Decrease In Wave Velocity Research Articles

Mechanical Properties of Metasandstone under Uniaxial Graded Cyclic Loading and Unloading

The acoustic emission and wave velocity characteristics of metasandstone under graded cyclic loading and unloading were revealed by conducting graded cyclic loading and unloading tests. The results show that the acoustic emission signals of metasandstone samples are mainly generated in the loading phase, and almost no acoustic emission activity is generated in the unloading phase. The quiet period feature can be used to monitor and predict the destabilization of metasandstone. There is a stress threshold for wave velocity variation in metasandstone, below which wave velocity does not change significantly with increasing stress. When the stress exceeds this threshold, the wave velocity of the rock sample will decrease rapidly with the increase in stress. The phenomenon of a rapid decrease in wave velocity can be used to predict the damage instability of rock masses in engineering.

Real-time laser ultrasonic monitoring of laser-induced thermal processes

Intra- and inter-layer integrity of components fabricated with advanced manufacturing techniques, such as laser powder bed fusion, is dependent upon rapid heating, melting, and solidification processes. There is a need for new techniques to provide in situ feedback of these processes. Here a laser-based ultrasonic technique to probe thermal effects induced by a high-power continuous wave laser in titanium samples is described. Numerical simulations were performed to show that, for a spatially uniform heating beam, laser-induced surface acoustic waves are strongly influenced by surface heating conditions, are dispersive in the case of rapid heating, and that an abrupt velocity reduction happens upon the onset of surface melting. Furthermore, laser-based ultrasound experimental results which monitor the transient change of surface wave travel time associated with high power laser surface heating are provided. A pulsed laser is used to generate high frequency surface acoustic waves that propagate through the laser-heated region and are detected using a photorefractive crystal-based interferometer. Qualitative agreement is observed between theory and experiment with both showing a rapid reduction in the surface wave velocity at the onset of illumination and further decrease in surface wave velocity associated with melting. It is demonstrated that changes in the surface wave velocity can be used to track local heating and detect the onset of surface melting in real time.

Comparative Efficacy of Single Pill Combinations of Azilsartan Medoxomil/Chlorthalidone and Losartan/Hydrochlorothiazide in Patients with Hypertension and Heart Failure with Preserved Ejection Fraction

Aim. To study the effects of azilsartan medoxomil/chlorthalidone (AZM/CTD) and losartan/hydrochlorothiazide (LOS/HCT) combinations for NTproBNP levels, 6-minute walk test results, hydration status along with their antihypertensive efficacy according to clinical and 24-hour blood pressure in patients with hypertension and heart failure with preserved ejection fraction (HFpEF).Material and methods. An open randomized study included 56 patients with uncontrolled or untreated hypertension and HFpEF. Patients randomized to receive the AZM/CTD 40/12.5 mg/day (group 1; n=28) or LOS/HCT 100/12.5 (group 2; n=28) within 4 weeks. Patients who did not achieve the target BP <140/<90 mm Hg study drug dose was intensified: in the first group, an increase in the dose of AZM/CTD 40/25 mg/day, in the second group, an increase in the dose of LOS/HCT 100/25 mg/day. The observation period was 12 weeks. All patients underwent a clinical examination with an assessment of symptoms and/or signs of HF, laboratory and instrumental studies, including NT-proBNP, ambulatory blood pressure (BP) monitoring, applanation tonometry, a 6-minute walk test (6MWT), echocardiography. In order to assess the status of hydration, bioimpedance vector analysis (BIVA) was performed. HFpEF was diagnosed according to the HFA-PEFF algorithm. The results were considered statistically significant at p<0.05.Results. After 12 weeks, 92% of patients in the first and 78% of patients in the second group reached the target clinical BP (р<0,05). Average daily BP <130/ <80 mm Hg was reached by 82% of patients treated with the combination of AZM/CTD, compared with 67% treated with the combination of losartan/HCT (p<0.05). After 12 weeks, patients from both groups showed a significant decrease in systolic and diastolic blood pressure, central blood pressure, and a decrease in pulse wave velocity, which was more significantly significant in the first group of patients (p<0.05). During therapy in both groups of patients, a significant decrease in the level of NT-proBNP was observed: in the first group from 300 [199; 669] pg/ml to 156 [157; 448] pg/ml (p=0,003), in the second group from 298 [180; 590] pg/ml to 194 [140; 360] pg/ml (p=0,006), an increase in the distance during the 6MWT from 317 [210; 398] m to 380 [247; 455] m (p=0,006) in in the first group and an improvement in the hydration status according to the BIA data, but more significantly significant in the first group (p<0.001).Conclusion. In patients with hypertension and HFpEF, therapy with the AZM/CTD combination compared with LOS/HCT is accompanied by a more pronounced antihypertensive effect in terms of ambulatory and peripheral blood pressure, central blood pressure, NTproBNP levels, increased distance in 6MWT and achievement of euvolemia status.

