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Elastic Properties (elastic + property)

Distribution by Scientific Domains

Polymers and Materials Science	26%
Medical Sciences	20%
Physics and Astronomy	16%
Engineering	12%
Earth and Environmental Science	9%
Life Sciences	6%
Chemistry	6%

Distribution within Polymers and Materials Science

Polymer Science & Technology General	50%
General & Introductory Materials Science	30%

Selected Abstracts

ASSESSMENT OF ELASTIC PROPERTIES OF ISOTROPIC PLATES BY DYNAMIC TESTS

EXPERIMENTAL TECHNIQUES, Issue 2 2010
L. Pagnotta
First page of article [source]

Nondestructive Evaluation of Elastic Properties of Concrete Using Simulation of Surface Waves

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2008
Jae Hong Kim
In this study, to evaluate information of a surface waveform beyond the simple wave velocity, artificial intelligence engines are employed to estimate simulation parameters, that is, the properties of elastic materials. The developed artificial neural networks are trained with a numerical database having secured its stability. In the process, the appropriate shape of the force,time function for an impact load is assumed so as to avoid Gibbs phenomenon, and the proposed principal wavelet-component analysis accomplishes a feature extraction with a wavelet transformed signal. The results of estimation are validated with experiments focused on concrete materials. [source]

Assessment of Elastic Properties of the Descending Thoracic Aorta By Transesophageal Echocardiography with Acoustic Quantification in Patients with a Stroke

ECHOCARDIOGRAPHY, Issue 8 2000
Seok-Min Kang M.D.
Previous studies have described the use of transesophageal echocardiography (TEE) with acoustic quantification (AQ) in assessing aortic elastic properties. We hypothesized that patients with a prior history of stroke (ST) may have a higher risk of atherosclerotic change in great vessels compared to nonstroke subjects (NST) and thus have decreased elastic properties. We assessed the elastic properties of the descending thoracic aorta (DTA) by TEE in ST patients and compared them with data in NST patients. Subjects included 31 with ST without any evidence of emboli originating from the heart (age 51 ± 10 years, M: F = 20: 11) and 25 age-matched NST (M: F= 8: 17). Patients with significant valvular heart disease including aortic and mitral regurgitation, left ventricular dysfunction (ejection fraction < 55%), and congenital heart disease were excluded. Compliance (C), distensibility (D), and stiffness index (SI) were measured using AQ and M-mode measurement at a level of the left atrium. We scored atherosclerotic risk factors (ARF) such as a history of diabetes, hypertension, smoking, hypercholesterolemia, and the presence of atheroma of DTA. There was no evidence of atheroma of DTA in NST. There were no significant differences in heart rate and systolic and diastolic blood pressure between ST and NST patients. Fractional area change (FAC) of DTA was significantly lower in ST than in NST patients (3.2 ± 1.6 vs 5.4 ± 2.5%, P= 0.000). ST patients had significantly lower C (1.2 ± 0.4 vs 1.5 ± 0.7 times 10 -3 cm2 mmHg -1, P= 0.039), lower D (0.8 ± 0.3 vs 1.5 ± 0.8 times 10 -3 mmHg -1, P= 0.000), and higher SI (10.3 ± 8.8 vs 5.3 ± 2.9, P= 0.006) than NST patients. ST patients without atheroma of DTA (n± 21) also had significantly lower C (1.1 ± 0.4 vs 1.5 ±0.7 times 10 -3 cm -2 mmHg -1, P= 0.038) and lower D (3.5 ± 1.4 vs 4.8 ± 2.4 times 10 -3 mmHg -1, P= 0.021) than NST patients. There was a significant positive correlation between SI and the score of ARF (r= 0.51, P= 0.000). The regional elastic properties of DTA measured by TEE with AQ and M-mode method were abnormal in ST. Therefore, TEE with AQ technique may have a possible clinical application for the detection of early atherosclerotic changes such as alteration of elastic properties in morphological normal DTA. [source]

