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Wave Velocity (wave + velocity)
Kinds of Wave Velocity Selected AbstractsInvolvement of Helicobacter pylori Infection and Impaired Glucose Metabolism in the Increase of Brachial,Ankle Pulse Wave VelocityHELICOBACTER, Issue 5 2007Hiroyuki Yoshikawa Abstract Background: The role of Helicobacter pylori in the pathogenesis of atherosclerosis remains controversial. The present study was designed to elucidate the pathogenic role of H. pylori in the early stages of atherosclerosis by measurement of brachial,ankle pulse wave velocity (baPWV) in relation to glucose metabolism. Materials and methods: baPWV level, anti- H. pylori antibody, fasting blood glucose (FBG), and glycosylated hemoglobin A1c (HbA1c) and other conventional risk factors for cardiovascular diseases were measured in 947 subjects who attended their annual medical check-up. Results: Multiple regression analyses indicated that age, gender (male), body mass index, FBG, systolic blood pressure, and smoking habits were each independently related to baPWV values. In younger subjects (30,49 years), H. pylori seropositivity was significantly correlated with an increase of baPWV levels (r = 0.100, p = .0445). baPWV values in the H. pylori- positive subjects with impaired glucose metabolism (IG: FBG , 110 mg/dL and/or HbA1c , 5.9%) were significantly greater than those in the H. pylori- negative subjects with IG (p = .0078). Furthermore, H. pylori- positive subjects with IG were at higher risk for increase of baPWV, in younger (r = 0.203, p < .0001) as well as in older subjects (50,69 years, r = 0.099, p = .0009). Conclusions: These results suggest that H. pylori seropositivity is a potential risk factor for increased baPWV levels, and that H. pylori infection accelerates the effect of IG on an increase of baPWV, especially in younger subjects. Thus, the possible interaction between H. pylori infection and IG may contribute to the early development of atherosclerosis. [source] Left Ventricular Function in Male Patients with Secondary HypogonadismECHOCARDIOGRAPHY, Issue 3 2007Oben Baysan M.D. Background: In addition to the effects on ventricular repolarization, testosterone could also affect left ventricular performance. The enhancement of left ventricular contractility in testosterone-deficient rats following testosterone replacement implies to the possible testosterone effect. Objectives: The aim of the current study is to reveal the alterations of left ventricular functions, if any, in secondary hypogonadal male patients. Methods: Thirty-four males with secondary hypogonadism comprised the study group. The control group consisted of 30 healthy subjects. Echocardiographic measurements including left ventricular dimensions, ejection fraction, mitral inflow, and left ventricular outflow parameters were obtained from all subjects. Tissue Doppler parameters were also measured from left ventricular lateral wall and interventricular septum. Results: Left ventricular diameters, wall thicknesses, and performance parameters were similar in both groups. Mitral inflow parameters showed a statistically insignificant difference. Pulse-wave tissue Doppler interpretation of hypogonadal and healthy subjects were similar in terms of lateral and septal basal segment Sm, Em, and Am wave velocities. Conclusions: Regarding the findings of previous studies that showed impaired myocardial contractility and lusitropy in testosterone deficient rats and our study results, further studies are needed for better understanding of testosterone's effects on human myocardium. [source] The preservation of seismic anisotropy in the Earth's mantle during diffusion creepGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2009J. Wheeler SUMMARY Seismic anisotropy in the Earth, particularly in the mantle, is commonly interpreted as the result of solid-state deformation by dislocation creep that induces a lattice preferred orientation (LPO). Diffusion creep operates where stress levels are lower and/or grain sizes smaller. It is often assumed that diffusion creep induces grain rotations that eventually destroy any existing LPO. A new numerical test of this assumption shows that it is not necessarily the case: diffusion creep will create some relative grain rotations, but rotation rates decrease through time. Hence, when microstructural change due to diffusion creep dominates that due to grain growth, defined here as ,type P' behaviour (the converse being ,type O' behaviour), the model indicates that LPO will be weakened but preserved (for a variety of strain paths including both pure and simple shear). One measure of anisotropy is the proportional difference in shear wave velocities for different polarization vectors (AVs). A model olivine microstructure with equant grains and initial maximum AVs of 10.0 percent has this value reduced to 6.7 per cent when ,rotational steady state' is attained. Other models with different initial maximum AVs values exhibit final maximum AVs values more than half the initial values. If the grains are initially elongate by a factor of 2, maximum AVs is reduced just slightly, to 8.5 per cent. Thus, when grain growth plays a subordinate role to the deformation, diffusion creep weakens seismic anisotropy by a factor of less than 2 (using maximum AVs as a measure and olivine as an example). Consequently, the link between seismic anisotropy and deformation mechanism in the mantle requires reappraisal: regions with LPO may comprise material which once deformed by dislocation creep, but is now deforming by diffusion creep in a rotational steady state. [source] Waveform modelling of teleseismic S, Sp, SsPmP, and shear-coupled PL waves for crust- and upper-mantle velocity structure beneath AfricaGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2007Abhijit