Experimental theater

Experimental theater

See improvisational and experimental theater.

References

Pacific

Pronunciation key

( pə-sif′ik )

Pa•cif•ic

[OFr. pacifique < L. pacificus : pax peace + facere to make < pacificare; see PACIFY].

Called Pacific by Magellan because of the ocean's tranquil appearance.
Largest from among the earth's ocean and is located between Asia and the American continents with an area of 63,750,000 square miles.

adj.

Pertaining to (of, in, on or near) the Pacific Ocean.
Relating to location in relation with (on, along or near) the Pacific Ocean.
To make or tending to make peace; serene; appeasing; conciliatory.
Of a peaceful disposition or nature. Tending to put an end to conflict. In opposition to being warlike; mild, temperate; tranquil; calm.

Also pa•cif•i•cal (-i-kəl) adj. —pa•cif′i•cal•ly adv.

Exploration and Discovery of the Pacific

In the 1600's many European explorers were already familiar with the Atlantic but the Pacific remained largely unknown. The Dutch navigator Willem Jansz became the first European known to reach the shores of Australia in 1606, sailing there from Indonesia and exploring the eastern shore of Gulf of Carpentaria. The Dutch seaman Abel Janszoon Tasman was the first European to reach Tasmania and New Zealand in 1642.

A captain of the British Navy, James Cook undertook three voyages during the 1760's and 1770's making him the most prominent among explorers of the Pacific Ocean. Cook searched for a continent that was believed by geographers to lay south of Australia.

During the first voyage, 1768-1771 Cook visited New Zealand and several other islands in the South Pacific which were at that time unknown to Europe. The second voyage (1772-1775) he traveled farther south than any European had ever journeyed, sailing into frigid Antarctic waters, and carefully navigating around icebergs which were obscured by fog. Dense ice prevented him from getting close enough to make an actual sighting of the continent of Antarctica.

Cook sailed for the northwest coast of North America in 1776 in search of a western route to the long sought after Northwest Passage. During that voyage, he became the first European to make a visit to the Hawaiian islands. Cook sailed onward along the western coastline of Canada, entering the Arctic Ocean. Ice blocked his path and he thus turned back to Hawaii. While there, in 1779, Cook was killed during a battle.

References

expropriation

Pronunciation key

( eks-prō′pri-ā′shən )
( eks′prō-pri-ā′shən )

ex•pro•pri•a•tion

Act of expropriating or being expropriated.

References

Express rifle

Express rifle

A hunting rifle with a low trajectory, which uses a large charge, light bullet of high calibre which is dicharged with a high initial velocity and used at short range to kill large game.

References

expressionistically

Pronunciation key

( iks-presh′ən-is′ti-kʼl-i )
( iks-presh′ən-is′tik-li )

ex•pres•sion•is•ti•cal•ly

adv.

Performed in an expressionistic manner.

References

expression

Pronunciation key

( iks-presh′ən )

ex•pres•sion

[L. expressio < expressus; see EXPRESS adj].

Pressing or squeezing out, such as liquid.
Stating something; putting into words; representing thoughts in form of spoken or written language. Something that expresses or communicates.
Illustrating, representation or symbolizing to convey a theme through speaking, writing, art, music, movement or another creative medium. Manifestation.
The manner one chooses to communicate with, especially when constructed in a meaningful and eloquent manner such as speaking, singing, etc.
A particular word, phrase or sentence such as a slang expression or catch cold is an expression known as an idiom.
Show of emotion, such as laughter. Display of feelings, character, etc. such as an expression of love.
A facial aspect such as a look or intonation which conveys a feeling; a glare, smile, etc. Outward manifestation of a mood or disposition.
Algebra. Symbol or set of symbols, that imply algebraic fact such as quantities or an operation. Designation of symbols in mathematical form such as an equation.
To show by using a symbol, sign, figures, etc.

Exemplification of emotional and spiritual qualities through the medium of music; tempo, accent, time, the level of softness or loud. In modern artistic compositions these are indicated by the composer, however substantial room is permitted for individual interpretation. These qualities were recognized in the 17th and 18th century when composers such as Bach and Handel rarely ever commented on them. Domenico Mazzochi is the first to have used the terms crescendo and diminuendo in 1636.

Expression in other forms of art are achieved by proper used of the forms available to the artist. Therefore, a painter will use color, texture and shape to evoke particular emotional response. The poet uses meter, cadence and verbal contrast. The dramatist, not unlike the composer, leaves interpretation to the skills of the actor to do the interpreting and the technical crew who create the setting for the drama.

References

Related Terms

expositive

Pronunciation key

( ik-spoz′ə-tiv )

ex•pos•i•tive

adj.

