Biomedical subjects

J E Bischoff

Publications and source records attributed to J E Bischoff.

3 recordsLinked to original sources

PubMed2006

Comparison of mechanical behavior among the extrapulmonary arteries from rats.

Results of comparative tests on pulmonary arteries from untreated Long-Evans rats are presented from three sections of the artery: the trunk, and the right and left main extrapulmonary arteries. Analyses were conducted looking for mechanical differences between the flow (longitudinal) and circumferential directions, between the right and left main arteries, and between each of the mains and the trunk. The mechanical properties of rat pulmonary arteries were obtained with a bubble inflation technique. A flat disk of rat pulmonary artery was constrained at the periphery and inflated, and the geometry of the resulting bubble of material recorded from six different angles. To analyze the data, the area under the stress-strain curve was calculated for each test and orientation. This area, related to the strain-energy density, was calculated at stress equal to 200kPa, for the purpose of statistical comparison. The mean values for the area show that the trunk is less compliant than the main arteries; this difference is supported by histological evidence. When comparing the circumferential and longitudinal properties of the arteries, differences are found for the trunk and left main arteries, but with opposite orientations being more compliant. The mean values for the two orientations for the right main artery are statistically identical. There was indication of significant difference in mechanical properties between the trunk and the main arteries. The left main artery in the circumferential orientation is highly compliant and appears to strongly influence the likelihood that significant differences will exist when included in a statistical population. These data show that each section of the extrapulmonary arterial system should not be expected to behave identically, and they provide the baseline mechanical behavior of the pulmonary artery from normotensive rats.

Animals↗

PubMed2000

Finite element modeling of human skin using an isotropic, nonlinear elastic constitutive model.

The collagen network in skin is largely responsible for the nonlinear mechanical stress-strain response of skin. We hypothesize that the force-stretch response of collagen is governed by the entropics of long-chain molecules. We show that a constitutive model derived from the statistical mechanics of long-chain molecules, corresponding to the fibrous collagen network in skin, captures the mechanical response of skin. A connection between the physiologically meaningful parameters of network molecular chain density and free length of collagen fibers and the constitutively significant parameters of initial modulus and limiting stretch is thus established. The relevant constitutive law is shown to have predictive capabilities related to skin histology by replicating in vivo and in vitro experimental results. From finite element simulations, this modeling approach predicts that the collagen network in hypertrophic scars is more dense and the constituent collagen fibers have shorter free lengths than in healthy skin. Additionally, the model is shown to predict that as rat skin ages, collagen network density increases and fiber free length decreases. The importance of knowledge of the in situ stress state for analyzing skin response and validating constitutive laws is also demonstrated.

Aging↗

PubMed1997

Identification and correlation of human footfall load parameters using multivariate analysis.

This research had two main objectives: to identify and quantify the multiple reaction parameters of human footfall load histories for 24 subjects; and to seek statistical correlations of the reaction parameters with two gaits: fitness walking and running, with two footfall surfaces: rigid and mat, and with two subject attributes: gender and arch index. These reaction parameters, measured with a force plate, include the subjects' foot reaction forces in the three orthogonal directions and the particular features of these forces such as their duration, average values, peak values, and rates of loading. An automated data retrieval-software system evaluated these reaction parameters. The statistical correlations were made using principal component analysis (PCA), a method that projected the 13 identified footfall reaction parameters onto subsets of three or four parameters called principal components that contained most of the variance of the original thirteen. The results, among others, show couplings between the vertical and the peak medial load, but an uncoupling of the posterior-anterior loads with the loads in the other two directions.

Adult↗