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Results for “Elastic Modulus”

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PubMed1990

Muscle elasticity: effect of muscle length and temperature.

The present study describes a new method which allows the determination of muscle elasticity by applying quick releases at one end of a muscle and measuring the resulting tension drops at both ends, and simultaneously the propagation time of the mechanical impulse. The elasticity determined by both methods was examined on resting as well as on tetanized frog muscles (Rana esculenta, M. flexor hallucis brevis) in relation to muscle length and at two different temperatures 1 degree C and 20 degrees C. The average propagation velocity of the mechanical impulse of resting muscle was 55.7 +/- 4.7 m/s and of the contracting muscle 104.8 +/- 24.7 m/s at 1 degree C (L0, n = 6), which corresponds to elasticities of 3.3 +/- 0.5 N/mm2 and 14.4 +/- 6.2 N/mm2, respectively. The elasticity modulus calculated from the tension drop was for the resting muscle 2.3 +/- 0.5 N/mm2 and for the contracting muscle 11.1 +/- 2.1 N/mm2 (L0, 1 degree C, n = 6). When the muscle length is varied, the elasticity modulus corresponds to the length-tension relation of the resting and the isometrically contracting muscle. There is a strong correlation between the elasticity moduli which was determined by both methods for measurement of resting (r = 0.99, n = 19, p less than 0.05) and contracting muscle (r = 0.97, n = 19, p less than 0.05). This relation between elasticity and tetanic tension, i.e. filament overlap at constant temperature, can be interpreted in accordance with the sliding filament theory. But if the temperature is increased from 1 degree C to 20 degrees C, an increase of the tetanic tension (Q10 = 1.56) and a decrease of the elasticity measured by both methods (Q10 of 0.86 and 0.84) were obtained. This suggests that the increased tetanic force is generated by a smaller number of attached cross-bridges, but with a higher amount of force generated by each cross-bridge.

Animals↗

PubMed1998

Airway-parenchymal interdependence after airway contraction in rat lung explants.

The constriction of pulmonary airways is limited by the tethering effect exerted by parenchymal attachments. To characterize this tethering effect at the scale of intraparenchymal airways, we studied the pattern of parenchymal distortion due to bronchoconstriction in a rat lung explant system. First, we measured the elastic modulus under tension for 2% (wt/vol) agarose alone (37.6 +/- 1.5 kPa) and for agarose-filled lung (5.7 +/- 1.3 kPa). The latter is similar to the elastic modulus of air-filled lung at total lung capacity (4.5-6 kPa) (S. J. Lai-Fook, T. A. Wilson, R. E. Hyatt, and J. R. Rodarte. J. Appl. Physiol. 40: 508-513, 1976), suggesting that explants can be used as a model of lung tissue distortion. Subsequently, confocal microscopic images of fluorescently labeled 0.5-mm-thick explants prepared from agarose-filled rat lungs inflated to total lung capacity (48 ml/kg) were acquired. Images were taken before and after airway constriction was induced by direct application of 10 mM methacholine, and the pattern of parenchymal distortion was measured from the displacement of tissue landmarks identified in each image for 14 explants. The magnitude of the radial component of tissue displacement was calculated as a function of distance from the airway wall and characterized by a parameter, b, describing the rate at which tissue movement decreased with radial distance. The parameter b was 0.994 +/- 0.19 (SE), which is close to the prediction of b = 1 of micromechanical modeling (T. A. Wilson. J. Appl. Physiol. 33: 472-478, 1972). There was significant variability in b, however, which was correlated with the fractional reduction in airway diameter (r = 0.496). Additionally, parenchymal distortion showed significant torsion with respect to the radial direction. This torsion was similar in concentric zones around the airway, suggesting that it originates from inhomogeneity in the parenchyma rather than inhomogeneous airway constriction. Our results demonstrate the significance of the nonlinear mechanical properties of alveolar walls and the anisotropy of the parenchyma in determining the nature of airway-parenchymal interdependence.

Animals↗

PubMed2000

Determination of biomechanical properties in guinea pig esophagus by means of high frequency ultrasound and impedance planimetry.