Descriptive, expository, explanatory.

References

exposé

Pronunciation key

( ek′spō-zā′ )

ex•po•sé

[Fr. pp. of exposer, to expose, < OFr. see EXPOSE].

Public disclosure of something discreditable; a scandal, crime, etc.
Opposition using facts.

References

export

Pronunciation key

( ik-spôrt′ )
( ik-spōrt′ )

(also, and for n. & adj. always, ek′spôrt)

ex•port

v.t.

[L. exportare; ex- out + portare to carry out. Compare with import, in + portare to carry in.].

To transport a commodity abroad by sending out goods and services from one country to another esp. for trade and profit.

A product that is exported.
The act or process of exporting goods. Exportation.

adj.

Pertaining to exporting or exports; for exportation.

—ex•port′a•bil′i•ty n. —ex•port′a•ble adj. —ex•port′er n.

Abbreviated as exp., ex.

Export and Import

In economics, exports are commodities which are produced or manufactured in one country and shipped to another. When the exported products reach their destination they are documented as an import by the nation which receive them. Among the leading commodities exported from the U.S. are machinery and vehicles, textiles, fibers and manufactures, nonmetallic minerals, vegetable food products and beverages. Listed below according to their respective significance as of December 1951.

Total U.S. export trade in dollars for the period 1941-1950.
1941	…………………	$ 5,147,154,000
1942	…………………	8,078,988,000
1943	…………………	12,964,906,000
1944	…………………	14,258,702,000
1945	…………………	9,805,625,000
1946	…………………	9,738,321,000
1947	…………………	14,429,747,000
1948	…………………	12,653,058,000
1949	…………………	12,051,055,000
1950	…………………	15,744,000,000

The following table lists the major U.S. exports and the respective monetary values in January 1951 and 1952

COMMODITY	MILLIONS OF DOLLARS
	Jan. 1951	Jan. 1952
Industrial machinery	97.5	123.4
Grains and preparations	89.4	129.7
Automobiles, parts, accessories	72.8	77.9
Raw cotton	70.1	146.9
Iron and steel mill products	46.3	63.0
Electrical machinery	42.0	41.6
Petroleum and related products	40.3	65.0
Construction machinery	29.6	39.6
Cotton manufactures	27.3	27.4
Coal and related products	26.6	58.7
Tractors, Parts, Accessories	24.1	27.3
Tobacco and tobacco manufactures	22.5	25.7
Wood and Paper	21.3	28.0

A nation will export products under certain conditions such as being one of the world's sole suppliers of a certain product; or if it produces a product at a significantly lower cost than other nations and if the products are in high demand due to quality factors, or due to its ability to produce during a season of the year other nations need to import the product. Technical requirements of modern industry have tended to make nations more dependent upon one another for vital goods and services. Factors that determine any country's trade status include its natural resources, tastes, skills of its inhabitants, climate, location and the industrial development of the nation. Exports may include foodstuffs, raw materials and manufactured products. Industrialized nations with dense populations tend toward export of industrial products. The opposite is true in nations rich in minerals and agricultural resources, such as those in Latin America.

Many imports consist of products that are not produced domestically. For instance, the United States imports coffee from Africa and Latin America because the climate is not suitable for growing it at home. Olives, an export of the Mediterranean region are another product imported into the United States, however some states such as Arizona and California can produce olives, they simply do not produce enough quantity to meet demand of U.S. consumers and at a competitive price with the foreign market. It is for much of the same reason French perfume and Irish linens are imported into the United States.

National trends on imports and exports may change due to various factors such as developments in technology. For instance, if a discovery is made of synthetic substitutes for natural products it may reduce or nearly eliminate a need to import the natural products. A former importer may then become an exporter.

Innovations and new developments often create new patterns of trade. People in nations abroad want new products indifferent to whom produces them. Through the export and import process, people abroad share benefits of production. Foreign investors create change in international trading patterns with the addition of factories and jobs in foreign countries.

Policies at the federal level may affect exports and imports. For instance, a reduction in trade barriers increases imports of some products which are more efficiently produced abroad. Similarly, reduction of barriers to trade in foreign governments opens the market for domestic exports.

Federal policies are sometimes designed with certain economic developments in mind and have a significant effect on overall trade patterns of the country and its trade partners. It is these reasons which lead to conferences through international organizations where agreements are struck, such as the General Agreement on Tariffs and Trade.

The total value of imports by a nation must be at least equal in value to its total exports. Each purchase by an importing nation represents a sale by an exporting country and payment must be made. This equivalence is called the balance of payments. Nations may import more goods than they export just as long as a means of payment will be made available. Such supplementary sources of foreign exchange are known as invisible exports and might be comprised of items such as receipts from tourists, shipping, grants or loans from the government of foreign countries, insurance and interest or profit from international investment. Payments might also be balanced through the export of gold.