The Left Ventricular End-Systolic Pressure Correlation with Aortic Valve Timing; a Novel Inotropic Index Description Using a Dual Pressure Catheter

Myocardial contraction is generated by ventricular pressure in early systole by the isometric force against closed valves, as ventricle is contracting without changing volume. This initial contractile phase of cardiac cycle (early systole) is followed by rapid shortening, isotonic contraction, allowing ejection of the blood against changing LV afterload. LV is coupled to the systemic arterial pressure; hence LV ejection is closely linked to the properties of the aortic valve, aorta, and its distributing arteries. Isometric relationship in the LV was characterized using the load-dependent example (naïve vs. post-dobutamine), observed mostly in case of rate of rise of LVP, LV ESP and decrease of pulse wave velocity, characteristics of LV baroinometry. Furthermore, by performing load-independent maneuver, afterload (LV ESP) was adjusting at every cardiac cycle, while an assessment of LV ESP and aortic valve timing was able to be established. By plotting decaying LV ESP against aortic valve timing, highly linear correlation of load-independent isotonic, but also an isometric contractility was captured. Steeper linear slope and time-axis intercept (IC) were identified in case of post-inotropic challenge, recapitulating changes otherwise measured during pressure-volume exam. This relationship, measured by dual-pressure catheter, could serve as novel inotropic index of functional cardiac contractility. Keywords: Left Ventricle (LV); Contractility; Inotropy; Load-Dependent and Independent; Stressed Volume; Dual Pressure Catheter. 1. Assessment of cardiac contractility using dual pressure catheter. 2. IVCO inferior vena cava occlusion, ECC excitation-contraction coupling, EF ejection fraction, TTE transthoracic echocardiography, Ea end arterial elastance, PRSW preload recruitable stroke work, IC intercept, PWV pulse wave velocity.

The effect of breastfeeding during infancy on arterial stiffness in young adults.

Breastfeeding has many benefits for health, also later in life. However, its effects on the cardiovascular system are still unclear. The aim of the present study was to evaluate the effect of exclusive breastfeeding as infants on arterial stiffness in young adults having no cardiovascular risk factors, using aortic pulse wave velocity, and brachial and aortic augmentation index. Eighty-six subjects were included in the study from similar socioeconomic status. 46 subjects who had received exclusive breastfeeding for the first 4-6 months in infancy (26 women, mean age 26.7±4 years) (group 1) and 40 subjects who had received exclusive breastfeeding for less than 3 months or had never been breast-fed (22 women, mean age: 28±3.8 years) (group 2) were recruited. Parameters of arterial stiffness (aortic pulse wave velocity, brachial and aortic augmentation index) were investigated using an arteriograph (TensioMed, Budapest, Hungary), which works on an ossilometric basis. A significant decrease in pulse wave velocity in the breast-fed group was detected compared to the non-breast-fed group (P<0.05) but no significant difference was detected for aortic and brachial augmentation index. In addition there was a significant relationship between breastfeeding duration and aortic pulse wave velocity. Breast milk intake in infancy reduces the risk of cardiovascular disease in young adults, independent of other cardiovascular risk factors. It seems that there is a negative relationship between the duration of breastfeeding and the risk reduction.