Stress-Dependent Elastic Properties of Porous Microcracked Ceramics,

ADVANCED ENGINEERING MATERIALS, Issue 12 2009
Irina Pozdnyakova
Abstract Although ceramics are considered linear elastic materials, we have observed a non-linear pseudo-elastic behavior in porous cellular microcracked ceramics such as , -eucryptite. This is attributed to the evolution of microstructure in these materials. This behavior is particularly different from that of non-microcracked ceramics such as silicon carbide. It is shown that in microcracked materials two processes, namely stiffening and softening, always compete when a compressive external load is applied. The first regime is attributed to microcrack closure, and the second to microcracks opening, i.e. to a damage introduced by the applied stress. On the other hand rather a continuous damage is observed in the non-microcracked case. A comparison has been done between the microscopic (as measured by neutron diffraction) and the macroscopic stress-strain response. Also, it has been found that at constant load a significant strain relaxation occurs, which has two timescales, possibly driven by the two phenomena quoted above. Indeed, no such relaxation is observed for non-microcracked SiC. Implications of these findings are discussed. [source]

Prediction of the Elastic Properties of Polycrystalline Microcomponents by Numerical Homogenization

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Katja Jöchen
Polycrystalline microcomponents made of Stabilor®G, a dental alloy mainly consisting of gold, are examined in terms of their elastic properties. Finite element calculations of uniaxial tensile tests are carried out with ABAQUS so as to identify the characteristic parameters of the distribution of Young's modulus. It is shown that the statistics of mechanical properties observed experimentally can be estimated by using the finite element method. The findings are generalized to microcomponents consisting of crystals with a cubic symmetry. [source]

FEM-Simulation of Real and Artificial Microstructures of Mo-Si-B Alloys for Elastic Properties and Comparison with Analytical Methods,

ADVANCED ENGINEERING MATERIALS, Issue 10 2007
G. Biragoni
Various three phase microstructures of Mo-Si-B alloys were simulated in tensile loading conditions using a 2D finite element method to predict the elastic properties of the composite material. Voronoi structures with the same areal fraction of phases as the real microstructures have been generated and simulated similarly. Also, with these Voronoi structures a variation of grain or phase sizes, respectively, was carried out for different compositions in order to study on the elastic properties of the composite. Finally, a comparison was made over the whole temperature range between the above numerical methods, classical analytical approaches and experimentally determined values for Young's modulus E, shear modulus G and Poisson's ratio ,. [source]

Boson Peak, Elastic Properties, and Rigidification Induced by the Substitution of Nitrogen for Oxygen in Oxynitride Glasses

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2010
Nicolas F. Richet
The effects of the substitution of nitrogen for oxygen on the heat capacity and vibrational entropy of three yttrium aluminosilicate glasses with 0, 3.4, and 7.4 mol% Si3N4 have been investigated from 10 to 300 K. The partial molar heat capacity and entropy of Si3N4 calculated from these and previous measurements indicate stronger average bonding than for SiO2 units, whereas the values derived for Y2O3 are consistent with the dual network modifying and Al3+ charge-compensating role of yttrium. The low-frequency part of the vibrational densities of states g(,) and the boson peaks g(,)/,2 derived from the inversion of the heat capacities indicate that nitrogen rigidifies the TO4 (T=Si, Al) tetrahedral network and that yttrium hampers the librational motion of the AlO4 tetrahedra, which contribute to the excitations associated with the boson peak. Along with data reported previously for borate and silicate glasses, these results for oxynitrides show a general monotonically increasing relation between transverse acoustic velocities and the temperature of the calorimetric boson peak. Illustrating the universal phenomenology of the boson peak, all these data collapse on the same master curve when plotted in a reduced form. [source]

Cross-Linked Poly(, -caprolactone/D,L -lactide) Copolymers with Elastic Properties

