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Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

A taxonomic order of insects comprising the cockroaches and termites. The order Blattodea, also referred to as Blattaria, contains at least 4500 species of cockroaches (Fig. 1) and 3000 species of termites. Previously, termites were assigned to a…

Any member of the grass family (Poaceae or Gramineae) that produces edible grains usable as food by humans and livestock. Cereals are important cultivated crops. Common cereals include rice, wheat, barley, oats, maize (corn), sorghum, rye, and…

The common name for three living species of mammals in the family Elephantidae (order Proboscidea). Elephants are extant members of the mammalian family Elephantidae, which is one of several families included in the order Proboscidea. The remaining…

Any interaction between objects that causes motion. Fundamentally, objects interact through the four known physical forces: gravity, electromagnetism, and the strong and weak nuclear interactions. In practice, however, many of the forces worked with…

The science, art, and practice of managing and using the natural resources that occur on and in association with forested lands. Forestry is the management of forested lands (see illustration). It involves the planning and implementation of…

The highest-energy form of electromagnetic radiation, or light. The energies of gamma rays range from a few kiloelectronvolts [(keV), where the prefix kilo (k) means 103] to several hundreds of megaelectronvolts [(MeV), where the prefix mega (M)…

Plants that have altered genetic material (DNA) through recombinant DNA (rDNA) manipulation. Genetic engineering of plants allows for very specific genetic changes to be made to a plant's deoxyribonucleic acid (DNA), as opposed to the random…

Commercially grown plants that have altered genetic material through artificial recombinant manipulation. Genetic modification is the latest scientific tool for developing improved crop varieties. Such genetically modified (GM) crops can help to…

Electromagnetic radiation whose wavelengths are in the range from about 0.75 micrometer (μm) to 1 millimeter (mm). Infrared radiation (Fig. 1) is outside the range of visible light and cannot be seen with the unaided eye. Infrared radiation was…

The artificial application of water to the soil to produce plant growth. Irrigation also cools the soil and atmosphere, making the environment favorable for plant growth. The use of some form of irrigation (Fig. 1) is well documented throughout the…

A mammalian order containing the egg-laying platypus and echidnas. Members of the order Monotremata (monotremes) are egg-laying mammals belonging to the subclass Prototheria (in some alternative classifications, the monotremes have been assigned to…

The change in the position of an object in a physical space over time. A familiarly encountered phenomenon, motion (see illustration) occurs on all levels of reality, from the constant movements of subatomic particles (conveyed by probabilities of…

The branch of acoustics that deals with the generation of sound by musical instruments, the transmission of sound to the listener, and the perception of musical sound. Musical acoustics has fascinated scientists at least since the time of the Greek…

An annual leafy leguminous vine, Pisum sativum (order Fabales), cultivated for its smooth or wrinkled, round edible seeds, which are borne in dehiscent pods. The garden pea (Fig. 1) is one of the world's oldest cultivated crops. It is a native of…

An order of placental mammals containing the largest and most powerful living terrestrial mammals—the elephants. Proboscideans once had a wide distribution, reaching every continent except Australia and Antarctica. Although early forms lacked both…

The planning and implementation of actions to establish, protect, restore, and maintain trees and forests in cities and smaller communities. When the field of urban forestry began in the 1960s, it focused on individual trees along streets and…

In physics, the transference of energy that occurs when a force is applied to a body that is moving in such a way that the force has a component in the direction of the body's motion. Work is accordingly done on a weight that is being lifted (Fig.…

A nocturnal, burrowing, insectivorous, piglike mammal (Orycteropus afer) in the order Tubulidentata. The mammalian order Tubulidentata contains a single family, Orycteropodidae, and a single extant aardvark species, Orycteropus afer (Fig. 1).…

A departure of an optical image-forming system from ideal behavior. Ideally, such a system will produce a unique image point corresponding to each object point. In addition, every straight line in the object space will have as its corresponding…

The time rate of change of velocity. Acceleration is a physics term that measures the rate of change of velocity per unit of time. Because velocity is a directed or vector quantity involving both magnitude and direction, a velocity may change by a…

The technique of measuring the magnitude and direction of acceleration. Measurement of acceleration (see illustration) includes translational acceleration with tangential and radial components and angular acceleration. Acceleration The May 16, 2011…

The use of a combination of mass spectrometers and an accelerator to measure the natural abundances of very rare radioactive isotopes. These abundances are frequently lower than parts per trillion. The most important applications of accelerator mass…

An instrument that utilizes focused acoustic waves to produce images of surface and subsurface features in materials, and to measure elastic properties on a microscopic scale. It has been used to image and measure local elastic properties in metals,…

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 discipline of acoustic phonetics can be narrowly defined as the study of the acoustic output of the vocal tract for speech, but ultimately it encompasses much more. Acoustic phonetics makes direct contact with, and in many cases is the…

