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Results for “Elastic Modulus”

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PubMed1990

The elastic modulus of fibrin clots and fibrinogen gels: the effect of fibronectin and dithiothreitol.

The elastic modulus (G') of factor XIIIa induced fibrinogen gels was found to be substantially lower than the G' of fibrin gels that were formed by clotting fibrinogen with thrombin. The addition of fibronectin and/or the reducing reagent dithiothreitol (DTT) to the factor XIIIa coagulation mixture led to the formation of a weaker gel structure, while the rigidity of thrombin induced clots was not appreciably affected by the inclusion of the DTT but increased somewhat in the presence of fibronectin. The reasons for the differing clot rigidities are discussed in terms of biochemical mechanisms.

Dithiothreitol↗

PubMedDate not supplied

The nano-hardness and elastic modulus of carious and sound primary canine dentin.

This study measured the nanohardness and elastic modulus- of carious and sound primary canine dentin and compared the values obtained under the lesion and in sound regions of incisal, center and cervical areas, and outer, middle and inner layers. Six extracted or exfoliated primary canines (three with dentin caries on both proximal surfaces and three sound teeth) were mesiodistally sectioned parallel to the long axis of the tooth and polished. The hardness (H), plastic hardness (PH) and Young's modulus (Y) were measured by a nano-indentation tester. Ten indentations at intervals of 10 microm on all regions, areas and layers were made using a load of 1 gf for one second. All indentations were observed using a microscope attached to the tester. All data were statistically analyzed using ANOVA and Scheffe's test at p < 0.05. For sound teeth, the H, PH and Y values of the inner layer were significantly lower than the outer and middle layers in all areas. The H, PH and Y values of the cervical area were significantly lower than the incisal area in almost all of the outer, middle and inner layers. For carious teeth, the H, PH and Y values of the inner layer were significantly lower than the outer and middle layers in the center area. For the center area, the H, PH and Y values under the lesion were significantly lower than sound teeth in the outer and middle layers. Dentin under the lesion, near the pulp and cervical areas showed significantly lower nanohardness and elasticity.

Analysis of Variance↗

PubMed1980

The elastic modulus of soft denture liners.

Under certain circumstances, e.g., when treating "denture sore mouth" or after the provision of immediate dentures, dentures may be lined with soft rubberlike materials which have Young's moduli within the range congruent to 10(5) N m-2. Measurement of the compression modulus Ec of such soft liners is described and Gent and Lindley's method of calculating Young's modulus E was evaluated. It was established that the Young's modulus may be calculated using: Ec = E(1 + 2kS2), where k = 1 for soft rubbers, and for disks S is a shape factor and = radius/2 X thickness. It is also shown that Young's modulus is a linear function of log(rate of strain) for both tension and compression measurements. When gellation has occurred subsequent to mixing there is an increase in Young's modulus due to loss of ethanol. When immersed in brine the elastic modulus remains approximately constant from a day to a week or longer.

Denture Liners↗

PubMed2005

Elastic modulus of resin-based dental restorative materials: a microindentation approach.

This research aimed to determine the elastic modulus of resin-based dental composite restoratives using the microindentation test method. Results were then compared with those obtained with the ISO three-point bending test method. Five materials from the same manufacturer (3M ESPE) were selected for the study. They included microfill (A110), minifill (Z100 and Filtek Z250), poly-acid modified (F2000), and flowable (Filtek Flowable [FF]) composites. The indentation moduli of the composites were determined using a custom-designed microindentation test set up after conditioning in water at 37 degrees C for 1 week and 1 month. The indentation test was carried out at peak load of 10 N and Oliver & Pharr's method was used to determine the maximum projected contact area. Data was analyzed using ANOVA/post-hoc Scheffe's test at significance level 0.05 and Pearson's correlation at significance level 0.01. The mean indentation modulus ranged from 5.80 to 15.64 GPa and 5.71 to 15.35 GPa at 1 week and 1 month, respectively. At both time periods, the indentation modulus of Z100 was significantly higher than all other materials. F2000 was significantly higher than Z250, which was significantly stiffer than A110 and FF. The rankings were in good agreement with the ISO flexural test. A significant, positive, and strong correlation (r = 0.93 and 0.94 at 1 week and 1 month, respectively) in modulus between ISO three-point bending and microindentation test methods was observed. In view of the small specimen size and good reproducibility, the microindentation reflects a potential test method for determining the elastic properties of dental composite restoratives.