A multivariate statistical approach in correlating the acoustic properties with petrophysics and mineralogy on sandstones

SUMMARYWe examined the effects of the petrophysical and mineralogical variables on the acoustic properties of Upper Assam sandstones. All parameters were evaluated in the laboratory using recognized standard laboratory methods. Compressional wave velocity was measured in the laboratory using piezoelectric transducers of 54 kHz by using the ultrasonic-through transmission technique. Single parameter correlations among bulk density, porosity, permeability and mineralogy with compressional wave velocity showed that the compressional wave velocity correlated inversely with porosity, permeability and feldspar content and directly with bulk density and quartz content. For instance, a plug with a higher amount of feldspar content showed a corresponding decrease in compressional wave velocity. Similarly, higher quartz content showed a higher compressional wave velocity. Nevertheless, to depict a clear correlation among different parameters, a multiparameter analysis was performed. It was observed that the coefficient of determination improved from 0.596 to 0.899 when compressional wave velocity was modelled in terms of bulk density, porosity, quartz and feldspar content collectively, rather than when compressional wave velocity was modelled as a function of porosity alone. Hence, our study suggests that multiple parameters exhibit a coherent influence on compressional wave velocity. Therefore, a multivariate statistical approach involving petrophysical and mineralogical influences would be more realistic. Furthermore, major mineral fractions of sandstone rock type, that is quartz and feldspar fractions were varied for a range of porosity to determine the variations in compressional wave velocity for different saturation conditions. Capturing the fluctuations in compressional wave velocity within the geological constraints will aid in possible reservoir characterization away from the well-control or beyond the available data range. The integrated approach can result in more accurate and precise rock physics models that may help to infer key reservoir parameters. The developed models can be used in quantitative seismic interpretation for reservoir characterization and to identify prospective reservoirs.

Research Progress on Cenozoic Volcano Genesis and Fluid Action in Northeast China

The tectonic evolution of northeast China is closely related to the subduction of the Pacific plate. The dehydration of the slab subduction process produces metasomatic agents that have important effects on the physical and chemical properties of the mantle wedge, including the decrease of seismic wave velocity and the increase of Poisson’s ratio and electrical conductivity. In order to investigate the tectonic evolution and fluid action of northeast China, this paper compares the previous seismic and electromagnetic imaging results of northeast China and explores the relationship between the genesis of Cenozoic volcanoes and fluid action in northeast China through rheological analysis. The results show that the western Pacific plate subducted into the mantle transition zone beneath northeast China, and sustained dehydration occurred. The upward migration of these released water caused partial melting at the base of the upper mantle. Some of the upwelling streams pierced the weak tectonic boundary under the buoyancy effect, which finally formed the large-scale Cenozoic volcanic events in northeast China.

Study on Multiphase Pressure Wave Velocity Characteristics of Automatic Kill Annulus in Chuanyu Fractured Formation

The virtual mass force, annulus pressure, gas-liquid resistance, gas slippage, void fraction and other factors were considered, the equation was combined with small perturbation theory, the mathematical model of annular multiphase pressure wave velocity for automatic killing the well in fractured formation is proposed. Taking pengzhou pz-5-3d well (vertical depth 5827m) as an example, the model is solved programmatically with the semi-display difference method, and the results show that: The gas of fractured formation is characterized by slug flow. With the increase of void fraction, the pressure wave velocity firstly decreases and then increases. When the void fraction is between 0% and 16%, The pressure wave velocity is mainly liquid projectile, and the pressure wave velocity decreases sharply. When the void fraction is between 16% and 40%, and the pressure wave velocity tends to be flat and constant. When the void fraction is between 42% and 100%, and the pressure wave velocity shows an increasing trend, and the pressure wave velocity is mainly aeroelastic. As the annulus well depth decreases, the void fraction decreases and the pressure wave velocity decreases. The pressure wave velocity increases with the increase of the back pressure of the kill circulating exhaust wellhead. When the void fraction is between 0% and 13%, the gas slippage velocity has little influence on the pressure wave velocity. In the range of 13% to 85%, the pressure wave velocity decreases with the increase of gas slippage velocity. The time interval of throttle regulating valve follows the response time of bottom hole pressure. The time interval of throttle regulating valve increases with the increase of response time.

