Scientific dictionary main page

Scientific dictionary

science park

Table of Elements

Chemical information

Science dictionary

scientific data

site map

Gift Shop

Index (C)









Moment of truth
As at 2005, the major source of antioxidants in the US diet is coffee, followed by tea, bananas and dried beans.

A   B   C   D   E   F   G   H   I   J   K   L   M  
N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

back to dictionary home CA - CC next page (CD-CF)

cache memory Comp.
A relatively fast computer memory, such as the static RAM, which is used to store data or instruction that is likely to be needed by the central processing unit (CPU). The access time of cache memory by the CPU is generally much faster than the normal memory and hence large cache memory size usually speeds up the computational processes. There are different types of cache memory, loosely differentiated by the location of the memory. Primary cache, or L1 is usually integrated within the CPU, while L2 or secondary cache is usually located in an external circuit on the motherboard.

calcination Chem.
(1) The formation of a calcium carbonate deposit from hard water.
(2) Process in which a material is subjected to prolonged heating at high temperatures without melting it.

calcination Min. Ext.
A process in which limestone (calcium carbonate) is heated to chemically drive off carbon dioxide to obtain lime (calcium oxide). It is now referred, in a general sense, to mineral extraction process in which the ore is heated to drive of water and carbon dioxide.

calcinosis Med.
Deposits of calcium salts in various tissues of the bodies, for example, most commonly occur on the hands, or near the joint such as knees or elbows, as in systemic scleroderma.

calorie Metro., Food Sci.
Abbreviated as cal, the quantity of heat required to increase the temperature of 1 g of water by 1C (1 K). It is now replaced by the standard SI energy unit, joule (J), where 1 calorie = 4.1868 J. However, it is still widely used in food products to indicate the amount of energy in food. Sometimes it is referred to as kilocalorie (kcal) in food labels, where 1 kcal = 1000 cal.

Canada Balsam Bot., Biol.
A yellow-tinted resin dissolved in essential oil with a pleasant odor but biting taste and is derived from balsam fir, Abies balsamea in North America. On standing, the essential oil evaporates leaving behind a hard, transparent resin. It has a similar optical property to glass and hence is used as transparent adhesive or cement in optical devices, especially for specimen mounting in microscopy. It is also used in paints and polishes. It is also called Canada turpentine.

Canada turpentine Bot., Biol.
See Canada Balsam

candela Metro.
The SI unit of luminous intensity, symbol Cd. It is equal to the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 Hz (about 555 nm wavelength in air, corresponds to yellow-green color) and has a radiant intensity in that direction of 1/683 watt per steradian. The value of 1/683 is so chosen due to the previous definition of emmision from 1 cm2 of glowing, solidifying platinum.

carat Min.
1. A measure of purity of gold, abbreviated as K (karat). Pure gold is described as 24-carat gold. A 9 carat gold contains 9 parts in 24 of gold, the remainder is usually other metal such as copper.
2. A unit of mass equal to 1/5 gram or 200 milligrams, abbreviated as ct. It is commonly used in jewelry to measure the masses of diamonds and other gemstones.

carbohydrates Chem., Food
A class of organic compounds with the general formula Cx(H2O)y. The term is derived from 'hydrates of carbon' and is also called saccharides. The simplest forms are sugars (saccharides) such as glucose (a monosaccharide), with x = y = 6 and sucrose (a disaccharide), with x = y = 12. Starch and cellulose are called polysccharides and have much complex structures with x and y into hundreds and thousands. Carbohydrates are very important to living organisms. For instance, glucose is essential to body energy and starch serves as energy store in plants. Other polysacchrides such as cellulose and lignin form the cell walls and woody tissue of plants, while chitin forms body shells of insects and many other invertebrate animals.

Foods that are high in carbohydrates include breads, beans, potatoes, rice and other grain products. Carbohydrates require less water to digest than proteins or fats and are the most common source of energy.

carbon black Chem.
A fine carbon powder, consist of 97-99% elemental carbon, with a particle size about 0.4 mm. It is made by burning hydrocarbons in insufficient air. It is used as a pigment in printing and lithographic and as a filler for rubber products such as tyres, cable belts, etc. Carbon black is also known is a variety of names due to its production in different industrial processes, such as acetylene black, lamp black, furnace black, etc.

carcinogen Med.
Any substance or agent, including chemicals and radiations (gamma ray, x-rays and ultraviolet rays), that causes cancer. Some of the well known carcinogens are tobacco smoke and asbestos.

carcinogenesis Med.
The production and development of cancer.

Casimir effect Phys.
It is a small attractive force acts between two close parallel mirrors or uncharged, conducting plates in a vacuum. The attractive force is due to quantum vacuum fluctuations of the electromagnetic field (an effect that causes an excited atom to fall spontaneously into its ground state, emitting a photon). When two plates face each other in vaccum, with only in the order of micrometer or less apart, the fluctuation exert a 'radiation pressure' on them. The force, which is also known as the Casimir force, is related to the area of the plates as follows:

Casimir force

where h and c is the Planck constant and the speed of light respectively. A is the area of a plate and d is the distance between two plates. For example, two mirror plates with an area of 1 cm2 and 1mm (10-6 m) apart have an attractive Casimir force of 10-7 N. Casimir effect was first predicted by the Dutch physicist Hendrik Casimir in 1948.

In 2007, it was found that the effect can also be observed in a fluid. When two gold-plated surfaces submerged in ethanol they experienced the Casimir attraction when brought within 200 nm of each other. However, the force is two times weaker than the force that would be found in a vacuum.

catalysis Chem.
The lowering of the energy of activation of a chemical reaction by a substance (catalyst) which itself does not change chemically. The reaction usually occurs via the formation of complex intermediate involving the catalyst. This leads to the acceleration (or retardation) of the chemical reaction.

catheter ablation Med.
A technique that involves having a catheter (tube) inserted into the heart. An electrical energy is transmitted to either reset or stop the heart beat so that a mechanical pacemaker can be put in place. The technique is usually used to treat abnormal heart rhythms such as Wolff-Parkinson-White syndrome.

cathode Chem., Phys.
A negative electrode where electrons originate. In a chemical cell or during electrolysis, cations are attracted to cathode and subsequently reduced as they pick up electrons. For instance, copper cations in solution is attracted towards cathode where they are reduced and deposited as copper metal on the cathode. In vacuum electronic devices, electrons are emittedby the cathode and flow to the anode.

cation Chem.
A positively charged ion that is attracted to the cathode in electrolysis. For instance, magnesium ion (Mg2+) and sodium ion (Na+) are cations that can exist in water and in ionic compounds.

back to dictionary home CA - CC next page (CD-CF)

A   B   C   D   E   F   G   H   I   J   K   L   M  
N   O   P   Q   R   S   T   U   V   W   X   Y   Z  

| Copyright | Privacy | Disclaimer | Contact |

2004-2010, all rights reserved.