Also see Balance of Trade

References

Related Terms

exportation

Eximbank / Export Import Bank

exponential

Pronunciation key

( ek′spō-nen′shəl )

ex•po•nen•tial

adj.

Algebra. Containing or expressed in terms of powers, the base of natural logarithms. Relating to exponents; especially when involving variable or unknown quantities as an exponent.

—ex′po•nen′tial•ly adv.

Exponential Equation

An equation which expresses a relationship when the dependent variable is an exponential function of the independent variable.

Exponential Function

A function of the form

y = a^x

with a as any positive number. The graph of the exponential function crosses the y axis at (0,1) and to the right of the y axis its height increasingly rises, rapidly. To the left of the y axis the graph approaches the x axis as an asymptote. An exponential function is an inverse function of the logarithmic function. A particularly useful exponential function is that which the constant a has the value e that is approximately 2.71828. Exponential functions have many professional applications such as for business, especially in connection with the phenomena of growth and decay.

^{Image credit: The American Peoples Encyclopedia ©1960}
An Exponential Curve.

References

Related Terms

exponent

exponentiation

exponible

explosion

Pronunciation key

( iks-plō′zhən )

ex•plo•sion

[L. explosio, driving off stage by clapping < pp. of explodere see EXPLODE].

Blowing up, an exploding. Act of bursting with a loud noise; detonation.
The sharp, loud noise made by exploding.
Loud outburst or breaking forth; such as an emotional explosion of rage.
Sudden and great increase. Such as the explosion of social media..
Phonetics. Plosion. Sudden release of breath in the articulation of a plosive.

The sudden and instantaneous liberation of energy or violent expansion of a substance accompanied by a sudden release of energy. Explosions are created by rapid chemical reactions in various substances and mixtures, a nuclear reaction or bursting out of gases or vapors under pressure. Other phenomena, including the failure of pressure vessels such as steam boilers, compressed-air tanks and pressure cookers may also be called explosions. The cause of such is different and though the end result may be similar to an explosion they are more appropriately called pressure ruptures. The burst of energy associated with the Atom bomb, produced by rapid atomic fission and fusion are also called explosions.

The loud noise that is associated with an explosion is created when vibrations set up in the surrounding air by the sudden burst of energy. An explosion which is contained in a closed vessel strong enough to withstand the pressure may produce very limited noise.

Substances and mixtures which undergo chemical reactions typically produce gaseous products by those reactions. One exception is copper acetylide. It produces hot particles of copper and carbon but practically no gas. Gaseous reaction products and surrounding air are expanded quickly by the heat that is involved in an explosive chemical reaction. In confined conditions this expansion exerts force. A stimulus such as a spark, flame, friction or shock typically are needed to initiate an explosive chemical reaction. The stimulus material required to ignite such a reaction varies depending on the material or mixture. Generally, there are two types of explosive chemical reactions:

Rapid combustion. This is usually called deflagration and produces flash fires is not contained and explosive pressure when contained. Ordinarily it results from the chemical union of oxygen with other chemical substances (for further information see Combustion). Rapid combustion only occurs if conditions are right, such as in,
1. Highly flammable solids or liquids containing enough oxygen for near complete combustion
2. Particles of a combustible gas, vapor or dust are suspended in the air in close vicinity to each other permitting propagation of flame from one to the other yet separated far enough apart, leaving space for enough oxygen required for combustion./li>
The first condition is demonstrated by commercial explosives that contain within themselves the required oxygen levels for combustion of other chemical substances. The second condition is demonstrated through explosive mixtures like gasoline vapor and air.
With rare exception, combustible gases, vapors and dust are not explosive alone. However, their mixture in certain proportions can make them explosive. This fact is especially dangerous in regard to human safety factors. The minimal concentrations of combustible substances in the air that will produce an explosive reaction is known as the lower limit of flammability or lower explosive limit. There is also a maximum proportion of air to chemical material, above which the material is deemed non-explosive. This is known as the upper limit of flammability or upper explosive limit. Between these two limits is a concentration that provides the most powerful explosion of which the mixture has potential. Relationships between concentrations measured by volume of gasoline vapor in the air and the pressure which develops from such an explosion is demonstrated in the following graph.

Relationship between percent of gasoline vapor in the air and associated pressure by the explosion of the mixture.
The graph illustrates that a concentration of about 2.25% is the optimal concentration to produce the most powerful explosion. Graphs of other combustible substances in air also reveal that an increase in concentration over the lower limit result in an increase in pressure until reaching the maximum, after which pressure begins to decline until the upper limit is reached and the mixture will cease to be explosive.