Gangopadhyay SUMMARY We describe a waveform modelling technique and demonstrate its application to determine the crust- and upper-mantle velocity structure beneath Africa. Our technique uses a parallelized reflectivity method to compute synthetic seismograms and fits the observed waveforms by a global optimization technique based on a Very Fast Simulated Annealing (VFSA). We match the S, Sp, SsPmP and shear-coupled PL phases in seismograms of deep (200,800 km), moderate-to-large magnitude (5.5,7.0) earthquakes recorded teleseismically at permanent broad-band seismic stations in Africa. Using our technique we produce P - and S -wave velocity models of crust and upper mantle beneath Africa. Additionally, our use of the shear-coupled PL phase, wherever observed, improves the constraints for lower crust- and upper-mantle velocity structure beneath the corresponding seismic stations. Our technique retains the advantages of receiver function methods, uses a different part of the seismogram, is sensitive to both P - and S -wave velocities directly, and obtains helpful constraints in model parameters in the vicinity of the Moho. The resulting range of crustal thicknesses beneath Africa (21,46 km) indicates that the crust is thicker in south Africa, thinner in east Africa and intermediate in north and west Africa. Crustal P - (4.7,8 km s,1) and S -wave velocities (2.5,4.7 km s,1) obtained in this study show that in some parts of the models, these are slower in east Africa and faster in north, west and south Africa. Anomalous crustal low-velocity zones are also observed in the models for seismic stations in the cratonic regions of north, west and south Africa. Overall, the results of our study are consistent with earlier models and regional tectonics of Africa. [source] Lithospheric structure of an active backarc basin: the Taupo Volcanic Zone, New ZealandGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2006Antony Harrison SUMMARY Seismic data from both explosive and earthquake sources have been used to model the crustal and upper-mantle velocity structure beneath the Taupo Volcanic Zone (TVZ), an active backarc basin in central North Island, New Zealand. Volcanic sediments with P -wave velocities of 2.0,3.5 km s,1 reach a maximum thickness of 3 km beneath the central TVZ. Underlying these sediments to 16 km depth is material with velocities of 5.0,6.5 km s,1, interpreted as quartzo-feldspathic crust. East and west of the TVZ, crust with similar velocities is found to depths of 30 and 25 km, respectively. Beneath the TVZ, material with P -wave velocities of 6.9,7.3 km s,1 is found from 16 to 30 km depth and is interpreted as heavily intruded or underplated lower crust. The base of the crust at 30 km depth under the TVZ is marked by a strong seismic reflector, interpreted as the Moho. Modelling of arrivals from deep (>40 km) earthquakes near the top of the underlying subducting Pacific Plate reveals a region with low mantle velocities of 7.4,7.8 km s,1 beneath the crust of the TVZ. This region of low mantle velocities is best explained by the presence of partially hydrated upper mantle, resulting from dehydration of hydrous minerals (e.g. serpentinite) carried down by the underlying subducting plate. Within the lower crust beneath the TVZ, a region of high (0.34) Poisson's ratio is observed, indicating the presence of at least 1 per cent partial melt. This melt probably fractionates and assimilates crustal material before some of it migrates into the upper crust, where it provides a source for the voluminous rhyolitic magmas of the TVZ. [source] Elastic properties of dry clay mineral aggregates, suspensions and sandstonesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Tiziana 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] Crustal structure of central and northern Iceland from analysis of teleseismic receiver functionsGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2000Fiona A. Darbyshire We present results from a teleseismic receiver function study of central and northern Iceland, carried out during the period 1995,1998. Data from eight broad-band seismometers installed in the SIL network operated by the Icelandic Meteorological Office were used for analysis. Receiver functions for each station were generated from events for a wide range of backazimuths and a combination of inversion and forward modelling was used to infer the crustal structure below each station. The models generated show a considerable variation in the nature and thickness of the crust across Iceland. The thinnest crust (20,21 km) is found in the northern half of the Northern Volcanic Zone approximately 120 km north of the centre of the Iceland mantle plume. Thicker crust (24,30 km) is found elsewhere in northern and central Iceland and the thickest crust (37 km) is found close to the plume centre. Velocity,depth profiles show a distinct division of the crust into two main sections, an upper high-velocity-gradient section of thickness 2,8 km and a lower crustal section with small or zero overall velocity gradient. The thickness of the upper crust correlates with the tectonic structure of Iceland; the upper crust is thickest on the flanks of the northern and central volcanic rift zones and thinnest close to active or extinct central volcanoes. Below the Krafla central volcano in northeastern Iceland the receiver function models show a prominent low-velocity zone at 10,15 km depth with minimum shear wave velocities of 2.0,2.5 km s,1. We suggest that this feature results from the presence of partially molten sills in the lower crust. Less prominent low-velocity zones found in other regions of Iceland may arise from locally high temperatures in the crust or from acidic intrusive bodies at depth. A combination of the receiver