A device to measure the acoustic power or intensity of a sound beam by means of the force or torque that the beam exerts on an inserted object or interface. The underlying theory involves the concept of radiation pressure, which is the…

A discipline that deals generally with the extraction of information from acoustic signals in the presence of noise and uncertainty. Acoustic signal processing has expanded from the improvement of music and speech sounds and a tool to search for oil…

The ratio of the current to the voltage in an alternating-current circuit.In terms of complex current I and voltageV, the admittance of a circuit is given by Eq. (1), and is related to the impedance of the circuit Z by Eq. (2). Y is a complex number…

The force retarding an airplane, especially in supersonic flight, as a consequence of the formation of shock waves. Although the physical laws governing flight at speeds in excess of the speed of sound are the same as those for subsonic flight, the…

A branch of meteorology that examines the effects and impacts of weather and climate on crops, rangeland, livestock, and various agricultural operations. Agricultural meteorology, or agrometeorology, addresses topics that often require an…

The pure and applied science that is concerned with botany and management of crop and ornamental plants for utilization by humankind. As it relates to plants, agricultural science concerns itself with the application of scientific methods to…

The art and science of crop and livestock production. In its broadest sense, agriculture comprises the entire range of technologies associated with the production of useful products from plants and animals, including soil cultivation, crop and…

The science and study of crops and soils. Agronomy is the umbrella term for a number of technical research and teaching activities (see illustration): crop physiology and management, soil science, plant breeding, and weed management frequently are…

Helium nuclei, which are abundant throughout the universe both as radioactive-decay products and as key participants in stellar fusion reactions. Alpha particles can also be generated in the laboratory, either by ionizing helium or from nuclear…

One of the major classes composing the superclass Tetrapoda of the subphylum Vertebrata, and including frogs, toads, salamanders, and caecilians. Amphibians, that is, members of the class Amphibia, are tetrapod vertebrates. Modern amphibians number…

The analog of linear momentum for rotational motion. A particle with mass m moving with velocity v has linear momentum p = m v (Note: This article follows the convention of using bold, non-italicized variables for vectors and using non-bold,…

Any living organism taxonomically assigned to the classification kingdom known as Animalia. Members of the kingdom Animalia—that is, animals (see illustration)—possess certain characteristics that distinguish them from organisms belonging to the…

A discipline within the field of animal behavior that focuses on the reception and use of signals. Animal communication could well include all of animal behavior because a liberal definition of the term signal could encompass all stimuli perceived…

The group of primates most closely related to humans. The primates included in the ape group are the African great apes, the gorillas (Fig. 1) and chimpanzees; the Asian great apes, the orangutans; and the lesser apes from Asia, the gibbons. Humans…

A deciduous tree (genus Malus) in the order Rosales, which produces an edible, simple, fleshy, pome-type fruit. Apples (Fig. 1) belong to the family Rosaceae, which includes many other deciduous fruits, including pears, peaches, and cherries. There…

An order of leeches (subclass Hirudinida) characterized by the absence of a protrusible proboscis and including both blood-feeding and macrophagous (predatory) varieties. Most notorious among the blood-feeding leeches in the Arhynchobdellida is the…

Vegetables that are prevalent in Asian cuisines, but less well known in Western diets. Asian vegetables (Fig. 1), also referred to as Asian greens or oriental vegetables, are very important in Asian countries, but are not as popular in North America…

A class of the asterozoan group of the phylum Echinodermata, often known as sea stars or starfish. Members of the class Asteroidea, that is, asteroids, are notable echinoderms with a star-shaped body plan (Fig. 1). Unlike members of their sister…

An analytical technique for determining the composition of a sample in terms of the chemical elements present and their quantities or concentrations. Unlike other methods of elemental analysis, however, the sample is decomposed into its constituent…

A large tropical plant of the genus Musa and its edible fruit. The banana belongs to the family Musaceae (order Zingiberales). The banana of commerce (Musa acuminata), which is believed to have originated in the Asian tropics, was one of the…

Any member of the mammalian family Ursidae, which contains the largest terrestrial carnivores. The bear family Ursidae comprises a number of carnivorous mammalian species. There are eight extant species of bears in three subfamilies: Ursinae…

The management and maintenance of colonies of honeybees for human purposes. Beekeeping is an ancient art. Although the commonly known honeybee species (Fig. 1) is native to Europe and Africa, humans have transported them to other continents. The…

A sound-reproducing system in which sound is recorded or transmitted by using two microphones mounted at the ears of a dummy human head. To preserve the binaural effect, the sound must be monitored by a listener wearing a set of earphones…

The use of parasitoids, predators, and pathogens to reduce injurious pest insect populations and consequently the damage that they cause. Biological insect control (or insect biocontrol) is the regulation of insect populations by biological means.…