SEARCH · PubMed Health

Results for “Elastic Modulus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources

PubMed1999

[Changes of biomechanical properties in goats at different times after ovariectomy].

This paper presents the changes of biomechanical properties in goats at different times after ovariectomy. 14 goats were randomly divided into three groups. These goats were ovariectomized and sacrificed at 180 days (n = 4), 360 days (n = 5) and 540 days (n = 5) after the operation. The right femur, tibia and metatarsus were taken out. The structure mechanical properties of femora were measured with the three-point bending method and those of metatarsus were measured with the compressing method. The material mechanical properties of flexure, compress and tensile strength in the compact bone specimens of femora and tibiae taken from broken ends were also measured. The results showed that the one-year group, compared with the half-year group, had all the bone geometric parameters decreased, but not statistically significant (P > 0.05); the elastic modulus of three-point bending of femora decreased by 23.27% and the others had no significant difference (P > 0.05); all the material parameters of flexurel, compress and tensile strength in compact bone specimens decreased, but only the ultimate strength of tibiae of flexure, compress and tensile strength decreased obviously (P < 0.05). The one and a half year group, compared with the one year group, had the bone density of femora and tibiae decreased, but not statistically significant (P > 0.05). All the bone geometric parameters of tibiae and the thickness of bone of femora increased (P < 0.05). The break load of three-point bending of femora increased (P < 0.05). Probably, it was related to the increase of the body weight in the one and a half year group. The elastic modulus and the ultimate strength decreased, but not statistically significant (P > 0.05). When compact bone specimens were used, the ultimate strength and elastic modulus of femora and tibiae in compress and the elastic module of tibiae in flexure decreased obviously (P < 0.05); and the others had no significant changes (P > 0.05). This study indicated that the degree of osteoporosis in ovariectomized goats increased at half a year, one year, and one and a half year postoperation, and hence suggested that the ovariectomized goat be a pretty useful big animal model of osteoporosis.

Animals↗

PubMedDate not supplied

Effects of cavity configuration on composite restoration.

This study evaluated the effects of various cavity configurations on the bond strength, microleakage, flexural strength and elastic modulus of a hybrid (Clearfil AP-X) and a microhybrid (Esthet-X) composite restorative. After the specimens were made with C-factors of less than 1, 2.4 and 3.4, flexural strength and elastic modulus were evaluated in three-point bending using a mechanical testing machine. Fragments of the fractured specimens were selected randomly and the fracture surfaces were examined in SEM. To evaluate the microtensile bond strength and microleakage of composite restorations in bovine cavities, C-factors (ratio of bonded to non-bonded cavity surface) were controlled as 1.0, 2.3, 3.0 and 3.7. All specimens were stored in distilled water at 37 degrees C for 24 hours and tested in a universal testing machine (EZ Test, Shimadzu, Japan). For the microleakage test, teeth with restorations were stained with silver nitrate and examined by two examiners under a stereomicroscope at 40x magnification. The hybrid composite showed higher mechanical properties than the microhybrid composite. The flexural strength and elastic modulus of both composites decreased when polymerized under greater constraint, that is, with increasing C-factor. Mean microtensile bond strength to dentin was also decreased with increasing C-factor for both types of composites. Microleakage scores for the hybrid composite restorations were generally higher than the microhybrid composite.

Analysis of Variance↗

PubMed2001

Plasticisation of amylodextrin by moisture. Consequences for compaction behaviour and tablet properties.

