hedgehog: …hedgehogs (genus Hemiechinus), and two steppe hedgehogs (genus Mesechinus). European hedgehogs are kept as pets, as is the African pygmy hedgehog (Atelerix albiventris).

Matthew Meselson is an American molecular biologist notable for his experimental confirmation of the Watson-Crick theory of the structure and method of replication of deoxyribonucleic acid (DNA). Meselson obtained a Ph.D. at the California Institute of Technology (Caltech), Pasadena, in 1957. His

Matthew Meselson: …model was known as the Meselson-Radding model. Meselson’s later work concentrated on the anomalous evolutionary success of bdelloid rotifers, a type of invertebrate that reproduces solely through asexual means.

Nesebŭr, historic town and resort, eastern Bulgaria, on the Black Sea coast. Nesebŭr is situated on an island connected to the mainland by a narrow strip of land. The Greek colony of Mesembria was founded on the site late in the 6th century bc and thrived on the trade between Greece and Thrace. It

ice plant: Highway ice plant (Carpobrotus edulis, formerly Mesembryanthemum edule) is one of the most commonly grown species and is named for the transparent glistening swellings on its edible leaves. It is cultivated in gardens and as an indoor potted plant. It is naturalized in California, where…

death: Descartes, the pineal soul, and brain-stem death: …pineal gland there lies the mesencephalic tegmentum (the uppermost part of the brain stem), which is crucial to generating alertness (the capacity for consciousness), without which, of course, there can be no volition, cognition, or reason.

midbrain, region of the developing vertebrate brain that is composed of the tectum and tegmentum. The midbrain serves important functions in motor movement, particularly movements of the eye, and in auditory and visual processing. It is located within the brainstem and between the two other

cryopreservation: …that hematopoietic stem cells and mesenchymal stem cells (derived from embryonic connective tissue) are capable of differentiating into skeletal and cardiac muscle tissues, nerve tissue, and bone. Today there is intense interest in the growth of these cells in tissue culture systems, as well as in the cryopreservation of these…

cell: The extracellular matrix: The first type, mesenchymal tissue, is made up of clusters of cells grouped together but not closely adherent to one another. They synthesize a highly hydrated gel, rich in salts, fluid, and fibres, known as the interstitial matrix. Connective tissue is a mesenchyme that fastens together other more…

Mesene, ancient Parthian vassal state located in the south of Babylonia (modern southern Iraq). After the fall of the Seleucid king Antiochus VII Sidetes in 129 bc, a local prince, Hyspaosines (also called Aspasine, or Spasines), founded the Mesene kingdom, which survived until the rise of the

human cardiovascular system: The aorta and its principal branches: The superior mesenteric artery arises from the abdominal aorta just below the celiac artery. Its branches supply the small intestine and part of the large intestine. Arising several centimetres above the termination of the aorta is the inferior mesenteric artery, which branches to supply the lower part…

crustacean: The digestive system: …between the mill and the midgut is guarded by a filter of setae, which prevent particles from passing into the midgut until they have been degraded into a sufficiently small size. The structure of the midgut is also variable among species but generally has one or more diverticula, or pouches,…

mesentery, a continuous folded band of membranous tissue (peritoneum) that is attached to the wall of the abdomen and encloses the viscera. In humans, the mesentery wraps around the pancreas and the small intestine and extends down around the colon and the upper portion of the rectum. One of its

Robert Preston was a versatile American actor best known for his role as Professor Harold Hill in The Music Man on the Broadway stage in 1957 and in the 1962 film. The son of a minor-league baseball player, Preston attended school in Hollywood, Calif., but quit at the age of 16 to become an actor.

Meseta Central, great interior meseta (plateau) of the Iberian Peninsula, central Spain. With Madrid at its centre, it extends over 81,000 square miles (210,000 square km) and has an average elevation of 2,165 feet (660 metres). It constitutes the oldest and most complex geologic formation of the

Valle Central, highland valley in central Costa Rica, containing most of the country’s large cities and about seven-tenths of the total population. The valley is divided by low volcanic hills (the Continental Divide) 3,000 to 5,000 feet (900 to 1,500 metres) above sea level, which lie between the

semiconductor device: Metal-semiconductor field-effect transistors: The metal-semiconductor field-effect transistor (MESFET) is a unipolar device, because its conduction process involves predominantly only one kind of carrier. The MESFET offers many attractive features for applications in both analog and digital circuits. It is particularly useful for microwave amplifications and…

electric generator: Phases: …c′ to a—to form a delta connection. The output can then be transmitted using only three conductors connected to the three junction points. Other advantages of the three-phase system will become evident in the discussion of electric motors below.