Evaluation of longitudinal wave velocity and elasticity modulus of concrete at different ages considering mixing ratios

Concrete is a material that the mechanical properties of which change over time. This change is due to chemical reactions within the concrete known as hydration. One of these properties is the modulus of elasticity and longitudinal wave velocity, which has a direct relation with the concrete age and its setting. Just after the materials mixing, the concrete setting is fast, and over time its rate decreases. Here, a series of cubic concrete specimens are prepared and changing in longitudinal wave velocity and modulus of elasticity in different ages is monitored during the process of curing and a relationship has been presented. Materials specifications impact and concrete mixing ratios, including the water to cement ratio and fine to coarse aggregates ratio is studied. Ultrasonic wave velocity has been increased faster at early ages of specimens where the concrete setting process is fast and in last days, rates of increasing the longitudinal wave velocity decreases. An increase in the water to cement ratio leads to increases in the longitudinal wave velocity over time. The empirical equations have been formulated as logarithmic curves. These empirical equations have been developed and a model with more efficiency and precision has been presented. These empirical equations can be used in the analytical and numerical analysis of structures. These models can be used to determine the loading time of concrete structures and to predicting their other physical and mechanical properties, such as strength and stiffness.

Effect of Dispersed Reinforcement on Ultrasonic Pulse Velocity in Stabilized Soil.

One of the fundamental techniques for road subgrades is soil stabilization. Considering the high emission of carbon dioxide during the production of binders, novel techniques to reduce the binder are being studied. Thus, we investigated dispersed reinforcement in stabilized soils. A study was conducted to determine the ultrasonic pulse velocity in nine mixtures of soil, cement, and polypropylene fibers and then correlate the results with other destructive tests. The results show a decrease in wave velocity in mixes with fiber addition by up to 18.5%. The result is dependent on the curing time and whether the samples were stored in a water tank. Immersion in water increases the obtained results by about 6.3%. Based on the analysis, for mixtures with fibers, boundary velocities of waves above which lower values of modulus of elasticity were obtained were determined. Depending on the mix and the module analyzed, the limits range from 2194 m/s to 2498 m/s.

Effect of Fiber on Residual Strength and High Temperature Burst Performance of Ultra High Performance Concrete

In this paper, the effects of fiber on the residual strength and high temperature burst performance of ultra-high performance concrete are studied. This paper analyzes the performance change law of concrete after high temperature from three aspects: mass loss, ultrasonic wave velocity and compressive strength. The results show that with the increase of heating temperature, the mass loss increases and the ultrasonic wave velocity decreases. The compressive strength of concrete increases gradually before 300 ℃ and decreases gradually after 400 ℃. Mixing PVA fiber and steel fiber can not only improve the burst resistance of ultra-high performance concrete at high temperature, but also have high residual strength. This paper discusses the high temperature burst mechanism of ultra-high performance concrete, which is caused by the change of steam pressure and microstructure.

How do the liquid properties affect the entrapment of bubbles in gas sheared liquid flows?

