a pencil lead, graphite is mixed with fine clay – the soft that is used in the finest porcelain and bone china. The two ingredients are combined in different proportions to produce leads of different blackness and hardness.

The most widely used type of pencil is the HB (hard and black). Softer and blacker pencils (B and BB) have more graphite, and harder ones – graded from H (hard) to 10H – have progressively more clay.

The leads for coloured pencils or crayons contain no graphite at all. They are made from pure clay and wax, coloured with pigments.

 

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                         Most modern photocopiers use a process called xerography, which was invented back in 1937. Photocopiers contain a drum, which is coated with a photosensitive substance. It only conducts electricity when light falls on it. The drum is charged with static electricity. An image of the document to be copied is focused onto the drum. Where it strikes the drum’s surface, the static electrical charge is removed, leaving an electrostatic image of the document. The drum is then coated with black toner powder, which sticks to the charged areas. It transfers the powder to a sheet of paper, which is heated to make the impression permanent. Some older types of copier use a ‘wet’ process. These machines are used to make large prints of engineering drawings.

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                      Natural gas is widely used to supply energy for domestic use and for industrial processes. It was formed millions of years ago by the same process that produced oil. Gas flows or is pumped out of boreholes, often mixed with oil and water. The gas is separated and passes through a refinery. Some of its constituents, such as propane and butane, are removed and liquefied so they can be pumped into cylinders and used as fuel. Liquefied gases held under pressure can be carried all around the world in specially constructed ships.

                       The remaining gas, which consists mostly of methane, is pumped along pipelines for domestic use. Methane has no smell, so a strong-smelling additive is used to make people aware of gas leaks.

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                 Most powered devices in the home contain an electric motor, which turns electric energy into movement. When an electric current passes along a wire in the field of a magnet, it exerts a force to move the wire. Usually the magnet is still, while the coil carrying the current spins round inside it. Domestic motors run on alternating current, and the current in the coil is rapidly reversed so the magnet’s poles change direction too, forcing the coil to make another half-turn. This process is repeated very rapidly as the motor turns.

                 When a motor runs from direct current, which flows in only one direction, a device called a commutator reverses the current and causes the coil to rotate.

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                 Electricity is generated by burning gas, coal or oil, by water or hydroelectric power, or by nuclear power. The distribution of power to homes varies in different countries, but in Britain the voltage from the power station is between 100,000 and 400,000 volts. The electricity is carried on cables strung between high pylons, where insulators prevent it from escaping to the ground. The cables are connected across the country in a system called the National Grid. If there is a fault with one power station, power can still be obtained from the grid.

                The electricity is drawn off in substations, which reduce it to 240 volts. This voltage is used through most of Europe, while in North America 120 volts are used.

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                      The huge quantities of domestic and industrial waste that we produce cause a major environmental problem. Sometimes waste is buried in vast landfill sites, which are often old quarries. Alternatively,  waste can be burned or in some cases recycled.

                      Waste from our toilets, baths and washing machines is collected in sewers and carried to a treatment plant. Bacterial action breaks down solid waste into a harmless form, and the waste is stirred in huge pools while this process takes place. After treatment, purified water is run off and can safely be drained into rivers. The solid material remaining is usually processed into fertilizer, after further treatment to make sure it contains no dangerous microbes.

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               An adequate supply of clean water is essential for life and for health. Water is often drawn from rivers, or may be pumped up out of the ground. Rainwater soaks into the ground and collects in areas where an impervious rocky layer stops the water from draining away. Wells are bored down into this layer to extract the water. A huge mass of fresh water in porous rock beneath the Sahara desert could supply all the water needs of North Africa for hundreds of years. Water from wells is usually stored in reservoirs. Before being used it is purified. The water goes to a settling tank where mud and sediment are removed. Chlorine is added to kill any microbes.

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