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2002
Antti O. Helminen
Abstract Cross-linked , -caprolactone (CL) and D,L -lactide (DLLA) copolymers with elastic properties were synthesized in three steps. First, the monomers were copolymerized in ring-opening polymerization to obtain telechelic star-shaped oligomers with almost completely random monomer distribution. The oligomers were methacrylated with methacrylic anhydride in the second step and cured in a third. Molar CL/DLLA compositions of 30/70, 50/50, 70/30, 90/10, and 100/0 were used to obtain elastic structures with a wide range of properties. The effect of the average length of the copolymer block on the properties of the networks was evaluated with three different co-initiator contents (0.5, 1.0, and 2.0/100) in the oligomer synthesis. The oligomers were characterized by 13C NMR spectroscopy, size-exclusion chromatography (SEC), and differential-scanning calorimetry (DSC). The formation of elastic networks was confirmed by the absence of a flow region in dynamic mechanical analysis (DMA), the increase in Tg in DSC, and the full recovery of the sample dimensions after tensile testing. In addition, gel contents were high and the samples swelled in CH2Cl2. The networks possessed break stresses from 0.7,9.7 MPa with elongations from 80,350%. Networks with 100 or 90% of , -caprolactone retained their form in vitro for 12 weeks, but an increase in lactide content made the networks more vulnerable to hydrolysis. Water absorption of the polymers during hydrolysis. [source]

Surface Elastic Properties of Human Retinal Pigment Epithelium Melanosomes,

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2008
Senli Guo
Atomic force microscope (AFM) imaging and nanoindentation measurements in water were used to probe the mechanical properties of retinal pigment epithelium melanosomes isolated from 14-year-old and 76-year-old donors. Topographic imaging reveals surface roughness similar to previous measurements on dry melanosomes. Force-indentation measurements show different types of responses that were catalogued into four different categories. In these measurements no permanent surface damage of melanosomes was observed as revealed by imaging before and after indentation measurements. The indentation measurements that exhibited nearly elastic responses were used to determine the Young's modulus of melanosomes. The average Young's modulus values are similar for 14-year-old and 76-year-old melanosomes with a somewhat narrower distribution for the 14-year-old sample. These elastic modulus values are considerably higher than the modulus of organelles with cytoplasm (<1 MPa) and approaching values of the modulus of protein crystals (,100 MPa) indicating rather high packing density of biologic material in melanosomes. The width of the Young's modulus distributions is considerable spanning from few megapascals to few tens of megapascals indicating large heterogeneity in the structure. A fraction of the force curves cannot be described by the homogeneous elastic sample model; these force curves are consistent with ,10 nm structural heterogeneity in melanosomes. The approach-withdraw hysteresis indicates a significant viscoelasticity, particularly in the samples from the 14-year-old sample. Adhesion of the AFM probe was detected on ,3% and ,20% of the surface of 14-year-old and 76-year-old samples, respectively. In light of previous studies on these same melanosomes using photoelectron emission microscopy, this adhesion is attributed to the presence of lipofuscin on the surface of the melanosomes. This suggestion indicates that part of the difference in photochemical properties between the old and young melanosomes originates from surface lipofuscin. [source]

Electronic Structure Calculations for LaNi5 and LaNi5H7: Energetics and Elastic Properties.

CHEMINFORM, Issue 24 2003
L. G. Jr. Hector
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Elastic properties of dry clay mineral aggregates, suspensions and sandstones