Al-Karak: In the mid-9th century bce, Mesha, king of Moab, was attacked by the combined forces of Israel, Judah, and Edom for his failure to pay tribute. The siege of the ancient Moabite stronghold of Qir-hareseth and the forces’ subsequent withdrawal after Mesha offered his heir as a burnt offering on…

Meïr was a rabbi who was among the greatest of the tannaim, the group of some 225 masters of the Jewish Oral Law that flourished in Palestine for roughly the first 200 years ad. He continued the work of his teacher, Rabbi Akiba, in compiling by subject the Halakhot (laws) that came to be

Dibon: …in 1868 of the so-called Moabite Stone, bearing an inscription of Mesha, king of Moab, about the 9th century bce; its 34-line inscription commemorates a victory over the Israelites that reestablished the independence of Moab.

Khaled Meshaal is an exiled Palestinian politician who served as the head of the political bureau of the Palestinian Islamist movement Hamas from 1996 until 2017. In 2021 he was tapped to head Hamas’s office for Palestinian refugees and exiles. After the assassination in 2024 of Ismail Haniyeh, who

Khaled Meshaal is an exiled Palestinian politician who served as the head of the political bureau of the Palestinian Islamist movement Hamas from 1996 until 2017. In 2021 he was tapped to head Hamas’s office for Palestinian refugees and exiles. After the assassination in 2024 of Ismail Haniyeh, who

Mesene, ancient Parthian vassal state located in the south of Babylonia (modern southern Iraq). After the fall of the Seleucid king Antiochus VII Sidetes in 129 bc, a local prince, Hyspaosines (also called Aspasine, or Spasines), founded the Mesene kingdom, which survived until the rise of the

Moscow: City site: …swampy clay plain of the Meshchera Lowland, which extends far beyond the city limits.

Phrygia: … of peoples (identified as “Mushki” in Assyrian records) that dominated the entire Anatolian peninsula. This early civilization borrowed heavily from the Hittites, whom they had replaced, and established a system of roads later utilized by the Persians. About 730 the Assyrians detached the eastern part of the confederation, and…

education: Organization of education: …third type of college, the meshed (shrine college), was usually a madrasa built next to a pilgrimage centre. Whatever their particularities, all three types of college specialized in legal instruction, each turning out experts in one of the four schools of Sunni, or orthodox, Islamic law.

Mashhad, city, capital of Khorāsān-e Razavī ostān (province), northeastern Iran. It is located in the Kashaf River valley at an elevation of about 1,000 metres. As the burial place of ʿAlī al-Riḍā, the eighth imam in Twelver Shiʿism (Ithnā ʿAshariyyah), Mashhad is an important pilgrimage site.

Bābol: Meshed-e Sar, now called Bābol Sar, was formerly the port of Bābol on the Caspian, but it lost its function after the water level dropped. It is now a fashionable resort and has an airport. Pop. (2011) 219,467; (2016) 250,217.

Maya Deren: …and in 1943 they codirected Meshes of the Afternoon. They shot the film in their own home, with Hammid serving as cinematographer and Deren playing the central character (Hammid appears in a smaller role). The film’s innovative camera work and narrative structure depict a web of dream events that move…

Mashhad, city, capital of Khorāsān-e Razavī ostān (province), northeastern Iran. It is located in the Kashaf River valley at an elevation of about 1,000 metres. As the burial place of ʿAlī al-Riḍā, the eighth imam in Twelver Shiʿism (Ithnā ʿAshariyyah), Mashhad is an important pilgrimage site.

Ukraine: State building and diplomacy: …increased in 1994: separatist leader Yury Meshkov was elected Crimean president in January, and a referendum calling for sovereignty was passed two months later. Meshkov proved to be an inept leader, however, and he quickly alienated his own supporters. By September he and the Crimean parliament were locked in a…

Fox, an Algonquian-speaking tribe of North American Indians who called themselves Meshkwakihug, the “Red-Earth People.” When they first met French traders in 1667, the tribe lived in the forest zone of what is now northeastern Wisconsin. Tribes to their east referred to them as “foxes,” a custom

Cochin Jews: …Malabaris (Black Jews), and the Meshuchrarim (Brown Jews). Whereas they once numbered in the thousands, only about 50 Cochin Jews remained on the Malabar Coast in the early 21st century.