The lower explosive limit for most flammable vapors is very low. With gasoline, about 1.4% at normal temperature and less at increased temperatures. Its upper limit is about 6%. Explosive limits of flammable vapors vary, for example,
1. Benzene 1.5-8%
2. Carbon disulfide 1-50%
3. Ether 1.9-36.6%
Most flammable vapors produce a detectable odor in the air at their lower limit which explains why a spark does not always produce an explosive reaction. Needless to add, a sense of smell does not provide a reliable hazard meter.

Lower explosive limits in many common flammable gases are quite low. The typical limits are
1. Methane 5.3-14
2. Butane 1.6-8.5
3. Propane 2.3-9.5
4. Hydrogen 4-74
5. Carbon monoxide and ammonia are exceptions, with comparably higher limits in the low range at 12.5 and 16.
Explosive limits for dust cannot be determined as effectively as those for vapors and gas, however, any mixtures permitting rapid combustion of particles are said to be within the explosive limit range. Dust explosions occur when combustible dust is lingering in the air. The degree of its flammability depends on moisture content and upon size of particles. Increased flammability occurs when the particles are drier and finer. Substances that cause such explosions are from products such as powdered starch, sugar, flour, wood, coal, certain plastics, powdered milk, cocoa, sulfur, aluminum, magnesium and similar substances.

The only exception to the rule, is acetylene (when it comes to necessitating a mixture of air with explosive materials to produce an explosion). If this substance is under the pressure of 2 or more atmospheres it tends to undergo explosive decomposition if exposed to a spark or some other source that may ignite it. For this reaction to occur, air is not necessary.

Solids that undergo rapid combustion and cause explosion when confined are known as explosives. They are classified as low explosives to distinguish them from explosives that are detonated. Some typical examples are black powder and smokeless powders which will rapidly burn when compared to the speed of other substances, but are relatively slow when compared to detonated explosive reactions. Due to the slower reaction the explosions created by them exert a push rather than the shattering shock produced by detonation. This characteristic makes them especially useful for propellant charges in firearms and blasting in mines and quarries, as it is likely more desirable to break material vs shattering it.

The chemical transformation of low explosives occur at the surface of particles, proceeding inward to their center. Deflagration is accelerated by the hot gases that develop, especially when the substance in confined. The rate of deflagration depends on the size and shape of the explosive particles and the pressure and temperature, including chemical composition.
Detonation. This reaction is almost instantaneous in chemical change of a substance to the liberation of heat energy and production of gases. It is a shock wave maintained by a chemical reaction and advances through the explosive substance at a constant speed. The part of any detonating substance that has not yet been hit by the shock wave, or the detonation front, remains at its initial pressure. However, when hit by the front its pressure will rise nearly instantaneously to its highest value, possibly 10-100x the original pressure in gases and possibly as much as 200,000 atmospheres in dense solid explosives. The detonation front travels about 3500 meters per second in gases and 8000 meters per second in solids and liquids which is relatively rapid. Such detonations are by far more abrupt and violent than deflagration explosions.
Detonations are created by heat or impact. Perhaps both. Heat may be produced by a spark, flame, friction or other source. Usually, it first produces deflagration, which is changed to detonation. The transformation from deflagration to detonation is assisted by the confinement of the substance. Many high explosives burn without detonation if ignited in the open. Impact may require a mechanical blow or the detonation of an alternative explosive. The effect is the production of an immediate detonation in the explosive substance which is subjected to the impact.

Some chemical mixtures producing deflagration also detonate under certain conditions. Such as a mixture of gasoline vapor and air will ordinarily burn in the cylinders of an automobile engine, producing a relatively slower reaction that delivers smooth power to the pistons. However, under different circumstances, the mixture can detonate and produce an extreme blow to the pistons and cause the engine to lose power, followed by producing a noise called a knock or a ping.

In many military or civilian jobs, there are useful purposes for the violent force associated with such explosions as they are used in bursting charges in shells, bombs, mines, depth charges and similar weapons. Also, they are used commercially for demolition projects and blasting when the purpose is to shatter rather than breaking material.

Explosions in aircraft are often caused by the vapors of gasoline and other liquid fuel. Generally an explosion tends to be followed by fire and if in flight, a crash landing. Breaks and leaks in the fuel system are attributed to vibration or causes that permit formation of an explosive mixture of vapor and air in the fuselage and this may be ignited by the electrical, heating system or static electricity. Another cause on military aircraft can be ammunition and transport-planes which carried explosives as cargo. Other explosions in aircraft, were formerly caused by hydrogen used as a lifting gas. By changing over to Helium (non-explosive) has eliminated this problem.