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003
Tiziana Vanorio
SUMMARY The presence of clay minerals can alter the elastic behaviour of rocks significantly. Although clay minerals are common in sedimentary formations and seismic measurements are our main tools for studying subsurface lithologies, measurements of elastic properties of clay minerals have proven difficult. Theoretical values for the bulk modulus of clay are reported between 20 and 50 GPa. The only published experimental measurement of Young's modulus in a clay mineral using atomic force acoustic microscopy (AFAM) gave a much lower value of 6.2 GPa. This study has concentrated on using independent experimental methods to measure the elastic moduli of clay minerals as functions of pressure and saturation. First, ultrasonic P - and S -wave velocities were measured as functions of hydrostatic pressure in cold-pressed clay aggregates with porosity and grain density ranging from 4 to 43 per cent and 2.13 to 2.83 g cm,3, respectively. In the second experiment, P - and S -wave velocities in clay powders were measured under uniaxial stresses compaction. In the third experiment, P -wave velocity and attenuation in a kaolinite,water suspension with clay concentrations between 0 and 60 per cent were measured at ambient conditions. Our elastic moduli measurements of kaolinite, montmorillonite and smectite are consistent for all experiments and with reported AFAM measurements on a nanometre scale. The bulk modulus values of the solid clay phase (Ks) lie between 6 and 12 GPa and shear (,s) modulus values vary between 4 and 6 GPa. A comparison is made between the accuracy of velocity prediction in shaley sandstones and clay,water and clay,sand mixtures using the values measured in this study and those from theoretical models. Using Ks= 12 GPa and ,s= 6 GPa from this study, the models give a much better prediction both of experimental velocity reduction due to increase in clay content in sandstones and velocity measurements in a kaolinite,water suspension. [source]

Elastic properties of nanowires

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2010
Claus-Christian Röhlig
Abstract The elastic properties of metallic and semiconducting nanowires were analyzed by different techniques employing static and dynamic loads. The reliability of the methods is verified by analyzing well defined microstructures and a good agreement for the values of the Young's modulus determined by the different methods was achieved. For the investigated materials systems (Au, W, Si, InN), basically no differences in the Young's moduli were observed between microstructures, bulk material, and nanowires with radii of 20,300,nm. Microstructure, morphological undulation, defects, and contaminations, however, can drastically change the apparent Young's moduli of nanowires. Examples are given, where an apparent increasing or decreasing of the Young's modulus with decreasing diameter is caused by such effects. The same effects have also influence on the fracture strength in nanowires. While perfect Au nanowires exhibit fracture strengths exceeding the bulk values up to two orders of magnitude, any anomaly causes earlier failure. In addition, failure mechanisms are observed to be dependent on the microstructure. While single crystalline Au nanowires have shown a pure elastic deformation upon load, polycrystalline nanowires show a remarkable plastic deformation before breaking. [source]

Elastic properties and pressure-induced phase transitions of single-walled carbon nanotubes

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2003
S. Reich
Abstract We studied the structure of single-walled carbon nanotubes under hydrostatic pressure by first-principles calculations. The circular tubes collapse at high pressure (7 GPa) to a phase with an elliptical cross-section. The elliptical structure leads to the formation of diamond-like bonds between the tubes at the point of strongest curvature. The bulk modulus of the circular, ambient-pressure phase that we found from our calculations is very similar to graphite (37 GPa). The interlinked phase also shows graphite-like behavior in the low- and high-pressure range: between 3.5 and 6.5 GPa its compressibility is very large. We compare our theoretical predicitions to X-ray scattering and piston,cylinder experiments. [source]

Extension rheology of liquid-crystalline solution/layered silicate hybrids

POLYMER ENGINEERING & SCIENCE, Issue 4 2010
Gleb B. Vasilyev
The extension rheology of polymer/layered silicate composites based on liquid-crystalline (LC) solution of hydroxypropylcellulose (HPC) in oligomeric polyethyleneglycole (PEG) was studied. The HPC concentration was 60 wt%. Extension experiments have been carried out for materials in the different phase states. Compositions containing Na-montmorillonite (MMT) were prepared by a two-stage method. Final systems may be attributed to solutions of HPC in PEG, which intercalates into MMT galleries. The ordered domain structure of the LC matrix as well as hydrogen-bonded network between HPC and PEG molecules significantly reduce deformation at break and provide a strong nonlinear viscoelastic behavior at extension. Appearance of isotropic phase in solutions leads to a sharp drop of the elongation viscosity. The introduction of clay into LC solution only slightly affects the viscosity value but significantly suppresses the strain-hardening scale. In contrast, loading in biphasic state of HPC-PEG solution with even small amount (1 wt%) of MMT leads to the drastic viscosity increase that does not change in further growth of the filler concentration. Elastic properties of the systems under study demonstrate the similar behavior. This effect likely is caused by the interrelationship between deformability of the LC domain structure and the network strength formed by the clay particles. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers [source]