ancient Egypt: The early 20th dynasty: Setnakht and Ramses III: …great Libyan invasion by the Meshwesh tribes. Meshwesh prisoners of war, branded with the king’s name, were settled in military camps in Egypt, and in later centuries their descendants became politically important because of their ethnic cohesiveness and their military role.

mesia, (species Leiothrix argentauris), songbird of the babbler family Timaliidae (order Passeriformes). It is found from Pakistan through the Indochinese peninsula in scrub and secondary jungle. This 15-centimetre- (6-inch-) long bird is olive above and yellow below, with a black crown, silver ear

mesic atom, atom in which one electron is replaced by a negative muon or a negative pion (pi meson). The muon or pion, after being slowed down in matter, is captured in a high atomic orbit and cascades down, ejecting electrons by the Auger effect or radiating visible light or X-ray photons, to an

Stipe Mesić is a Croatian politician who served as president of Croatia (2000–10). Mesić earned a degree in law from the University of Zagreb (1961), after which he returned to his hometown of Orahovica in eastern Croatia, which was then part of the Kingdom of Yugoslavia, and served as mayor. In

Stipe Mesić is a Croatian politician who served as president of Croatia (2000–10). Mesić earned a degree in law from the University of Zagreb (1961), after which he returned to his hometown of Orahovica in eastern Croatia, which was then part of the Kingdom of Yugoslavia, and served as mayor. In

Kish: A king of Kish, Mesilim, is known to have been the author of the earliest extant royal inscription, in which he recorded his arbitration of a boundary dispute between the south Babylonian cities of Lagash and Umma. The dynasty ended when its last king, Agga, was defeated about 2660…

Las Cruces: Historic Mesilla (briefly the Confederate capital of the Arizona Territory) and the Indian community of Tortugas are nearby. At the end of the 1990s, Las Cruces was one of the fastest-growing cities in the western United States. Inc. 1907. Pop. (2000) 74,267; Las Cruces Metro Area,…

weather forecasting: Numerical weather prediction (NWP) models: …developed by Serbian atmospheric scientist Fedor Mesinger and Serbian-born American atmospheric scientist Zaviša Janjić. The meso-eta model is a finer-scale version of a regional numerical weather prediction model used by the National Weather Service in the United States. The national weather services of several countries produce numerical forecasts of considerable…

mesite, any of several species of small, brownish ground-dwelling birds constituting the family Mesitornithidae (sometimes Mesoenatidae), order Gruiformes. They are about 30 cm (12 inches) long, have short wings and a thick tail, and inhabit Madagascar. They differ from all other gruiform birds in

mesite: Mesitornis (sometimes Mesoenas) unicolor and M. variegata inhabit forests. Bensch’s rail (not a true rail), also called Bensch’s monias (Monias, or Mesoenas, benschi), inhabits brushland. All three species build platform nests low in bushes.

mesite, any of several species of small, brownish ground-dwelling birds constituting the family Mesitornithidae (sometimes Mesoenatidae), order Gruiformes. They are about 30 cm (12 inches) long, have short wings and a thick tail, and inhabit Madagascar. They differ from all other gruiform birds in

Georgia: Relief, drainage, and soils: …trough is crossed by the Meskhet and Likh ranges, linking the Greater and Lesser Caucasus and marking the watershed between the basins of the Black and Caspian seas. In central Georgia, between the cities of Khashuri and Mtsʿkhetʿa (the ancient capital), lies the inner high plateau known as the Kartli…

Georgia: Relief, drainage, and soils: …trough is crossed by the Meskhet and Likh ranges, linking the Greater and Lesser Caucasus and marking the watershed between the basins of the Black and Caspian seas. In central Georgia, between the cities of Khashuri and Mtsʿkhetʿa (the ancient capital), lies the inner high plateau known as the Kartli…

Native American: Allotment: …inalienable except through condemnation; the Meskwaki Settlement, as it became known, had grown to more than 7,000 acres (2,800 hectares) by 2000. In a number of other areas, native individuals simply refused to sign for or otherwise accept their parcels, leaving the property in a sort of bureaucratic limbo.

