IF ONE HAS A DRINK SOON AFTER EATING MINTS THE INSIDE OF THE MOUTH FEELS MUCH COLDER THAN NORMAL, WHAT CAUSES THIS ??

     Mint tastes ‘cool’ because of its anaesthetic properties. Menthol, the essential oil in the mint, deadens the hot receptors in the mouth over the cold receptors.

     Nerve endings constantly generate a low background signal that the brain generally ignores. When the noise from the hot receptors is reduced by exposure to mint oils, the noise from the cold receptors stands out in comparison. The brain then interprets these signals as a cold sensation.

     Other essential oils have similar anaesthetic or analgesic properties. Oil of clover is effective in reducing low-level, topical pains and was commonly prescribed by dentists for relieving both toothache and sore gums.

     Oil of wintergreen has a wonderful ‘icy-hot’ feel that can soothe aching muscles. The cool sensation comes from the differential anaesthetic action on the hot receptors in the skin. When this wears off, the rebound of activity from the awakening receptors feels ‘hot’. These two essential oils are still an ingredient in some over-the-counter ointments.Courtesy : The Hindu.

WHY DO INFANTS CRY SOON AFTER BIRTH ??

        Inside the womb the child  is in a warm protected environment. When it is brought out it experiences a total change in the environment. The outside temperature and air stimulates the skin (proprioceptive impulse). This stimulation makes the child take a deep breath (a good gasp). When the air gets into the lungs in the first gasp it results in a cry. It repeatedly takes up this deep breathing and establishes the regular respiratory cycle.

       This cry is one of the five parameters (Apgar count) to assess the child’s condition soon after birth. This is done at one minute and five minute after birth. In a normal child the first cry is expected to be a vigorous or lustrous one. A varied cry is also a way of interpreting the condition of the child (normal or otherwise), according to Dr. Ananthakrishna, an eminent paediatrician.

       If the cry is irritable in nature it may be a child with brain injury. If it is feeble cry it could be due to a respiratory problem or a brain problem such as intracranial bleeding or asphyxia. The feeble cry may also indicate a problem in the lung such as immaturity of the lungs in a low birth weight baby (pre-maturity). It could also be due to aspiration of fluid from the bag of membranes (bag in which the child floats in the intrauterine period) which encircles the child.

       The aspiration contents could also be the meconium (first dark motion passed by the child). The cry thus becomes a very valuable index for assessment as a routine in the newborn nurseries.Courtesy : The Hindu.

WHAT MAKES THE EARTH ROTATE ??

          The earth rotates simply because it has not yet stopped moving. The Solar system, and indeed the Galaxy, were formed by the condensation of a rotating mass of gas. 

   

          Conservation of angular momentum meant that any bodies formed from the gas would themselves be rotating. As frictional and other forces in space are very small, rotating bodies, including the Earth, slow only very gradually.Courtesy : The Hindu.

WHY DOES OUR HAIR CHANGE ITS COLOUR AS WE AGE ??

          Hairs are the appendages of the skin generated from the epidermal layer. Hair is a made up of keratin a highly insoluble and mechanically stable fibrous protein. This keratin is not only found in hairs but also in the skin. Actually keratin is produced from the keratinization zone of the epidermis, which is the outer most layer of the skin. In the skin it provides water proofing quality.

          
              The keratin is generally pigmented. It is intensively pigmented in the hair. The dark colour of the hair is due to the presence of high concentration of melanin pigments in it. The skin colour is also due to the presence of this pigment in the keratinocytes. The keratin gets its melanin pigments from melanocytes, which found in the inner layer of the epidermis, which is found just beneath the keratinizing layer. The melanocytes gave long processes which extent between and under the cells of the epidermis. The melanin granules formed in the melanocytes pass along their branches and are secreted at their tips. The granules are subsequently engulfed by the keratinocytes, which make up 90 per cent of the epidermal cells.

         

Melanin is a protein like polymer of the amino acid tyrocin. In its biosynthesis tyrocin is converted into dihydroxy phenyl alanine (DHPA) by oxidative enzymes amongst which tyrocin is particularly important. Then a series of reactions take place during which polymerization occurs to form the final melanoprotein.