A large number of industries use fossil fuels for the purpose of cooling and lubrication utilizing a gas stream that acts as a shearing force on the liquid surface. Decreasing the carbon footprint of these processes needs an improved understanding of the effect of liquid properties. To this end this study investigates experimentally the effect of varying surface tension and liquid viscosity on the bubble generation and film statistics in a gas-sheared liquid flow. The experiments were conducted in a horizontal rectangular channel using high speed imaging in conjunction with the Brightness-Based Laser-induced Fluorescence technique (BBLIF) to measure film thickness over an area with a spatial resolution of 40 μm and a temporal resolution of 10 kHz. Two butanol–water solutions were used to give reduced surface tensions (namely 0.049 N/m and 0.04 N/m) compared to our previously-studied water only value. Also, two glycerol-water solutions were chosen to yield surface tension values closer to those of an oil of interest (namely 1.4 cP and 1.9 cP).The results show that compared to water, an increase in film thickness and a decrease in the disturbance wave velocity was observed with either the reduction in the surface tension or increase in the liquid viscosity. The frequency and size of the waves were found to be dominated by the liquid surface tension. Moreover, surface tension was found to have more of an effect on aeration as compared to viscosity. The bubble velocity was found to decrease with increase in viscosity, while it increases with decrease in surface tension. It is suggested that these changes would affect heat transfer and hence should be studied in more detail.

Артеріальна жорсткість та синдром обструктивного апное сну в пацієнтів з артеріальною гіпертензією на фоні терапії постійним позитивним тиском у дихальних шляхах

Актуальність. Синдром обструктивного апное сну (СОАС), особливо тяжкого ступеня, пов’язаний із фатальними та нефатальними серцево-судинними подіями. СОАС та артеріальна гіпертензія (АГ) мають достовірні взаємозв’язки, і дана супутня патологія є дуже поширеною та пов’язана зі збільшеним ризиком серцево-судинних захворювань. Однією з причин є підвищена жорсткість артерій. Неінвазивним показником жорсткості артерій є швидкість поширення пульсової хвилі в аорті, що рекомендована сучасними настановами для оцінки серцево-судинного ризику. Метою дослідження було оцінити зміни жорсткості артерій у пацієнтів з АГ та СОАС та можливості її корекції при лікуванні постійним позитивним тиском у дихальних шляхах (СРАР-терапія). Матеріали та методи. У дослідження були включені 185 пацієнтів із легкою та середньою АГ (49,8 ± 0,8 року), які були розподілені на групи: 1-ша — пацієнти, у яких був СОАС (n = 148), 2-га — пацієнти без СОАС (контрольна група, n = 37). Вони пройшли клінічне та спеціальне обстеження: сомнологічне дослідження за допомогою двоканального портативного монітора, оцінку денної сонливості за опитувальною шкалою Епворта, вимірювання офісного артеріального тиску та добове моніторування артеріального тиску, ехокардіографію, вимірювання швидкості поширення пульсової хвилі. За 10 місяців подальшого дослідження були включені 105 пацієнтів, які були розподілені на 4 підгрупи: А — пацієнти із середнім та тяжким ступенями СОАС на СРАР-терапії (n = 23), В — пацієнти із середнім та тяжким ступенями СОАС без СРАР-терапії (n=29), С— пацієнти з легким ступенем СОАС (n = 29), D — пацієнти без СОАС (контрольна група, n =24). Усі пацієнти отримували подібну антигіпертензивну терапію відповідно до Рекомендацій ESC/ESC 2013 року. Результати. У пацієнтів з АГ та СОАС (середній індекс апное/гіпопное — 38,10±2,51 події/год) порівняно з пацієнтами без СОАС (середній рівень AГI — 3,02 ± 0,25 події/год) був значно вищий індекс маси тіла (35,20 ± 0,57 проти 30,60 ± 0,79 кг/м2, Р &lt; 0,001), а також рівень глюкози в крові (107,2 ±2,2 проти 98,0 ± 2,5 мг/дл, Р = 0,045), рівень сечової кислоти (6,17 ± 0,10 проти 5,5 ± 0,3мг/дл, Р = 0,048) та індекс маси міокарда лівого шлуночка (115,80 ± 2,39 проти 104,60 ± 4,56 г/м2, Р = 0,035). Протягом 10 місяців спостереження в пацієнтів з АГ та СОАС на фоні CPAP-терапії спостерігалося достовірне зниження швидкості поширення пульсової хвилі по артеріях еластичного типу (із 12,20±0,63 до 10,05±0,43м/с, Р = 0,009), офісного систолічного артеріального тиску (від 143,80±132,70 до 132,70±2,33 мм рт.ст., Р= 0,021) та офісного діастолічного артеріального тиску (від 93,80 ± 3,31 до 86,00 ± 3,19 мм рт.ст., Р=0,012). У пацієнтів центральний систолічний артеріальний тиск зменшився з 130,30 ± 3,97 до 119,70± 2,97 мм рт.ст., Р = 0,012). Висновки. Поєднання терапії постійним позитивним тиском у дихальних шляхах та антигіпертензивної терапії покращує еластичність артерій та допомагає досягти цільового рівня артеріального тиску в пацієнтів з артеріальною гіпертензією та синдромом обструктивного апное сну середнього та тяжкого ступенів.

