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Moment of truth
The Voyager I spacecraft is the most distant man-made object in the universe. It was launched in 1977 and as in 2002, it was more than 8 billions miles from the Earth. ||
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elastic deformation Eng.
Changes in shape which are proportional to an applied force. When the force is removed, the shape will return to its original form.
elastic modulus Eng.
See Young's modulus.
Rubber (either natural or synthetic) which has the ability to deform due to an applied force and regain its original shape once the force is removed. Depend on the specific materials, elastomers can extend up to about 700 %.
The elasticity of the material is due to extensive cross linking among the polymer chains that made up elastomers.
A permanently dielectric and insulating substance that has opposite charges at its opposite ends (polarized). The magnetic equivalent is a permanent magnet.
It can be made by cooling certain wax, such as Carnauba wax, in a strong electric field. The material has found its use in condense microphones.
A liquid that conducts electricity as a result of the presence of mobile positive and negative ions (cations and anions). Electrolytes are usually molten or solution of ionic compounds. Solid ionic compound is not an electrolyte because the movement of ions are restricted about the
crystal lattice. Solid metals or liquid metals are also not considered as electrolytes because the electrical conduction is due to the movement of free electrons.
electromagnetic interactions Phys.
The interactions between electric charges, currents and magnetic moments. The interaction is due to the exchange of massless gauge boson, photons, with spin 1.
For instance, the interaction between electric charges is described by the Coulombic interactions.
electron affinity Chem.
The amount of energy release as a neutral atom or molecule, X, in gas phase gains an electron to become negatively charged species, X-. Usually, a more electronegative species will have a stronger affinity to receive an electron.
For instance, chlorine has an electron affinity of 348.6 kJ/mol, where as sodium is 52.9 kJ/mol. Sometimes, the quantity is also quoted in unit electronvolt.
electronvolt Metro., Phys.
Unit of kinetic energy acquired by an electron in passing through a potential difference of 1 volt in vacuum. Abbreviated as eV and 1 eV = 1.6022 x 10-19 J. It is commonly used for describing the energy of a
moving subatomic particles, in unit MeV (1 x 106 eV) or GeV (1 x 109 eV).
A technique for the analysis and separation of colloids or other molecules based on the movement of charged particles under an electric field in a fluid:
positive species move to the cathode and negative species to the anode. For a given field strength, the rate of motion depends on charges, size and shapes of the molecules.
It is used in studying mixtures of proteins, enzymes and other biological molecules, and to determine the protein content of body fluids.
An electrochemical process in which a metal is coated onto an object in a solution that contains the metal cation. The object to be coated (plated) is connected to the negative terminal of an electrical supply as a cathode while the positive terminal is connected to an object made of the
coating metal (anode). For instance, electroplating of nickel onto copper in a solution containing nickel ion Ni2+.
A substance that cannot be resolved into simpler substance by chemical means. It consists of atoms with identical proton number. Elements are unique and placed systematically in the Periodic Table of the Elements according to the
number of protons in the nucleus of the atom. Example of elements are gold, which consists of 100 % gold atoms and copper, which consists of 100 % copper atoms. The identity of an element is destroyed if its atoms are
Trade name for a nickel-chromium steel containing about 36% nickel, 12% chromium and a small amount of tungsten, manganese or titanium. The alloy is notable for its constant elasticity with respect to temperature and is found its use as hairsprings for watches.
endemic Biol., Eco.
The constant presence of threats, to a greater or lesser extent in a particular geographical area or locality. Examples are diseases such as Malaria which is endemic to the tropics. It can also refer to the presence of other tragic events such as starvation, famine,
It also means a plant or animal that is native to certain limited area.
The process whereby biological cells absorb macromolecules such as proteins and other particulate substances by enclosing it with their cell membrane. If the engulfed material is a fluid (such as proteins), it is called pinocytosis, meaning 'cellular drinking'. If the engulfed materials are large particles such as cell debris or
microorganisms, the digestive process is called phagocytosis, meaning 'cellular eating'. In both cases, the enclosures inviginate and pinches off the cell membrane to form an intracellular (within-cell) vesicle during pinocytosis or phagasome during the phagosytosis process.
These processes only occur in eukaryotic cells and do not occur in prokaryotes.
Inside (of cell or body). For example, edogenous proteins are proteins that are synthesized within the cell. Endogenous cholesterol is cholesterol that is made inside the body and not from the food diet.
endoplasmic reticulum Biol.
Abbreviated as ER, it is an organelle found in all eukaryotic cells and consists of a network of membranes throughout the matrix of cytoplasm. These membranes form a complex
interconnected network of vesicles, tubules or large flattened sacs. The membranes run parallel to each other, creating channels called cisternae (see diagram below).
This effectively forms a large membrane surface area. The surface may be bound with ribosomes (small magenta dot as shown above) where the site of protein synthesis being taken place. This gives rise to the name rough endoplasmic reticulum (RER).
Surface where there is no ribosome is called smooth endoplasmic reticulum (SER). It is important for synthesis of complex lipids for used in the cell membrane and for drug metabolism.
A warm blooded animal. It generates heat to maintain its body temperature. It derives from the Greek word means the ‘heat within’.
A chemical reaction that draws heat from its surrounding, leading to the drop in temperature of the system.
end point Chem.
The point in titration at which the reaction is complete as shown by an indicator. For instance, in the titration of hydrochloric acid with sodium hydroxide using phenolphthalein as an indicator. The end point is reached when the last drop of sodium hydroxide is added that causes the first permanent change in
colors of the indicator (in this example, from colorless to pink).
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