According to the theory of rhythm perception, the perception of rhythm involves the motor system just as much as the sensory system. It postulates that a ‘beat’ is actually perceived as a movement.
The theory then suggests that because a beat is perceived as a movement, the activation of a stereotyped behaviour such as tapping your foot in time with the beat is a natural extension of the way motor and sensory systems often work together to produce a percept.
A pencil mark actually consists of graphite particles abraded from the pencil point by the paper. These particles, which have an angular, gritty look under the microscope, are for an HB lead pencil, typically between 2 and 10 micrometers in diameter. The particles lie slightly below the surface of the paper, interlocked between its fibres.
A signal rub using a rubber sufficiently soft to reach between the fibres will pick up most of them. Inspection of the rubber shows the undamaged particles adhering to the surface.
An effective erasing material is also abraded by the paper surface, producing the familiar small spindles of rubber or eraser material, which wrap up the graphite particles. At 200 x magnification, these look like roly-poly puddings studded with graphite raisins.
Parboiling involves soaking paddy in water for a short time followed by heating once or twice in steam and drying before milling. Dehusking of parboiled rice is easy and the grain becomes tougher resulting in reduced losses during milling.
The nutritive value of rice increases after parboiling, because the water dissolves the vitamins and minerals present in the hull and brancoat carries them into the endosperm. So the loss of vitamin B1, riboflavin and niacin due to milling and polishing is comparatively low in the parboiled rice than raw rice. Parboiled rice will not turn into glutinous mass when cooked. Baking of leavened dough of wheat helps to make bread. Baking is done in an oven preheated to 204 degrees C. During the first 10-12 minutes of baking there is an increase in dough volume. This is called oven spring. This is caused by an expansion of gases owing to the high temperature of the oven and due to increased enzyme activity in the centre of the dough. As baking continues, gluten a constituent of wheat dough expands without breaking and finally forms a rigid structure due to coagulation.
This helps in the retention to the rapidly expanding gases. Excess gases, CO2, alcohol and water vapour help to gelatinize the starch and structure is established. This aerated and finely vesicated crumb is very helpful for easy mastication of bread.
Using heat to bring about desirable changes in foods is called cooking. Cooking improves flavour and appearance and makes the food more palatable and digestible. Legumes and cereal grains contain trypsin inhibitors and other toxic substances which affect the digestibility and availability of sulphur containing amino acids.
Cooking destroys these toxic proteins and favours easy digestion Starch molecules which are the main source of calories in many diets when in an aqueous or moist environment swell and rupture and this permits greater enzymatic digestion by enzymes like amylase. Cooking thus increases the digestibility of carbohydrates.
We can’t fry food with water because its boiling point is lower than that of oil. Generally all food materials contain water in an occluded from or as water of hydration.
We fry food essentially to remove this water. For this, the food needs to be heated beyond the boiling point of water (100 degrees C). If we use water as the frying medium, the water from the food cannot be removed as the medium itself gets vapourized.
However, oil can be heated to more than without charring the food. Being nonvolatile at this temperature, heat from the oil facilities frying.
Fuel has to be heated to a minimum temperature, know as kindling temperature or ignition temperature for a successful and continuous burning. We largely depend upon match sticks for creating fire. It contains combustible W (oxidisable) substance and an oxidizing (oxygen supplying) agent. We supply heat energy by rubbing the head against rough surface. Every fuel has to mix up with oxygen present in air to form a mixture of right composition for successful combustion.
The composition of the mixture can be between two limits namely lower and upper limits. Those limits are called limits of inflammability or explosive range. We should know that even when the temperature maintained is equal to kindling temperature, we cannot produce fire with fuel only or with oxygen only.
Kindling temperature depends upon the chemical nature and explosive range depends upon the volatile (vapour forming) nature of the fuel. Those two properties do not have any direct relation with size or shape of the fuel. But, of course, it seems that powdered fuel, say saw-dust in case of wood catches fire quickly rather than large log.
This difference in size or shape affects neither the kindling temperature nor the volatile nature of the fuel. The rapidity in catching fire is due to different reasons. In case of powdered fuel, small fuel particle is introduced into a large flame. That means supply of activation energy in the form of heat is very fast. In this case, availability of oxygen will also be a very high. Hence the quick ignition. But in case of logs, large mass is heated by relatively small flame. That means supply of activation energy in the form of heat is very slow.
Also, a large portion of the heat supplied to the log will be dissipated to other parts due to conduction. Chance for loss of heat energy to the surrounding cannot be also neglected. This will further slow down the process of attainment of ignition temperature.
Even when the whole log attains the ignition temperature, only the particles present on the surface can form explosive mixture combining the oxygen present, in air. Hence the delayed ignition.
Ignition temperature is specific to a substance. It is temperature at which the substance starts burning. A piece of wood catches fire quickly attain the fire point quickly. But in case of a large log when you apply flame a point of edge, the temperature transfer takes of big log a long time.
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.
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