carbon nanotubes

known as CNT is actually a carbon molecule. they are very thin and can be used for many applications. They are synthesized by many methods. Important methods are pyrolysis method and arc discharge method. it assumes three forms namely armchair, zigzag and chiral. They are mechanically strong, highly elastic, possess high thermal conductivity, very stable, metallic or semiconducting depending upon size and have high current carrying capacity.

DVD and ISDN

DVD is Digital Video Disk
ISDN is Integrated Sevices Digital Network

Mach Number

It is defined as the speed of the object (v) to the speed of sound (a) in the given medium.

M=v/a.

Since it is the ratio of speeds, it doesn’t have a unit. In aerodynamics, the speeds of bodies moving in a fluid medium are classified into different categories on the basis of Mach Number. Mach Number is named after the German scientist Ernst Mach.

Bore

The diameter of the cylinder of an engine is called its bore.

Metallograph

Metallograph is an instrument which photographs microstructure (the structure seen using microscope).

Bacillus thuringiensis

Bacillus thuringiensis is a bacterium species which infects and even kills a number of caterpillar species.