The hair grows only from the keratinocytes of the germinal matrix of the hair follicle. This germinal matrix lies in the proximal enlargement of the root hair, called the hair bulb. The hair shaft, which projects from the surface, consists of an inner medulla, an intermediate cortex and an outer cuticle. All these parts are made up of cornified cells.

           The medulla is composed of polyhedral cells; the cortex consists of elongated cells with inner lumen. These cells are united to form flattened fusiform fibres. The lumens of these cells contain pigmented granules in dark hair and air space in white hair.

          The development of white hairs because of the absence of melanin pigments, may be due to the absence of one or more enzymes, necessary for the DHPA path way. It will lead to the failure of melanin accumulation in the keratinocytes, found in the hair bulb, from which hair is growing. Usually such physiological disorder occurs in the old age, which results in the growing of gray and white hairs in the body.Courtesy : The Hindu.

WHY DO BIRDS FLY IN FORMATION SHAPED LIKE THE ALPHABET “V” ? WHICH BIRD WORKS THE HARDEST IN SUCH A FORMATION AND WHY ??

          The bird in the lead (at the forward point of the “V”  formation) works the hardest by being the first to ‘break through’ the air ,which offers resistance to its flight. Just as a boat leaves a V-shaped wake of smoother water behind it, the lead bird leaves a V-shaped wake of slightly ‘smoother’ air behind it (actually the lead bird creates a trial of air turbulence that helps lift along the V-shaped direction),and it is a bit easier for the other birds to fly in the wake of the lead bird. 

          If you watch a V-formation carefully, you’ll notice that the lead bird does not stay in that position for very long and will drop back into the formation , while another, not-as-tired bird takes the lead, breaking through the air first. Courtesy : The Hindu.

why does snow melt faster around a tree trunks?

  Most of the tree trunks are dark in colour and absorb heat energy from the sun, so that the heat travel at the base of a tree is higher than it is just outside the ring that appears in the snow. Tree trunks also reduce wind currents somewhat, so there is less snow buildup to begin with.

Courtesy : The Hindu

Why do we see rainbow colours on a CD?

Display of colours by a CD can be understood in terms of the working of a plane optical reflection grating. It is a flat optical device whose surface is ruled (striped) with a set of closely and uniformly spaced lines, such that light is reflected by the gaps and absorbed by the lines. , When light falls on a plane reflection grating, it is scattered in all directions by each of its reflecting stripes. These waves from individual gaps are termed wavelets. When we look at the grating from a distance, wavelets from different stripes travel different distances to reach the retina of our eye. Their crests (or troughs) do not reach a given point at the same time. Usually crests of some wavelets and troughs of others reach a point. Troughs have the property of partially or totally nullifying crests and vice versa, depending on their strengths. In this case the wavelets are said to interfere destructively.

But for certain orientations of the grating, it so happens that troughs (or crests) of all wavelets reach a point together, enhancing the effect of each other. The wavelets are then said to interfere constructively. Ordinarily, when light falls on a grating, wavelets corresponding to all wavelengths (or colours) are sent out by the reflecting gaps. Since the conditions of constructive interference hold good only for some particular wavelength, light intensity at the receiving point is exceptionally high only for that wavelength. Light from the grating from the related direction is thus rich in the corresponding colour. Similarly light from slightly different direction is rich in another colour. A CD has a data recording track, which spirals from its outer periphery to the inner circular boundary. This takes many tens of thousand rounds about the CD's centre. When examined along a radius of the CD, it is found to have a structure similar to that of a reflection grating — a set of almost straight tracks running perpendicular to the radius and separated by gaps. Therefore, like a grating the CD also displays colours. Courtesy : The Hindu

Why are diesel driven vehicles noisy?

Diesel engines are inherently noisy because of the auto-ignition of the initially formed mixture of fuel-vapour and air, which causes rapid rate of pressure rise producing the characteristic noise. This abnormality is due to the inborn feature of a diesel engine, which uses a high compression ratio to obtain high fuel efficiency and a high compression-temperature for ignition of the fuel injected into the cylinder at high pressure. In a diesel engine, unlike a petrol engine, the air and fuel do not mix outside the engine.