Impedance planimetry and high-frequency ultrasound were used to determine circumferential stress and strain from measurements of luminal cross-sectional area and wall thickness during balloon distension of the guinea pig esophagus in vitro (N = 30). The excised esophagus was mounted on two plastic tubes in an organ bath containing oxygenated calcium-free Krebs-Ringer solution with 10(-2) M MgCl2 to abolish smooth muscle contractile activity. One of the plastic tubes was movable in order to stretch the esophagus longitudinally by 15% (elongated state). The impedance planimetry probe was placed with the balloon inside the lumen of the esophagus. A 20-MHz ultrasound transducer was mounted above the esophagus and provided scans in the transverse and longitudinal directions. The luminal cross-sectional area at the highest applied pressure of 2.9 kPa was 13.3 +/- 0.3 mm2 in the resting state. In the elongated state the luminal cross-sectional area at the highest pressure was 12.5 +/- 0.1 mm2 (P < 0.02). The wall thickness decreased from 990 +/- 21 microm at 0 kPa to 640 +/- 9 microm at 2.9 kPa at in vitro length. In the elongated state, the values were 940 +/- 32 microm to 480 +/- 13 microm (P < 0.01). The stress-strain relation was exponential (sigma = alpha(ebetaepsilon - 1), r2 > 0.98, P < 0.01). The circumferential elastic modulus calculated at a Green strain of 0.95 was 44.5 +/- 10.5 kPa in the in vitro state and 81.7 +/- 13.1 kPa in the elongated state. The elastic modulus differed between the resting and elongated states (P < 0.02).

Animals↗

PubMedDate not supplied

Poly(vinyl alcohol) hydrogel as a biocompatible viscoelastic mimetic for articular cartilage.

The prevalence of suboptimal outcome for surgical interventions in the treatment of full-thickness articular cartilage damage suggests that there is scope for a materials-based strategy to deliver a more durable repair. Given that the superficial layer of articular cartilage creates and sustains the tribological function of synovial joints, it is logical that candidate materials should have surface viscoelastic properties that mimic native articular cartilage. The present paper describes force spectroscopy analysis by nano-indentation to measure the elastic modulus of the surface of a novel poly(vinyl alcohol) hydrogel with therapeutic potential as a joint implant. More than 1 order of magnitude decrease in the elastic modulus was detected after adsorption of a hyaluronic acid layer onto the hydrogel, bringing it very close to previously reported values for articular cartilage. Covalent derivatization of the hydrogel surface with fibronectin facilitated the adhesion and growth of cultured rat tibial condyle chondrocytes as evidenced morphologically and by the observance of metachromatic staining with toluidine blue dye. The present results indicate that hydrogel materials with potential therapeutic benefit for injured and diseased joints can be engineered with surfaces with biomechanical properties similar to those of native tissue and are accepted as such by their constituent cell type.

Animals↗

PubMedDate not supplied

Variations in epidural catheter manufacture: implications for bending and stiffness.

BACKGROUND AND OBJECTIVES: There is no formal evaluation method used to relate epidural catheter design and manufacture to clinical outcomes, such as subarachnoid or intravascular catheter placement. We analyzed catheter bending stiffness to determine the range of stiffness of catheters commonly used. We hypothesized that catheter material has a greater influence on stiffness than does cross-sectional shape. METHODS: We determined the elastic modulus by axial load testing and the area moment of inertia using calibrated microscopic measurements of cross-sectional geometry for 6 different catheter types, including 2 types of wire styletted catheters. We calculated bending stiffness as the product of the elastic modulus and the area moment of inertia. RESULTS: Catheters had similar area moments of inertia, but markedly different elastic moduli. Nylon and polyurethane catheters had the same bending stiffness, which was twice as high as that of coil reinforced catheters (P <.05), but 35% lower than that of radiopaque catheters (P <.05). Nylon and radiopaque wire styletted catheters had similar bending stiffness, which were 23-fold to 90-fold greater than that of the nonstyletted catheters (P <.05). CONCLUSIONS: Catheters currently available establish the range of bending stiffness that should not be exceeded, only optimized to clinical outcome. Clinical studies are needed to correlate the incidence of unintentional intravascular or subarachnoid catheter placement or migration and bending stiffness. Catheter technology improvements may enhance safety and increase the likelihood of successful catheter insertion, maintenance, and removal.

Algorithms↗

PubMed1980

The effect of dextran 70 on the structure of plasma-derived fibrin gels.