Composite Resins↗

PubMed2001

Determination of elastic modulus of dentin by small spherical diamond indenters.

A nano-indentation test was applied to determine elastic modulus (E) and hardness (H) of dentin. Three spherical indenters with nominal radii of 20, 5 and 1 microns were used and load/partial-unload cycles were repeated. Each cycle provided E and contact pressure or Meyer's hardness. The plot of contact pressure versus penetration depth was converted into a normalized indentation stress-strain relationship, which was used to select the optimum maximum indentation force for each indenter. The results were compared with those determined by the conventional triangular pyramidal (Berkovich) indenter technique. The comparable E value, irrespective of radius, was 19.5-20.9 GPa and the 1 micron indenter was able to provide E values of peritubular (28.0 GPa) and intertubular dentin (14.9 GPa). The H values generated with the Berkovich indentation technique were comparable to those determined by the spherical indenter technique at indentation strains of 0.9 and 0.5 for the 1 and 5 microns indenters.

Adolescent↗

PubMed1995

A New Pressure Probe Method to Determine the Average Volumetric Elastic Modulus of Cells in Plant Tissue.

A new in vivo method was used to determine an average volumetric elastic modulus ([epsilon]ave) for nongrowing cells in plant tissue. This method requires that both the relative transpiration rate, T, of the tissue and the average turgor pressure decay rate, (dP/dt)ave, of the cells are measured after the water source is removed from the plant tissue. Then [epsilon]ave is calculated from the equation [epsilon]ave = (-dP/dt)ave/T. This method was used to determine [epsilon]ave for cortical cells in stems of pea seedlings (Pisum sativum L.). The results demonstrate that [epsilon]ave increases from virtually zero at low P (approximately 0.01MPa) to approximately 10 MPa at high P (approximately 0.5 MPa). Analyses of the results indicate that the relationship between [epsilon]ave and P can be approximated by a linear function and more accurately approximated by a saturating exponential function: [epsilon]ave = [epsilon][infinity symbol][1 - exp {-k(P - Po)}], where Po is a plateau pressure (approximately 0.01 MPa), k is a rate constant (approximately 7 per MPa), and [epsilon][infinity symbol] (approximately 10 MPa) is the hypothetical maximum value of [epsilon]ave as P -> [infinity symbol]. Solutions for the turgor pressure decay (due to transpiration) as functions of time and symplasmic water mass (after the water source is removed) are derived.

Journal Article↗

PubMed1994

The elastic modulus of dentine determined by static and dynamic methods.

The purpose of this investigation was to determine a static elastic modulus of dentine using a three point beam test and a dynamic modulus in the frequency range of 0.1 Hz and 10 Hz across a temperature range of 27-37 degrees C. At body temperature, the mean static modulus was 8.6 GPa, (standard deviation 0.86 GPa). The dynamic test produced a range of modulus values. At 0.1 Hz the modulus ranged from 14.3 to 15.2 GPa; for 1.0 Hz the range was 14.6-15.5 GPa and for 10 Hz the range was 14.9-15.8 GPa. The results are of value in the design and analysis of restorative materials.

Biomechanical Phenomena↗

PubMed2006

The bulk elastic modulus and the reversible properties of cell walls in developing Quercus leaves.

We examined the relationship between the bulk elastic modulus (epsilon) of an individual leaf obtained by the pressure-volume (P-V) technique and the mechanical properties of cell walls in the leaf. The plants used were Quercus glauca and Q. serrata, an evergreen and a deciduous broad-leaved tree species, respectively. We compared epsilon and Young's modulus of leaf specimens determined by the stretch technique at various stages of their leaf development. The results showed that epsilon increased from approximately 5 to 20 MPa during leaf development, although other potential determinants of epsilon such as the apoplastic water content in the leaf and the diameter of a palisade tissue cells remained almost constant. epsilon in these two species was similar at every developmental stages, although the apparent mechanical strength of the leaf lamina and thickness of mesophyll cell walls were greater in Q. glauca. There were significant linear relationships between Young's modulus and epsilon (P < 0.01; R (2) = 0.78 and 0.84 in Q. glauca and Q. serrata, respectively) with small y-intercepts. From these results, we conclude that epsilon is closely related to the reversible properties of the cell walls. From the estimation of epsilon based on a physical model, we suggest that the effective thickness of cell walls responsible for epsilon is smaller than the observed wall thickness.