تاثیر باران های اسیدی بر خواص فیزیکی و مکانیکی سنگ تراورتن

One of the problems caused by air pollution is acid rain. The development of urban communities and subsequent use of air polluting vehicles on the one hand and the widespread use of travertine in building facades in Iran on the other hand have doubled the study of the effect of acid rain on the properties of travertine. In this study, three types of travertine (Travertine B, Travertine D and Travertine R) were studied. This paper investigates the effect of the rain at four pH (2.5, 4, 5.5 and 7) on its physical properties including effective porosity, longitudinal wave velocity and permeability, and its mechanical properties including tensile strength and uniaxial compressive strength. The results showed that as the pH decreases, the effective porosity increased and the longitudinal wave velocity, tensile strength and uniaxial compressive strength decreased. The highest increase in effective porosity due to decreasing pH was related to travertine B and the lowest increase was related to travertine R. The highest decrease in longitudinal wave velocity, tensile strength, and uniaxial compressive strength due to decreasing pH was related to travertine B and the lowest decrease was related to travertine R.

Effects of Exercise and Weight Loss on Proximal Aortic Stiffness in Older Adults With Obesity.

Obesity may accelerate age-related increases in aortic stiffness. Although aerobic exercise training generally has favorable effects on aortic structure and function, exercise alone may not be sufficient to improve aortic stiffness in older adults with obesity. We determined the effects of aerobic exercise training with and without moderate- to high-caloric restriction (CR) on the structure and function of the proximal aorta in 160 older (65-79 years) men and women with obesity (body mass index=30-45 kg/m2). Participants were randomly assigned to 1 of 3 groups: aerobic exercise training only (treadmill 4 days/week for 30 minutes at 65% to 70% of heart rate reserve; n=56), aerobic exercise training plus moderate CR (n=55), or aerobic exercise training plus more intensive CR (n=49) for 20 weeks. Aortic pulse wave velocity, aortic distensibility, and other measures of aortic structure and function were assessed by cardiovascular magnetic resonance imaging. Pearson correlation coefficients were examined to assess associations between changes in proximal aortic stiffness and changes in fitness, fatness, and other potential confounders. Weight loss in the aerobic exercise training plus moderate CR (-8.0 kg [95% CI, -9.17 to -6.87]) and aerobic exercise training plus more intensive CR (-8.98 kg [95% CI, -10.23 to -7.73) groups was significantly greater compared with the aerobic exercise training-only group (-1.66 kg [95% CI, -2.94 to -0.38]; P<0.017 for both). There were significant treatment effects for descending aorta distensibility (P=0.008) and strain (P=0.004) and aortic arch pulse wave velocity (P=0.01) with the aerobic exercise training plus moderate CR group having a 21% increase in distensibility (P=0.016) and an 8% decrease in pulse wave velocity (P=0.058). None of the aortic stiffness measures changed significantly in the aerobic exercise training-only or aerobic exercise training plus more intensive CR groups, and there were no significant changes in any other measure of aortic structure or function in these groups. Overall, increases in aortic distensibility were correlated with improvements in body weight and body fat distribution, but these associations were not statistically significant after adjustment for multiple comparisons. In older adults with obesity, combining aerobic exercise with moderate CR leads to greater improvements in proximal aortic stiffness than exercise alone. Registration: URL: https://clinicaltrials.gov; Unique identifier: NCT01048736.