Meslamtaea, in Mesopotamian religion, city god of Cuthah in Akkad. His temple in Cuthah was called Emeslam, or Meslam (Luxuriant Mesu Tree). His name, which means “He Who Comes Forth from Meslam,” perhaps indicates that he was originally a tree god, which would agree with his general chthonian, or

Pierre de Ronsard: …of 1554 and in the Meslanges (“Miscellany”) of that year, which contain some of his most exquisite nature poems, and in the Continuation des amours and Nouvelles Continuations, addressed to a country girl, Marie. In 1555 he began to write a series of long poems, such as the “Hymne du…

Franz Anton Mesmer was a German physician whose system of therapeutics, known as mesmerism, was the forerunner of the modern practice of hypnotism. Mesmer’s dissertation at the University of Vienna (M.D., 1766), which borrowed heavily from the work of the British physician Richard Mead, suggested

Charles Baudelaire: Maturity and decline of Charles Baudelaire: His translation of Poe’s Mesmeric Revelation appeared as early as July 1848, and thereafter translations appeared regularly in reviews before being collected in book form in Histoires extraordinaires (1856; “Extraordinary Tales”) and Nouvelles Histoires extraordinaires (1857; “New Extraordinary Tales”), each preceded by an important critical introduction by Baudelaire. These…

Franz Anton Mesmer: …system of therapeutics, known as mesmerism, was the forerunner of the modern practice of hypnotism.

French literature: Refinement of the French language: … (1639; “Treatise on Poetry”) of Hippolyte-Jules Pilet de La Mesnardière and the Abbé d’Aubignac’s Pratique du théâtre (1657; “The Practice of Theatre”), both treatises instigated by Cardinal de Richelieu’s personal patronage, which strongly influenced the development of Classical doctrine.

mas̄navī, a series of distichs (couplets) in rhymed pairs (aa, bb, cc, and so on) that makes up a characteristic type of Persian verse, used chiefly for heroic, historical, and romantic epic poetry and didactic poetry. The form originated in the Middle Persian period (roughly from the 3rd century

isomerism: Stereoisomers of more complex molecules: …molecule C, called a “meso compound.” A meso compound is an achiral molecule that nonetheless contains a stereogenic atom.

Mesoamerican Indian, member of any of the indigenous peoples inhabiting Mexico and Central America (roughly between latitudes 14° N and 22° N). Mesoamerican Indian cultures have a common origin in the pre-Columbian civilizations of the area. The three largest linguistic groups are the Mayan, the

Mesoamerican Indian languages, group of more than 125 languages classified into some 10 language families (including language isolates) that are native to Mesoamerica. The term “Mesoamerica” refers to a culture area originally defined by a number of culture traits shared among the pre-Columbian

vitamin: Myo-inositol: The biological significance of myo-inositol has not yet been established with certainty. It is present in large amounts—principally as a constituent of phospholipids—in humans. Inositol is a carbohydrate that closely resembles glucose in structure; inositol can be converted to phytic acid, which is found…

coastal landforms: Tides: …micro-tidal (less than two metres), meso-tidal (two to four metres), and macro-tidal (more than four metres). Micro-tidal coasts constitute the largest percentage of the world’s coasts, but the other two categories also are widespread.

Mesoamerican architecture, building traditions of the indigenous cultures in parts of Mexico and Central America before the 16th-century Spanish conquest. For the later tradition, see Latin American architecture. The idea of constructing temple-pyramids appears to have taken hold early. La Venta,

Mesoamerican civilization, the complex of indigenous cultures that developed in parts of Mexico and Central America prior to Spanish exploration and conquest in the 16th century. In the organization of its kingdoms and empires, the sophistication of its monuments and cities, and the extent and

Mesoamerican Indian, member of any of the indigenous peoples inhabiting Mexico and Central America (roughly between latitudes 14° N and 22° N). Mesoamerican Indian cultures have a common origin in the pre-Columbian civilizations of the area. The three largest linguistic groups are the Mayan, the

Mesoamerican Indian languages, group of more than 125 languages classified into some 10 language families (including language isolates) that are native to Mesoamerica. The term “Mesoamerica” refers to a culture area originally defined by a number of culture traits shared among the pre-Columbian

hutia: Size ranges from the rat-sized dwarf hutia (Mesocapromys nanus), with a body length of 20 to 30 cm (8 to 12 inches), to the raccoon-sized Desmarest’s Cuban hutia (Capromys pilorides), with a body 32 to 60 cm long and weight of up to 8.5 kg (19 pounds). The tail ranges…

angiosperm: Fruits: …endocarp; the middle layer, or mesocarp; and the outer layer, or exocarp. These regions may be fleshy or dry (sclerified) or any combination of the two, but they are classified as either one or the other.

