Category Applied Science & Technology

How do certain beverages give a feeling of freshness?

Most of the beverages contain alkaloids which act as mild stimulants. Caffeine, for example, is found in coffee, tea, cocoa, milk chocolate and also in cola drinks. Tea has a trace of theophylline. Cocaine is found in products. These alkaloids are collectively referred to as methyl xanthenes. They share a number of pharmacological actions of much therapeutic interest: they relax, smoothen the muscles (notably bronchial muscle), and stimulate the central nervous system and cardiac muscle. They induce the kidneys to excrete more urine, stimulate mental activity, and quicken the reflexes, increase vigilance and decrease motor reactions time in response to both visual and auditory stimuli. They increase stamina and reduce fatigue. They give the users a feeling of confidence and power. They even induce euphoria in some users. These stimulant effects are short lived: they last for about an hour. They are then subsequently followed by depression. Overdose or repeated use may lead to paranoia, psychosis.

What is meant by empty calories got by drinking alcoholic beverages?

Alcohol generally refers to drinks which contain varying amounts of absolute alcohol (chemically termed ethyl alcohol). Alcoholic beverages are usually made by fermentation of sugars and carbohydrates (from different sources). Yeast is used to convert these into ethyl alcohol and carbon dioxide. As a food substance, alcoholic drinks have a restricted food value in the form of sugar (as in sweet wine) and carbohydrates (in beer). About 190-240 grams of pure alcohol per day is equivalent to 1300-1600 calories which is enough to provide basic energy for the body for a day. Inspite of its high calorific value it is better known as ‘empty calories’ because it does not provide the essential nutrients to the body. In addition, alcohol impairs absorption and metabolism of essential nutrients from other foods. ‘Alcoholics’ usually suffer from such deficiencies. This can be reduced by the type and manner of alcoholic beverage consumption.

Why is red meat red and white meat white? What is the difference between the various animals that makes their flesh differently coloured?

Red meat is red because the muscle fibres which make up the bulk of the meat contain a high content of myoglobin and mitochondria, which are coloured red. Myoglobin, a protein similar to haemoglobin in red blood cells, acts as a store for oxygen within the muscle fibres.

            Mitochondria are organelles within cells which use oxygen to manufacture the compound ATP which supplies the energy for muscle contraction.

            The muscle fibres of white meat, by contrast, have a low content of myoglobin and mitochondria. The difference in colour between the fleshes of various animals is determined by the relative proportions of these two basic muscle fibre types. The fibres in red muscle fatigue slowly, whereas the fibres in white muscle fatigue rapidly.

            An active, fast swimming fish such as a tuna has a high proportion of fatigue-resistant red muscle in its flesh, whereas a much less active fish such as the plaise has mostly white muscle.

The colour of meat is governed by the concentration of myoglobin in the muscle tissue which produces the brown colouring during cooking.

 Chickens and turkeys are always assumed to have white meat, but free-range meat from these species (especially from the legs) is brown. This is because birds reared in the open exercise and become fitter than poultry grown in cages. The fitter the bird, the greater the ease of muscular respiration, and hence increased myoglobin levels in the muscle tissue, making the meat browner. All beef is brown because cattle are allowed to run around in fields, but pork is whiter because pigs are lazy. 

 

What constitutes bullet-proof glass?

High-strength ceramics such as silicon nitride, dual hardness steel and layers of heavy nylon fabric make a bullet-proof glass impervious to bullets. The hard ceramic stops the bullet abruptly, dissipates its energy as it destroys the first layers of the glass at the point of impact and entangles it in as coarse mesh.

A textile bullet-proof vest is fashioned of 16-24 layers of nylon cloth of heavy weave, the layers stitched together like a quiet. Such vests or full-torso protectors can be worn undetected under regular clothing. A vest of 16 layers will stop regular handgun and submachine-gun bullets, those of 24 layers will stop the move powerful magnum bullets from the same weapons. 

How does noise shatter glass?

Shattering of panes can be explained using the well-known principle of resonance. We have seen window panes vibrate when heavy vehicles such as a lorry pass by.

Likewise the panes of houses near airports also vibrate when aircraft fly nearby. In these cases, the noise (a mixture of sound waves of varying frequencies) generated by the vehicle sets up vibrations in the atmospheric air surrounding it. These vibrations (sound waves) transfer the energy from the source (vehicle) to the surrounding and dissipate it. If the noise is not intense, the sound dies away with in a short distance.

If it is intense, the waves travel long distances. When these waves come across solid objects such as window panes, they transfer their energy to the object and force them to vibrate.

 If the frequency of the sound wave matches with the natural frequency (Any object will have a natural frequency of vibration which depends on the nature of the material) of the object, resonance sets in the object begins to absorb the incident energy and forced to vibrate with large amplitudes. In case of window panes, its edges are held (if not tightly) by the window frame which prevent the oscillation. This results in shattering. 

How does a shaving brush help generate more lather from soap or shaving cream?

The bristles of a shaving brush are bunched together to ensure that there are a large number of thin columns of air in-between them. When the brush is moved to and fro, the soap solution seeps into the brush, due to surface tension, partially filling the air columns.

 While shaving, the soap solution stuck to the skin is dragged to form thin films. But when stretched beyond a certain length, limited by surface tension, the films break and in that process trap a little bit of air to form small bubbles. As there are hundreds of bristles involved in the bubble making process, we get lather within a short time.

 The same principle applies to tooth brush and the brushes used for washing.