function results and seismic refraction results constrains the crustal thickness across a large part of Iceland. Melting by passive decompression of the hot mantle below the rift zone in northern Iceland forms a crust of thickness ,20 km. In contrast, the larger crustal thickness below central Iceland probably arises from enhanced melt production due to active upwelling in the plume core. [source] The seismic response to overpressure: a modelling study based on laboratory, well and seismic dataGEOPHYSICAL PROSPECTING, Issue 5 2001José M. Carcione We investigate the seismic detectability of an overpressured reservoir in the North Sea by computing synthetic seismograms for different pore-pressure conditions. The modelling procedure requires the construction of a geological model from seismic, well and laboratory data. Seismic inversion and AVO techniques are used to obtain the P-wave velocity with higher reliability than conventional velocity analysis. From laboratory experiments, we obtain the wave velocities of the reservoir units versus confining and pore pressures. Laboratory experiments yield an estimate of the relationship between wave velocities and effective pressure under in situ conditions. These measurements provide the basis for calibrating the pressure model. Overpressures are caused by different mechanisms. We do not consider processes such as gas generation and diagenesis, which imply changes in phase composition, but focus on the effects of pure pore-pressure variations. The results indicate that changes in pore pressure can be detected with seismic methods under circumstances such as those of moderately deep North Sea reservoirs. [source] Wave propagation in an inhomogeneous cross-anisotropic mediumINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 7 2010Cheng-Der Wang Abstract Analytical solutions for wave velocities and wave vectors are yielded for a continuously inhomogeneous cross-anisotropic medium, in which Young's moduli (E, E,) and shear modulus (G,) varied exponentially as depth increased. However, for the rest moduli in cross-anisotropic materials, , and ,, remained constant regardless of depth. We assume that cross-anisotropy planes are parallel to the horizontal surface. The generalized Hooke's law, strain,displacement relationships, and equilibrium equations are integrated to constitute governing equations. In these equations, displacement components are fundamental variables and, hence, the solutions of three quasi-wave velocities, VP, VSV, and VSH, and the wave vectors, , and , can be generated for the inhomogeneous cross-anisotropic media. The proposed solutions and those obtained by Daley and Hron, and Levin correlate well with each other when the inhomogeneity parameter, k, is 0. Additionally, parametric study results indicate that the magnitudes and directions of wave velocity are markedly affected by (1) the inhomogeneous parameter, k; (2) the type and degree of geomaterial anisotropy (E/E,, G,/E,, and ,/,,); and (3) the phase angle, ,. Consequently, one must consider the influence of inhomogeneous characteristic when investigating the behaviors of wave propagation in a cross-anisotropic medium. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fabric evolution of granular assembly under K0 loading/unloadingINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2003Jyh-Chau Liou Abstract This study attempted to investigate the fabric evolution in K0 loading/unloading. The work made use of a field simulator to control K0 loading/unloading in large specimens prepared by air-pluviation. In each loading stage, wave velocities along various propagation directions were measured. On the basis of the theories of micro-mechanics and wave propagation, the microscopic parameters of the granular assembly were back calculated to investigate the fabric evolution of granular soil during K0 loading/unloading. In this study, the Geometric fabric was modelled by fabric tensors of ranks 2 and 4. The comparison of calibrated results using ranks 2 and 4 revealed the advantage of the usage of rank-4 fabric tensor in modelling fabric evolution in spite of its complexity. By comparing relative magnitudes of vertical and horizontal components of geometric fabric, it was demonstrated that relative constraint in lateral directions increased during K0 -unloading in order to maintain a K0 condition. It revealed that fabric evolution was responsible for a higher K0 in unloading than K0 in loading. Copyright © 2003 John Wiley & Sons, Ltd. [source] Output feedback control design for station keeping of AUVs under shallow water wave disturbancesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 13 2009Shuyong Liu Abstract In this paper, we consider the problem of autonomous underwater vehicle (AUV) station keeping (SK) in shallow water area. During SK, an AUV is required to maintain position and orientation with respect to a fixed reference point at the sea floor. When AUV operates in shallow water, high-frequency disturbances due to waves will significantly affect the motion of the AUV. In order to derive wave disturbance information for control purposes, a nonlinear observer is first designed to estimate the shallow water wave velocities and AUV relative velocities by using position and attitude measurement. Using the observer estimates, a nonlinear output feedback controller is subsequently synthesized by applying observer backstepping technique. Global exponential stability (GES) of the proposed nonlinear observer,controller design is proved through Lyapunov stability theory. Simulation studies on a model based on an actual AUV were performed to verify the performance of the proposed nonlinear observer and output feedback controller. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ultrasonic Velocity Technique for Nondestructive Quantification of Elastic Moduli Degradation during Creep in Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2003Franti, ek Lofaj The ultrasonic velocity technique was used for nondestructive quantification of creep damage during interrupted tensile creep tests at 1400°C in an advanced silicon nitride to investigate the possibilities of this technique for creep damage monitoring in ceramic components. The longitudinal and shear wave velocities, Poisson's ratio, and Young's, shear, and bulk moduli linearly decreased with strain. Precise density change measurements indicated a linear relationship with a coefficient of proportionality of 0.69 between the volume fraction of cavities and tensile strain. Cavitation was identified as the main creep mechanism in the studied silicon nitride and the reason for ultrasonic velocity and elastic moduli degradation. The measurement of just the longitudinal wave velocity changes was found to be sufficient for quantification of cavitation during creep. The capability of the ultrasonic velocity technique for simple, sensitive, and reliable nondestructive monitoring of creep damage during intermittent creep was demonstrated in silicon nitride. [source] Temperature dependence of elastic parameters and internal frictions for MnCu20Ni5Fe2 alloyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2004Mikio Fukuhara Abstract Using ultrasonics, MnCu20Ni5Fe2 (M2052) alloy's acoustic characteristics were observed in order to understand its high damping properties. Longitudinal and shear wave velocities, eight kinds of elastic parameters, and dilational and shear internal frictions were simultaneously measured as functions of temperature in cooling and heating runs between 218 and 373 K in M2052 alloy. A valley in Young and shear moduli, Debye temperature and internal friction peaks at around 345 K showed a M2052 fcc/fct trans-formation, accompanied by volume-nonpreserving lattice softening. The increment of dilational friction in the low temperature can be interpreted as boundary effect of the misfit domain, associated with nonharmonity of potential between pairs of atoms. The M2052 alloy shows highest elasticity below 300 K, indicating large resistance for volume-preserving distortion. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Phase transition and elasticity of CdO under pressurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 1 2009Feng Peng Abstract First-principles calculations of the crystal structures, and phase transition, and elastic properties of cadmium oxide (CdO) have been carried out with the plane-wave pseudopotential within the generalized gradient approximation in the frame of density functional theory method. The calculated values (for crystal structures) are in good agreement with experimental data as well as with some of the existing model calculations. For CsCl-type CdO, the dependence of the elastic constants cij, the aggregate elastic modulus (B, G, E), and the elastic anisotropy on the pressure have been investigated. Moreover, the pressure dependences of the Poisson ratio, Debye temperature, and the compressional and shear elastic wave velocities have been investigated for the first time. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Estimates of effective stress beneath a modern West Antarctic ice stream from till preconsolidation and void ratioBOREAS, Issue 2 2001SLAWEK TULACZYK Preconsolidation stress recorded in subglacial sediments provides important information about subglacial effective stresses. It is commonly used to reconstruct past effective stresses from sediments left after ice retreat. In this article, we use properties of sub-ice-stream till samples to estimate effective stresses beneath a modern West Antarctic ice stream. Two previous estimates of sub-ice-stream effective stress were derived for the Upstream B (UpB) area of Ice Stream B from shear wave velocities (50 ± 40 kPa, Blankenship et al 1987) and borehole water level measurements (63 ± 24 kPa, Engelhardt & Kamb 1997). However, geotechnical tests performed on samples of the UpB till have shown that if subjected to effective stress of 50,63 kPa this till would have significantly lower porosity (,0.32,0.35) and higher strength (,-22,28 kPa) than it apparently has in situ (,0.4 and ,2kPa). We derive new estimates of sub-ice-stream effective stress using: (1) Casagrande's construction applied to the results of six confined uniaxial tests, and (2) a combination of void-ratio data for 51 till samples and 3 experimentally constrained equations describing compressibility of the UpB till under normal consolidation, overconsolidation and in the critical state. Casagrande's method yields an upper bound on effective stress of 25 kPa for four till samples and values of 13, and 4.4kPa for two other samples. The void-ratio approach gives 11.7 ± 2.6 (normal consolidation), 18.3 ± 4.4 (overconsolidation) and 2.0 ± 0.8 kPa (critical state). These new, lower estimates of effective stress are consistent with the low till strength that has been independently measured and inferred from recent theoretical ice-stream models. Our interpretation of data on till void ratio in terms of sub-ice-stream effective stress means that we can qualitatively evaluate the nature of the vertical distribution of this stress in the UpB till layer. We infer that in the sampled top 3 m of till the effective-stress distribution is non-hydrostatic, probably close to lithostatic. The results may be useful in future modeling of ice-stream behavior and may aid efforts to delineate paleo-ice streams based on their geologic record. [source] 2325: Dynamic retinal vessel analysis , how different parameters create the whole pictureACTA OPHTHALMOLOGICA, Issue 2010I LANZL Purpose Dynamic vessel analysis is