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M Kothari

Publications and source records attributed to M Kothari.

4 recordsLinked to original sources
PubMed1989

A capacitance pressure sensor using a phase-locked loop.

We are using a Hercules (model #F4-4R, 100 psi) pressure sensor to measure the pressure between the foot and shoe. An interface circuit converts the capacitance change into voltage. Over the pressure range from 0 to 1300 kPa, the capacitance changes from 275 to 580 pF. A 555 timer circuit converts the capacitance into a frequency range from 30 to 63 kHz. A phase-locked loop (PLL) converts this frequency to voltage from 0 to 5 V, which is then filtered using a first-order, low-pass filter, having a corner frequency of 20 Hz to reduce the ripple to 10 mV. The sensor's hysteresis is about 8 percent at 40 degrees Celsius (C) and 12 percent at 20 degrees C. The sensor has a maximal nonlinearity of 8 percent and a worst-case nonrepeatibility of 7 percent. Its temperature coefficient is -0.147 percent per degree C. Its spatial sensitivity decreases nonlinearly from 1 to 0.17 from the center towards the periphery. The sensitivity of the system is 2.77 mV/kPa and the temperature drift is +0.53 percent per degree C. We monitor the pressure at 7 locations under each foot (the rear and the front heel, great toe, and 4 of the 5 metatarsal heads). A portable data-acquisition system permits continuous monitoring for 7 minutes. Test results for pressure distribution for normal walk and run are presented. Results are useful when studying normal and abnormal gait, and for possibly providing feedback (sensory substitution) to diabetic patients with insensate feet in order to help them dynamically adjust pressure distribution under their feet.

Biomechanical Phenomena↗
PubMed1975

Changes in total body composition during normal and diabetic pregnancy. Relation to oxygen consumption.

Serial changes in body composition during pregnancy have been measured in 5 normal and 2 diabetic women on controlled diets to compare with simultaneous measurements of oxygen consumption (V-O2). Total body water (TBW) was measured by D2O dilution, total body fat (TBF) calculated as 100-%TBW/0.732 and body cell mass (BCM) derived from total body 40K count by Moore's formula, BCM equals K-e times 8.33. Two normal subjects in caloric equilibrium lost 1.2 kg TBF, gained 5.5 kg TBW and 4.1 kg BCM. Two obese subjects in negative caloric balance lost 4.7 kg TBF, gained 7.3 kg TBW and 4.3 kg BCM. One subject on ad lib diet gained 7.7 kg TBF, 0.6 kg TBW, and 2.6 kg BCM. She continued to gain fat postpartum. Two diabetic subjects gained fat up to 28 weeks, lost it thereafter, and showed no net gain in BCM. Basal V-O2 correlated with BCM, while 24-hour resting V-O2 related to total body weight. It is concluded that fat storage in human pregnancy depends on food intake, as in the nonpregnant. BCM accumulation is independent of food intake, except protein, and depends on normal physiologic adjustments of pregnancy, which are upset by insulin lack in diabetes. The extra basal energy needs of gestation are determined by BCM acquisition, not total body weight.

Adipose Tissue↗