Recombinant DNA, gene cloning and Plasmid

Artificially created DNA is known as recombinant DNA. During synthesis, DNA from two or more sources is used and are incorporated into a single recombinant molecule. BamHI endonuclease is treated with the DNA obtained from different sources. This endonuclease cuts ends of DNA molecules.  These sticky ends help in linking different molecules and thus form recombinant DNA. These recombinant molecules are then replicated to several times. This process is called cloning. There exist two processes of cloning- vitro and vivo. Vitro cloning is achieved by polymerase chain reaction. In vivo cloning, DNA is incorporated in a vector like bacterial cells, mammalian cells etc. Plasmid is an extra-chromosomal DNA molecule which is entirely different from chromosomal DNA. They usually occur in bacteria with circular shape or double-stranded shape. Plasmids are capable of replicating independently the chromosomal DNA.

Hydraulic pumps

Hydraulic pumps are used to shift oil from a tank to the other parts of the system by raising oil pressure to the required level. A three phase AC induction motor is used to drive hydraulic pumps. The two basic types of hydraulic pump are hydrodynamic pump and positive displacement pump. Positive displacement pumps are further divided into three categories: gear pumps, vane pumps and piston pumps. Gear pump is a simple pump with only two moving parts. These parts move at constant speed and are nonreciprocating experiencing uniform force. The factors used for the determination of pump displacement are fluid volume between each pair of teeth, number of teeth and rotation speed. The leakage problem is a main concern in gear pumps. This can be minimized by using vane pumps. Here spring loaded vanes slotted into a driven rotor is used. But the vane pumps have disadvantages like lower capacity and pressure ratings. Piston pumps are simple single cylinder pumps similar to a motor car engine.

Rear axles

Rear axles are important component of an automobile unit.  Cars of front engine rear wheel type uses rear axles for transmitting power from differential to the driving wheels. Rear axles also serve two more functions. One is acting as a bearing rod for road wheels and the other providing attachments for the springs.  Broadly there are two types of axles. They are dead axle and live axle. Bullock cart employs dead axle which itself does not rotate, but wheels on this axle rotate. Automobiles use live axles which rotates itself.  The three types of rear axles are half floating rear axles, three-quarter floating rear axles and fully floating rear axles.  Lubrication of rear axles is necessary for the proper functioning and lubricating oil is always poured in the axle casing.  Leakage or overflow of the oil in the axle casing will lead to brake slipping.