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Results for “Elastic Modulus”

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At least 163 records · Page 9Linked to original sources
PubMed2001

In vivo measurement of the elastic modulus of the human periodontal ligament.

The present study was designated to determine the elastic properties of the periodontal ligament (PDL) in human subjects. A maxillary central incisor was experimentally translated so that stress or strain could be uniformly distributed in the PDL by applying a single force passing through the center of resistance. Displacements were measured under different magnitudes of load using a magnet-magnetic sensing system. From the load-displacement relations, Young's modulus of the PDL was calculated. The values determined were approximately 0.12 MPa under load ranging from 0 to 0.5 N, 0.25 MPa within the range of 0.5-1.0 N, 0.44 MPa under load 1.0-1.5 N, and between 0.69 and 0.96 MPa with 1.5-2.0 N. The values of Young's moduli increased almost exponentially with the increment of load due to a non-linear elasticity of the PDL.

Adult↗
PubMed2003

Measuring the elastic modulus of ex vivo small tissue samples.

Over the past decade, several methods have been proposed to image tissue elasticity based on imaging methods collectively called elastography. While progress in developing these systems has been rapid, the basic understanding of tissue properties to interpret elastography images is generally lacking. To address this limitation, we developed a system to measure the Young's modulus of small soft tissue specimens. This system was designed to accommodate biological soft tissue constraints such as sample size, geometry imperfection and heterogeneity. The measurement technique consists of indenting an unconfined small block of tissue while measuring the resulting force. We show that the measured force-displacement slope of such a geometry can be transformed to the tissue Young's modulus via a conversion factor related to the sample's geometry and boundary conditions using finite element analysis. We also demonstrate another measurement technique for tissue elasticity based on quasi-static magnetic resonance elastography in which a tissue specimen encased in a gelatine-agarose block undergoes cyclical compression with resulting displacements measured using a phase contrast MRI technique. The tissue Young's modulus is then reconstructed from the measured displacements using an inversion technique. Finally, preliminary elasticity measurement results of various breast tissues are presented and discussed.

Adult↗
PubMed1991

The elastic modulus of the temporomandibular joint disc from adult dogs.

The present study was designed to measure the elastic properties of temporomandibular joint (TMJ) discs from six adult dogs. Each disc was divided mediolaterally into medial, middle, and lateral parts. Under tension, the articular disc exhibited a non-linear stress-strain relationship, which could be represented as two lines (two moduli of elasticity) connected at a point of stress around 1.5 MPa. These two elastic moduli of the disc were approximately 44 MPa and 92 MPa in the lower- and higher-stress regions, respectively. Elastic moduli of the articular disc in the middle area were significantly different from that in the lateral area of the disc. The reaction to external force appeared to be different in the medial, middle, and lateral regions of the disc.

Animals↗
PubMed2005

Proteolysis of mitotic chromosomes induces gradual and anisotropic decondensation correlated with a reduction of elastic modulus and structural sensitivity to rarely cutting restriction enzymes.

The effect of nonspecific proteolysis on the structure of single isolated mitotic newt chromosomes was studied using chromosome elastic response as an assay. Exposure to either trypsin or proteinase K gradually decondensed and softened chromosomes but without entirely eliminating their elastic response. Analysis of chromosome morphology revealed anisotropic decondensation upon digestion, with length increasing more than width. Prolonged protease treatment resulted only in further swelling of the chromosome without complete dissolution. Mild trypsinization induced sensitivity of chromosome elasticity to five- and six-base-specific restriction enzymes. These results, combined with previous studies of effects of nucleases on mitotic chromosome structure, indicate that mild proteolysis gradually reduces the density of chromatin-constraining elements in the mitotic chromosome, providing evidence consistent with an anisotropically folded "chromatin network" model of mitotic chromosome architecture.

Animals↗