Science: Technoquest

Q: Do bears hibernate?

Hibernation, a state of torpor, dormancy or inactivity, is used by some bears and other animals to adapt to a shortage of nutrition during the winter. Bear hibernation differs from that of other animals.

Not all bears hibernate. Bears that live where the winter does not get too cold do not hibernate. Similarly, bears that have not put on sufficient fat stores may not hibernate, or do so only for a short time. During the hibernation of bears, they do not eat, drink or defecate. Their urea is re absorbed through the bladder wall and safely converted into usable amino acids and protein. Their metabolism slows down. Their body temperature drops, but never below 89 degrees. They require only half their normal oxygen intake. Their digestive organs and kidneys shut down almost completely. There is no permanent loss of muscle functioning or bone mass. They exist solely on fat and fluids in their body. They do not dehydrate. They lose up to 40 per cent of their weight, from fatty tissues. They use approximately 4,000 calories per day to maintain their body. Blood circulates more to the brain and upper body. Some bears hibernate for seven or eight months.

Q How do rechargeable batteries work?

Normal batteries are actually distorted and largely destroyed in the process of making electricity. In the recharging process, a current from an outside source is pushed through the cell in a direction opposite to that from which it was drawn originally. This reverses the reaction that happened during discharge, restoring the anode to its metallic state, reoxidizing the positive electrode.

Nickel-cadmium rechargeable cells comprise alternating layers of porous, negative cadmium anode and porous, positive nickel oxide cathode separated by absorbent layers, all permeated with electrolyte and all inside a nickel- plated steel case. Both the cadmium anode and the nickel oxide cathode material are contained in plates. The plates are conductive, increasing efficiency. Because of this design, the anode structure is not seriously distorted as the cadmium is oxidized, nor is the cathode structure as the nickel is reduced. This gets over the biggest problem of recharging batteries - the distortion.

You can also visit the technoquest World Wide Web site at http://www.sciencenet. org.uk