These instruments belong to the category of versatile instruments. These instruments are generally used for measurement and record of process variables such as vacuum, pressure, angle of rotation, flow etc. The basic principle employed here is null balance principle. Differential amplifiers, induction transducers, ferrodynamic converters etc. are used here in an effective way. Supporting instruments used here are balancing motor, linkage and chart drive mechanisms. A ferrodynamic converter is composed of a powerful moving coil placed in an alternating magnetic field. The magnitude and phase of the e.m.f induced in the coil is proportional to the angle of rotation of the coil.
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Tuesday, April 12, 2011
Wednesday, February 2, 2011
Hemoglobin
Hemoglobin efficiently controls the biological activity. Hemoglobin is a tetramer with two alpha chains and two beta chains. Hemoglobin is a symmetrical molecule made up of two assymetrical protomers. The sequence of the myoglobin chains and hemoglobin chains are homologous. But there exist some differences in the region where the chains in hemoglobin contact one another. When hemoglobin binds oxygen to form oxyhemoglobin, there is a change in the quaternary structure. This causes tertiary structure to change by the movement of the proximal histidine. These changes cause the breakage of the constraining salt links between the terminal groups of the four chains. kb
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