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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,…

The branch of biological science that embraces the study of plants and plant life. Botany is the scientific study of plants (see illustration), encompassing investigations of plant anatomy, physiology, genetics, phylogeny, ecology, pathology, and…

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…

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…

A theory expressing the idea that life on Earth passed through an era when biological processes were carried out predominantly by ribonucleic acids, without the involvement of deoxyribonucleic acids or proteins. The RNA World theory (or hypothesis)…

An electronic display that allows a user to interact with a computer system by touching an area or areas on the display. Touch-screen displays have been in use for many years in ATMs, checkout registers, and other applications, but gained mass…

An early mechanical calculator. The abacus likely originated in Babylonia sometime before 1000 BCE. Over the subsequent centuries, it became a commonplace device in many regions of the world. The abacus is still occasionally used as a cognitive…

A chemical compound, (CH3)2CO; the first member of the homologous series of aliphatic ketones. Acetone (see illustration) is a colorless, volatile, and flammable liquid. Acetone occurs naturally in plants and animals. Its physical properties include…

In the Brönsted classification, an acid is any chemical species, ionic or molecular, capable of donating a proton (hydrogen ion) to another substance; the other substance acts as a base in accepting the proton. For these two interrelated classes of…

One of a large group of organic substances possessing the halocarbonyl group in which X stands for fluorine, chlorine, bromine, or iodine. The terms acyl and aroyl halides refer to aliphatic or aromatic derivatives, respectively.The great inherent…

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…

A group of software development methods in which requirements and solutions evolve through collaboration between the developers and the customers. Agile methods have significantly changed the practice of software development since their inception…

An informal assemblage of predominantly aquatic organisms that carry out oxygen-evolving photosynthesis, but lack specialized water-conducting and food-conducting tissues. Algae (Fig. 1) may be either prokaryotic organisms (lacking an organized…

Any compound having highly basic properties, strong acrid taste, and ability to neutralize acids. Aqueous solutions of alkalies are high in hydroxyl ions, have a pH above 7, and turn litmus paper from red to blue. Caustic alkalies include sodium…

The elements of group 1 in the periodic table. Of the alkali metals, lithium differs most from the rest of the group, and tends to resemble the alkaline-earth metals (group 2 of the periodic table) in many ways. In this respect lithium behaves as do…

Usually calcium, strontium, and barium, the heaviest members of group 2 of the periodic table (excepting radium). Other members of the group are beryllium, magnesium, and radium, sometimes included among the alkaline-earth metals. Beryllium…

A natural process in which harmful or beneficial effects are caused by secondary metabolites that spread from a donor organism to a recipient and are produced by plants, algae, bacteria, and fungi. Allelopathy is a key ecological process and has…

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…

The subfield of computer science concerned with understanding the nature of intelligence and constructing computer systems capable of intelligent behavior. Many activities, such as perception, learning, planning, natural language, and understanding,…

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 white, crystalline compound, 1-aspartyl-1-phenylalanine methyl ester (APM), used as an artificial sweetener. Aspartame is composed of two amino acids: aspartic acid and phenylalanine [structure (1)]. Amino acid Artificial sweetener Aspartame…

A nonsteroidal anti-inflammatory drug used to control pain, fever, and inflammation. Aspirin is one of the most prevalent medicines in the world and is used to reduce fever and treat minor aches, pains, and inflammation. Furthermore, it is the only…

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 weapon that consists of integral rocket propulsion, means of pointing or guiding the weapon's velocity vector to a prescribed orientation at the position and time of rocket engine shutoff or burnout, and a warhead. In certain applications, means…

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…

A fermented beverage produced from grain. Beer is a generic term used to describe alcoholic beverages made from cereal grains, especially barley (Fig. 1), in the form of malt. Ale, lager, porter, and stout are different kinds of beer made by…

An organic acid, C6H5COOH; also known as benzene carboxylic acid. Benzoic acid is a crystalline solid, with the structure below. Benzoic acid has a melting point of 122°C, and sublimes at 100°C. Benzoic acid is only slightly soluble in water but is…

A chemical element, chemical symbol Be, atomic number 4, and atomic weight 9.0122. Beryllium is the first element in the group called alkaline-earth metals on the periodic table (Fig. 1). Alkaline-earth metals Atomic number Chemical element Periodic…

