Category Science

    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.