Explosions in ships are due to their structure. Ships are generally airtight in their construction, therefore increasing the hazard of explosive gas or vapor spreading from oil-fired boilers, internal combustion engines and fuel tanks. The ventilation system on ships may create an especially dangerous setup due to an explosion traveling through the ducts from one deck to the next.
Tankers which transport fuel oil, gasoline or explosives in general have special explosion hazards.

Explosion crater. A large crater that is formed when meteorites having a velocity of greater than 3-4 km per second strike the surface of the Earth. The meteorite and adjacent soil are broken up by the shock wave that spreads from the point of impact. The wave overcomes the molecular cohesion of the solid meteorite, transforming it into a highly compressed gas that expands and explodes. Typically, only tiny fragments will remain of the meteorite's original material.
Explosion craters range in size, anywhere from 100 meters to several kilometers in diameter. Rock flour and impactites (fragments of bedrock that fuse, forming bubble-like, glassy masses) are generally discovered within. The largest craters formed by meteorites are produced by explosion, the largest of which is the Ungava-Quebec Crater of Canada. The diameter is more than three kilometers or about two miles. See meteorite impacts and crater design and meteorite impact stimulation.

Explosion seismology. The use of man-made explosions which aide in the determination of structures of the earth, generally on a larger scale. Large chemical explosive detonations and underground nuclear blasts generate seismic waves which can then be interpreted to learn about the interior of the Earth. This method provides an advantage over earthquake sources being controllable in size, location and timing of the source impulses. After correlating the different acoustical refracted and reflected recorded vibrations, it is possible to ascertain estimations of depth and character of subsurface geologic structures. Explosion seismology is often used to locate petroleum and mineral deposits. Major limitations of the explosion seismology method are receiver sensitivity and the inhomogeneity of the earth structures. For more information see marine sediment composition and structure.

References

exploratory

Pronunciation key

( iks-plôr′ə-tô′ri )
( iks-plō′rə-tō′ri )

ex•plor•a•to•ry

adj.

[L. exploratorius].

Pertaining to or for, exploration.

Exploratory behavior. Play or other activities in juvenile animals that seem to be directed toward learning features of their behavioral and physical environment. See Learning theories and studies.

References

Related Terms

exploitation

Pronunciation key

( eks′ploi-tā′shən )

ex•ploi•ta•tion

Act of exploiting or being exploited.
Utilizing another person or resource for personal gain.
Marketing program; advertising, publicity.

Exploitation of Labor. (Economics). See Surplus value.

References

Related Terms

exploit

exosporium

Pronunciation key

( ĕk′sō-spôr′ē-əm )
( -spōr′ )

ex•o•spor•i•um

n. [pl. -i•a ĕk′sō-spôr′ē-ə].

[NLat. < exo + spora spore].

Botany. Exine.

References

exoergic

Pronunciation key

( ĕk′sō-ûr′jǐk )

ex•o•er•gic

adj.

[exo- + Gk. ergon work, + (ic)].

Exothermic.

References

exocyclic

Pronunciation key

( ĕk′sō-sī′klik )
( -sǐk′lǐk )

ex•o•cy•clic

adj.

Occurring outside of a chemical ring structure.

References

exoticism

Pronunciation key

( ǐg-zŏt′ə-sǐz′əm )

ex•ot•i•cism

Tendency to adopt the exotic.
Character, condition or quality of being exotic.
Anything exotic, such as a foreign word or idiom.

References

exodermis

Pronunciation key

( ĕk′sō-dûr′mǐs )

ex•o•der•mis

Botany. Temporary protective layer of cells in some roots such as in certain species of orchids.

Usborne Science Encyclopedia ©2002: "All parts of a juvenile plant are surrounded by a thin layer of tender tissue called the epidermis. In older stems, the epidermis is replaced by bark. In other roots is is replaced by a layer of hardened cells called an exodermis, then by bark. An outer tissue which encloses the plant such as the epidermis is known as dermal tissue."

References

exocentric construction

Pronunciation key

( ĕk′sō-sĕn′trik )

ex•o•cen•tric construction

Ling.

Contruction of grammar which as a unit does not function in an identical manner as any of of its immediate parts. Examples are as follows,
- in the pool
- for him
- David played
Contrast with endocentric construction.

References

Exoreic

Pronunciation key

( ek′sə-rē′ik )

ex•o•re•ic

adj.

[< exo- + Gk. rheen flow].

Designates or pertains to a region whose surface drainage extends to the ocean such as the greater part of North and South America.