Biomechanical Phenomena↗

PubMed1982

Water Relations of Seagrasses: STATIONARY VOLUMETRIC ELASTIC MODULUS AND OSMOTIC PRESSURE OF THE LEAF CELLS OF HALOPHILA OVALIS, ZOSTERA CAPRICORNI, AND POSIDONIA AUSTRALIS.

The stationary volumetric elastic modulus (epsilon(s)) of the leaf cells of three seagrasses (Halophila ovalis (R.Br.) Hook, Zostera capricorni Aschers, and Posidonia australis Hook f.) was evaluated from estimates of epsilon(s) plus intracellular osmotic pressure (epsilon(s) + II(i)) and II(i). The estimates of (epsilon(s) + II(i)) were made using a linear displacement transducer to measure very small changes in thickness of leaf tissue produced by changes in external osmotic pressure (II(o)). epsilon(s) increases with increasing turgor pressure in each of the species and the maximum values of epsilon(s) are: 22 megapascals for H. ovalis, 17 megapascals for Z. capricorni, and 51 megapascals for P. australis.There is a hysteresis in thickness changes versus changes in II(o) which indicates a hysteresis in the relationship between volume and turgor pressure. The hysteresis results in epsilon(s) being different for swelling and for shrinking cells over the same range of II(o) and this may be important in other aspects of plant-water relations.A new design of an apparatus employing a linear displacement transducer for measuring very small changes in tissue thickness is described. The new design has the advantages of virtually frictionless movement and a precision of 0.05 micrometer.

Journal Article↗

PubMed1984

The apparent elastic modulus of the juxtarticular subchondral bone of the femoral head.

An experiment was undertaken to obtain approximate values for the intrinsic elastic modulus of subchondral bone. Shallow spherical caps, with uniform and incrementally controlled thickness, were machined from subchondral bone in the weight-bearing regions of 11 fresh-frozen normal femoral head autopsy specimens. Under application of polar point loads, the measured deflections were compared with a corresponding analytical shell solution, thus allowing back-calculation of the apparent modulus. Analogous tests were performed on similarly shaped specimens of stock Plexiglas of known modulus in order to estimate the precision of the testing method. The aggregate results for subchondral bone showed that its intrinsic stiffness correlated inversely with nominal shell thickness, but even the thinnest (1.0 mm thick) of these shells had an apparent modulus (mean = 1.372 GN/m2, SD = 414 MN/m2) well below that generally accepted for "pure" cortical bone (about 14 GN/m2). This stiffness deficit was very likely due to the presence of histologically evident marrow spaces. However, the low apparent modulus values measured in this study may not be fully representative of complex in vivo behavior, because in the testing of excised shells there is no radial compressive stress transfer to underlying cancellous bone.

Cartilage, Articular↗

PubMed1992

Intraoperative measurement of the elastic modulus of the vocal fold. Part 2. Preliminary results.

This paper presents initial clinical experience using a device capable of measuring the transverse elastic modulus of the vocal fold. These initial results indicated that the device may be useful in determining stiffness inequalities between the vocal folds.

Adult↗

PubMed2005

The nano-hardness and elastic modulus of sound deciduous canine dentin and young premolar dentin--preliminary study.

