My Science School

When a candle is lit, paraffin wax (a hydrocarbon) vaporuizes and mixes with air to form a combustible mixture, and burns. The air-fuel ratio changes as we move away from the wick. As a result, broadly, we have three different flame regions – blue, violet and yellow.

 

 

 

The region immediately close to the wick is fuel rich and there is insufficient oxygen. Hence the mix does not burn and the region is dark. Outside this region, the fuel-air ratio of the mixture is right enough to burn. The blue-violet colour is due to the presence of CH radicals formed during the combustion reactions. The outer yellow region is due to the radiation from fine hot soot (carbon) particles.

Milk fat as it occurs in milk has unusual characteristics. It is made up of fat globules which are 4-10 microns in diameter. These globules are covered by protective membranes made of bipolar compounds phospholipids, protein, diacylglycerides and monoacylglycerides and other surface active materials. They are collectively designated the milk fat globule membrane (MFGM).

It is likely that the violent mixing of milk, during churning, disrupts a sufficient portion of the milk fat globule membrane (MFGM) to render milk fat globules ‘sticky’.

            Further churning simply cause the ‘sticky’ fat globules to aggregrate, form bigger butter granules and rise rapidly. Excessive churning increase abrasion and leads to quicker separation.

    Lie detector, also known as polygraph, is generally used during interrogation by police.

The instrument works by recording our physiological functions such as blood pressure, heartbeat, respiration and perspiration. An anemograph tube is fastened around the subject’s chest and a blood-pressure-pulse cuff is strapped around the arm. Psycho-galvanic skin reflex (electro-dermal response) and flow of current between different parts of the body are also measured.

Sensitive electrodes are used to pick up the impulses which are recorded on a moving graph paper. The parameters are recorded when a suspect answers questions put to him by an operator. The data is then used as a basis for deciding whether the person is lying or not.

When a person lies, the graph deviates from the normal shape in one or core of the body functions. Such changes occur due to our emotional response to telling a lie.

While most of the questions asked are interrelated, some are included to improve the test’s accuracy. The questions are usually answered in ‘yes’ or ‘no’ mode only.

The modern polygraph was first constructed in 1921 by John A. Lagoon, a medical student at the University of California, along with a police officer. His instrument was capable of continuously recording blood pressure, pulse and respiration. As it recorded these conditions simultaneously it was called a polygraph. Though this has been in use since 124, it has not developed into a complete fool-proof system and is yet to be accepted judicially.

         

 

 

 

  A speech synthesizer converts computer based text (usually ASCII- American Standard Code of Information Interchange) into the spoken word. Text-to-speech technology transforms ordinary text into natural-sounding, highly intelligible speech. Speech synthesis is widely used by blind and other handicapped persons to make use of computer technology.

            Now, synthesized speech is also used in a wide range of commercial applications to tell us the phone numbers we request when we dial Information, to announce station stops, to vocalize instrument readings, and so on. The speech synthesizers used to give instrument readings and to make brief informational announcements vocalize pre-stored speech.

            A speech synthesizers converts ASCII text into speech in real time, by stringing together phonemes according to an algorithm that encodes rules for the relation of English spelling to English pronunciation. Such algorithms can be extremely sophisticated. It first parses sentences and words, then checks for any matches in a stored dictionary; if no match is found, it invokes rules for converting letters to phonemes, then applies prosodic rules for speaking in phrases and finally applies rules for converting phonemes to speech.

            It provides the highest level of speech quality and accuracy, producing clear, correct pronunciation of single characters, words even homograph pronunciations, phrases, and proper names.

            Wheat flour is kneaded with water to get a homogenous paste. This flour is made into a poori and fried in oil heated to more than  C. This temperature is higher than the boiling point of water ( C) and so the water (in liquid state) in the poori is converted into steam (in gaseous state) which occupies a greater volume. This results in the poori swelling up.

            One can see steam bubbles escaping from the oil before the poori is completely fried. Actually, only a small quantity of water converted into steam is trapped between the layers of poori. When the volume of the steam trapped exceeds a certain level, the poori bursts.

 

 

 

 

 

 

We have seen weathercocks fixed on tall towers to indicate the direction of the wind. A weathercock is essentially an arrow free to rotate on a horizontal plane about a vertical axis. It has two fins symmetrically placed on either side of the rod forming the arrow.

As the wind blows, the arrow turns and faces the direction of the wind. If the arrows does not face the wind, the pressure exerted by the wind on one fin will be lesser or greater than that on the other. Consequently the cock is forced to rotate up to a position in which the force acting on the fins are equal and opposite, is reached.