Air is compressed to a high compression ratio leading to high fuel efficiency, and also to a high compression temperature to initiate combustion. They just meet inside the combustion chamber for a brief period, while all the processes of mixture formation like fuel-jet break-up, evaporation and mixing should take place within a short time called ignition delay period. Combustion follows this after the initially formed fuel-air vapour auto-ignites with a noise, forming the sources of ignition (chemical spark plugs if you wish to call) for the bulk of the fuel remaining. Diesel engine can be made less noisy by using common rail high-pressure injection system and electronic control. Courtesy : The Hindu

Why does a mushroom shaped cloud form after a nuclear bomb explosion?

ANSWER I: When a nuclear weapon explodes, there is a rapid release of a large amount of energy within a small volume. This results in significant increase in temperature and pressure. The temperature may be a few tens of million degrees and pressure a few million times the atmospheric pressure. At this temperature, all the material present in the weapon will be converted into hot compressed gases.

Within a fraction of a millionth of a second of the explosion, the weapon's residues emit large amounts of energy mainly in the form of X-rays. The surrounding atmosphere absorbs this energy. This results in the formation of a blazing, highly luminous, spherical mass of air and gaseous weapon residues called the fireball.

Within an extremely short time after the explosion, the fire ball from a high yield nuclear weapon will be about 130 metres across increasing to about 1700 metres in ten seconds.

The fireball expands rapidly engulfing the surrounding air. The ball of hot air is less dense than the surrounding air. It rises swiftly like a hot air balloon.

This rising column pulls up debris of the weapon, dust and moisture along with it forming a cloud. As it moves up, it cools gradually and reaches about 10 km where the atmosphere is extremely stable.

The ball of air mass moving up does not have enough energy to penetrate this stable layer. It flattens out. As the relatively warmer layers at the bottom push up, the top layers spread laterally and equally in all directions, and the cooler denser layers descend at the edges, giving a distinct mushroom shape.

ANSWER II: Atmospheric nuclear explosion leads to sudden formation of a massive fireball near the ground, setting aflame whatever is in its vicinity. Since the fireball is very hot and thus less dense than the surrounding air, it rises very quickly. The massive updraft due to the rapidly rising fireball leaves a column of low-pressure. This acts as a chimney, sucking in smoke, dust and debris from the surroundings. This forms the stem of the mushroom.

At first the mixture of hot air and dust rises vertically, forming the column of the cloud. But as the hot cloud meets the colder air at higher altitudes, it slowly cools. Eventually the cloud reaches the temperature of the surrounding air and ceases to rise, but spreads horizontally along air levels at the same altitude, which are at the same temperature. This forms the cap of the mushroom.

The smoke, dust and debris gushing into the central column cause toroidal eddy currents in the horizontally spreading hot cloud. This introduces curling under the cap of the mushroom. Mushroom clouds are most commonly associated with nuclear weapons. However, any massive explosion capable of creating the same conditions would produce a mushroom cloud. Volcanic eruptions are typical natural mushroom clouds. Courtesy : The Hindu

Why are we unable to walk straight and tend to lose our balance when we walk with our eyes closed?

ANSWER I: When one wants to walk in a straight line the brain takes a visual reference point and uses this reference point to maintain the movement in a straight line. In the absence of a visual reference point the brain is unable to ascertain the exact direction in which the body is moving and hence most of us will be unable to walk in a straight line with our eyes closed.

However visual reference is not the only mechanism of maintaining balance or direction in our movements. We can judge the direction of movement very accurately with the balance sense from the balance mechanism in our inner ear and by kinesthetic sense, which is sensations we derive from our muscles, joints and ligaments.

Both these sensations will tell us very accurately as to the balance and direction of movement and position of the body at any point of time. This is highly developed in acrobats, gymnasts and ice skaters. They would be able walk in a straight line even with their eyes closed.

ANSWER II: Human balance is maintained by three pillars namely vestibular system — balance organ in the inner ear and its connections — eye and proprioceptors in the joints of the body. Man can maintain balance with any two pillars but not with one pillar alone. Imagine a blind man who can walk without losing balance.

If the same person develops any disorder in the vestibular system or proprioceptive system, then he cannot stand or walk. Similarly if a normal person develops a disorder in the inner ear or proprioceptive system and tries to stand with eyes closed and feet together, he will lose balance. Courtesy : The Hindu

Why do pregnant women like eating tamarind and raw mangoes?