The purpose of this study was to compare the nano-hardness and elastic modulus among deciduous and permanent dentin, buccal and lingual sides, incisal, center and cervical areas, and outer, middle and inner layers. Three premolars and three deciduous canines were bucco lingually (BL) sectioned, and three deciduous canines were mesio-distally (MD) sectioned parallel to the long axis at the center of the tooth. Hardness (H), plastic hardness (PH) and Young's modulus (Y) were measured using a nano-indentation tester. The H, PH and Y values from the deciduous canine dentin were significantly lower than those from the premolar dentin at most sites. For deciduous canine dentin, the H and PH values of the MD sectioned dentin were significantly higher than those of the BL sectioned dentin in many layers of many areas. Generally deciduous canine dentin had H, PH and Y values that decreased from outer toward the inner layers and significant differences were obtained among the layers in many areas. For MD sectioned deciduous canine and BD sectioned premolar dentin, the H, PH and Y values of the cervical area were significantly lower than those of the incisal and center areas in many layers. It is possible that optimum bonding may require different treatments for deciduous and permanent dentin and perhaps also for different intratooth locations.

Anisotropy↗

PubMed2002

Patients with coronary artery disease who present with chest pain have significantly elevated platelet contractile force and clot elastic modulus.

Rapid laboratory markers that correlate with patient risk would facilitate the decision making regarding admission of patients with chest pain (CP). Platelet contractile force (PCF) and clot elastic modulus (CEM) are elevated in patients undergoing coronary bypass grafting. This study assessed PCF, CEM, and platelet aggregation in patients presenting to the emergency department with chest pain (CP). Results were compared with fifty normal controls. Both the total group of CP patients (n = 100) and the subset of patients (n = 36) with documented coronary artery disease (CAD) had significantly elevated PCF and CEM, and significantly decreased platelet aggregation relative to normal (p <0.001 for the total group, p </=0.008 for patients with CAD). Patients with electrocardiographic evidence of ischemia had the highest PCF and CEM values of any patient group. Increased PCF and CEM were not due to higher platelet counts, and PCF did not differ by race.

Adult↗

PubMed1981

The influence of implant elastic modulus on the stress distribution around LTI carbon and aluminum oxide dental implants.

A three-dimensional finite element analysis (FEA) has been used to determine the effect of implant elastic modulus on stresses in tissues around LTI carbon and aluminum oxide dental implants. The finite element model was constructed to represent a baboon mandible containing a blade type dental implant. A three unit fixed bridge was modeled connecting the dental implant to a natural molar. The results of the study indicate that stress levels of approximately a factor of 3 lower in the crestal region can be expected for aluminum oxide implants when compared to the LTI carbon implants. It was also observed that the use of LTI carbon and aluminum oxide dental implants as an abutment in a fixed bridge results in a reduction of stresses in tissues around the natural tooth when compared to normal physiological stress levels.

Aluminum↗

PubMed2004

The gaussian curvature elastic modulus of N-monomethylated dioleoylphosphatidylethanolamine: relevance to membrane fusion and lipid phase behavior.

The energy of intermediates in fusion of phospholipid bilayers is sensitive to kappa(m), the saddle splay (Gaussian curvature) elastic modulus of the lipid monolayers. The value kappa(m) is also important in understanding the stability of inverted cubic (Q(II)) and rhombohedral (R) phases relative to the lamellar (L(alpha)) and inverted hexagonal (H(II)) phases in phospholipids. However, kappa(m) cannot be measured directly. It was previously measured by observing changes in Q(II) phase lattice dimensions as a function of water content. Here we use observations of the phase behavior of N-mono-methylated dioleoylphosphatidylethanolamine (DOPE-Me) to determine kappa(m). At the temperature of the L(alpha)/Q(II) phase transition, T(Q), the partial energies of the two phases are equal, and we can express kappa(m) in terms of known lipid monolayer parameters: the spontaneous curvature of DOPE-Me, the monolayer bending modulus kappa(m), and the distance of the monolayer neutral surface from the bilayer midplane, delta. The calculated ratio kappa(m)/kappa(m) is -0.83 +/- 0.08 at T(Q) approximately 55 degrees C. The uncertainty is due primarily to uncertainty in the value of delta for the L(alpha) phase. This value of kappa(m)/kappa(m) is in accord with theoretical expectations, including recent estimates of the value required to rationalize observations of rhombohedral (R) phase stability in phospholipids. The value kappa(m) substantially affects the free energy of formation of fusion intermediates: more energy (tens of k(B)T) is required to form stalks and fusion pores (ILAs) than estimated solely on the basis of the bending elastic energy. In particular, ILAs are much higher in energy than previously estimated. This rationalizes the action of fusion-catalyzing proteins in stabilizing nascent fusion pores in biomembranes; a function inferred from recent experiments in viral systems. These results change predictions of earlier work on ILA and Q(II) phase stability and L(alpha)/Q(II) phase transition mechanisms. To our knowledge, this is the first determination of the saddle splay (Gaussian) modulus in a lipid system consisting only of phospholipids.