This argument can be extended to a flying flag. When the flag faces the wind, the wind blows from edge which is secured by the rope to the free edge. As it blows, the flag is subject to frictional drag. Friction is a reaction force and, in this case, it acts in a horizontal direction opposite to that of the wind force. Depending on wind turbulence (the changes in the wind speed and direction) the horizontal component of the frictional force on the flag moves from one side to the other. This causes fluttering.

 

 

 

 

 

 Flames heat a few layers of air nearby and make them less dense. Due to buoyancy this lot air moves vertically upwards creating a sort of low pressure near the flames. This causes the cool air from faraway layers to flow towards the flame form the sides and below. Oxygen present in the air keeps the fuel burning. The air near the flame gets heated very much and moves up faster. The dynamics of air flow near the flame is a complex process however mathematicians have modelled it and found that there is a greater (faster) outflow of hot air right above the flame with a smaller (slower) inflow from the sides and below. The hot air goes up and then mixes with the environment and cools down. This theory holds good only the candles or wick stoves and not for welders torch or the like where the fuel is forced in a particular direction.

            Corn is generic term to describe the fruit (grain) of cereal plants in particular. Popping corn and sweet corn are just two of the many varieties of maize grown commercially. Each variety has different properties and is grown for different reasons.

            The bulk of tissue within a grain of corn is called the endosperm. Endosperm is specialized storage tissue providing nutrients for the embryo when the seed germinates. It is also a source of carbohydrate for humans.

            In popcorn the outer part of the endosperm is hard but the centre is soft. When the corn is heated the water in the central part turns to steam causing the seed to burst (the pop that we hear) and turn inside out. Sweet corn contains more sucrose in the endosperm than other varieties, which is what makes it sweet.

            Maize, like all cereals, stores a carbohydrate food reserve in its seeds. Sugars enter the developing seed and are converted into starch. As the grain matures, excess water is removed leaving a hard, dry starch.

            In the maize varieties used for most purposes the sugar is all converted to dry starch: this type of corn is called flint corn. In sweet corn the process is not completed by the time the plant is harvested, leaving the grain moist and sweet.

            There are other forms of maize including flour corn where the starch remains soft- this was used by Native Americans because it is easy to grind and waxy corn which on milling produces flour with the texture of tapioca.

            Corn is classified into five principal commercial types according to the structure of the kernel: dent maize, flint maize, flour maize, popcorn and sweet corn.

            These crops were cultivated in the Americas before the arrival of Europeans, maize being the basic food plant of all pre-Colombian American civilizations. The grain of sweet corn contains a glossy, sweetish endosperm which is translucent when immature. A recessive gene on the fourth chromosome prevents the conversation of some of the sugar into starch. It is harvested when young and immature, when the kernels are plump but still soft and milky. As soon as the silk threads above the winter husk wither and turn brown, the cobs can be broken off, boiled and eaten as a vegetable. However, 20 minutes after picking, the sugar begins to converting to starch.

            Therefore, corn on the cob should be absolutely fresh if one wants it to be sweet. For the same reason canned or frozen sweet corn is processed as soon as possible after harvesting. The grains of popcorn are small with a high proportion of very hard endosperm and a little soft starch in the centre. On heating, the moisture in the centre expands as steam, causing the grain to pop and explode, the endosperm becoming averted as a palatable and fluffy mass. Other types of corn will crack but will not explode.

     The layer that forms on top beverages consists of fat. Such a layer is formed only on top of hot liquids because in the unheated milk the fat globules are surrounded by a thin film of protein, phospholipids and neutral fats.

When the milk is heated, this thin film breaks, making the fat globules free. These then coalesce on the surface which then come to contact with the air and forms a layer. Formation of this layer can be prevented by beating of string the heated milk continuously, as the process of homogenization increased the surface tension of the milk. But when the heated milk is allowed to cool and left undisturbed the layer formation occurs. In this condition the surface tension gets lowered and the freed fat globules rise to the surface because their specific gravity is less than that of the aqueous portion of the milk. Also black tea or coffee will not be able to form any such layer.

Bar codes are simple machine readable codes that the computer can reproduce directly into the bit streams of zeros and ones which is the machine language of computers. The information or data is encoded using the width of printed bars, width of space between bars, and relative positions of wide or narrow bars and spaces (that is, a unique thick and thin combination of black and white bars).

The equipment used to read the code is called the scanner, which converts the dark bars and white spaces into equivalent Os and Is which computers can understand.

 The information in the bar code can contain anything from country of origin, manufacturer's name and product detail. In fact, the amount of information that can be stored in these labels is limited only by the choice of symbology.  Symbology is the term used to describe the rules specifying the way data is encoded into bars and white spaces.