PURPOSE: Amylodextrin, a starch-based controlled release excipient, spontaneously absorbs moisture during storage. The aim of this study was to investigate plasticisation of amylodextrin by moisture and its effect on compaction and tablet characteristics. METHODS: The glass transition temperature (T(g)) of amylodextrin powders with moisture fractions (x(w)) 0.070<x(w)<0.40 was studied by conventional and modulated DSC. Elastic modulus and yield stress were determined from compressive stress-strain experiments. Compaction behaviour was studied at 3 and 300 mm/s using a compaction simulator. RESULTS: The T(g) of amylodextrin-water blends showed a smooth reduction with increasing x(w), equalling room temperature at x(w)=0.19. Experimentally obtained T(g) values were close to temperatures as predicted by the Gordon-Taylor/Kelley-Bueche model and the modified Couchman-Karasz model. The elastic modulus decreased steeply between x(w)=0.17 and 0.23. Compaction experiments showed that moisture facilitated consolidation due to increasing powder compressibility and reduced compact relaxation. However, at x(w)=0.23, compressibility was reduced and relaxation significantly higher due to the rubbery character of this powder. Consequently, the lowest tablet porosities were obtained around x(w)=0.15. Although decreasing porosities enhanced tablet strengths, the maximum obtainable tablet strengths decreased with moisture due to reduced particle bonding and lowering of the elastic modulus. CONCLUSION: Moisture largely affects the visco-elastic and compaction characteristics of amylodextrin. Hence, control over moisture content is essential to produce tablets with reproducible porosity, strength and dissolution characteristics.

Calorimetry, Differential Scanning↗

PubMed2001

The influence of bone volume fraction and ash fraction on bone strength and modulus.

Although bone strength and modulus are known to be influenced by both volume fraction and mineral content (ash fraction), the relative influence of these two parameters remains unknown. Single-parameter power law functions are used widely to relate bone volume or ash fraction to bone strength and elastic modulus. In this study we evaluate the potential for predicting bone mechanical properties with two-parameter power law functions of bone volume fraction (BV/TV) and ash fraction (alpha) of the form y = a(BV/TV)(b) alpha(c) (where y is either ultimate strength or elastic modulus). We derived an expression for bone volume fraction as a function of apparent density and ash fraction to perform a new analysis of data presented by Keller in 1994. Exponents b and c for the prediction of bone strength were found to be 1.92 +/- 0.02 and 2.79 +/- 0.09 (mean +/- SE), respectively, with r(2) = 0.97. The value of b was found to be consistent with that found previously, whereas the value of c was lower than values previously reported. For the prediction of elastic modulus we found b and c to be 2.58 +/- 0.02 and 2.74 +/- 0.13, respectively, with r(2) = 0.97. The exponent related to ash fraction was typically larger than that associated with bone volume fraction, suggesting that a change in mineral content will, in general, generate a larger change in bone strength and stiffness than a similar change in bone volume fraction. These findings are important for interpreting the results of antiresorptive drug treatments that can cause changes in both ash and bone volume fraction.

Biomechanical Phenomena↗

PubMed2001

Development of Ag-Pd-Au-Cu alloys for multiple dental applications. Part 2. Mechanical properties of experimental Ag-Pd-Au-Cu alloys containing Sn or Ga for ceramic-metal restorations.

Eighteen Ag-Pd-Au-Cu alloys, consisting of nine Ag-Pd-Au-Cu mother compositions (Pd: 20, 30 or 40%, Au: 20%, Cu: 10, 15 or 20%, Ag: balance) containing either 5% Sn or 5% Ga as an additive metal, were experimentally prepared. Tensile strength, proof stress, elongation, elastic modulus, and Vickers hardness of these alloys were evaluated to clarify the potential of these alloys for use as ceramic-metal restorations as well as the effects of the Pd and Cu contents on their mechanical properties. The tensile strength, proof stress, elongation, elastic modulus and Vickers hardness of the 18 experimental alloys were in the range of 410.0-984.0 MPa, 289.7-774.3 MPa, 2.2-23.7%, 81.3-123.0 GPa and 135.7-332.3 HV1, respectively. Ten of the 18 experimental alloys can be used for ultra-low fusing ceramics based on their proof stress, elastic modulus, elongation and hardness. Between the Ga- and Sn-added alloys, differences in tensile strength, proof stress, elongation and hardness were found at several Ag-Pd-Au-Cu compositions.