Algorithms↗

PubMed2002

Platelet contractile force (PCF) and clot elastic modulus (CEM) are elevated in diabetic patients with chest pain.

AIMS: Platelet function and clot structure may be altered in diabetes. We have noted increased platelet contractile force (PCF) and clot elastic modulus (CEM) in patients presenting to the emergency department with chest pain. Twenty-six of the chest pain patients were diabetic. Here, we compare the PCF, CEM and platelet aggregation in diabetic chest pain patients, non-diabetic patients with chest pain and asymptomatic controls. PATIENTS AND METHODS: PCF, CEM and collagen whole blood aggregations were measured in 100 chest pain patients and 25 asymptomatic controls. RESULTS: Platelet concentrations for diabetic patients, non-diabetic patients and controls were identical. PCF was significantly (P < 0.05) elevated in diabetic chest pain patients (9.42 +/- 0.59 kdynes) vs. controls (7.40 +/- 0.32 kdynes). CEM in diabetic patients (29.96 +/- 2.19 kdynes/cm2) was significantly elevated relative to that in non-diabetic chest pain patients (25.22 +/- 0.84 kdynes/cm2) and normal controls (23.18 +/- 0.74 kdynes/cm2). Collagen-induced whole blood aggregation was decreased (P < 0.05) in diabetic chest pain patients vs. controls. PCF values (10.23 +/- 0.76 kdynes) in diabetic patients with haemoglobin A1c > 7% were higher than in any other group. CONCLUSION: PCF and CEM are elevated in diabetic chest pain patients. The significance of these laboratory findings awaits additional clinical studies.

Adult↗

PubMed1997

Incremental elastic modulus--a challenge to compliance.

Rectal compliance has theoretical and practical drawbacks resulting in wide variation in the reported normal values. Slope of stress-strain relation, a measure of rectal wall stiffness (Incremental elastic modulus; IEM) may be an effective alternative. The aim of this study was to compare IEM with rectal compliance during ramp inflation. In a group of 15 normal adults [Median age 51.5 years (range 31 to 74); 11 female and 4 male], these parameters were assessed at three rates of inflation, using a proctometrogram-catheter-balloon (PCB) complex and endorectal ultrasound scanner (7 Mhz; B & K) to measure intrarectal pressure and radius respectively. IEM had a linear relation with strain (Slope 33.55; R2 = 0.9815) in contrast to compliance (R2 = 0.0088). Series elastic component (SEC), a measure of passive viscoelasticity, was rate independent elasticity [Slope 1.02 (0.98 to 1.15); P = ns] and a rate dependent viscosity (P = 0.004; One way ANOVA). Both IEM and SEC were reproducible (R = 0.985; P < 0.01). This study emphasises the importance of rectal wall viscoelastic evaluation based on stress and strain rather than compliance.

Adult↗

PubMed1993

Measurement of elastic modulus of the bovine cornea by means of holographic interferometry. Part 1. Method and experiment.

Holographic interferometry of the cornea of fresh, enucleated bovine eyes placed in air was used for determination of the elastic modulus of the central part of the cornea. The high sensitivity of the method enables measurement of the radial distension of the cornea even for intraocular pressure (IOP) changes equal to 5 Pa (0.05 mbar or approximately 0.0375 mm Hg). The method of calculation of the tangent Young's modulus of the cornea Et, based on data obtained from double exposure as well as real-time holographic interferograms and on some geometrical data describing the form of the cornea are presented. The average value of Et amounting to 1.42.10(5) Pa was calculated from 2 interferograms of the same eye.

Animals↗