Changes in elastic wave velocity during brittle deformation of gabbro and peridotite: Implications for oceanic Moho reflectivity

Cracks that develop during brittle deformation easily modify rocks' physical properties; therefore, understanding of seismic properties of oceanic rocks during deformation is essential for interpretation of the seismic observations of the oceanic lithosphere. Here we measured elastic wave velocities of gabbro and peridotite during triaxial deformation experiments at room temperature, a confining pressure of 20 MPa, and a strain rate of ∼10−6 s−1. Gabbroic rocks showed significant decrease in elastic wave velocities approaching the maximum stress, which is comparable to that of typical crystalline rocks. On the other hand, peridotite showed relatively sudden and small decrease in elastic wave velocities close to the maximum stress. We inverted the observed velocities to crack density tensor based on an effective medium theory. The different changes in elastic wave velocities between gabbroic rocks and peridotites were interpreted by different characteristics of crack development, where limited number of cracks were opened in peridotite than in gabbroic rocks. The calculated reflection coefficient of the interface between the gabbro and peridotite increases from <0.1 to ∼0.25 as approaching the maximum stress. Synthetic seismograms computed from the crack-dependent velocity structures of the oceanic lithosphere indicate that the Moho reflectivity is highly sensitive to the contrast of crack-damage across the crust-mantle boundary. The existence of a heterogeneous crack-damaged zone in the oceanic lithosphere, which is likely related to intra-plate earthquakes, may result in the spatial variations of Moho reflection.

Effect of soil-structure interaction on wind-induced responses of supertall buildings with large pile groups

A simplified three-dimensional soil-structural interaction (SSI) model is established for large pile groups-supertall buildings (>300 m height) to simulate the dynamic response of the building to wind loading. The displacement and acceleration responses to wind loading at the top of the supertall building are calculated using the established model. The effects of SSI on the wind-induced mean displacement, root-mean-square (RMS) displacement and RMS acceleration are analyzed considering different values of soil shear wave velocity and material damping, and different total mass, first natural frequency and damping ratio of the superstructure as well as different terrain conditions. The results from the comprehensive parametric study are used to derive empirical equations of the mean displacement, RMS displacement and RMS acceleration SSI factors. The findings demonstrate that the mean displacement of the top of supertall building increases considering SSI. As the soil shear wave velocity decreases, the mean displacement SSI factor increases. It was also found that the mean displacement SSI factor increases with the increase in total mass and first natural frequency of the superstructure. In addition, the RMS displacement and acceleration SSI factors decrease with the increase of the soil shear wave velocity and material damping. Finally, the RMS displacement and acceleration SSI factors increase as the superstructure first damping ratio increases.

Experimental Study on the Difference of Shale Mechanical Properties

This paper studies the anisotropic characteristics of shale and the difference in mechanical performance between deep shale and outcrop shale. The outcrop shale was collected from the Shuanghe section in Changning County, southern Sichuan, and the deep shale was collected from the Wells Yi201 and Lu202. Study their basic mechanical parameters, failure modes, and wave velocity responses through laboratory tests. Research shows that with the increase of bedding angle, the deformation mode has the trend from elastic deformation to plastic deformation in high-stress state. When the bedding angles are 0°, 30°, and 45°, the weak bedding surface plays a leading role in the formation of the failure surface trend. As the bedding angle increases to 60° and 90°, its influence is weakened. The tensile strength, elastic modulus, and wave velocity decrease with the increase of bedding angle. The compressive strength and Poisson’s ratio have the law of U-type change, there are higher values at 0° and 90°, and the lowest values are at 30°. The brittleness index first increases and then decreases with the increase of the bedding angle. The tensile strength and Poisson’s ratio of outcrop shale and deep shale are close, but the compressive strength of deep shale is only 1/3 of outcrop shale, the elastic modulus is only 3/4 of outcrop shale, and the failure of deep shale is accompanied by instability failure.