Measurements of fiber mass-length ratios and fibrin gel elastic modulus as a function of dextran 70 concentration are reported for fibrin gels derived from human plasma. Dextran 70 at 0.1 mg/ml produces a 50% reduction in the storage modulus of fibrin gels obtained from human plasma diluted 1:10 with saline. Since the fibrin fiber diameter increases as only a weak function of the dextran 70 concentration, the lower elastic modulus most likely results from a reduction in network branch points. Aprotinin is also shown to modulate the dextran effect.

Aprotinin↗

PubMed2006

[An experimental study on mechanical properties of fiber layers in anulus fibrosus of lumbar interverbral disc 4,5].

We tested the mechanical properties of fiber layers in adult anulus fibrosus of lumbar interverbral disc 4,5. Aulus fibrosus of lumbar interverbral disc was delaminated by using microsurgical technique. 8 testing points were taken in each layer according to the fibers going and 5 testing specimens were taken from each testing point. The length was 15-20mm, the width 1-2mm, and the thickness 0. 1-0. 5mm. By using tension test,the relationship curves of stress and strain were tested, the fitting curves and equations were obtained, and then the elastic modulus, damage strain and damage stress were obtained. Therefore we knew the parameters and equations of mechanical properties of each testing point. We got the result that the elastic modulus of each testing point, along the radius from outside to inside, decreased with the increase of layers. The damage stress decreased linearly from outside to inside. The damage strains of the outside 9 layers increased slightly with the increase of layers, and the others were almost constants, i. e. 0.34 +/- 0.14. We get the conclusion that analus fibrosus of intervertebral disc has special mechanical properties corresponding with its functions, which is in a close relationship with lumbar vertebral diseases.

Adult↗

PubMed1990

[Finite element analysis on physiological mobility of individual teeth].

The initial movement of the tooth was investigated by the finite element method. The mechanical properties of the periodontal membrane were estimated from the results of the simulation. The analysis was made by using an 8 point isoparametric finite element method. The upper central incisor with an axial directional load was simulated. The concept of the apparent elastic modulus was introduced to the stress-strain relation of the soft tissue, that is, soft tissue such as the periodontal membrane and the gingiva was considered to have stress dependent elastic moduli. At the first stage of the simulation, the stress and strain distributions in the paradentium were calculated by the conventional method. From the next stage, the apparent elastic moduli for the soft tissue were introduced to the calculation, that is, the elastic moduli for the soft tissue were computed from the calculated equivalent stresses of the previous stage. The calculations were repeated until the displacement values converged. The initial displacement of the tooth was not proportional to the applied load but showed a non-linear relationship. The relationship between load and displacement was approxiated by the n-th power equation. These results were in agreement with the clinical experimental results. The periodontal membrane is built up of different elastic moduli. The elastic moduli were low at the alveolar edge and the root apex. The equivalent stresses of the periodontal membrane were marked low in the alveolar edge and the root apex. In conclusion, the concept of the apparent elastic modulus is useful to investigate the initial movement of the tooth and estimate the mechanical properties of the periodontal membrane.

Computer Simulation↗

PubMed1982

Changes in the distensibility of the intrapulmonary arteries in the normal newborn and growing pig.

The static elastic properties and structure of the intra-pulmonary arteries have been studied in pigs from fetal life to 4 months old, by radiographic and histological methods. During this period the average radius of the vessels examined varied from approximately equal to 0.9 mm at birth to 3.3 mm at the age of 4 months. The form of the pressure radius curves was similar to that observed in the systemic circulation and was characteristic of the gradual recruitment of collagen fibres with increasing pressure. In vessels near the hilum, wall thickness decreased from approximately equal to 180 microns to 100 microns during the first 2 weeks and thereafter increased to approximately equal to 250 microns. Throughout the lung and in all age groups there was a linear relationship between the logarithm of pressure strain elastic modulus (used as a measure of functional stiffness) and pressure. In contrast to the systemic arteries there was little change in functional stiffness towards the periphery, although the incremental elastic modulus (structural stiffness) did increase at sites further removed from the heart. During the first two weeks of life there was little change in functional stiffness (Ep approximately equal to 1.1 X 10(4) Nm2) although by 4 months Ep had increased by a factor of three. During this period despite fluctuations with age, an overall increase in structural stiffness was also observed (EINC approximately equal to 1 X 10(5) at 4 to 6 h to 2 X 10(5) Nm-2 at 4 months). The observations suggest that the changes in elasticity observed in early life are a consequence of the adaptation of the circulation to the lower pulmonary arterial pressure of extra-uterine life.