Elastic properties of two-dimensional quasicrystals

ACTA CRYSTALLOGRAPHICA SECTION A, Issue 4 2008
Hans Grimmer
Quasicrystals (QC) with two-dimensional quasiperiodic and one-dimensional periodic structure are considered. Their symmetry can be described by embedding the three-dimensional physical space VE in a five-dimensional superspace V, which is the direct sum of VE and a two-dimensional internal space VI. A displacement v in V can be written as v = u + w, where u,VE and w ,VI. If the QC has a point group P in VE that is crystallographic, it is assumed that w and a vector u,,VE lying in the plane in which the crystal is quasiperiodic transform under equivalent representations of P, inequivalent ones if the point group is 5-, 8-, 10- or 12-gonal. From the Neumann principle follow restrictions on the form of the phonon, phason and phonon,phason coupling contributions to the elastic stiffness matrix that can be determined by combining the restrictions obtained for a set of elements generating the point group of interest. For the phonon part, the restrictions obtained for the generating elements do not depend on the system to which the point group belongs. This remains true for the phason and coupling parts in the case of crystallographic point groups but, in general, breaks down for the non-crystallographic ones. The form of the symmetric 12 × 12 matrix giving the phonon, phason and phonon,phason coupling contributions to the elastic stiffness is presented in graphic notation. [source]

Full waveform seismic inversion using a distributed system of computers

CONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 11 2005
Indrajit G. Roy
Abstract The aim of seismic waveform inversion is to estimate the elastic properties of the Earth's subsurface layers from recordings of seismic waveform data. This is usually accomplished by using constrained optimization often based on very simplistic assumptions. Full waveform inversion uses a more accurate wave propagation model but is extremely difficult to use for routine analysis and interpretation. This is because computational difficulties arise due to: (1) strong nonlinearity of the inverse problem; (2) extreme ill-posedness; and (3) large dimensions of data and model spaces. We show that some of these difficulties can be overcome by using: (1) an improved forward problem solver and efficient technique to generate sensitivity matrix; (2) an iteration adaptive regularized truncated Gauss,Newton technique; (3) an efficient technique for matrix,matrix and matrix,vector multiplication; and (4) a parallel programming implementation with a distributed system of processors. We use a message-passing interface in the parallel programming environment. We present inversion results for synthetic and field data, and a performance analysis of our parallel implementation. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Contribution to the study of elastic properties of KGd(WO4)2:Er3+ single crystals by Brillouin spectroscopy

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2009
D. Kasprowicz
Abstract In this paper we present the study of the acoustic phonons propagating in Er3+ -doped KGd(WO4)2 single crystals by Brillouin spectroscopy. For the investigated crystals the velocities of the longitudinal and transverse acoustic phonons [100], [010], [001], [101] and [110] have been determined. Moreover, the values of the elastic constants: C22, C44 and C66 of Er3+ -doped KGd(WO4)2 single crystals have been estimated. It was revealed that the presence of the Er3+ -ions in KGd(WO4)2 crystals, for the used doping concentration 1 at% does not influence their elastic properties. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A theory for elastic properties of single crystals with microstructure and its application to diffusion induced segregation

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2008
T. Blesgen
Abstract In this article a general theory for elastically stressed single crystals in the presence of microstructure is presented and an explicit formula for the resulting non-linear stored mechanical energy is obtained. The optimal microstructure under applied stress is characterised and the optimal laminates are identified in 2D. The analysis is based on a sharp lower estimate of the energy that relies on relaxation. The new theory is then used to extend existing models for diffusion induced segregation (DIS) in the case of (Zn,Fe)S single crystals. Numerical simulations based on finite elements are carried out and the results are compared with former computations of the homogeneous case. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Classification of Compression Bandages: Practical Aspects