usually associated with the observation of the reaction of retinal vessels to a defined stimulus. The data which is generated this way may be further analysed with respect to the dynamic unstimulated and stimulated vessel behaviour. Assessment of different parameters may highlight different aspects of the underlying disease. Methods Vessel diameters of retinal vessel segments were assessed by Dynamic Vessel Analyzer (DVA) in healthy volunteers of different age groups and patients with diabetes, glaucoma and systemic hypertension. Mathematical analysis of unstimulated vessels was used to describe vessel wall characteristics. Methods of signal analysis including Fourier Transformation, spectral filtration, auto- and cross correlation were applied to evaluate characteristic oscillations and pulse wave propagation along the vessel. Results Characteristic different vessel behaviour and vessel wall conformation are obtained by dynamic quantitative evaluations from the unstimulated vessels in physiologic aging and disease. Conclusion Dynamic vessel analysis includes information which may lead to further understanding of the vascular status and underlying disease pathology. It is also feasible to assess pulse wave velocities in retinal arterioles und thus clinically characterize the elasticity of the upstream vasculature in health and disease. [source] Nondestructive Evaluation of Elastic Properties of Concrete Using Simulation of Surface WavesCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 8 2008Jae 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] Brachial-ankle pulse wave velocity and cardiovascular risk factors in the non-diabetic and newly diagnosed diabetic Chinese: Guangzhou Biobank Cohort Study-CVDDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 2 2010Lin Xu Abstract Background Increased arterial stiffness is an important cause of cardiovascular disease (CVD). We examined determinants of arterial stiffness in subjects across strata of glycaemic status. Methods A total of 1249 subjects from a sub-study of the Guangzhou Biobank Cohort Study (GBCS-CVD) had brachial-ankle pulse wave velocity (baPWV) measured by automatic oscillometric method. Major cardiovascular risk factors including glycosylated haemoglobin A1c (HbA1c), high sensitivity C-reactive protein (hsCRP), fasting triglyceride, low- and high-density lipoprotein cholesterol and both fasting and post 2-h oral glucose-load glucose, systolic and diastolic blood pressure were assessed. Results In all, 649, 479 and 121 subjects were classified into normoglycaemia, impaired glucose metabolism (IGM) and newly diagnosed diabetes groups, respectively. Both age and systolic blood pressure were significantly associated with increased baPWV in all three groups (all p < 0.001). In both normoglycaemic and IGM groups, hsCRP and HbA1c were positively associated with baPWV (p from 0.04 to < 0.001), whereas current smoking and triglyceride were associated with baPWV in the normoglycaemic and IGM group, respectively (p = 0.04 and 0.001). No gender difference in baPWV was observed in the normoglycaemic or IGM groups. However, in the newly diagnosed diabetes group, men had higher baPWV than women (p = 0.01). Conclusions In the normoglycaemic and IGM subjects, after adjusting for age, blood pressure and other confounders, increasing HbA1c was associated with increased baPWV, suggesting a pathophysiological role of chronic glycaemia that can contribute to vascular disease risk in persons without diabetes. Copyright © 2010 John Wiley & Sons, Ltd. [source] Higher arterial stiffness, greater peripheral vascular resistance and lower blood flow in lower-leg arteries are associated with long-term hyperglycaemia in type 2 diabetic patients with normal ankle-brachial indexDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 4 2009Eiji Suzuki Abstract Background Higher arterial stiffness and greater peripheral vascular resistance reduce blood flow in lower-leg arteries and contribute to the development of ischaemic limb in diabetic patients even without peripheral artery occlusive disease. The aim of this study was to clarify whether these vascular parameters are associated with long-term hyperglycaemia in diabetic patients. Methods We examined 45 type 2 diabetic patients and 38 age-matched nondiabetic subjects without peripheral artery occlusive disease assessed by ankle-brachial index consecutively admitted to our hospital, and followed them over a 3-year period (3.7 ± 0.7 years) with no vasodilative medication. Blood flow and resistive index, a measure of peripheral vascular resistance, at the popliteal artery were evaluated using gated two-dimensional cine-mode phase-contrast magnetic resonance imaging. Brachial-ankle pulse wave velocity was measured to assess arterial stiffness. Results At baseline, consistent with our previous report, diabetic patients showed higher brachial-ankle pulse wave velocity (p < 0.0001) and resistive index (p < 0.0001) and lower flow volume (p = 0.0044) than those of nondiabetic subjects. Stepwise multiple regression analysis revealed that duration of diabetes, mean HbA1c during the study, use of renin-angiotensin system inhibitors and change per year in resistive index were identified as significant independent variables predicting change per year in blood flow (r2 = 0.733, p < 0.0001) in diabetic patients. Mean HbA1c during the study was positively correlated with changes per year in brachial-ankle pulse wave velocity (p = 0.00007) and resistive index (p = 0.0014) and was negatively correlated with that in blood flow (p < 0.0001) in diabetic patients. Conclusions Long-term hyperglycaemia is a major cause of impaired peripheral circulation in lower-leg arteries in diabetic patients without peripheral artery occlusive disease. Copyright © 2009 John