Analysis of Variance↗

PubMed1987

The variation of sonic plesio-velocity in dose dependent lathyritic rabbit femurs.

It has been hypothesized that the origin of the increased elastic modulus of mineralized bone compared with the demineralized bone matrix is in the higher crosslinking density of the collagen in bone. Osteolathyrism is ascribed to an inhibition of crosslinking of the collagen by the lathyrogen and should be accompanied by a decrease in the elastic modulus of the bone. Dose dependent osteolathyrism was induced by varying the amount of BAPN ingested per day by young New Zealand white rabbits until they were mature. The femurs exhibited dose dependent properties, including wet bone density and sonic plesio-velocity in the radial direction. It was found that there is no minimum critical dose. Even though no overt osteolathyritic stigmata could be observed, both the sonic properties and the wet bone density could be affected at any dose level. The sonic plesio-velocity and the longitudinal elastic modulus decreased with BAPN dose level, most rapidly at the lower dose levels and then less so at higher dosages. Since BAPN acts to inhibit the crosslinking density, it appears that the elastic moduli of bone are dependent on the crosslinking density.

Aminopropionitrile↗

PubMed2004

Comparison of three brands of round stainless steel wires used in the Begg and tip-edge techniques.

OBJECTIVE: To compare the properties of three brands of stainless steel orthodontic wires: "Bow-Flex Wire", "TP Original Wire Premier Plus" and "Australian Wire Special Plus". METHOD: The surface appearance, stiffness, elastic modulus and relaxation of coiled and straight round wires in four diameters 10.016 inch, 0.018 inch, 0.020 inch and 0.022 inch) were compared. RESULTS: "Australian Wire Special Plus" wire had a rougher surface than "Bow-Flex" and "TP Original Wire Premier Plus" wires. For all diameters "Australian Wire Special Plus" coiled wire was stiffer, had a higher elastic modulus, and lower relaxation than the corresponding "Bow-Flex" and "TP Original Wire Premier Plus" wires. All coiled samples were stiffer and had a higher elastic modulus than corresponding straight wires from the same manufacturer. CONCLUSION: "Australian Wire Special Plus" 0.016 inch coiled wire is recommended for the initial treatment phase in the Begg and the Tip-Edge techniques. Either coiled or straight 0.018 inch, 0.020 inch or 0.022 inch wires from both manufacturers are suitable for phases II and III in both techniques.

Dental Alloys↗

PubMedDate not supplied

[Changes in the elastic properties of lipid bilayers as a result of different procedures].

The bilayer elasticity modulus approximately E perpendicular is sensitive to alternative electrical field, addition of different detergents and proteins incorporation. The detergents modify the value E1APPROXIMATELY E perpendicular] several times, the kinetics of this effect is more frequently biphasic and its shape and time parameters are characterized with a considerable dispersion; in general the [approximately E perpendicular] value increase for soft membranes and decrease for the membranes and high elasticity modulus. The proteins incorporation as well as the destruction of the membrane is accompanied with the general structure transition of the whole membrane. The measurement of the elasticity modulus is an effective test of protein incorporation in bilayers.

Cetrimonium Compounds↗

PubMed1991

Elastography: a quantitative method for imaging the elasticity of biological tissues.

We describe a new method for quantitative imaging of strain and elastic modulus distributions in soft tissues. The method is based on external tissue compression, with subsequent computation of the strain profile along the transducer axis, which is derived from cross-correlation analysis of pre- and post-compression A-line pairs. The strain profile can then be converted to an elastic modulus profile by measuring the stresses applied by the compressing device and applying certain corrections for the nonuniform stress field. We report initial results of several phantom and excised animal tissue experiments which demonstrate the ability of this technique to quantitatively image strain and elastic modulus distributions with good resolution, sensitivity and with diminished speckle. We discuss several potential clinical uses of this technique.