DERMATOLOGIC SURGERY, Issue 5 2008
HUGO PARTSCH MD
BACKGROUND Compression bandages appear to be simple medical devices. However, there is a lack of agreement over their classification and confusion over the use of important terms such as elastic, inelastic, and stiffness. OBJECTIVES The objectives were to propose terms to describe both simple and complex compression bandage systems and to offer classification based on in vivo measurements of subbandage pressure and stiffness. METHODS A consensus meeting of experts including members from medical professions and from companies producing compression products discussed a proposal that was sent out beforehand and agreed on by the authors after correction. RESULTS Pressure, layers, components, and elastic properties (P-LA-C-E) are the important characteristics of compression bandages. Based on simple in vivo measurements, pressure ranges and elastic properties of different bandage systems can be described. Descriptions of composite bandages should also report the number of layers of bandage material applied to the leg and the components that have been used to create the final bandage system. CONCLUSION Future descriptions of compression bandages should include the subbandage pressure range measured in the medial gaiter area, the number of layers, and a specification of the bandage components and of the elastic property (stiffness) of the final bandage. [source]

Simplified seismic analysis of asymmetric building systems

EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2007
Jui-Liang Lin
Abstract The paper reviews the uncoupled modal response history analysis (UMRHA) and modal pushover analysis (MPA) procedure in the analysis of asymmetric structures. From the pushover curves in ADRS format, showing the relationships of base shear versus roof translation and base torque versus roof rotation, a bifurcating characteristic of the pushover curves of an asymmetric structure is observed. A two-degree-of-freedom (2DOF) modal stick is constructed using lump mass eccentrically placed at the end of beam which is connected with the column by a rotational spring. By converting the equation of motion of a whole structure into 2DOF modal equations, all of the elastic properties in the 2DOF modal sticks can be determined accurately. A mathematical proof is carried out to demonstrate that the 2DOF modal stick is consistent with the single-degree-of-freedom (SDOF) modal stick at elastic state. The bifurcating characteristic of modal pushover curves and the interaction of modal translation and rotation can be considered rationally by this 2DOF modal stick. In order to verify the effectiveness of this proposed 2DOF modal stick, a two-storey asymmetric building structure was analysed by the UMRHA procedure incorporating this novel 2DOF modal sticks (2DMPA) and conventional SDOF modal sticks (SDMPA), respectively. The analytical results are compared with those obtained by nonlinear response history analysis (RHA). It is illustrated that the accuracy of the rotational response histories obtained by 2DMPA is much better than those obtained by SDMPA. Consequently, the estimations of translational response histories on flexible side (FS) and stiff side (SS) of the building structure are also improved. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Aortic Upper Wall Tissue Doppler Image Velocity: Relation to Aortic Elasticity and Left Ventricular Diastolic Function

ECHOCARDIOGRAPHY, Issue 9 2009
Soon Yong Suh M.D.
Background: Aortic stiffening contributes to the left ventricular (LV) afterload, hypertrophy, and substrate for diastolic dysfunction. It is also known that aortic elastic properties could be investigated with color tissue Doppler imaging (TDI) in aortic upper wall. The purpose of this study is to evaluate the relation of aortic upper wall TDI and aortic stiffness and other parameters of LV diastolic function. Methods: We examined aortic upper wall by TDI at the 3 cm above the aortic valves because of patient's chest discomfort or dyspnea. We excluded the patient with arterial hypertension or reduced left ventricular ejection fraction (LVEF) or significant valvular heart disease. So a total of 126 (mean age 53.8 ± 13.9 years, male 49.2%) patients were enrolled in this study and divided normal LV filling group (N = 31) and abnormal LV filling group (N = 95). Results: Aortic upper wall early systolic velocity and late diastolic velocity were not different between the two groups. Only aortic upper wall early diastolic velocity (AWEDV) was related to aortic stiffness index (r =,0.25, P = 0.008), distensibility (r = 0.28, P = 0.003), early diastolic (Em) (r = 0.45, P = 0.001), E/Em (r =,0.26, P = 0.003), and significantly reduced in abnormal LV filling group (6.19 ± 2.50 vs 8.18 ± 2.87, P = 0.001). Conclusions: AWEDV is decreased significantly in abnormal LV filling patients. It is statistically related to aortic stiffness, distensibility and parameters of abnormal LV filling, Em, E/Em. TDI velocity of the aortic upper wall can be a helpful tool for evaluating aortic stiffness, distensibility, and diastolic function. [source]

