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AG - AJ

AK - AM

AN - AN

AO - AR

AS - AV

AW - AZ

Moment of truth
The fastest man-made object that ever leave the Earth is the New Horizon spacecraft, launched in January 2006, and attained a speed of more than 36000 mph.


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anarchic principle Phys.
In particle physics, the statement that all interactions that are not forbidden by symmteries will occur. It was first coined by the physicist Jonathan Flynn. It refers to a feature of quantum field theory that all particle interactions that can happen will happen. The interactions can include both real and virtual particles. The net interaction particles is therefore the sum of all possible contributions including those from virtual particles.

anemometer Meteor.
An instrument for measuring the speed of wind. The most common type consists of four hemispherical 'cups' attached at the ends of four radial arms pivoted so that as the wind blows, the cups make horizontal rotation about the pivot. The speed of rotation measures the wind speed directly which can be read off from a calibrated dial.

anion Chem.
A negatively charged atom or molecule that contains more electrons than protons. For instance, chloride (Cl-) is an anion, as in sodium chloride (common salt).

anisotropy Chem., Phys.
Describes a property or a physical state that depends on direction axes. A measurement made in one direction is different from the other direction. For example, refractive index of liquid crystals is direction-dependant over a certain range of temperature. Hence, they are also called anisotropic liquid.

annular eclipse Astron.
Apparent view of incomplete covering of the Moon over the Sun, resulting a bright ring of sunlight surrounding the dark Moon's disk. Annular eclipse can occur because Moon's orbit round the Earth is slightly oval in shape. When the Moon is farther to Earth than average, the apparent size of the Moon's disk (as view from Earth) is too small to completely cover the Sun.

anode Chem.
A positive electrode at which oxidation occurs in a chemical cell. In electrolysis, anions are attracted to anode. For instance, the chloride ions (Cl-) are attracted to anode, releasing electrons to the external circuit. The anions are said to be oxidised to give neutral chlorine (Cl) and subsequently combine with each other to give chlorine gas.

anthrax Med.
A disease caused by the organism bacillus anthracis. It does not spread easily from person to person but it can be produced as powder spores that easily inhaled by human and has been manufactured as a biological weapon. Symptoms and fatalities vary according to the way the disease is infected. Via the skin is usually not fatal. Eating infected food (gastro-intestinal) can have 25% mortality rate. However, infection by pulmonary or inhalation is the most dangerous. Symptoms including itchy boils that turn to black colored open sores (skin); fever, abdominal pain, vomiting blood and diarrhoea (gastro-intestinal); flu-like, chest pain, shock and severe breathing problems (inhalation).

anthropic principle Phys.
A theoretical principle that assumes human existence is possibly only if the fundamental constants such as the speed of light and gravitatioanl constant are not higher or lower than what is observed now. The idea is used by some cosmologists in order to explain the reason why we exist in the universe, that quantum fluctuation gives rise to an infinite number of universe, each with their own set of physical law, and one of them happen to be ours that enable to harbor life. However, the nature of quantum fluctuation is not known, neither is it thought possible to prove the existence of the other universe.

anthropogenic Eco.
Change of plants habitation or environmental conditions as a result of man's activities. For example, plant communities of anthropogenic origin - foreign plants introduce by man.

antibiotic Biochem.
A class of natural or synthetic organic compound that kills microorganisms such as bacteria. An antibiotic starve bacteria by either preventing them from converting glucose into energy or by preventing them from building cell walls. However, antibiotic will not kill virus. Examples of antibiotics are penicillin obtained from penicillium molds and used in the treatment of various infections and diseases.

antibody Biochem.
A protein that is produced by the immune body system to fight or neutralize infections or malignant cells.

antigen Biochem.
Any foreign substance in the body, such as bacterium, virus or protein that triggers an immune response by stimulating the production of antibodies.

antigenic drift Biol.
The change of virus protein structure involving mutations within the antibody binding sites so that the resulting virus cannot be effectively killed by antibiotics against previous strains. The flu viruses possess such capability especially the influenza A virus and drifts to more virulent form have been reponsible to heavier than normal flu seasons in the past.

antihydrogen Phys.
An antimatter which is the reverse counter part of a normal hydrogen. Instead of a proton in the atomic nucleus and an electron, which made up a hydrogen atom, antihydrogen consists of an antiproton at the nucleus and a positron (antielectron) that bound to it. It was first produced in CERN in 1995 and later in a greater quantity and more stable by the ATHENA and ATRAP experiments in CERN in 2002. Antihydrogen does not exist naturally and will annihilate spontaneously when come into contact with any ordinary matter, into energy.

antipodal point Math.
A point on the surface of a sphere that is farthest from another point on the same object. The distance between these points is equal to the diameter of the sphere.

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