Abdomen↗

PubMed2004

Increased stiffness of the carotid wall material in patients with spontaneous cervical artery dissection.

BACKGROUND AND PURPOSE: The cause of spontaneous cervical artery dissection (sCAD) is largely unknown. An underlying connective tissue disorder has often been postulated, but arterial mechanical properties have rarely been studied. The study aim was to determine the elastic properties of a cervical artery, the common carotid artery, and a distal muscular artery, the radial artery in sCAD patients. METHODS: We studied 32 patients with previous sCAD (median delay: 2.2 years) and 32 control subjects with similar age and blood pressure. Internal diameter, intima-media thickness, distensibility, and Young's elastic modulus were determined at the site of the right and left common carotid arteries and the radial artery using noninvasive high-resolution echotracking systems. RESULTS: In patients with previous sCAD, cross-sectional distensibility and compliance of the affected carotid artery did not differ from those of the contralateral carotid artery. Young's elastic modulus (ie, the stiffness of the wall material) was 58% higher (0.44+/-0.32 versus 0.28+/-0.15 kPa.10(3), P<0.001) and circumferential wall stress was 14% higher (56+/-12 versus 49+/-12 kPa, P<0.001) in sCAD patients than in controls. The highest tertile of common carotid artery Young's elastic modulus was associated with an 8-fold higher risk of sCAD. Aortic stiffness, assessed from the carotid-femoral pulse wave velocity, and radial artery parameters did not differ between sCAD and controls. CONCLUSIONS: Carotid arteries, but not aorta and radial artery, displayed abnormal elastic properties in sCAD patients. Higher stiffness of carotid wall material and circumferential wall stress could increase the risk of dissection in these patients.

Adult↗

PubMed1988

Analysis of the effects of pH and tensile deformation on the small-deformation modulus of calf skin.

A dynamic technique was used to measure the elastic modulus of the reticular dermis of calf skin at a small (0.1%), non-perturbing oscillating deformation. The elastic modulus increases by over an order of magnitude when the tissue is stretched by only 10% before the measurement is made. The results are interpreted by a stochastic model of fiber orientation that includes the orientation of fibers and their straightening out from slack configurations into the load-bearing structure. An equation is derived that accurately describes the course of the modulus-extension curve over a range of pH from 3 to 11, and allows the calculations of the properties and configurations of the slack fibers. One of these is the Young's modulus of a fiber, which agrees well with the previous determinations in neutral medium.

Animals↗

PubMed1999

Ultrasonographic measurement of the mechanical properties of the sole under the metatarsal heads.

The sole under the metatarsal heads functions as a shock absorber during walking and running. The mechanical properties of the sole provide the primary defense against the development of metatarsalgia and foot ulceration. However, limited information about these properties has been documented. In this study, we used ultrasonography to evaluate the mechanical properties, including unloaded thickness, compressibility index, elastic modulus, and energy dissipation ratio, of the sole in 20 healthy subjects. The unloaded thickness decreased progressively from the first to the fifth metatarsal heads, with values of 1.50, 1.36, 1.25, 1.14, and 1.04 cm. The sole under the first metatarsal head had the greatest values for the compressibility index and elastic modulus (55.9% and 1.39 kg/cm2), and the sole under the third metatarsal head had the smallest values (50.8% and 1.23 kg/cm2). The sole under the fifth metatarsal head had the greatest energy dissipation ratio (33.7%), followed by that under the third, second, first, and fourth metatarsal heads. Multivariate adjusted linear regression showed that the unloaded thickness, compressibility index, and elastic modulus values increased significantly with age and body weight (p < 0.05) and that the energy dissipation ratio increased significantly with body weight (p < 0.05)

Adolescent↗

PubMedDate not supplied

Biological thermal detection: micromechanical and microthermal properties of biological infrared receptors.