Aging↗

PubMed2006

Generation of a torsion wave and measuring its propagation velocity in the circumferential direction of arterial wall.

Increased stiffness of the arteries has recently gained acceptance as a potential risk for cardiovascular and many other diseases. Pulse wave velocity (PWV) is widely used for estimating the stiffness of an artery. However, PWV is an indicator of average artery stiffness between two measuring points. In addition to measured PWV, the diameter and thickness are needed to calculate the elastic modulus of the artery. We present a new method to generate a torsion wave in the artery wall and measure its propagation speed in the circumferential direction of the artery. The elastic modulus of the artery can be calculated from the torsion wave velocity without the knowledge of the thickness of the artery, which is difficult to measure with accuracy.

Algorithms↗

PubMed1997

Venous elasticity after treatment with Daflon 500 mg.

It has been demonstrated that patients predisposed to the development of varicose veins have an abnormal venous tone, and may have symptoms in the absence of obvious varicosities. It has been suggested that venotonic drugs relieve the symptoms of chronic venous insufficiency by decreasing capillary leakage and improving venous tone. The aim of this study was to determine the effect of Daflon 500 mg in patients with abnormal venous elasticity without varicose veins. Twenty-five healthy female volunteers aged 18-35 were included in the study. They presented with symptomatic varicose veins in one leg and an abnormal elastic modulus without varicosities in the opposite leg. Treatment group: 12 patients received 2 tablets of Daflon 500 mg (1000 mg/day); control group: 13 patients received no treatment. The elastic modulus K was determined using the air plethysmograph. Simultaneous measurements of calf volume changes were made in response to different venous pressures produced by a thigh pneumatic cuff. In the control group K (mean +/- sd) was 10.8 x 10(3) +/- 4.1 x 10(3) N/m2 at the beginning and 10.2 x 10(3) +/- 3.1 x 10(3) N/m2 at the end of the study (P > 0.1). In the treatment group the initial K was 10.2 x 10(3) +/- 3.9 x 10(3) N/m2 and 14.2 x 10(3) +/- 5.1 x 10(3) N/m2 at the end (P < 0.02). The results of the Wilcoxon rank sum test indicated that 4 weeks' therapy with Daflon 500 mg is effective in improving venous tone in patients with symptoms but without varicose veins.

Adolescent↗

PubMed1999

[Comparative study of the effect on stress distribution of porcelain laminate complex with different elastic moduli].

Porcelain laminate has been a kind of popular treatment modality for its aesthetics and less tooth reduction. The models of 3-D FEA of left upper permanent central incisor were designed by microtomy. Comparative studies of stress distribution were carried out to reveal the stress of three designs of tooth preparation with two kinds of occlusions. The results showed that under loads imitating of central occlusion, the stress level increased a little with the rising of elastic modulus of the porcelain material, while the stress values of type II veneer seemed the highest under loads imitating of protruding occlusion. For the designing of laminate, it implies that porcelain material with low elastic modulus should be used in case of type II veneers.

Dental Porcelain↗

PubMed1977

Osmotic relations of nerve fiber.

The volumetric elastic modulus of the sheath and the osmotic swelling pressure of the axoplasmic polymer network of the giant axon of Loligo vulgaris were measured. Evidence was obtained that (1) the elastic modulus of the sheath, (2) the swelling pressure of axoplasm, and (3) the effective osmotic pressure difference due to mobile solutes determine axonal volume. The contributions of the sheath and the axoplasm were significant because the effective osmotic pressure due to mobile solutes was a small fraction of the theoretical bulk osmotic pressure due to these solutes. The giant axon was converted from an imperfect to a near perfect osmometer by minimizing the contribution of the sheath and the axoplasmic gel.

Animals↗

PubMed1994

Mechanical comparison of 10 suture materials before and after in vivo incubation.