Wiley & Sons, Ltd. [source] Higher carotid-radial pulse wave velocity in healthy offspring of patients with Type 2 diabetesDIABETIC MEDICINE, Issue 3 2004O. D. McEleavy Abstract Aims, To determine whether carotid-radial pulse wave velocity (crPWV), a simple non-invasive measurement of muscular artery structure and function, is increased in offspring of patients with Type 2 diabetes compared with well-matched controls with no family history of diabetes. Serum levels of intercellular adhesion molecule-1 (sICAM-1) were also examined. Methods, Offspring (n = 19, M = 8) were recruited via contact with patients attending clinics. Controls (n = 19, M = 8) were recruited by advertisement. crPWV was measured using COMPLIOR. Blood pressure and heart rate were determined and fasting blood taken for measurement of metabolic and endothelial parameters. Results, Offspring and controls were well matched [mean (sd)] for age [33.1 (9.6) vs. 32.8 (9.5) years], body mass index [24.8 (4.9) vs. 24.3 (3.4) kg/m2], waist circumference [78.3 (2.3) vs. 76.3 (2.5) cm], and systolic blood pressure [120 (9.3) vs. 119 (14.2) mmHg]. crPWV was 10% higher in the offspring [9.94 (1.3) m/s] compared with controls [9.01 (1.2) m/s, P = 0.02] despite similar pulse pressure [52 (10.5) vs. 53.5 (9.3) mmHg] and resting heart rate [71 (8.7) vs. 69 (14.0) beats/min]. They also showed a trend toward higher sICAM-1 [217 (55) vs. 188 (40) ng/ml, P = 0.07] concentrations which were also strongly correlated to crPWV in offspring (r = 0.63, P = 0.004). Conclusions, Vascular dysfunction in the form of increased muscular artery stiffness is present from an early stage in subjects at higher risk of developing diabetes. This may be secondary to impaired activation of endothelial signalling pathways in the context of inherited insulin resistance. [source] Brachial-ankle pulse wave velocity measured automatically by oscillometric method is elevated in diabetic patients with incipient nephropathyDIABETIC MEDICINE, Issue 11 2003H. Yokoyama Abstract Aims To examine whether brachial-ankle pulse wave velocity (baPWV), a possible early marker of atherosclerotic vascular damage, is associated with albuminuria in patients with Type 2 diabetes. Methods BaPWV was measured by automatic oscillometric method in 346 Type 2 diabetic patients with normoalbuminuria (a mean level of three times measurements of albumin-to-creatinine (ACR) < 30 µg/mg creatinine; n = 200), incipient nephropathy (a mean level of ACR , 30 and < 300 µg/mg creatinine; n = 119), and clinical nephropathy (a mean level of ACR , 300 µg/mg creatinine; n = 27), and without peripheral vascular disease. Results BaPWV (cm/s) was significantly higher in patients with incipient nephropathy (1722 ± 382) and clinical nephropathy (1763 ± 322) than in patients with normoalbuminuria (1559 ± 343, P < 0.0001, respectively). By univariate analysis it correlated significantly with age (r = 0.44, P < 0.0001), systolic blood pressure (r = 0.55, P < 0.0001), diastolic blood pressure (r = 0.42, P < 0.0001), albuminuria (r = 0.24, P < 0.0001) and HbA1C (r = 0.11, P < 0.05). Albuminuria revealed an independent significant association with baPWV (P < 0.01) after adjustment for age, sex, smoking, BMI, HbA1C, hyperlipidemia, and hypertension. Multiple regression analysis showed age, diastolic blood pressure and albuminuria were independently associated with baPWV (adjusted R2 = 0.42, P < 0.0001). Conclusions The results might indicate a possible link between the pathogenesis of atherosclerosis and diabetic nephropathy. Future studies are needed to clarify the usefulness and its predictable value. [source] "Supranormal" Cardiac Function in Athletes Related to Better Arterial and Endothelial FunctionECHOCARDIOGRAPHY, Issue 6 2010Maria Florescu M.D. Objective: Athlete's heart is associated with left ventricular (LV) hypertrophy (LVH), and "supranormal" cardiac function, suggesting that this is a physiological process. Hypertrophy alone cannot explain increase in cardiac function, therefore, other mechanisms, such as better ventriculo-arterial coupling might be involved. Methods: We studied 60 male (21 ± 3 years) subjects: 27 endurance athletes, and a control group of 33 age-matched sedentary subjects. We assessed global systolic and diastolic LV function, short- and long-axis myocardial velocities, arterial structure and function and ventriculo-arterial coupling, endothelial function by flow-mediated dilatation, and amino-terminal pro-brain natriuretic peptide (NT-proBNP) and biological markers of myocardial fibrosis and of oxidative stress. Results: Athletes had "supranormal" LV longitudinal function (12.4 ± 1.0 vs 10.1 ± 1.4 cm/s for longitudinal systolic velocity, and 17.4 ± 2.6 vs 15.1 ± 2.4 cm/s for longitudinal early diastolic velocity, both P < 0.01), whereas ejection fraction and short-axis function were similar to controls. Meanwhile, they had better endothelial function (16.7 ± 7.0 vs 13.3 ± 5.3%, P < 0.05) and lower arterial stiffness (pulse wave velocity 7.1 ± 0.6 vs 8.8 ± 1.1 m/s, P = 0.0001), related to lower oxidative stress (0.259 ± 0.71 vs 0.428 ± 0.88 nmol/mL, P = 0.0001), with improved ventriculo-arterial coupling (37.1 ± 21.5 vs 15.5 ± 13.4 mmHg.m/s3× 103, P = 0.0001). NT-proBNP and markers of myocardial fibrosis were not different from controls. LV longitudinal function was directly related to ventriculo-arterial coupling, and inversely related to arterial stiffness and to oxidative stress. Conclusions: "Supranormal" cardiac function in athletes is due to better endothelial and arterial function, related to lower oxidative stress, with optimized ventriculo-arterial coupling; athlete's heart is purely a physiological phenomenon, associated with "supranormal" cardiac function, and there are no markers of myocardial fibrosis. (Echocardiography 