Bioinspired design of biomimetic sensors relies upon the complete understanding of properties and functioning of biological analogues in conjunction with an understanding of their microstructural organization at various length scales. In the spirit of this approach, the microscopic properties of infrared (IR) receptors of snakes with "infrared vision" were studied with scanning thermal microscopy and micromechanical analysis. Low surface thermal conductivity of 0.11 W/(m K) was measured for the IR receptor surfaces as compared to the nonspecific skin areas. This difference in surface thermal conductivity should result in a significant local temperature gradient around the receptor areas. Micromechanical analysis showed that pit organs were more compliant than surrounding skin areas with an elastic modulus close to 40 MPa. In addition, the maximum elastic modulus was detected for the outermost layer with gradually reduced elastic resistance for the interior. The porous microstructure of the underlying tissue combined with the highly branched microfibrillar network (Biomacromolecules 2001, 2, 757) is thought to be responsible for such a combination of biomaterial properties. Considering these biomaterials features, we postulated a possible design of an artificial photothermal detector inspired by the microstructure of natural receptors. This bioinspired design would include a microfabricated cavity filled with an ordered lattice of microspheres with a gradient periodicity from the surface to the interior. Such a "photonic cavity" could provide an opportunity for multiple scattering at wavelength tuned to 8-12 microm as a range of highest sensitivity.

Animals↗

PubMed2004

Correlating the mechanical properties to the mineral content of carious dentine--a comparative study using an ultra-micro indentation system (UMIS) and SEM-BSE signals.

The deterioration of the mechanical properties of carious dentine was assumed to be associated with the decrease in mineral content due to the carious process. This study aimed to compare the mechanical properties of carious dentine studied by an ultra-micro-indentation-system (UMIS) and the mineral content determined using backscattered scanning electron (BSE) imaging. Eight axial sectioned and fine polished primary molar teeth with untreated carious dentine were measured for hardness and elastic modulus using the UMIS. On each specimen two centrally located linear arrays of indentations were made from the pulp to lesion cavity floor, followed by the capture of a BSE image using a solid-state detector. The BSE intensity at the same spot as the indentation array on each specimen was analysed and compared to the UMIS results. The results show that the mechanical properties of dentine are dependent on its mineral content. The decrease in mechanical properties of carious dentine, namely hardness and elastic modulus are directly linked to the reduction in its mineral content (r2 = 0.93 and 0.92, respectively). The relationship between dentine hardness and elastic modulus values (y) can be expressed as an exponential function of the mineral content in wt.% (x) that is y = ae(bx).

Child↗

PubMed1993

Non-invasive measurement of pulsatile vessel diameter change and elastic properties in human arteries: a methodological study.

A recently developed ultrasound phase-locked echo-tracking system makes it possible to measure non-invasive pulsatile vessel diameter changes, and, in combination with blood-pressure measurement, to calculate pressure strain elastic modulus (Ep) and stiffness (beta). The reproducibility in measurements of pulsatile diameter changes with this system was evaluated. Also the precision of indirect blood-pressure measurements, as compared to the simultaneously measured intra-arterial blood pressure was tested. The resulting reproducibility in pressure strain elastic modulus (Ep) and stiffness (beta) was evaluated. Intra-observer variabilities in measuring pulsatile diameter changes were 16% for the abdominal aorta, 10% for the common carotid artery, and 15% for the common femoral artery, respectively. Intra-observer variabilities for Ep and beta were 21% for both in the abdominal aorta, 17% for both in the common carotid artery, and 18% for both in the common femoral artery, respectively. There were only small differences in indirect and direct measurement of systolic blood pressure, whereas indirect blood pressure measurement systematically overestimated the diastolic blood pressure, on average by 20%. The variabilities in indirect blood pressure measurements were 2% for the systolic and 3% for the diastolic blood pressure, respectively. Inter-observer variability in the investigation of the common carotid artery was 10% for the pulsatile diameter changes, and 21% and 23% for Ep and beta, respectively. Thus, the echo-tracking system represents a reliable system for estimation of pressure strain elastic modulus and stiffness. However, Ep and beta are systematically underestimated by 25-30%, when used in combination with indirect blood pressure measurements.

