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Biomedical subjects

J Q Sun

Publications and source records attributed to J Q Sun.

9 recordsLinked to original sources
PubMed2005

A prototype rehabilitation device with variable resistance and joint motion control.

Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents the design of a versatile rehabilitation device in the form of a rotating joint arm mounted on the adjustable seat that provides passive resistance during strength training for muscles. The resistance is supplied by a magnetorheological damper. Intelligent controls are developed to produce resistance force based on the prescription of the therapist. The device provides both isometric and isokinetic strength training and is reconfigurable for several human joints. Special consideration has been given to the human-machine interaction in the adaptive control algorithms that can modify the behavior of the device to account for strength gains or muscle fatigue.

Computer-Aided Design↗
PubMed2005

Rehabilitation device with variable resistance and intelligent control.

Resistance exercise has been widely reported to have positive rehabilitation effects for patients with neuromuscular and orthopaedic conditions. This paper presents an optimal design of magneto-rheological fluid dampers for variable resistance exercise device in the form of a knee brace. An intelligent supervisory control for regulating the resistive force or torque of the knee brace has also been studied. The device provides both isometric and isokinetic strength training for the knee.

Artificial Intelligence↗
PubMed2000

The effect of coal combustion flue gas components on low-level chlorine speciation using EPA method 26A.

U.S. Environmental Protection Agency (EPA) Method 26A is the recommended procedure for capturing and speciating halogen (X2) and hydrogen halide (HX) stack emissions from combustion sources. Previous evaluation studies of Method 26A have focused primarily on hydrogen chloride (HCl) speciation. Capture efficiency, bias, and the potential interference of Cl2 at high levels (> 20 ppm [microgram/m3]) and NH4Cl in the flue gas stream have been investigated. It has been suggested that precise Cl2 measurement and accuracy in quantifying HX or X2 using Method 26A are difficult to achieve at Cl2 concentrations < 5 ppm; however, no performance data exist to support this. Coal contains low levels of Cl, in the range of 5-2000 ppmw, which results in the presence of HCl and Cl2 in the products of combustion. HCl is the predominant Cl compound formed in the high-temperature combustion process, and it persists in the gas as the products of combustion cool. Concentrations of Cl2 in coal combustion flue gas at stack temperatures typically do not exceed 5 ppm. For this research, bench-scale experiments using simulated combustion flue gas were designed to validate the ability of Method 26A to speciate low levels of Cl2 accurately. This paper presents the results of the bench-scale tests. The effect of various flue gas components is discussed. The results indicate that SO2 is the only component in coal combustion flue gas that has an appreciable effect on Cl2 distribution in Method 26A impingers, and that Method 26A cannot accurately speciate HCl and Cl2 in coal combustion flue gas without modification.

Air Pollutants↗
PubMed1997

A stiffness-varying model of human gait.

We report on a conceptual two degrees of freedom (2 DOF) human gait model, which incorporates nonlinear joint stiffness as a stabilizing agent. Specifically, muscle spring-like property provides inherent stability during gait movement using a nonlinear angular spring and dash pot at each joint. The instability problem of the gait model in direct dynamic analysis is overcome by simulating the human co-contraction muscle function. By developing dynamic system stability requirements and hypothesizing a minimum joint stiffness criterion, we determine time-varying joint stiffness. Optimum joint stiffnesses are present for varying gait pattern, stride lengths and cadences. We conclude that nonlinear joint stiffness can be incorporated into gait models to overcome stability problems inherent in such linkage models.

Ankle Joint↗
PubMed1986

Aging affects the drug metabolism systems of rat liver, kidney, colon and lung in a differential fashion.

Microsomes prepared from the liver, lungs, colon and kidney cortex of Sprague Dawley rats of ages 2, 4, 10, 24 and 78 weeks were assessed for hydroxylation activity with the substrate benzo[alpha]pyrene. Liver microsomal activity declined after reaching a peak of activity at 10 weeks. The hydroxylation of benzo[alpha]pyrene by colon, kidney and lung microsomes, however, either remained the same or decreased only slightly. During the age range examined inducibility of hydroxylation activity by beta-naphthoflavone decreased with age in liver but actually increased with age in the extrahepatic tissues. Although phenobarbital did not elicit any increases in liver, kidney or lung, it increased substantially benzo[alpha]pyrene hydroxylation activity in colon microsomes of 78 week old rats. Total cytochrome P-450 content was induced at all age groups in all tissues by beta-naphthoflavone and in all tissues except lung by phenobarbital. Induction of cytochrome P-450 in kidney by phenobarbital was only observed in 24 and 78 week old rats. These data suggest an increased role for extrahepatic activation of benzo[alpha]pyrene with aging. In contrast to total content of cytochrome P-450, the beta-naphthoflavone inducible amount of Form 5 which has a high turnover number for benzo[alpha]pyrene, declined by 55% in liver between 2 weeks and 78 weeks while it increases dramatically in all extrahepatic tissues (from 80 to 138%).

Aging↗
PubMed1986

Aging modifies the expression of hepatic microsomal cytochromes P-450 after pretreatment of rats with beta-naphthoflavone or phenobarbital.

The various forms of hepatic cytochrome P-450 respond differentially to aging and induction. We examined the levels of six forms of cytochrome P-450, designated as Forms 1 through 5 and Form b, as a function of age and induction. Radial immunodiffusion analysis of rat liver microsomes indicate that cytochrome P-450 Forms 1 and 2 respond to induction by beta-naphthoflavone or phenobarbital less well in aging rats than in young rats. beta-naphthoflavone is less effective in inducing Forms 3, 4, and 5 in aging rats than in young rats. Phenobarbital, however, is more effective in inducing Forms 3 and 4 in aging rats than in young rats but does not induce Form 5 in either young or aging rats. Although Form b is induced predominantly by phenobarbital, beta-naphthoflavone induces Form b moderately in aging rats. Phenobarbital induces Form b to approximately the same extent in aging rats and in young rats. In untreated rats Form 2 is the predominant form, while Forms 1 and 3 are present in moderate amounts. The results of the immunodiffusion analysis were confirmed by the resolution and partial purification of cytochromes P-450 from microsomes of aging and young rats pretreated with beta-naphthoflavone or phenobarbital. These results identify changes with age in specific forms of cytochrome P-450 as a function of the aging process in rats.

Aging↗