A system is described which measures directly the driving-point force, velocity and complex mechanical impedance of biological, non-biological and viscoelastic materials and structures. The system uses a single transducer and is capable of measuring the velocity responses to sinusoidal, linear, step and other forcing functions.
The behaviour and handling of a flexible three variable--parameter function is presented, which is suitable for unbiased regression analysis. The function is defined by an intercept, a slope or coefficient and an exponent on the independent variable. Analog and digital problems and solutions are defined. Handling is simple and the program is run without operator intervention. The range of curves include linear, convex, concave and asymptotic forms and can be extended to include sigmoid and parabolic forms. Some application results are presented for different situations.
Critical parameters involved in the selection of porous glass for use as support materials in the immobilization of biologically active materials are discussed. The importance of physical properties such as pore morphology, surface area and particle size relative to the final activity of the enzyme is shown using glucoamylase IME as a model system. The process of selection of specific materials with respect to the environmental conditions of the enzyme and the chemical durability of the support is considered, as are the mechanical properties required in the scale-up of an application.
Flow between two contiguous elastic sheets (valve leaflets) generates one of two types of behavior. At low pressure differences, e.g. 1 cm H2O, the sheets part slightly and the fluid passes silently between them. The aperture under these silent conditions varies with the square of the length of the orifice, the transvalvular pressure difference and the kinetic energy, divided by the thickness of the leaflets. At higher transvalvular pressure differences the downstream end of the bicuspid valve alternately closes and reopens (flitter), and functions as an acoustic oscillator. The recurrence rate of flitter varies with the tension on the leaflets and inversely with the thickness. The threshold of the onset of flitter varies with the product of the pressure and the square of the length of the valve aperture, divided by the wall tension and thickness. The significance of these data in the onset of the flitter and of the recurrence rate is discussed in terms of the production of sounds and murmurs at the heart valves, vocal cords and other sites.
Distinguishing acoustical signatures of sound emitted by normal and pathological knee joints are picked up using a double microphone-differential amplifier setup. Extraneous background noise is minimized using the principle of "noise cancellation". Two identical sensitive condenser microphones and an F.M. recorder with flat responses in the audio range were used. Preliminary studies covering normal and diseased knee joints showed that their respective waveforms and spectral patterns are unique and proved to be a promising nondestructive diagnostic tool for early detection of knee joint cartilage damage.
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