Craving for unusual food (and some non food items like ash called pica) is considered as the first sign of pregnancy. In reality, although some women do get strong cravings, many do notNo one knows for sure what causes food cravings. Many women find that their senses of taste and smell are changed by pregnancy. For example, some women experience an odd metallic taste in their mouths very early in pregnancy (maybe the first sign of pregnancy for an `experienced' mother); others find that taste and smell are dulled. It is possible that these changes affect food likes and dislikes.

Some people think that cravings happen in response to temporary deficiency of specific nutrients. There is probably some truth in this, but it is not the whole story. We only need minute quantities of each vitamin and mineral — certainly not enough to justify a continual craving for just one food. For some women, food cravings may be a conscious or subconscious response to emotion.

They may crave a favourite childhood food, or a food that is of special significance to their religion or culture. Craving unusual foods may also be a private way of marking the special state of being pregnant.

Rather than develop a food craving, many women find they suddenly go off certain foods or drinks like fried foods and coffee.

This is often related to pregnancy sickness, but may also be the body's way of ensuring that they eat and drink wisely. Generally, there's no harm in giving into food cravings, especially if doing so helps getting through phases like early morning sickness which can be pretty distressing. However this must be done in moderation.

Eating a lot of one food only means eating less of other foods and therefore running the risk of becoming deficient in important nutrient. A craving for non-food items — such as ash or soap or toothpaste — is known as `pica'.Pica is potentially very harmful if indulged in and must be resisted.

Also, substances like soaps and ash may prevent the absorption of nutrients and other food substances. Courtesy : The Hindu

Why do doctors prescribe some medicines to be taken before and some after food?

When we take a medication, it is absorbed from various parts of our gut — some get absorbed in the stomach, some pass through the stomach into the intestines and get absorbed there.

The most important reason for timing a medication that is taken orally is to maximise its absorption so that more of the medication goes through the stomach into the blood.

Many medicines get absorbed better when food is not present and hence are taken on an empty stomach (an example is the hormone thyroxine which must be taken first thing in the morning). A few actually get absorbed better when food is present — an example of this is the antibiotic azithromycin. Some drugs are taken specifically with or after food because this may reduce the side effects of the drug on the stomach.

For example pain medications and certain antibiotics all can irritate the lining of the stomach and therefore are best taken with or after food. Some drugs work in the wall of the stomach to reduce the absorption of food and this is the desired therapeutic effect — an example of this is the anti-diabetic drug called acarbose.

This drug must be taken with the first bite of food. Similarly other oral anti-diabetic drugs and the injection insulin are taken before food because that is when they need to act — just after you eat a meal. The long and short of it is that the timing of a drug has important effects on its absorption, action, potency and even side effects and it is a good idea not to leave the doctor's office without being sure when you should be taking your medicine. Courtesy : The Hindu

A hen lays an egg every day. From where does it get the calcium required to make the eggshell?

 A commercial layer that lays an egg almost everyday derives its calcium requirements entirely from the feed it consumes. The nutritional requirements of chicken have been understood completely over the years. Today's layer bird yields 325 eggs in 365 days.

The chicken feed is mainly composed of maize, broken rice, soya, groundnut and sunflower cake, oyster shell grit and dicalcium phosphate.

The calcium requirements are mainly contributed by the shell grit. The feed is a precisely formulated one and the nutritional requirements of the layer are fully met by the feed it consumes daily. Courtesy : The Hindu

Why does it take a longer time to copy a file to a computer than delete it?

An Operating System (OS) is a program that acts as an intermediary between a user of a computer and the computer hardware.

Depending on the storage device being used, computers can store information in several physical forms. Each device has its own characteristics and physical organization, and hence different views of information are created. To unify all these views of information, a uniform logical view called a file is created.

A file is a contiguous set of data. It is the job of the OS to map this sequence of data into physical devices. The part of the OS responsible for this is the file system.

So the main task of the file system is to free the users of the details of storing of information in the physical devices. That is, when the storage device is changed, from disk to CD for example, the user still sees the same information.

In the most basic form, a file system consists of two distinct parts: a collection of files and a directory structure. The directory structure organizes and provides information about all the files in the system.