References

Exonian

Pronunciation key

( ek-sō′nē-ən )

Ex•o•ni•an

An inhabitant or native of Exeter.

adj.

Pertaining to Exeter.

References

exodic

Pronunciation key

( ek-sod′ik )

ex•od•ic

adj.

Pertaining to an exodus.
Efferent.

References

exoderm

Pronunciation key

( ek′sō-dûrm )

ex•o•derm

The ectoderm.

References

exocentric

Pronunciation key

( ek′sō-sen′trik )

ex•o•cen•tric

adj. Ling.

This denotes a syntactic construction which as a unit functions differently from any of its component parts. Such an example is, Mary works hard.

Compare to endocentric.

References

exocardiac

Pronunciation key

( ek′sō-kär′dē-ak )

ex•o•car•di•ac

adj.

Situated externally on the heart.

References

exotery

Pronunciation key

( ek′so-tẽr-i )

exotery

What is plain, obvious, common, public.

Compare with esotery.

References

exossate

Pronunciation key

( ek-sos′āt )

exossate

v.t.

Deprivation of bones.
To cause fruit to grow without kernals.

References

exonerative

Pronunciation key

( ig-zon′ə-rā-tiv )

exonerative

adj.

That which tends to exonerate.

Another example of exothermic reaction is the formation of ammonia from its constituent elements, nitrogen and hydrogen; and the solution of hydrogen chloride gas in water to make hydrochloric acid.

Such processes are exothermic reactions, and are characteristic of many chemical reactions that reach completion at ordinary temperatures since they are accompanied by an evolution of heat.

The remaining chemical reactions absorb heat in the process of the reaction and are classified as endothermic reactions. Endothermic reactions are not limited to chemical processes. For instance when steam is condensed into water, 536 calories of heat are expelled for each gram of steam involved.

See Thermochemistry.

See exothermic.

References

exophagy

Pronunciation key

( ek-sof′å-ji )

exophagy

Cannibalism outside of one's kindred, clan or tribe.

See cannibalism.

References

exosphere

Pronunciation key

( ek′sō-sfir )

ex•o•sphere

The outermost region of Earth's atmosphere, with its base located at altitudes exceeding 400-600 kilometers (280-370 miles) above the surface of the earth. The outer boundary is defined as that level where the molecular density falls off to that typical of the interplanetary medium of our solar system, approximately 5000 kilometers or 3000 miles above the earth's surface. At this altitude, molecules are so low in numbers that atoms of atmospheric gas readily escape into space after impacting each other. The numbers of such molecules is so low that the probability of collision between particles is very small. These particles are acted only upon by the gravitational field of the Earth and follow what are called ballistic trajectories. Due to this molecules in this atmospheric region having a greater chance of escaping into outer space, the base of the exosphere is called the critical level of escape; but because most molecules have speeds considerably lower than the escape velocity, the rate of escape is relatively low.

One element, Helium, is the most abundant gas in the exosphere. Atomic hydrogen is more common than atomic oxygen above 850 kilometers (530 miles) and molecular nitrogen (N₂), molecular oxygen (O₂) and argon become quite rare with greater altitude.

Temperatures in the exosphere is about 700°C (1,300°F), but may vary from only 300°C (570°F) during decreased sunspot activity. Temperatures may rise as high as 1,700°C (3,090°F) during maximums in sunspot activity.

( ek′so-fo′re-ah )

exophoria

HETEROPHORIA in which there is deviation of the visual axis of an eye away from that of the other eye in the absence of visual fusional stimuli.

[exo- + Gk. krinein to separate].

External secretion through a duct.
Pertaining to secretion of a gland having a duct.

The active cells of many glands are epithelial cells. A gland is an organ specialized to secrete substances that are sent out to other parts of an organism's body. These secretions are produced from blood constituents.

Glands are divided into two types

Exocrine These glands have ducts or tubes to carry secretions away from the gland. They may be transported to another organ, cavity or surface. They are effective in a limited proximity near their source. Examples of such processes are digestive fluids, secretions from the sebaceous glands in the skin and tears from the lacrimal glands.
Endocrine These glands depend on blood flowing through the gland to carry secretions to other organs. These substances are called hormones and have specific effect on other tissue. They are called ductless glands.

References

exocolitis

Pronunciation key

( ek′so-ko-li′tis )

exocolitis

Inflammation of the exterior layer of the colon.

References

exocardial

Pronunciation key

( ek′so-kar′de-al )

ex•o•car•di•al

adj.

A development which occurs, situated outside of the heart.

References

exocardia

Pronunciation key

( ek′so-kar′de-ah )

ex•o•car•di•a

[< NL. < Gk. exo- out + kardia heart].