2010;27:659-667) [source] Variations in carotid arterial compliance during the menstrual cycle in young womenEXPERIMENTAL PHYSIOLOGY, Issue 2 2006Koichiro 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] Importance of arterial stiffness as cardiovascular risk factor for future development of new type of drugsFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 3 2008Pierre Boutouyrie Abstract Cardiovascular risk prediction relies on classical risk factors such as age, gender, lipids, hypertension, smoking and diabetes. Although the value of such scales of risk is high for populations, its value for individual is reduced and too much influenced by non-modifiable risk factors (age and gender). Biomarkers of risk have been deceiving and genome wide scan approach is too recent. Target organ damage may help in selecting patients at high risk and in determining intervention. Aortic pulse wave velocity, an index of aortic stiffness, has been widely validated as providing additional risk predictions beyond and above classical risk factors, and has now entered into official guidelines. Many interventions (dietary, behaviour, drug treatment) were shown to influence arterial stiffness positively, but little evidence of a direct effect of intervention on arterial stiffness independent of blood pressure is available. New pharmacological targets and new drugs need to be identified. To become a surrogate endpoint for drug development, there is a need to demonstrate that regression arterial stiffness is associated with improved outcome. In parallel to this demonstration, points to be improved are the homogenization and spreading of the technique of measurement, the establishment of a reference value database. [source] The Influence of the Parameter "Temperature" on the Abrasiveness of RockGEOMECHANICS AND TUNNELLING, Issue 1 2008Stefan Eberl cand.rer.mont. The article deals with the influence of temperature produced in the cutting process on rock abrasiveness and tool wear. Basically it was to clarify which effects take place when quartz or rock with significant quartz content is heated up to a certain temperature. Does the quartz jump from low into high quartz happening at 573 °C cause an increase in abrasiveness of mineral and rock or not? To find out, a certain number of Cerchar abrasiveness index tests were done for a detailed investigation of this topic. Additionally, to get a better understanding what really happens inside rock structure additionally other rock parameters like unconfined compressive strength, Brazilian tensile strength, ultrasonic wave velocity and density were determined on untreated and heated and subsequently cooled down rock samples. The final output of the research work showed that rocks show a very specific and significant reaction to thermal stresses induced into their structure resulting in a different behaviour regarding abrasiveness and fracturing. Einfluss des Parameters "Temperatur" auf die Abrasivität von Fels Der Artikel beschäftigt sich mit dem Einfluss der während des Schneidprozesses entstehenden Temperatur auf die Abrasivität von Gestein und auf den Verschleiß des Schneidwerkzeugs. Es sollte geklärt werden, welche Effekte auftreten, wenn Quarz und Gestein mit erheblichem Quarzgehalt bis zu einer bestimmten Temperatur erhitzt werden. Erzeugt der Quarzsprung, der bei 573 °C stattfindet, von Tiefquarz zu Hochquarz einen Anstieg in der Abrasivität von Mineralen und Gesteinen oder nicht? Um dies herauszufinden, sind eine bestimmte Anzahl von Cerchar Abrasivitätstests durchgeführt worden. Um ein besseres Verständnis zu erhalten, was wirklich in der Struktur des Gesteins passiert, sind weitere Parameter wie einachsiale Druckfestigkeit, Spaltzugfestigkeit, Ultraschallwellengeschwindigkeit und Dichte an unbehandelten und aufgeheizten und wieder abgekühlten Gesteinsproben bestimmt worden. Die Forschungsarbeit hat gezeigt, dass Gesteine eine sehr spezifische und signifikante Reaktion auf thermische Beanspruchungen ihres Gefüges zeigen, was letztlich in einem verschiedenartigen Verhalten hinsichtlich Abrasivität und Bruchverhalten zum Ausdruck kommt. [source] Constraints on deformation mechanisms during folding provided by rock physical properties: a case study at Sheep Mountain anticline (Wyoming, USA)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010K. Amrouch SUMMARY The Sheep Mountain anticline (Wyoming, USA) is a well-exposed asymmetric, basement-cored anticline that formed during the Laramide orogeny in the early Tertiary. In order to unravel the history of strain during folding, we carried out combined anisotropy of magnetic susceptibility (AMS), anisotropy of P -wave velocity (APWV) and Fry strain analyses. The results are compared to previously published stress,strain data from calcite twins at the microscopic scale and from fracture sets at the mesoscopic scale, and are used to discuss the kinematics and mechanics of forced folding. The results obtained in sandstone and carbonate lithologies demonstrate a good agreement between (1) the principal axes of the AMS and APWV tensors, (2) stress,strain tensors derived from calcite twins, (3) Fry strain axes and mesoscopic fracture sets. Furthermore, these tensors are coaxial with the main structural trends of the anticline. The differences between AMS and APWV fabrics on one hand, and the differential stress values of the forelimb and the backlimb on the other hand, emphasize how the macroscopic asymmetry of Sheep Mountain anticline affects the strain pattern at the microscopic scale. The data set presented in this paper offers a consistent mechanical scenario for the development of Sheep Mountain anticline. [source] Shear wave velocity model of the Santiago de Chile basin derived from ambient noise measurements: a comparison of