MO754THE INTERRELATIONSHIP BETWEEN FLUID OVERLOAD AND VASCULAR STIFFNESS IN HEMODIALYSIS PATIENTS: A SCOPING REVIEW

Abstract Background and Aims Fluid overload and vascular stiffness are two independent predictors of cardiovascular events in hemodialysis (HD) patients. To date, observational and interventional studies that investigated the effect of inter- and intradialytic fluid overload changes on vascular stiffness in HD patients are very limited. We performed a scoping review to explore existing reports about effects of fluid overload on vascular stiffness in adults receiving HD treatment and to identify knowledge gaps for future research. Method We followed the framework originally developed by Arksey and O’Malley. We searched Medline, Embase, CINAHL, and Cochrane Database of systematic reviews from inception to October 29, 2019. References of review papers were screened for relevant studies not identified from the initial search until saturation is achieved. Results Of 666 eligible studies, nineteen studies met the inclusion criteria. These included clinical observational studies (n=16) and randomized controlled trials (n=3). In general, most of the identified studies had small sample size and short term of follow up. Studies use different definitions of fluid overload and vascular stiffness. Measures of relative fluid overload like the ratio of extracellular fluid/intracellular fluid, fluid overload/extracellular fluid, and/or extracellular fluid/total body fluid were used as a representative of fluid status. Pulse wave velocity and augmentation index were used interchangeably as vascular stiffness measures. The accumulated findings were inconsistent and inconclusive. There was no consensus whether intradialytic fluid volume changes affected vascular stiffness. In the majority of the observational studies, a decrease in pulse wave velocity or augmentation index correlated with a decrease in blood pressure after fluid correction by HD treatment. The randomized clinical trials used different methods and technologies for the correction of fluid overload, thereby, results were conflicting. Conclusion Current literature is insufficient to justify whether fluid overload changes have a direct effect on vascular stiffness in HD patients. The findings were conflicting which limits the comparisons of studies and generalization of findings. These knowledge gaps urge the need for further clinical studies to enhance the understanding and to improve the quality of research in this topic. This includes standardized definitions and methodologies as well as longer term of follow up.

The physiological effects of cardiac resynchronization therapy on aortic and pulmonary flow and dynamic and static components of systemic impedance.

BackgroundPatients who improve following cardiac resynchronization therapy (CRT) have left ventricular (LV) remodeling and improved cardiac output (CO). Effects on the systemic circulation are unknown.ObjectiveTo explore the effects of CRT on aortic and pulmonary blood flow and systemic afterload.MethodsAt CRT implant patients underwent a noninvasive assessment of central hemodynamics, including wave intensity analysis (n = 28). This was repeated at 6 months after CRT. A subsample (n = 11) underwent an invasive electrophysiological and hemodynamic assessment immediately following CRT. CRT response was defined as reduction in LV end-systolic volume ≥15% at 6 months.ResultsIn CRT responders (75% of those in the noninvasive arm), there was a significant increase in CO (from 3 ± 2 L/min to 4 ± 2 L/min, P = .002) and LV dP/dtmax (from 846 ± 162 mm Hg/s to 958 ± 194 mm Hg/s, P = .001), immediately after CRT in those in the invasive arm. They demonstrated a significant increase in aortic forward compression wave (FCW) both acutely and at follow-up. The relative change in LV dP/dtmax strongly correlated with changes in the aortic FCW (Rs 0.733, P = .025). CRT responders displayed a significant reduction in afterload, and a decrease in systemic vascular resistance and pulse wave velocity acutely; there was a significant decrease in acute pulmonary afterload measured by the pulmonary FCW and forward expansion wave.ConclusionImproved cardiac function following CRT is attributable to a combination of changes in the cardiac and cardiovascular system. The relative importance of these 2 mechanisms may then be important for optimizing CRT.