Pathol. Congenital displacement of the heart from its normal position; ectocardia.

References

exobiology

Pronunciation key

( ĕk′sō-bī-ŏl′ə-jē )

ex•o•bi•ol•o•gy

The branch of space biology in science which focuses on the study of life on planets other than Earth and the search for living organisms, especially intelligent life outside our own solar system.
A branch of biology that focuses on the effects of extraterrestrial space on living organisms.

Also known as Xenobiology, Astrobiology and Extraterrestrial Life.

The word exobiology was coined by the U.S. geneticist Joshua Lederberg. The word commonly used in the Soviet Union, translates to English as Astrobiology.

Exobiology: Matter, Energy, and Information in the Origin and Evolution of Life in the Universe: Proceedings of the Fifth Trieste Conference on Chemical Evolution: An Abdus Salam Memorial Trieste, Italy, 22 26 September 1997

The Living Universe: NASA and the Development of Astrobiology

Remote observations of planets and other bodies in outer space provide information about their unique physical environment. However determining the presence of life is much more difficult. Techniques have been designed and implemented to detect life-forms, artifacts produced by intelligent life, waste products of metabolic reactions, remnants of past life, pre-biological molecules that may represent early stages of evolution, or substances such as carbon which are crucial in the development of life as it is experienced on Earth. Communication efforts range from broadcasting radio transmissions and pictorial diagrams by satellite, as well as monitoring for radio signals from stars and other objects for long periods of time.

Though extraterrestrial life may never be found, some experiments have been conducted in space under environmental conditions difficult to establish on Earth are valuable. One example is testing in a zero gravity environment. By doing so allows testing not only accepted theories about life processes, but also of the relationships between physical and biological factors.

—ex′o•bi′o•log′i•cal (-ə-lŏj′ǐ-kəl) adj.
—ex′o•bi•ol′o•gist n.

Also see Life, Extraterrestrial

References

exotically

Pronunciation key

( ig-zot′i-kʼl-i )
( ig-zot′ik-li )

ex•ot•i•cal•ly

adv.

A manner that is exotic.

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exotic

Pronunciation key

( ig-zot′ik )

ex•ot•ic

adj.

[L. exoticus; Gr. exōtikōs foreign, alien < exō coming from outside].

By nature belonging to another part of the world.
Imported. Introduced from abroad, but not fully naturalized or acclimated. Foreign origin, therefore
Having the charm of being unfamiliar, beautiful in a strange and enticing way. Unusual. Different.
From another part of the world. A product or thing that is foreign or imported.
Colloq. Strikingly colorful, unusual in effect and appearance.
Of or relating to striptease or performer.

A plant, animal, person, word or other organism that is not native.

See botany for Exotic plants. Cultivated plants which are native to foreign lands. Frequently this term applies to plants which require artificial heat and other special care, such as glass-enclosed forcing beds, which would not be necessary for indigenous plants.

—ex•ot′i•cal•ly adv. —ex•ot′i•cism n. —ex•ot′ic•ness n.

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exothermic

Pronunciation key

( ek′sō-thũr′mik )

ex•o•ther•mic

adj.

[exo + thermic < exo- out, + Gk. thermē heat].

Chem. Designates or noting reactions which are accompanied with liberation of heat.
Release of heat (as in combustion) due to a chemical change. See also exothermal. Release of heat, in opposition to absorbing heat. Compare to endothermic.

Also ex’o•ther′mal. (-məl) adj.

See Exothermic reaction and Thermochemistry.

References

exoterically

Pronunciation key

( ek′sə-ter′i-kʼl-i )
( ek′sə-ter′ik-li )

ex•o•ter•i•cal•ly

adv.

In an exoteric manner.

References

exoteric

Pronunciation key

( ek′sə-ter′ik )

ex•o•ter•ic

adj.

[LL. exotericus; Gr. exōterikos, external < compar. of exō, outside < exōterō comparative of exō, outside.].

Adapted to be intelligible such as a doctrine to common comprehension, suitable for the general public.
Comprehensible to the outside world; public, external.
Capable of being quickly comprehended. Not intended for only a chosen few or an inner-circle of disciples or initiates and is suitable for outsiders.
A concept, idea or thing which is understood by the public; common, simple and popular. Compare with esoteric.
Pertains to the outside; External.

See Esoteric.

Also ex´o-ter′i-cal, ex´o-ter′i-cal-ly (adv.) — ex´o-ter′i-cism (n).

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exosmosis

Pronunciation key

( ek′sos-mō′sis )
( ek′soz-mō′sis )

ex•os•mo•sis

[Mod. L.; ex- + osmosis].

