What causes Hiccups?
Hiccuping is just a reflex action of the body which it protects itself.There is a diaphragm located between the chest and the stomach.While inhaling air this diaphragm goes down and presses the stomach due to which the lungs are filled with air,while exhaling the air,the diaphragm goes up and the air comes out from the lungs.Thus the diaphragm goes up and down and the process of respiration continues incessantly without making any sound.
What are the refrigerators? How are they Chill the contents inside a fridge?
To understand refrigeration,pour a small quantity of petrol in your hand and expose it to atmosphere. The petrol evaporates leaving a cooling sensation.This is because the petrol has taken the heat from the hand transformed into vapour.
The working substance in the refrigerator is called as refrigerant.It is compressed to a high 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 the heat from the space inside the refrigerator and become a vapour. The above cycle is repeated in vapour compression refrigeration which differs fundamentally from vapour absorption system.
The major compounds in a refrigerator and halo carbon compounds (which includes halogens :chlorine,fluorine and bromine) hydrocarbons (such as methane,ethane and propane) ,inorganic carbons (such as ammonia,wtare and air) and unsaturated organic compounds (hydrocorbon with ethylene and propylene base).
How long can we survive without oxygen?
Humans can survive only for a few minutes without oxygen.This is because of the susceptibility of the brain cells. Even though the brain is only about 2 percent of the body's weight,it consumes about 20 percent of the oxygen we breathe in.
Hence if oxygen supplied by the blood is stopped for a fee minutes,the brain ceases its function resulting ind death.We will lose consciousness in 8-10 seconds after the blood supply to the brain is cut.
Brain cells can survive for long periods without oxygen at very low temperatures,as oxygen consumption is reduced.This technique,induced hypothermia,is made used of during major surgeries.Other tissues can survive for long periods without oxygen and that is why it is possible to remove organs,from brain dead persons for transplantation.