proxies for seismic site conditions and amplificationGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2010Marco Pilz SUMMARY We determined a high-resolution 3-D S -wave velocity model for a 26 km × 12 km area in the northern part of the basin of Santiago de Chile. To reach this goal, we used microtremor recordings at 125 sites for deriving the horizontal-to-vertical (H/V) spectral ratios that we inverted to retrieve local S -wave velocity profiles. In the inversion procedure, we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements, which were found to vary substantially over short distances in the investigated area. The resulting model was derived by interpolation with a kriging technique between the single S -wave velocity profiles and shows locally good agreement with the few existing velocity profile data, but allows the entire area, as well as deeper parts of the basin, to be represented in greater detail. The wealth of available data allowed us to check if any correlation between the S -wave velocity in the uppermost 30 m (v30S) and the slope of topography, a new technique recently proposed by Wald and Allen, exists on a local scale. We observed that while one lithology might provide a greater scatter in the velocity values for the investigated area, almost no correlation between topographic gradient and calculated v30S exists, whereas a better link is found between v30S and the local geology. Finally, we compared the v30S distribution with the MSK intensities for the 1985 Valparaiso event, pointing out that high intensities are found where the expected v30S values are low and over a thick sedimentary cover. Although this evidence cannot be generalized for all possible earthquakes, it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the Santiago basin. [source] Elastic properties of dry clay mineral aggregates, suspensions and sandstonesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2003Tiziana 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] P- and S-wave velocities of consolidated sediments from a seafloor seismic survey in the North Celtic Sea Basin, offshore IrelandGEOPHYSICAL PROSPECTING, Issue 2 2008Donna J. Shillington ABSTRACT A geophysical survey was conducted over a hydrocarbon prospect in the North Celtic Sea Basin using a small array of ocean-bottom seismographs (OBSs). The purpose of this study was to determine the ratio of compressional (P)- to shear (S)-wave velocity of consolidated sedimentary rocks in order to constrain possible subsurface variations in pore-fluid content. The ratio of VP and VS is known to be particularly sensitive to lithology, porosity and pore-fluid content, making it a useful parameter for evaluating hydrocarbon prospects. OBSs offer a relatively cheap and time-effective means of acquiring multi-component data compared with ocean-bottom cables. In this contribution, we demonstrate the ability of an OBS survey comprising three pairs of two OBSs spaced at 1.6 km to recover lateral variations in the VP/VS ratio. A key requirement of this type of study is that S waves will be generated by mode conversions in the subsurface, since they cannot be generated in nor travel through fluids. In this survey, the contrast in physical properties of the hard seabed of the North Celtic Sea Basin provided a means of generating converted S waves. Two-dimensional ray-tracing and forward modelling was used to create both VP and VS models along a profile crossing the Blackrock prospect in the North Celtic Sea Basin. These models comprise four layers and extend to a maximum depth of 1.1 km. The observed northward decrease in the VP/VS ratio at depths of 500,1000 m below the seafloor in the study area is interpreted to represent lateral variation in the amount of gas present in the pore space of Upper Cretaceous chalks and shales overlying the prospective reservoir. [source] Relation of hypertension and glucose tolerance impairment in elderly people to the development of arteriosclerosis: Investigation using pulse wave velocity,GERIATRICS & GERONTOLOGY INTERNATIONAL, Issue 1 2005Takeshi Isobe Background: The aim of the present study was to determine the correlation between the combination of hypertension and diabetes mellitus and arteriosclerosis using pulse wave velocity (PWV). Methods: The subjects were 186 men over the age of 60 years (mean age: 68.8 ± 5.8 years). PWV, systolic blood pressure (SBP), diastolic blood pressure, body mass index, fasting blood sugar (FBS), total cholesterol, triglyceride and HDL cholesterol were measured in all subjects. The subjects were divided into three groups on the basis of FBS level: a normal group (FBS < 110 mg/dL), an impaired fasting glucose group (110 , FBS < 126 mg/dL) and a diabetes mellitus group (FBS , 126 mg/dL or taking antidiabetics). The subjects were also divided into two groups on the basis of blood pressure level: a hypertension (HT) group (SBP , 140 mmHg and/or diastolic blood pressure , 90 mmHg or taking antihypertensives) and a normotension group (other subjects). Results: PWV showed positive correlations with SBP and FBS (r = 0.499 and r = 0.300, respectively). In all three groups classified by FBS level, PWV was higher in subjects with HT than in subjects with normotension (P < 0.01 in all three groups). In the HT group, PWV had already increased at the stage of impaired fasting glucose and was significantly higher in the diabetes mellitus group than in the normal FBS group (P = 0.002). In multiple regression analysis using PWV as a dependent variable, SBP and FBS were selected as independent variables. Conclusions: Even in the elderly, strict control of blood pressure and blood sugar level may be necessary in order to prevent the development of arteriosclerotic diseases. 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