Phys. Chem. Diffusion from within, outward or from an inner to an outer vessel.
Passage outwards through a membrane of gases or liquids.
Flow of a fluid through a permeable membrane into less dense fluid.
Chem. Osmosis in the direction which fluid crosses the septum most slowly. The slower diffusion of the more dense fluid through the semipermeable membrane to mingle with the less dense: opposed to endosmosis.

Also ex′os•mose, ex′os•mot′ic adj., ex•os′mic adj.

See Osmosis.

References

exostosis

Pronunciation key

( ek′sos-tō′sis )
( ek′so-stō′sis )

ex•os•to•sis

n. [pl. EXOSTOSES (-sēz) exosto′ses.]

[Mod. L.; Gr. exostōsis < ex- outside + osteon, a bone].

Pathology, Medicine. Abnormal, yet benign tumor or new bony growth on either inner or outer surface of a bone or tooth. Characteristically capped with cartilage.
A morbid formation and protuberance of bone. Morbid bony growth on a bone.
Formation of knots on trees.

Adj. exostot′ic. See Osteochondroma.

exostosis cartilagin′ea, a variety of osteoma consisting of a layer of cartilage developing beneath the periosteum of a bone.

hereditary multiple exostosis, a generally benign, hereditary disorder of enchondral growth of bone, marked by extoses near the extremities of the diaphysis of long bones.

References

exospore

Pronunciation key

( ek′sə-spôr′ )
( ek′sō-spôr )
( ek′sə-spōr′ )

ex•o•spore

[exo- + spore].

Botany. Outermost layer or covering of a spore.
The outer coat of the spores of some algae and certain fungi.

References

exoskeleton

Female giant wood spider hanging from web as the exoskeleton splits along the edges of the cephlothorax.

The old covering over the abdomen tears apart and away as the spider pulls its legs free.

The spider carefully pulls her long fragile legs free of the old skin. If something goes awry the spider could end up without its legs.

Upon freeing itself the giant wood spider dangles helplessly from the old exoskeleton as blood pumps and expands the new exoskeleton while it is still soft. The spider cannot return to its web for about 20 minutes, or long enough for the the exoskeleton to dry and harden.
[Footnote on Image & Credit]

Pronunciation key

( ek′sō-skel′ə-tʼn )

ex•o•skel•e•ton

Zoology, Biology. Bony or horned external protective covering, armor especially in many invertebrates such as insects or crustaceans. A hardened integument or shell such as of those of crustaceans, the scales and plates of fishes. An external skeleton or supporting structure such as a shell of an oyster, lobster, crab that protects soft tissues and organs of invertebrates (the lower animals) and is derived from the ectoderm. Exoskeletons are found only on lower animals. The best examples are shells of crustaceans or the protective shell of the turtle. Muscles and organ systems lie within the exoskeleton, unlike vertebrates where the muscles and organs surround most of the supportive skeleton. Dermoskeleton.

Anatomy. In vertebrates the term is sometimes applied to structures produced by the epidermis such as hair, nails, hoofs, teeth and so forth. Compare with endoskeleton.

Exoskeleton in the Crayfish

The exoskeleton is composed mainly of protein and a hard substance called chitin. In some crustaceans like the crayfish, the exoskeleton also contains calcium salts which make it especially durable. The exoskeleton is secreted by cells of a thin underlying layer called the epidermis. The exoskeleton consists of two regions. The front or anterior portion the exoskeleton is an unjointed, thick calcareous shell called the carapace. The section of the carapace toward the front between the two eyestalks is called the rostrum.

In the posterior the exoskeleton forms a series of six rings which are connected with each other at joints. Around the joints, the shell is flexible and thin.

Exoskeleton in the Millipede

The exoskeleton is made of chitin and may be hardened due to various calcium salts. The exoskeleton contains tiny canals that are outlets of glands or contain the extensions of sensory cells. The surface of the exoskeleton is covered with hairs, bristles, spines, ribs, granules and ridges of various forms. Some of these appendages such as the trichomes of the Pselaphognatha, are mobile.

ex′o•skel′e•tal adj.

See also Arthropod; Butterfly (Mature); Crustacean.

References

Additional References

The shedding of the exoskeleton. From Reader's Digest Pathfinders "Marvels of Nature," Dinosaurs, Earthquakes and Volcanoes, Insects and Spiders ©2003. If the weather is too dry a spider can get stuck in its old exoskeleton and die. The new one can stay soft for more than a day leaving the spider vulnerable to attack. Males tend to stop molting upon reaching maturity.

Other great books on exoskeletons...

Animals with Awesome Armor: Shells, Scales, and Exoskeletons
by Susan K Mitchell

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Exploration and Discovery of the Pacific

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