orchid: Natural history: …elongate, sometimes fluted part, the mesochile; and a bucket-shaped epichile. The epichile is partially filled with water during the last few hours before the flower opens and for a short time afterward by two faucetlike organs located at the base of the column, which drip water. Male euglossine bees are…

climate classification: General considerations: …part, but there will exist mesoclimates within these regions associated with climatic processes occurring at a scale of tens to hundreds of kilometres that are created by elevation differences, slope aspect, bodies of water, differences in vegetation cover, urban areas, and the like. Mesoclimates, in turn, may be resolved into…

golden hamster, (Mesocricetus auratus), a species of hamster commonly kept as a pet. Like other hamsters, it has a stout body with short, stocky legs and short, wide feet with small, sharp claws. The head has small, furry ears and huge internal cheek pouches that open inside the lips and extend to

golden hamster: …of the genus Mesocricetus are Brandt’s hamster (M. brandti), found in southern Turkey, Lebanon, and Israel eastward through Syria to northwestern Iran; the Romanian hamster (M. newtoni) is exclusive to eastern Romania and Bulgaria; the Ciscaucasian hamster (M. raddei) inhabits the steppes along the northern slopes of the Caucasus Mountains.

golden hamster: …Syria to northwestern Iran; the Romanian hamster (M. newtoni) is exclusive to eastern Romania and Bulgaria; the Ciscaucasian hamster (M. raddei) inhabits the steppes along the northern slopes of the Caucasus Mountains.

golden hamster: …eastern Romania and Bulgaria; the Ciscaucasian hamster (M. raddei) inhabits the steppes along the northern slopes of the Caucasus Mountains.

tornado: Prediction and detection of tornadoes: …watch the formation of a mesocyclone (that is, a region of rotating air within a thunderstorm). On Doppler radar, the presence of a well-organized mesocyclone is indicated by a small region of concentrated shear in the wind. On one side of the mesocyclone the rotating winds flow toward the radar;…

mesoderm, the middle of the three germ layers, or masses of cells (lying between the ectoderm and endoderm), which appears early in the development of an animal embryo. In vertebrates it subsequently gives rise to muscle, connective tissue, cartilage, bone, notochord, blood, bone marrow, lymphoid

protozoan: Ecological and industrial importance of protozoans: …endosymbiotic algae, and one species, Mesodinium rubrum, has formed such a successful relationship with its red-pigmented algal symbiont that it has lost the ability to feed and relies entirely on symbiosis for its livelihood. Mesodinium often forms dense red blooms, or red tides, when it reaches high densities in water.…

mesite: …a true rail), also called Bensch’s monias (Monias, or Mesoenas, benschi), inhabits brushland. All three species build platform nests low in bushes.

mesite, any of several species of small, brownish ground-dwelling birds constituting the family Mesitornithidae (sometimes Mesoenatidae), order Gruiformes. They are about 30 cm (12 inches) long, have short wings and a thick tail, and inhabit Madagascar. They differ from all other gruiform birds in

mesofauna, in soil science, intermediate-sized animals (those greater than 40 microns in length, which is about three times the thickness of a human hair). Nematodes, mites, springtails, proturans, and pauropods are typical members of the mesofauna. These animals may feed upon microorganisms, other

gastropod: Classification: Suborder Mesogastropoda (Taenioglossa) Radula taenioglossate (with 7 denticles, or teeth) or reduced; most taxa herbivorous; a few families parasites or predators. Superfamily Cyclophoracea Land snails; particularly abundant in the West Indies and southern Asia to Melanesia. Superfamily Viviparacea

cnidarian: Tissues and muscles: Between these is sandwiched the mesoglea, a largely noncellular layer composed of a jellylike material permeated by a complex network of supporting fibres that may be microscopically thin or very thick. The fibres and jelly are elastic. In medusae, mesoglea comprises the bulk of the animal and forms a resilient…

Mesohippus, genus of extinct early and middle Oligocene horses (the Oligocene Epoch occurred from 33.9 to 23 million years ago) commonly found as fossils in the rocks of the Badlands region of South Dakota, U.S. Mesohippus was the first of the three-toed horses and, although only the size of a

sponge: Sexual reproduction: …in the amorphous substance (mesohyl) that fills the sponge. In the amphiblastula, the choanocytes are derived from the forward flagellated region; the other cells and the mesohyl are derived from the posterior half. Choanocytes create the water currents through sponges and capture food particles.

kurtosis: …thus have negative kurtosis, whereas mesokurtic distributions (such as the normal distribution) have a kurtosis of zero.

