MEASUREMENT SYSTEM FOR INPUT BIAS –OFFSET CURRENTS OF AN OPERATIONAL AMPLIFIER
A very simple microprocessor (µP) -based dedicated instrument is designed here.' The Overall system design consists of both hardware and software designs. This set-up yields the exact values of input bias and input off-set currents on the µP display panel, one after the other, when the operational amplifier (OP- AMP) under test is connected across the test terminals.
Microprocessor Based Instrument for Resistance and Diode Testing
The component tester reported in this paper is a microprocessor based instrument. It is used for evaluating resistances in the range of 100–10M Ohms divided equally over five automatically selected ranges. It has also got the capability of testing silicon diodes for their usefulness. The diode can be connected in any particular fashion. The hardware circuit is IC based and includes resistance detector, relay drivers, buffer, constant current source, diode tester, analog to digital converter and Intel 8085 based programmable microprocessor kit.
Collagen dynamics in articular cartilage under osmotic pressure
Cartilage is a complex biological tissue consisting of collagen, proteoglycans and water. The structure and molecular mobility of the collagen component of cartilage were studied by 13C solid‐state NMR spectroscopy as a function of hydration. The hydration level of cartilage was adjusted between fully hydrated (∼80 wt% H2O) and highly dehydrated (∼30 wt% H2O) using the osmotic stress technique. Thus, the conditions of mechanical load could be simulated and the response of the tissue macromolecules to mechanical stress is reported. From the NMR measurements, the following results were obtained. (i) Measurements of motionally averaged dipolar 1H–13C couplings were carried out to study the segmental mobility in cartilage collagen at full hydration. Backbone segments undergo fast motions with amplitudes of ∼35° whereas the collagen side‐chains are somewhat more mobile with amplitudes between 40 and 50°. In spite of the high water content of cartilage, collagen remains essentially rigid. (ii) No chemical shift changes were observed in 13C cross‐polarization magic angle spinning spectra of cartilage tissue at varying hydration indicating that the collagen structure was not altered by application of high osmotic stress. (iii) The 1H–13C dipolar coupling values detected for collagen signals respond to dehydration. The dipolar coupling values gradually increase upon cartilage dehydration, reaching rigid limit values at ∼30 wt% H2O. This indicates that collagen is essentially dehydrated in cartilage tissue under very high mechanical load, which provides insights into the elastic properties of cartilage collagen, although the mechanical pressures applied here exceed the physiological limit. Copyright © 2006 John Wiley & Sons, Ltd.