Assessment of Elastic Properties of the Descending Thoracic Aorta By Transesophageal Echocardiography with Acoustic Quantification in Patients with a Stroke

Impaired aortic elastic properties in patients with systemic sarcoidosis

EUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 2 2008
I. Moyssakis
Abstract Background, Systemic sarcoidosis (Sar) is a granulomatous disorder involving multiple organs. Widespread vascular involvement and microangiopathy are common in patients with Sar. In addition, subclinical cardiac involvement is increasingly recognized in patients with Sar. However, data on the effect of Sar on the elastic properties of the arteries and myocardial performance are limited. In this study we looked for differences in aortic distensibility (AoD) which is an index of aortic elasticity, and myocardial performance of the ventricles, between patients with Sar and healthy subjects. In addition, we examined potential associations between AoD and clinical, respiratory and echocardiographic findings in patients with Sar. Materials and methods, A total of 83 consecutive patients (26 male/57 female, mean age 51·1 ± 13·3 years) with Sar, without cardiac symptoms, were included. All patients underwent echocardiographic and respiratory evaluation including lung function tests. Additionally, 83 age- and sex-matched healthy subjects served as controls. AoD was determined non-invasively by ultrasonography. Results, AoD was lower in the Sar compared to the control group (2·29 ± 0·26 vs. 2·45 ± 0·20 ·10,6 cm2· dyn,1, P < 0·01), while left ventricular mass (LVM) was higher in the Sar group (221·3 ± 50·2 vs. 195·6 ± 31·3 g, P = 0·007). Furthermore, myocardial performance of both ventricles was impaired in the Sar group. Multivariate linear regression analysis in the total sample population demonstrated a significant and independent inverse relationship between AoD and the presence of Sar (P < 0·001). The same analysis in the Sar patients showed that AoD was associated significantly and independently with the stage of Sar, age, systolic blood pressure, LVM and myocardial performance of both ventricles. No significant relationship was found between AoD and disease duration, pulmonary artery pressure or lung function tests. Conclusions, Presence and severity of Sar are associated with reduced aortic distensibility, irrespective of the disease duration, pulmonary artery pressure and lung function. In addition, patients with Sar have increased LVM and impaired myocardial performance. [source]

Prediction of the Elastic Properties of Polycrystalline Microcomponents by Numerical Homogenization

FEM-Simulation of Real and Artificial Microstructures of Mo-Si-B Alloys for Elastic Properties and Comparison with Analytical Methods,

Variations in carotid arterial compliance during the menstrual cycle in young women

EXPERIMENTAL PHYSIOLOGY, Issue 2 2006
Koichiro Hayashi
The effect of menstrual cycle phase on arterial elasticity is controversial. In 10 healthy women (20.6 ± 1.5 years old, mean ±s.d.), we investigated the variations in central and peripheral arterial elasticity, blood pressure (carotid and brachial), carotid intima,media thickness (IMT), and serum oestradiol and progesterone concentrations at five points in the menstrual cycle (menstrual, M; follicular, F; ovulatory, O; early luteal, EL; and late luteal, LL). Carotid arterial compliance (simultaneous ultrasound and applanation tonometry) varied cyclically, with significant increases from the values seen in M (0.164 ± 0.036 mm2 mmHg,1) and F (0.171 ± 0.029 mm2 mmHg,1) to that seen in the O phase (0.184 ± 0.029 mm2 mmHg,1). Sharp declines were observed in the EL (0.150 ± 0.033 mm2 mmHg,1) and LL phases (0.147 ± 0.026 mm2 mmHg,1; F= 8.51, P < 0.05). Pulse wave velocity in the leg (i.e. peripheral arterial stiffness) did not exhibit any significant changes. Fluctuations in carotid arterial elasticity correlated with the balance between oestradiol and progesterone concentrations. No significant changes were found in carotid and brachial blood pressures, carotid artery lumen diameter, or IMT throughout the menstrual cycle. These data provide evidence that the elastic properties of central, but not peripheral, arteries fluctuate significantly with the phases of the menstrual cycle. [source]