Adult↗

PubMed2005

Elastic properties of hoof horn on different positions in the bovine claw.

Hind claws of 15 adult, sound Fleckvieh cows were used for material analysis. The elastic modulus was tested in tension tests according to EN ISO 527 and ASTM D 638-03 at a universal material testing machine. Samples were taken from different segments of the bovine claw to find the differences in material properties. Samples orientation was parallel to the horn tubules and transversal, respectively. Dry matter of the test samples was determined at the time of testing. Elastic modulus values were highest with mean = 659.7 N/mm2 at the dorsal wall. Values dropped axial to 416.3 N/mm2, abaxial to 343.9 N/mm2 for longitudinal (parallel) samples and to 433.1 N/mm2 for transversal samples. The elastic modulus of the sole segment was found to be 172.1 N/mm2. No difference was calculated neither between right and left feet, lateral and medial claws, nor between longitudinal and transversal samples.

Animals↗

PubMed2004

A phenomenological model for predicting fatigue life in bovine trabecular bone.

Cyclic loading of bone during daily activities can lead to fatigue degradation and increased risk of fracture in both the young and elderly population. Damage processes under cyclic loading in trabecular bone result in the reduction of the elastic modulus and accumulation of residual strain. These effects increase with increasing stress levels, leading to a progressive reduction in fatigue life. The present work analyzes the effect of stress and strain variation on the above damage processes in bovine trabecular bone, and develops a phenomenological model relating fatigue life to the imposed stress level. The elastic modulus reduction of the bone specimens was observed to depend on the maximum compressive strain, while the rate of residual strain accumulation was a function of the stress level. A model was developed for the upper and lower bounds of bone elastic modulus reduction with increasing number of cycles, at each stress range. The experimental observations were described well by the model. The model predicted the bounds of the fatigue life with change in fatigue stress. The decrease in the fatigue life with increasing stress was related to corresponding increases in the residual strain accumulation rates at the elevated stress levels. The model shows the validity of fatigue predictions from relatively few cyclic experiments, by combining trends observed in the monotonic and the cyclic tests. The model also presents a relatively simple procedure for predicting the endurance limit for bovine trabecular bone specimens.

Adaptation, Physiological↗

PubMed1998

Mechanical properties of a self-assembling oligopeptide matrix.

We have begun studies of a novel type of biomaterial derived from a recently-discovered class of ionic self-complementary oligopeptides. These short peptides (typically 8, 16, 24, or 32 amino acid residues with internally-repeating sequences) self-assemble in aqueous salt solution into three-dimensional matrices capable of favorable interactions with cells, and offer promise for useful bioengineering design based on rational changes in sequence. In this paper we present preliminary results on mechanical properties, combining experimental and theoretical approaches, of one particular example of these peptide materials, EFK8. The static elastic modulus was measured using an apparatus designed to allow sample fabrication and mechanical testing in the same system with the sample in aqueous solution. The material microstructure was examined by SEM and the measurements interpreted with the aid of a model for cellular solids. Values for the elastic modulus increased from 1.59 +/- 0.06 to 14.7 +/- 1.0 kPa for peptide concentrations increasing from 2.7 to 10 mg ml-1. SEM photographs showed the microstructure to consist of a relatively homogeneous lattice with fiber thickness of 10-30 nm independent of peptide concentration, but with fiber density increasing with peptide concentration. This behavior is consistent with scaling predictions from the cellular solids model and yields an estimate for the individual fiber elastic modulus in the range of 1-20 MPa. We therefore have provided some initial physical principles for guiding improvement of the mechanical properties of these new materials.

Biomechanical Phenomena↗