Every file has certain attributes like its name, location (its address in the file system), size, access control information (whether the file can be read or written to or only executed etc), type (whether it is just a collection of data or has other special instructions), time, date and user identification.

If file A is to be copied to file B, then first a new file called B is created, next the contents of A are read and finally, this is written to B.

For this to happen, three steps are necessary. First, space must be found for B in the file system. Second, an entry for B must be made in the directory. The directory records the name of B and the location of B in the file system. Third, a request is sent to the OS to read the contents of A.

The OS finds the location information of A from the directory and reads the contents. Now to write to B, the OS again searches the directory for the address of B. Finally the content of A is written onto the space provided for B.

On the other hand if a file deletion is to take place, the process is much simpler. If file A is to be deleted, the OS just searches the directory for the named file.

Having found the entry, the space occupied by A is released so that it can be used by other files and the directory entry is erased.

As can be seen, the operations involved while copying a file are much more than those involved while deleting a file. Courtesy : The Hindu

How are snake pits formed?

ANSWER I: Snake pits are a network of caves and crevasses formed by underground water and collapsed limestone serving as perfect locations for hibernating snakes. In cold countries, these pits protect them from very cold temperatures, which tend to dip as low as minus 40 degrees Celsius during winter. The snakes huddle themselves below the frost lines during harsh winter.

Snakes of the tropical countries, however protect themselves from the heat of summer by staying in pits, which are formed far below the ground level. These are protected underground from surface heat.

ANSWER II : Most snakes do not make their own burrows, but inhabit the burrows made by other creatures, such as rodents. They also inhabit termite mounds.

Only a few species of snakes, such as sandboas and shieldtail snakes, are capable of making their own burrows, but even they prefer existing burrows, when available - Courtesy : The Hindu

How are some insects able to walk on the surface of water?

 ANSWER I :Water has a see-through film on its top layer that is created by surface tension. That means molecules of water are more likely to cling to other molecules of water than to something else. Some insects have a waxy coating on their body/feet. The surface tension of this coating [20 to 30 ergs/cm{+2}] is much less than water [72 ergs/cm{+2}] and hence water tends to bond to itself rather than wetting the insect's feet and unless the insect is too heavy, it can remain on top of the water surface. For example, water striders and carpenter ants are so light that they can support themselves by spreading their weight on the surface tension of the water.

ANSWER II: Insects like the pond skater are able to walk on the surface of water mainly because of two factors. The first is their water-repellent (hydrophobic) cuticle. The cuticle of a pond skater is coated with wax to make it waterproof.

Again, the insects are able to maintain floatation or stand on the surface because a sufficiently large amount of its surface area is in contact with the water. The heavier the object, the more surface area is necessary to maintain floatation. As insects are very light weight the area of contact with the water surface is enough for it to prevent it from drowning. Courtesy : The Hindu

Why is it easier to tear wet paper and not dry paper?

Tearing a paper involves overcoming the cohesive force between the cellulose fibres (of which paper is made). In the case of dry paper this force is high and hence tearing it is not very easy. However, the cohesive force that is of electrostatic origin becomes weakened in the presence of water.

 

This is akin to the way table salt (sodium chloride) dissolves in water due the weakening of the electrostatic attraction between the positively and negatively charged ions. In the case of paper, the effect becomes easily perceptible as paper is hydrophilic and absorbs water.

Once dipped in water, the water molecules can easily flow into the spaces between the fibres, weakening the cohesive force between them and making them susceptible to easy tearing. Courtesy : The Hindu

How is the speed of a computer measured?

Two important factors that determine the speed of a computer are the amount of data that the Central Processing Unit can process in a given period of time and the CPU's clock speed.

The speed at which a CPU executes instructions is called the clock rate.

Every system contains an internal clock that regulates the rate at which instructions are executed and synchronizes all the various computer components. The CPU requires a fixed number of clock ticks to execute each instruction.

The faster the clock, the more instructions the CPU can execute per second. Clock speeds are expressed in megahertz MHz or gigahertz GHz. Mega means million and hertz means times per second, 200 MHz is 200 million times per second (and 200 GHz is 200 billion times per second).

The internal architecture of a CPU has as much to do with a CPU's performance as the clock speed. One common architecture is parallel processing. For example, while an instruction is being executed, the next instruction can be fetched from memory and decoded.