The material properties of ten 2-O suture materials were evaluated tensiometrically at time = 0 and again after 6 weeks incubation in rats. All suture material was incubated and tested without knots. Specialized machinery was used with a custom securing apparatus to pull suture material apart at constant speed. Stress-strain curves were derived, and from these strength, toughness, strain at rupture, and elastic modulus were determined. Sutures tested included Vicryl [poly(glycolide-lactide)], Dexon (polyglycolic acid), Ethibond (polyester), silk, plain gut, chromic gut, Maxon (polyglyconate), PDS (polydioxanone), nylon, and Prolene (polypropylene). Elastic modulus was greatest for braided, least for monofilament, and intermediate for gut sutures, regardless of chemical composition (ANOVA, P = 0.0001). Strength, strain, and toughness decreased in all of the sutures over time in vivo with the exception of braided polyester (Ethibond), which remained stable. Silk demonstrated the least strength and toughness while PDS and Maxon were the strongest and toughest at time = 0. Vicryl, Dexon, and gut sutures were absorbed to the point that they could not be tested after 6 weeks in vivo. Performance tables are provided for all sutures.

Animals↗

PubMed1982

Measurement of erythrocyte membrane elasticity as a diagnostic aid in Duchenne muscular dystrophy.

Using a micropipette aspiration technique, erythrocyte membrane shear elastic modulus was determined for 23 patients with Duchenne muscular dystrophy, for 14 female carriers, and for three control groups (age matched boys and adult males and females). On average the elastic modulus was slightly greater than normal for both affected males and female carriers. However, there was overlap in the values from all groups. The decreased deformability of dystrophic membranes demonstrated by the test is not great enough to be used for carrier detection nor to make the possibility of prenatal diagnosis likely.

Adult↗

PubMed2006

Strongly nonlinear wave dynamics in a chain of polymer coated beads.

Strongly nonlinear phononic crystals were assembled from a chain of Parylene-C coated steel spheres in a polytetrafluoroethylene holder. This system exhibits strongly nonlinear properties and extends the range of materials supporting sonic-vacuum-type behavior. The combination of a high density core and a soft (low elastic modulus) coating ensures a relatively low velocity of wave propagation. The bead contact interaction caused by the deformation of the Parylene coating can be described by classical nonlinear elastic Hertz theory with an effective value of the elastic modulus equal to 15 GPa for the contact interaction. Strongly nonlinear solitary waves excited by impacts were investigated experimentally and compared to chains composed of uniform steel beads. Fracture of the polymer coating was detected under relatively large pulse amplitude.

Journal Article↗

PubMed2003

Are uniform regional safety factors an objective of adaptive modeling/remodeling in cortical bone?

It has been hypothesized that a major objective of morphological adaptation in limb-bone diaphyses is the achievement of uniform regional safety factors between discrete cortical locations (e.g. between cranial and caudal cortices at mid-diaphysis). This hypothesis has been tested, and appears to be supported in the diaphyses of ovine and equine radii. The present study more rigorously examined this question using the equine third metacarpal (MC3), which has had functionally generated intracortical strains estimated by a sophisticated finite element model. Mechanical properties of multiple mid-diaphyseal specimens were evaluated in both tension and compression, allowing for testing of habitually tensed or compressed regions in their respective habitual loading mode ("strain-mode-specific" loading). Elastic modulus, and yield and ultimate strength and strain, were correlated with in vivo strain data from a previously published finite element model. Mechanical tests revealed minor variations in elastic modulus, and yield and ultimate strength in both tension and compression loading, while physiological strains varied significantly between the cortices. Contrary to the hypothesis of uniform safety factors, the MC3 has a broad range of tension (caudo-medial, 4.0; cranio-lateral, 37.7) and compression (caudo-medial, 5.7; cranio-lateral, 68.9) safety factors.

Adaptation, Physiological↗

PubMed1981

Elastic arteries in invertebrates: mechanics of the octopus aorta.

The aorta of the octopus, Octopus dofleini, is a highly distensible, elastic tube. The circumferential elastic modulus increases with inflation in the physiological range from abut 10(4) to 10(5) newtons per square meter. Rubber-like fibers have been isolated, apparently for the first time, from the aorta of an invertebrate. These fibers have an elastic modulus, like elastin, of about 4 x 10(5) newtons per square meter and are present in sufficient quantity to account for the elastic properties of the intact vessel under physiological conditions. Thus the circulatory system of an invertebrate animal provides an "elastic reservoir" (much like that of the vertebrate system), which increases the efficiency of the circulation.

Animals↗