To give an example, the UPC A version bar code, is shown with the codes 05 1111 2 8 8 17. UPC is the Universal Product Code, widely adopted in retail stores to indentify products. The first digit 0 can stand for the country code, the next five digits (5 1 1 1 1) for the manufacturer’s code and the next five digits (2 8 8 1 7) for the product, and the last digit is called the check digit used for checking the accuracy of the reading system.

The computer checks the code and matches it with information in its own database and does the identification. It simplifies billing and inventory of products. The billing person has only to scan the label of different items sold and the bill is printed almost instatantaneously, saving time for the customer and the clerk. The other important benefit is that the inventory is automatically updated, without the need for laboriously checking each and every item, at the end of the day.

If EDI (electronic data interchange) is integrated, the system automatically  prepares a buying order for items which are about to be sold out based on a predetermined stock set by the store manager, Bar codes have helped organizations increase efficiency, reduce operational costs,  and in turn increase profits. 

            Black boxes which usually hold the clues to a plane’s crash are built strong enough to survive bomb blasts, violent impacts and intense fires. They measure approximately 4 by 6 by 8 inches and weigh about 30 kg and are kept in a which can withstand 30 minutes of 1100 degrees C at 50,000 (Btu’s) British Thermal Units per square foot per hour.

            They are actually orange in colour and a very high quality heat resistant paint is used, so that they can be spotted easily even at dimly lit crash sites. They are always placed in the tail end of the flight.

            The black box records voice and flight data. The cockpit voice recorder continuously collects data and retains a record of the most recent 30 minutes, the conversation between the pilot and the Ground Control Room.

            The flight data recorder keeps a record of the most recent 25 hours of a plane’s operating data, including altitude, air speed, vertical acceleration and heading.

            Flight data are recorded either by magnetic tape or in solid-state memory. Modern data recorders can log more than 200 different parameters and transmit data either 64 times or 128 times a second. Thus when recovered from the airplane crash sites the black helps to reconstruct a clear picture of the crash.

     Air conditioning system is the system which keeps on control and maintains the particular condition (that is required temperature and humidity of air) in the closed space.

            It is technically defined as a system which controls temperature, humidity, purity and motion of air to produce desired effects upon the occupants of the space. In case of air cooler, which has the capability to cool the air inside the space does not maintain particular temperature and humidity of the air. In response to atmospheric seasons we can have winter, or summer air-conditioning system, but any air cooler will not do so.

            A so-called air cooler or desert cooler is basically a humidifier (Humidity is the moisture or water content of air). An “air-cooler” mixes water vapour with air by means of a rolling pad of moist cloths of fibre, and makes the air seem cool, but actually more humid (high moisture content).

            An Air conditioner/refrigerator, basically a dehumidifier, works as follows:

            A fluorocarbon refrigerant gas (such as “a Freon”) is compressed. On compression it is pressurized and heated. The extra heat is removed by air (from a fan) or by cooling water as in the case of large (Central A/c) units.                                                                            

            The high-pressure refrigerant is expanded. In contrast to heating on compression the refrigerant, on expansion by sudden reduction in pressure, becomes very cold due to Joule Thomson effect.

            By heat exchange with the very cold refrigerant (which has now become liquid) passing through tubes (that have fins for good heat exchange) the air paning ore, becomes cold and is circulated in the space (room etc) to be cooled. Because the air is cooled considerably, extra moisture content on humid days may be seen dripping from the air conditioner.

            For efficient operation the room in which an air conditioner is used will have to have its doors & windows closed. On the other hand, when direct cooler are in use, at least one window should be kept open as otherwise the humidity will become very uncomfortable.

            P.S.: When humidity in the atmosphere is more, curcating will be more as the sweat will not dry fast enough. In contrast, when humidity is very less as in very cold days when all the moisture in the air would have condensed leaving the atmospheric air “dry”, lips and body skin may be seen getting cracks.

            The water for frost formation comes from the articles placed in the refrigerator and the occasional air that gets into the gadget when it is opened and closed.

            Refrigeration is the process of lowering the temperature and maintaining it in a given space. In mechanical refrigeration, constant cooling is achieved by the circulation of a refrigerant in a closed system, in which it evapourates to a gas and then condenses back into a liquid in an evapourates to a gas and then condenses back into a liquid in a continuous cycle.

            The two main types of mechanical refrigeration systems used are the compression system (used in domestic units for large cold-storage applications and for most air conditioning) and the absorption system (now employed largely for heat-operated air-conditioning units).