Instruction Prefetching is another idea where the CPU fetches the next instruction beforehand and places it in a queue for the execution unit to use the same.

The overall speed of a computer is also affected by the speed and size of the instruction/data bus. The instruction/data bus is the pathway for data communications between the computer's CPU and the various components in the computer.

The computer's bus has a certain size or width called the data path which is measured in bits and the speed of the bus is measured in MHz.

The larger the bus width and/or the faster the bus speed, the more data that can travel on it in a given amount of time.

Another factor affecting the speed is the size of the primary memory and cache. Increasing the size of the primary memory will speed up the performance if you run several applications at the same time or work with large files and documents. Cache is a small amount (normally less than 1 MegaByte) of high-speed memory residing on or close to the CPU. Cache memory supplies the CPU with the most frequently requested data and instructions.

Finally, effective interfacing of Input-Output devices to the CPU also increases the speed. Systems today use direct memory access (DMA) hardware wherein I/O device acts as a master and transfers large number of data to/from memory without intervention by the CPU. Courtesy : The Hindu

What is the powdery deposit found on some fruits like grapes? What is its use?

The white deposit seen on grapes and most other berries is cuticular wax. Cuticle is the outermost layer covering the plant surface and plays a role in the plant's interactions with its environment.Cuticular wax is part of the cuticle in several plant parts in almost all plant species. It is usually embedded in the cuticle and in some plant species crystalline wax structures overlay this layer and appear as powdery white/grey deposit (for example, grapes and other berries).

The wax is composed primarily of long-chain fatty acids, hydrocarbons, ketones, alcohols and alkaloids. Plants use cuticular wax primarily to regulate non-stomatal loss of water. 

Cuticular wax is also reported to play important roles in disease resistance against bacterial and fungal pathogens of plants and in plant-insect relationships.

Being reflective in nature, waxes are also thought to offer some protection against UV damage. In agriculture, waxes impede the uptake of foliar sprays without surfactants due their hydrophobicity (water repellent property). Courtesy : The Hindu

How do raw mangoes and bananas become ripe when treated with chemicals?

ANSWER I: The process of fruit ripening is chiefly regulated by a gaseous plant hormone called ethylene. Most fruits have elevated ethylene levels during ripening and sometimes just a peak in ethylene levels, just before the process of ripening begins.Ethylene regulates the expression of several genes involved in fruit ripening so as to modulate the activity of various enzymes involved in the process of ripening. These enzymes act to soften the `skin' of the fruit and also convert complex polysaccharides into simple sugars.

The chemical commonly used to ripen fruits commercially is ethephon (2-chloroethylphosphonic acid), which penetrates into the fruit and decomposes to ethylene. Incidentally, chemicals (e.g. calcium carbide) that produce acetylene, an analogue of ethylene, are also used in some places posing dangers of explosion and carryover of toxic materials to consumers.Ethylene is induced by several cues such as higher temperature, wounding, disease etc. Higher levels of ethylene and enhanced respiration might contribute to ripening when stored at higher temperatures.

ANSWER II: The ripening signal of a fruit comes form a hormone ethylene. Production of ethylene turns on some genes that are transcribed and translated to produce other enzymes. These enzymes are responsible for the conversion of starch into simple sugar, degradation of chlorophyll and appearance of other new pigments like carotenoids, change in the skin colour and the breakdown of acid, making the fruit taste neutral.

Hardy nature of the skin loosens when pectin is broken-down by an enzyme pectinase. Conversion of larger molecules into smaller volatile substances causes an aromatic odour.Natural process of fruit ripening is accelerated by using certain chemicals. Here, calcium carbide is used. When carbide is dissolved in water it produces acetylene, an analogue of ethylene, a natural fruit-ripening agent.

The ripening process is accelerated since acetylene imitates ethylene. Since the amount of carbide needed to ripen the immature fruit is more it makes the fruit become more tasteless and toxic. Presence of trace amount of arsenic and phosphorous in carbide makes the healthy fruits poisonous.One can distinguish the artificially ripenened fruit by the uniform skin colour in fruits like tomato, mango, papaws, etc and in the case of banana, yellow colour fruit with dark green stem. Courtesy : The Hindu