An aqueduct is an artificial channel, usually an elevated one, for carrying water. The ancient Romans and Greeks were enthusiastic builders of aqueducts. Before the end of the first century A.D., Rome was supplied by nine aqueducts with a total length of more than 386 km, of which about 56 km were raised above ground.

The term AMOLED stands for Active Matrix Organic Light Emitting Diode/ Device/ Display. An Organic Light Emitting Diode (OLED), also Light Emitting Polymer (LEP) and Organic Electro Luminescence (OEL), is any Light Emitting Diode (LED) whose emissive electroluminescent layer is composed of a film of organic compounds. The layer usually contains a polymer substance that allows suitable organic compounds to …

An aMap (argument map) is a visual representation of the structure of an argument in informal logic. It includes the components of an argument such as a main contention, premises, co-premises, objections, rebuttals and lemmas. Argument maps are often used in the teaching of reasoning and critical thinking and can support the analysis of pros and cons when deliberating over …

An alchemist was an early student of the science of chemistry. According to one theory the word “alchemy” is derived from “Khem”, the ancient name for Egypt. That country was the source of a great deal of the pioneer work in the various sciences. Much of the early work of the alchemists is frowned on by today’s scientists because it …

An albino is a person or an animal without any colour at all in their skin except red caused by blood vessels. This is quite rare, and means that person has very white skin, white hair and pink or red looking eyes. The red colour appears because there are lots of blood vessels in the eye. Albinos live all over …

An aerosol of fine particles of liquid or solid substances suspended in the air, or in any other gas. It is not, as many people think, merely a spray for use in applying paint easily, or getting rid of unpleasant smells. The germs of diseases, for example, are to be found suspended in the air, and these dangerous aerosols can …

In Peru, where I come from, an adobe is a brick made of mud mixed with other material such as cane, straw and stone to give consistency. It is dried in the sun. The adobe provides a cool atmosphere to buildings. In Peru, many archaeological places used this material, like the Huaca del Sol, a pre-Columbian construction in Trujillo, which …

Achilles was a legendary Greek hero. Before he was born the Fates had told his mother Thetis (who was a sea nymph) that he would die young. so when he was a baby she tried to make him immortal by plunging him into the River Styx, whose magic properties were supposed to give protection from all harm. But the heel …

The albedo of an object is the extent to which it diffusely reflects light from the Sun. It is a more specific form of reflectivity. Albedo is the ratio of the diffusely reflected to incident electromagnetic radiation. It is a unitless measure indicative of a surface’s or a body’s diffuse reflectivity. Albedo is a Latin word for whiteness. The range …

Air hunger is the urge to breathe, which is caused by the detection of high levels of carbon dioxide in the blood by sensors in the carotid sinus. It is one of the body’s homeostatic mechanisms to ensure proper oxygenation. Air hunger may be caused by insufficient pulmonary minute ventilation, a sustained breath-hold constriction of the alveoli of the lungs, …