Austenitic Stainless Steels from Quantum Mechanical Calculations,

ADVANCED ENGINEERING MATERIALS, Issue 4 2004
L. Vitos
Quantum mechanics is used to study the influence of the chemical composition on the elastic properties of austenitic stainless steels. Fe based alloys comprising approximately 15% Cr and 8% Ni are predicted to have the largest hardness among the usual austenitic steels, which, however, is associated with increased brittleness and susceptibility to various forms of localized corrosion. It is shown that few percent of additional Os or Ir to Fe15Cr8Ni alloy significantly improve on both of these shortcomings, without deteriorating the hardness. [source]

Three-dimensional models of elastostatic deformation in heterogeneous media, with applications to the Eastern California Shear Zone

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2009
Sylvain Barbot
SUMMARY We present a semi-analytic iterative procedure for evaluating the 3-D deformation due to faults in an arbitrarily heterogeneous elastic half-space. Spatially variable elastic properties are modelled with equivalent body forces and equivalent surface traction in a ,homogenized' elastic medium. The displacement field is obtained in the Fourier domain using a semi-analytic Green function. We apply this model to investigate the response of 3-D compliant zones (CZ) around major crustal faults to coseismic stressing by nearby earthquakes. We constrain the two elastic moduli, as well as the geometry of the fault zones by comparing the model predictions to Synthetic Aperture Radar inferferometric (InSAR) data. Our results confirm that the CZ models for the Rodman, Calico and Pinto Mountain faults in the Eastern California Shear Zone (ECSZ) can explain the coseismic InSAR data from both the Landers and the Hector Mine earthquakes. For the Pinto Mountain fault zone, InSAR data suggest a 50 per cent reduction in effective shear modulus and no significant change in Poisson's ratio compared to the ambient crust. The large wavelength of coseismic line-of-sight displacements around the Pinto Mountain fault requires a fairly wide (,1.9 km) CZ extending to a depth of at least 9 km. Best fit for the Calico CZ, north of Galway Dry Lake, is obtained for a 4 km deep structure, with a 60 per cent reduction in shear modulus, with no change in Poisson's ratio. We find that the required effective rigidity of the Calico fault zone south of Galway Dry Lake is not as low as that of the northern segment, suggesting along-strike variations of effective elastic moduli within the same fault zone. The ECSZ InSAR data is best explained by CZ models with reduction in both shear and bulk moduli. These observations suggest pervasive and widespread damage around active crustal faults. [source]

Seismic singularities at upper-mantle phase transitions: a site percolation model

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2004
Felix J. Herrmann
SUMMARY Mineralogical phase transitions are usually invoked to account for the sharpness of globally observed upper-mantle seismic discontinuities. We propose a percolation-based model for the elastic properties of the phase mixture in the coexistence regions associated with these transitions. The major consequence of the model is that the elastic moduli (but not the density) display a singularity at the percolation threshold of the high-pressure phase. This model not only explains the sharp but continuous change in seismic velocities across the phase transition, but also predicts its abruptness and scale invariance, which are characterized by a non-integral scale exponent. Using the receiver-function approach and new, powerful signal-processing techniques, we quantitatively determine the singularity exponent from recordings of converted seismic waves at two Australian stations (CAN and WRAB). Using the estimated values, we construct velocity,depth profiles across the singularities and verify that the calculated converted waveforms match the observations under CAN. Finally, we point out a series of additional predictions that may provide new insights into the physics and fine structure of the upper-mantle transition zone. [source]