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absorption, atmospheric

absorption, atmospheric  

The various components of the Earth's atmosphere act to reduce or completely block certain wavelengths of the radiation incident at upper levels. The principal active atoms are oxygen and nitrogen, ...
adrenal crisis

adrenal crisis  

Acute adrenocortical insufficiency characterized by headache, nausea, vomiting, rapid weak pulse, circulatory collapse, and coma. It may occur in response to the additional stress of dental treatment ...
air

air  

1 A mixture of gases that makes up the Earth's atmosphere. It comprises about 78% nitrogen, 21% oxygen, less than 1% of carbon dioxide and other gases, and varying amounts of water vapour that humans ...
air pollutants

air pollutants  

Gases, fumes, suspended aerosols, smoke, mist, vapor, or radioactive, biologically active, or malodorous substances or any combination of these that contaminates ambient air.
alcohol

alcohol  

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n. any of a class of organic compounds formed when a hydroxyl group (–OH) is substituted for a hydrogen atom in a hydrocarbon. The alcohol in alcoholic drinks is ethyl alcohol (ethanol), which has ...
aldehyde

aldehyde  

Organic compounds that contain the group –CHO (the aldehyde group; i.e. a carbonyl group (C=O) with a hydrogen atom bound to the carbon atom). In systematic chemical nomenclature, aldehyde names end ...
Alexander von Humboldt

Alexander von Humboldt  

(b. Berlin, 14 September 1769; d. Berlin, 6 May 1859)German naturalist and explorer who made major contributions to various sciences, including geology, geomagnetism, and meteorology. Together with ...
anaemia

anaemia  

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A condition in which the level of haemoglobin in the blood is reduced for any of various reasons, including haemorrhage. See aplastic anaemia; congenital dyserythropoietic anaemia; Diamond–Blackfan ...
argon

argon  

A natural, colourless, odourless, inertgas that is the third most abundant constituent of dry air (it comprises 0.93% of the Earth's atmosphere).
artificial ventilation

artificial ventilation  

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The body requires a certain volume of air to be inhaled and exhaled to maintain the correct levels of oxygen and carbon dioxide within the tissues. Tissue damage, which leads ...
atmosphere

atmosphere  

A gaseous envelope gravitationally bound to a celestial body; in the case of the Earth, with an average composition, by volume, of 79% nitrogen, 20% oxygen, 0.03% carbon dioxide, and traces of rare ...
aurora

aurora  

An emission of light from the Earth's high atmosphere, caused principally by oxygen atoms or nitrogen molecules that are excited by electrons accelerated within the magnetosphere. The visible aurora ...
biochemistry

biochemistry  

The study of the chemistry of living organisms, especially the structure and function of their chemical components (principally proteins, carbohydrates, lipids, and nucleic acids). Biochemistry has ...
biogeochemical cycle

biogeochemical cycle  

The cyclical movement of elements between living organisms (the biotic phase) and their nonliving (abiotic) surroundings (e.g. rocks, water, air). Examples of biogeochemical cycles are the carbon ...
blood

blood  

(blud)a fluid that circulates throughout the body, via the arteries and veins, providing a vehicle by which an immense variety of different substances are transported between the various organs and ...
blood circulation

blood circulation  

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The circulation of blood refers to its continual flow from the heart, through branching arteries, to reach and traverse the microscopic vessels in all parts of the body, reconverging in ...
brain death

brain death  

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The absence of functional brain activity. This is now the standard test for death. A series of tests have to be performed twice before a diagnosis can be given.
breathing during exercise

breathing during exercise  

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We breathe oxygen into the body from the atmosphere. While this oxygen does not itself contain useable energy, it is the key that unlocks the energy stored in previously-ingested food. ...
carbohydrate

carbohydrate  

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An abundant and diverse group of compounds that have the general formula Cn(H2O)n. The smallest are monosaccharides like glucose, the largest are complex polymers such as starch, cellulose, and ...
carbon monoxide

carbon monoxide  

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A colourless almost odourless gas that is very poisonous. When breathed in it combines with haemoglobin in the red blood cells to form carboxyhaemoglobin, which is bright red in colour. This compound ...

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