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The United Nations has proclaimed 2019 the International Year of the Periodic Table of Chemical Elements (IYPT2019). The same year also marks the 150th anniversary of the publication of Russian chemist Dmitri Mendeleev’s periodic table, containing…

A plant, Musa textilis, of the banana family that is valuable for its hard fiber (also known as Manila hemp) and native to Borneo and the Philippines. Abaca is one of the strongest of the hard fibers. Commercially, it is known as Manila hemp. The…

One of the major plant hormones that plays an important role in plant growth and development. Abscisic acid (ABA) is ubiquitous in vascular plants; the highest levels are found in young leaves and in developing fruits and seeds. Abscisic acid is…

The process whereby a plant sheds one of its parts. Leaves, flowers, seeds, and fruits are parts commonly abscised. Almost any plant part, such as very small buds and bracts to branches several inches in diameter, and scales or sheets of bark, may…

The temperature at which matter reaches a lowest energy state and all thermal activity theoretically ceases. Absolute zero is popularly conceived as the coldest possible temperature that a given system of matter, such as an atom, may reach.…

Either the taking up of energy from radiation by the medium through which radiation is passing, or the taking up of matter in bulk by other matter. A simple example of the absorption of energy is how sunlight warms a tree's leaves (see…

The reception of electromagnetic radiation by particles with electric charge, resulting in transference of the radiation's energy and momentum. Electromagnetic radiation is also referred to as electromagnetic waves, photons, and light. Photons are…

The technique of measuring the magnitude and direction of acceleration. Measurement of acceleration includes translational acceleration with tangential and radial components and angular acceleration. Acceleration Translation acceleration The…

A mechanical or electromechanical instrument that measures acceleration. The two general types of accelerometers measure either the components of translational acceleration or angular acceleration. Acceleration measurement Translational…

An impurity atom in a semiconductor which can accept or take up one or more electrons from the crystal and become negatively charged. An atom which substitutes for a regular atom of the material but has one less valence electron may be expected to…

A method of nondestructive testing and materials characterization that uses mechanical waves moving through materials. It is similar to seismology, except in being concerned with the scale of engineering structures, such as aircraft, bridges, and…

An instrument that is sensitive to the interference of two or more acoustic waves. It provides information on acoustic wavelengths that is useful in determining the velocity and absorption of sound in samples of gases, liquids, and materials, and it…

Unwanted sound. Noise control is the process of obtaining an acceptable noise environment for people in different situations. These definitions and the words “unwanted” and “acceptable” suggest that criteria need to be established to determine when…

The net pressure exerted on a surface or interface by an acoustic wave. One might presume that the back-and-forth oscillation of fluid caused by the passage of an acoustic wave will not exert any net force on an object, and this is true for sound…