mesolite, mineral of the zeolite family, similar to natrolite

Mesolithic, ancient cultural period that existed between the Paleolithic (Old Stone Age), with its chipped stone tools, and the Neolithic (New Stone Age), with its polished stone tools. Most often used to describe archaeological assemblages from the Eastern Hemisphere, the Mesolithic is broadly

Mesolithic, ancient cultural period that existed between the Paleolithic (Old Stone Age), with its chipped stone tools, and the Neolithic (New Stone Age), with its polished stone tools. Most often used to describe archaeological assemblages from the Eastern Hemisphere, the Mesolithic is broadly

Aléxandros Mavrokordátos: …of a regional government at Missolonghi, in western Greece. During December 1821–January 1822 he presided over the first National Assembly, at Epidaurus, and led in the drafting of a constitution.

theory of resonance, in chemistry, theory by which the actual normal state of a molecule is represented not by a single valence-bond structure but by a combination of several alternative distinct structures. The molecule is then said to resonate among the several valence-bond structures or to have

mesomorph, a human somatotype (physical type) that is marked by greater than average muscular development, as determined by the since-discredited physique-classification system developed in the 1940s by American psychologist W.H. Sheldon. Sheldon linked mesomorphy to certain character

angiosperm: Leaves: Mesomorphic leaves are adapted to conditions of abundant water and relatively humid conditions; xeromorphic leaves are adapted to dry conditions with relatively low humidity; and hydromorphic leaves are adapted to aquatic situations, either submerged or in standing water. Mesomorphic leaves (the most common type) are…

protozoan: Annotated classification: Mesomycetozoa At least 1 life stage consisting of round cells, either flagellated or amoeboid. Some taxa are parasitic. Choanomonada (choanoflagellates) Phagotrophic. Collar of microvilli around the single posterior flagellum. Cells may be solitary or colonial. May develop theca or lorica consisting of cellulose or silica,…

meson, any member of a family of subatomic particles composed of a quark and an antiquark. Mesons are sensitive to the strong force, the fundamental interaction that binds the components of the nucleus by governing the behaviour of their constituent quarks. Predicted theoretically in 1935 by the

animal development: Reproductive organs: …exterior by way of the mesonephric duct. In males of lower vertebrates, the mesonephric duct thus serves as a channel both for urine and for sex cells. In amniotes the development of the metanephros as the urine excreting organ has freed the mesonephric duct to carry products associated only with…

mesonephros, permanent kidney of amphibians and most fish, developing posterior to and replacing the pronephros of the embryonic and larval stages. It is a paired organ consisting of a set of nephrons having capsules that filter blood from the glomerulus and tubules whose cells reabsorb water and

costumbrismo: …Mariano José de Larra and Ramón de Mesonero Romanos, both of whom wrote about Madrid, and Serafín Estébanez Calderón, who wrote about Andalusia. Significant costumbrista writers of the last half of the 19th century included Fernán Caballero and Pedro Antonio de Alarcón, both of whom wrote novels set in Andalusia,…

colossal squid, (Mesonychoteuthis hamiltoni), a massive, elusive cephalopod species inhabiting cold, deep regions of the Southern Ocean at depths ranging from 20 to 2,000 meters (66 to 6,562 feet). Biologists consider the colossal squid either the largest or second largest invertebrate in the

Earth: The atmosphere of Earth: …above the surface, where the mesopause is defined. The minimum temperature attained there is extremely variable with season. Temperatures then rise with increasing height through the overlying layer known as the thermosphere. Also above about 80–90 km there is an increasing fraction of charged, or ionized, particles, which from this…

atmosphere: Stratosphere and mesosphere: The stratopause caps the top of the stratosphere, separating it from the mesosphere near 45–50 km (28–31 miles) in altitude and a pressure of 1 millibar (approximately equal to 0.75 mm of mercury at 0 °C, or 0.03 inch of mercury at 32 °F). In the…

marine ecosystem: Geography, oceanography, and topography: Below this zone lie the mesopelagic, ranging between 200 and 1,000 metres, the bathypelagic, from 1,000 to 4,000 metres, and the abyssalpelagic, which encompasses the deepest parts of the oceans from 4,000 metres to the recesses of the deep-sea trenches.

liquid crystal, substance that blends the structures and properties of the normally disparate liquid and crystalline solid states. Liquids can flow, for example, while solids cannot, and crystalline solids possess special symmetry properties that liquids lack. Ordinary solids melt into ordinary