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The ongoing lower level of species extinction intensity occurring between episodes of mass extinctions. Extinction is a normal part of the history of life. Out of every 100 species that have ever lived on Earth, 99 are no longer in existence.…

Cameras in mobile phones or smartphones that can capture images and videos.The cellphone, the world’s favorite must-have gadget, has been with us for nearly a half-century, while experiencing continuous and often phenomenal improvements. Much of the…

Light emitted by a high-speed charged particle when the particle passes through a transparent, nonconducting, solid material at a speed greater than the speed of light in the material. The emission of Cerenkov radiation—also spelled Cherenkov—is…

The extraction and refining of copper (Cu) from its ores. About 18 million metric tons per year of copper metal is produced from the mining and processing of copper ores, typically containing only about 1% Cu. About 80% of the world's primary copper…

The capture, processing, transmission, and storage of images in electronic form. Digital photography differs from film photography in that images are captured and recorded as electronic files rather than as recognizable images on a light-sensitive…

A general term referring to a system or part of a system of conducting parts and their interconnections through which electric currents are intended to flow. A circuit is made up of a voltage source along with active and passive elements, as well as…

The measure of the opposition that an electrical circuit presents to the passage of a current when a voltage is applied. In quantitative terms, electrical impedance is the complex ratio of the voltage to the current in an alternating-current (ac)…

The ability of a material to resist or allow the flow of electrical current. Material properties largely determine the resistance and conductance—quantified by electrical resistivity and conductivity—of a given object, such as a circuit or…

The measures of a material's opposition to the flow of electricity and a material's ability to conduct electricity, respectively. Resistivity quantifies resistance, which is a material's opposition to the flow of electrons (an electric current or…

The process in which an electron, which has been excited from the valence band to the conduction band of a semiconductor, falls back into an empty state in the valence band, which is known as a hole. When atoms come together to form a crystal, the…

Typically, an aquatic vertebrate with scales, gills, and paired fins. Fishes (Fig. 1) are found throughout the world's waterways, from saltwater oceans to freshwater streams and ponds. About 35,000 species of fishes have been described to date. Many…