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A common medicine used to relieve mild to moderate pain and reduce fever. Acetaminophen (N-acetyl-p-aminophenol), or paracetamol, is a white crystalline compound with the molecular formula C8H9NO2 (Fig. 1). It is a member of the aniline family of…

Natural and artificial substances in the atmosphere that affect human health or well-being, or the well-being of any other organisms in the environment. Air pollution also applies to situations in which contaminants affect structures and artifacts…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

A conductor whose purpose is to emit and/or receive electromagnetic waves using the bulk oscillations of electric charges within the conductor. The conduction electrons in antennas are free to move throughout the conductor. The electrons form a bulk…

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,…

Earth's oldest desert and the most arid place outside of Antarctica's Dry Valleys. Located along the edge of the Pacific Ocean and to the west of the Andes in Chile's Antofagasta Province, the Atacama Desert (Fig. 1) has long been recognized as…

Any of the cells within a tumor that possess the capacity to self-renew and cause the heterogeneous lineages of cancerous cells that comprise the tumor. Cancer stem cells (CSCs) typically represent a small percentage of all cells in a tumor (rarely…

Any clouding or opacity of the crystalline lens of the eye. Loss of the transparency of the lens (see illustration) prevents the normal passage of light onto the light-sensitive retina at the back of the eye and thus a loss of visual ability.…

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 administration of chemical substances for the treatment of disease, especially cancer, or for the prevention of aberrant growth of cells or tissues (neoplasms). In general, chemotherapy is the use of chemicals to treat any disease, but the term…

The scientific study of climate. Climate is the expected mean and variability of the weather conditions for a particular location, season, and time of day. For planet Earth, the climate is often described in terms of the mean values of…

A branch of computer science that deals with the theory and techniques of computer-generated images. Computers produce images by analyzing a collection of dots, or pixels (picture elements). Computer graphics is used to enhance the transfer and…

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 response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral skeleton visible. Corals (Fig. 1) are animals that live in a partnership (symbiosis) with…

A genome-engineering technique that allows precise targeting of specific stretches of genetic code and editing of DNA at designated locations. The CRISPR/Cas9 system has been used as a general tool to engineer the genomes of many different…

A syndrome characterized by a generalized decline in cognition that is severe enough to cause functional impairment in daily activities. Dementia is a term used to describe a collection of symptoms of severe cognitive decline. Individuals suffering…

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…

The interaction of the behavior and ecology of hosts with the biology of pathogens as relating to the impact of diseases on populations. Although human diseases have been studied from an ecological perspective for centuries, diseases in plant and…

A radar system used to measure the relative velocity of targets and their position. The operation of these systems is based on the fact that the Doppler frequency shift in the target echo is proportional to the radial component of target velocity.…

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…

A condition characterized by the paroxysmal recurrence of transient, uncontrollable episodes of abnormal neurological or mental function (or both). "Epilepsy" generally refers to the medical condition of recurrent, unprovoked seizures, and the term…

An interdisciplinary science area that is concerned with modeling aspects of natural evolution in order to solve real-world problems of optimization. Living organisms, as well as those that are long extinct, demonstrate optimized complex behavior at…

The use of pollen and spore evidence in legal cases. In its broader application, the field of forensic palynology also includes legal information derived from the analysis of a broad range of microscopic organisms that can be found in both fresh and…

A biological organism whose genetic material has been manipulated artificially through genetic or genomic editing techniques. In contrast to the long history of artificial selection (domestication), in which humans selectively breed organisms to…

An ordered, internally consistent, internationally recognized sequence of time intervals, each distinct in its own history and record of life on Earth, including the assignment of absolute time in years to each geologic interval. The geologic time…

Significant and persistent changes in the state of Earth’s climate. Earth's past climates, or paleoclimates, have alternated between ice ages and periods warmer than today over relatively long time scales (millions to tens of millions of years)…

The rise in the surface temperature of the Earth. Global warming is one of the names given to the systematic increase of globally averaged surface temperature that has been measured since the mid-nineteenth century. There is abundant evidence that…

A phaneritic (visibly crystalline) plutonic rock composed chiefly of sodic plagioclase (oligoclase or andesine), alkali feldspar (microcline or orthoclase, usually perthitic), quartz, and subordinate dark-colored (mafic) minerals (biotite,…

A strongly cemented or hardened (indurated) dark gray sandstone that is characterized by abundant dark-colored detrital rock fragments and more than 15% clay minerals (matrix) between sand grains. The term graywacke evolved from initially informal…

A space-traversing unmanned vehicle which contains the means for controlling its flight path and that delivers an explosive warhead with high accuracy. Various kinds of missiles are guided in the sense that they can aerodynamically adjust after…

The most common sulfate mineral, characterized by the chemical formula CaSO4 · 2H2O; it shows little variation from this composition.Gypsum is one of the several evaporite minerals. This mineral group includes chlorides, carbonates, borates,…

Pathologies or aberrations in structure or function of blood cells or the blood-clotting mechanism. Hematologic disorders affect the blood and blood-forming organs. Although many diseases and abnormal conditions may be reflected by the blood and its…

A vacant electron energy state near the top of an energy band in a solid. A hole, or more formally an electron hole, represents the absence of an electron where one could exist as part of an atom or within a crystal structure (an atomic lattice)…

A metamorphic rock that has been subjected to heating during contact metamorphism around intrusive igneous rocks. Hornfels is typically fine-grained, although where it is subjected to high temperatures, large crystals called porphyroblasts can form.…

An applied science and technology concerned with the mechanical properties and practical uses of liquids. The physical description of fluids in motion is based upon the conservation laws of mass, momentum, and energy. The mathematical statement of…

The process of tissue death (necrosis) resulting from a failure of blood supply and lack of oxygen (anoxia) reaching the tissue's cells. The usual cause of infarction is occlusion (blockage or closing) of an artery by a thrombus (blood clot; see…

The entrance, growth, and multiplication of a microorganism or pathogen in the body of a host. Infection may or may not result in the establishment of a disease process, depending on many variables including the pathogen involved, the health of the…

Fundamental laws dealing with electric currents at junctions and voltages around any loop within a network. Also known as Kirchhoff's circuit laws, the laws were first described by German physicist Gustav Kirchhoff in 1845. The laws are divided into…

A disease caused by members of the protozoan genus Plasmodium (a widespread group of protists that parasitize the human liver and red blood cells) and transmitted by the bite of the female Anopheles mosquito. Malaria is a serious mosquito-borne…

Impaired health caused by a dietary deficiency, excess, or imbalance. To support human life, energy (from fat, carbohydrate, and protein), water, and more than 40 different food substances must be obtained from the diet in appropriate amounts.…

The process of exploring the deep seabed and recovering minerals from seawater and from deposits on and under the seabed. While the world's demand for mineral commodities is increasing at a rapid rate, most of the developed countries have been…

A procedure used to remove toxins, fluids, and other substances from the body when the kidneys are unable to handle this removal naturally. In the medical field, medical dialysis is simply referred to as dialysis. The removal of toxins, fluids, and…

A machine that converts electrical energy into mechanical energy. Motors that develop rotational mechanical motion are most common, but linear motors are also used. A rotary motor delivers mechanical power by means of a rotating shaft extending from…

An autoimmune disease resulting from an abnormality in neuromuscular transmission, characterized by a fluctuating degree of muscle weakness. Myasthenia gravis is a chronic autoimmune neuromuscular disorder (see illustration) characterized by varying…

The relationship stating that the magnitude of the electrical current in a circuit is directly proportional to the applied voltage and inversely proportional to the circuit's resistance. One of the simplest and most intuitive electrical laws, Ohm's…