A binary digit. In the computer, electronics, and communications fields, “bit” is generally understood as a shortened form of “binary digit.” In a numerical binary system, a bit is either a 0 or 1. Bits are generally used to indicate situations that…

In glass blowing, a long straight tube on which molten glass is gathered and worked, partly by blowing into the tube. The blowpipe (see illustration) is spun to shape the glass object further by centrifugal force, or by a tool, in which case the…

A system that receives and processes television signals, as well as other digital forms of communications such as those related to high-speed Internet connectivity and cable telephony, from various sources and retransmits these signals through…

Desktop or, more often, portable electronic devices that are used to perform arithmetic, statistical, or other, more complex processing operations at the step-by-step direction of the user or by execution of a program (a stored sequence of…

A chemical element, Cf, atomic number 98, the ninth member of the actinide series of elements. Its discovery and production have been based upon artificial nuclear transmutation of radioactive isotopes of lighter elements. All isotopes of…

Mercury(I) chloride, Hg2Cl2, a covalent compound which is insoluble in water. The substance sublimes when heated. The formula weight is 472.086 and the specific gravity is 7.16 at 20°C (68°F). The material is a white, impalpable powder consisting of…

A genus comprising yeasts that cause a variety of human diseases referred to as candidiasis. All Candida species are single-celled yeasts (fungal organisms) that are ovoid in shape and 3–5 μm in size, and they multiply by a process called budding.…

A method of gathering best practices for various work processes into coherent groupings to facilitate quality and process improvement. Capability Maturity Models® (CMM®) represent a relatively recent step in the evolution of process improvement…

A functional group found in organic compounds in which a carbon atom is doubly bonded to an oxygen atom. Depending upon the nature of the other groups attached to carbon, the most common compounds containing the carbonyl group are aldehydes (X…

A cluster compound containing both carbon (C) and boron (B) atoms as well as hydrogen (H) atoms external to the framework of the cluster. A cluster compound is one with insufficient electrons to allow for classical two-center two-electron bonds…

One of a large family of organic substances widely distributed in nature, and characterized by the presence of one or more carboxyl groups (COOH). These groups typically yield protons in aqueous solution.Acid and baseIn the type formula,…

A periodic waveform upon which an information-bearing signal is impressed. This process is known as modulation and comprises a variety of forms such as amplitude, phase, and frequency modulation. The most common type of carrier is the sinusoidal…

A biennial umbellifer (Daucus carota) of Asiatic and Mediterranean origin belonging to the plant order Apiales. The carrot (Daucus carota; Fig. 1) is grown for its edible roots, which are eaten raw or cooked. Cultivated forms of the root vegetable…

Catenanes are compounds that are made of interlocking macrocycles. The interlocking rings are said to be mechanically rather than chemically bound. Catenanes are named according to the number of interlocking rings. The simplest catenane, containing…

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…

A cellular automaton is a hypothetical computer constructed of a regular array of cells that interact with neighboring cells according to a set of simple rules. Though conceptually simple, cellular automata can produce complex and surprising…

A chemical element, Ce, atomic number 58, atomic weight 140.12. It is the most abundant metallic element of the rare-earth group in the periodic table. The naturally occurring element is made up of the isotopes 136Ce, 138Ce, 140Ce, and 142Ce. A…

A chemical element, Cs, with an atomic number of 55 and an atomic weight of 132.905, the heaviest of the alkali metals in group 1 of the periodic table (except for francium, the radioactive member of the alkali metal family). Cesium is a soft,…

Charged particles can be accelerated to high velocities by electromagnetic fields. They are then able to travel through matter (termed an absorber), interacting with it, losing energy, and causing various effects important in many applications. In…

A branch of physical chemistry that seeks to explain time-dependent phenomena, such as energy transfer and chemical reaction, in terms of the detailed motion of the nuclei and electrons that constitute the system. As such, chemical dynamics seeks…

The study of ecological interactions mediated by chemicals that organisms produce. Chemical ecology seeks to integrate chemistry and biology in order to provide information about the chemical interactions among organisms and their environment (Fig.…

Atoms with the same atomic number; that is, the same number of protons in their atomic nucleus. Some common elements are oxygen, hydrogen, iron, copper, gold, silver, nitrogen, chlorine, and uranium (see illustration). Most of the elements are…