Pages of old books become brittle, why?
The brittle book syndrome strikes books printed on acidic paper. With time, moisture in the air hydrolyses the manufacturing residues forming acids throughout the paper, most cellulose of the paper fibers and breaks up the polymer chains which give the paper its strength. More and more such books are becoming brittle and
unusable every year. The American scientists have mow developed a new technology to save old vacuum chamber and the air is extracted. The books are dried and diethylzinc gas is pumped in. This neutralizes the acid residues in the paper and forms a buffer of zinc oxide that prevents future acid attack. The process deacidifies paper fibers uniformly throughout the paper, not just on the surface.
How does anesthesia make a patient unconscious?
Anesthesia is believed to produce unconsciousness by mechanisms similar to deep sleep. In the base of the brain, there are special sets of cells which keep us awake. These are called the ‘reticular formation’ essentially a network of nerve cells. Activity of these cells in relation of the other parts of the brain determines the state of consciousness. Brain cells communicate with each other using chemicals, generating small electrical currents by exchanging Na+ and k+ (sodium and potassium) ions, across the cell surface. Anesthesia temporarily interferes with this process of chemical and electrical communication o n the brain cell surface. This break in communication results in the person becoming unconscious. However, how exactly anesthesia works is still not known.
How does milk become curd?
Milk contains milk sugar, lactose. Curd contains the lactose enzyme and when a culture of surd is added to a large amount of milk, the lactose in the milk undergoes fermentation to give lactic acid. Lactic acid thus formed reacts with more lactose in milk to five the thick, solid substance we call curd. As the fermentation reaction takes place at optimum temperatures (250c-270c), curd formation is difficult at temperatures lower or higher than these.
Why does paper curl when it is burnt?
Sheets of paper are made of cellulose fibers that are matted together and pressed between rotating cylinders. As the matted sheet passes between the cylinders, it is pressed, dried as well as stretched so that the cellulose fibers get stretched and remain that way. The fibers in the sheet of paper are held together by hydrogen bonds. But as the sheet of paper starts burning, these bonds are randomly broken. This fives a crumpled appearance to the burnt paper just before it burns to ashes.
Why do person lose balance after spinning quickly for a number of times?
The sensing of motion by the brain of humans is done through a special set of structures in the inner ear called the vestibular organs-the utricle and the three semi-circular canals. These contain minute sensitive hairs in a fluid filled sac like structures. Whenever a change in the position of head occurs, as happens while moving or turning, the fluid in the vestibular organs is disturbed. The minute hairs sense this disturbance and the message is conveyed to the brain. The body is then directed by the brain to adjust so as to maintain the balance. During rapid spinning of the body, the fluid in the semi-circular canals also spins and continues to do so for some time even after the body has stopped spinning. This continued movement of the fluid conveys a false sense of motion to the brain. The result is giddiness or a fall.
Why do we sweat more when frightened?
Sweating is a natural phenomenon to get rid of the excess of heat from the body. The human usually dissipates, by radiating into the surrounding; the heat produced continuously by metabolic reactions and tries to maintain its organs at a comfortable 370c. On a hot summer day when the temperature in the surroundings is sufficiently high, the dissipation is slowed down and heat accumulated resulting in sweating. However, accumulation of heat can also occur in situations where the metabolism is speeded up. Such a thing happens due to a sudden increase in the blood pressure caused by the release of a hormone-adrenaline into the blood stream on fright. The body sweats when faced with such a situation to get rid of excess heat produced.
Why do our fingers make a cracking sound when bent or pressed?
Each finger has three small bones joined end to end with the next one. They are joined by long flexible muscle fibers called tendon which allow them to bend but not move forward or backward. This arrangement is more like keeping two pieces in place by fixing a thin metal strip in such fixtures; the tendons in fingers can be moved with a little pressure. Whenever so moved or slipped form their positions tendons produce a’ popping ‘sound which we call ‘the cracking’. It takes sometime for such tendons to regain their original positions. This is why a joint once cracked does not crack again if pressed immediately.
Why body shivers in severe cold?
Muscles are capable of utilizing, in their mechanical work, only about 20% to 40% of energy liberated form glucose. The unutilized energy is lost as ‘heat’ dissipated into the environment. This heat helps in maintenance of body temperature. Shivering with cold in winter is an involuntary action of striated muscles. It yields, not a mechanical work, but only some heat just to warm body.