            In the compression systems four elements – compressor, condenser, expansion valve, and evapourates are involved in the refrigeration cycle. In the evapourator the refrigerant is vapourized and heat is absorbed from the material contents or the space being cooled. The vapour is next drawn into a compressor and elevated to high pressure, which raises its temperature. The resulting superheated, high-pressure, gas is then condensed to liquid in an air-or-water-cooled condenser. From the condenser the liquid flows through an expansion valve, in which its pressure and temperature are reduced to the conditions that are maintained in the evapourator. The cycle thus continues. The amount of water vapour in the atmosphere is termed as humidity. Air at a given temperature can contain only a certain amount of water vapour. This amount increases as the temperature rises and decreases as temperature falls. In air containing a given amount of water vapour, the temperature at which dew (water that condenses on cool objects from the water vapour in warm air) begins to form is known as the dew point. If the dew point is below the freezing temperature of water, frost is formed.

            When the air surrounding the evapourator coil is cooled the moisture present in the air condenses and sticks on to the coil in the form of water droplets. These droplets are cooled in the subsequent cycle and results in frost.

            The moisture present in the items placed is absorbed by the air and carried to the evapourated coil. The condensation takes place as explained earlier.

   To understand refrigeration, pour a small quantity of petrol in your hand and expose it to the atmosphere. The petrol evaporates leaving a cooling sensation. This is because the petrol has taken the heat from the hand and transformed it into vapour. (This is known as latent heat of vaporization).

            The working substance in the refrigerator is called a refrigerant. It compressed to a high pressure and then pressure and then allowed to condense by rejecting its heat to the atmosphere surrounding it. The liquid is then allowed to expand at a low pressure. During this process it absorbs heat from the spaced inside the refrigerator and become a vapour. The above cycle is repeated in vapour-compression refrigerator which differs fundamentally from vapour absorption system.

            The major compounds in a refrigerant are halocarbon compounds (which includes halogens: chlorine, fluorine and bromine); hydrocarbons (such as methane, ethane and propane); inorganic compounds (such as ammonia, water and air) and unsaturated organic compounds (hydrocarbon with ethylene and propylene base).

            Refrigerant is the working fluid in a fridge. It should have a low boiling point so that it vaporizes at low temperatures and absorbs the heat from a substance. Some of the common refrigerants are ammonia, carbon-dioxide and Freon. Ammonia is often used as it is cheap and easily available. But it is toxic and explosive at high temperatures. Carbon-dioxide was one of the first refrigerants used but presently its use is limited. It is non-toxic and non explosive but causes suffocation when its concentration is high. Freon 12 has a boiling point of -30 degree Celsius. This refrigerant is fluorocarbon of methane and ethane series. It is a combination of halogens, chlorine and fluorine. It is the most commonly used refrigerant. Its chemical name is dichloro-difluoro-methane. It condenses at a moderate pressure under normal atmospheric temperature. This property makes it the most suitable refrigerant.

   Our retina can only respond to stimuli in one way: by sending a signal along optic nerve to the brain, which interprets this signal as light. Normally, the stimulus is light impinging on the retina, but other stimuli work too.

            One of the commonest is a mild trauma to the eyeball. If you close your eyes in a dark room and press gently on the front of your eye will see a faint flow in your peripheral vision.

            This can also happen when a blow to the head causes you to close your eyes hard for a moment. You sometimes see stars or flashes when you sneeze, which is again the result of eyeball compression as the eyelid is forced closed. The retina will also send a light signal response to the brain if it becomes torn or detached. This is a serious condition requiring treatment by an ophthalmologist. Another potential source of problem is the jelly-like vitreous humour that fills the rear two-thirds of the eye. It is attached to the retina at several points, and tugging on it can result in the sensation of light when, for example, you move your eyeball around rapidly under your lid.

            These attachments can fail as we age, which is normally not a problem unless the vitreous pulls some retina with it. This, incidentally, is the cause of floaters, the little bits of matter you can sometimes see floating about inside your eye. Light flashes can also be associated with migraine headache and central nervous system disorders, which can act on the vision centres of the brain to produce the sensation of light.

            This effect is the result of a marked increase in intra-ocular pressure (IOP) caused by the blow. This pressure is exerted on the eye by the vitreous humour – the fluid within the eye that gives it its shape.

            The increase in IOP triggers the rods and cones that make up the retina, sending an electrical signal via the optic nerve to the visual cortex at the back of the head. The visual cortex is where we perceive what we see, and hence we think we are seeing a star for a few second nicely matches the timescale of the temporary rise in IOP.