Changes In Wave Velocity Research Articles

Study on transmitted channel wave-based, horizontal multilayer 3-D velocity model inversion and quantitative coalbed thickness detection method

Most methods using transmitted channel wave (TCW) prospecting to quantitatively detect the thickness of coal seams based on the statistic relationship of group velocity in certain wave bands to the thickness of coal seams cannot be applied universally. To establish a universal applicable method, we first obtained the theoretical dispersion curve of TCW using the generalized reflection–transmission coefficient method and the 1-D horizontal multilayer velocity model, performed iteratively match calculation using the inversion model and the genetic algorithm and analyzed the distributive characteristics of shear wave velocity of coal and rock formations at a certain depth. We then obtained the 3-D velocity images of the coal seam working face based on TCW data using the 3-D back-projection technology. According to the changes of shear wave velocity at the coal–rock interface and the rate of inversion velocity change, we further proposed the quantitative discriminant model for coalbed thickness. Based on the model, we quantitatively interpreted the thickness of the coal seam by computing the depths corresponding to the extremes of the positive and negative rate of the shear wave velocity change and obtained the distribution characteristics of the coal thickness in the working surface. To verify the feasibility and validity of the proposed model for coalbed thickness, we conducted a 3-D physical similarity model experiment and subjected the collected two-component TCW data to inversion calculation and compared the obtained coal seam thickness with the known model parameters. Overall, our study achieved the universal 3-D quantitative detection of coalbed thickness and provided technical supports for intelligentized coalbed mining.

Habitual Night Eating Was Positively Associated With Progress of Arterial Stiffness in Chinese Adults.

BackgroundNight eating has been associated with an elevated risk of obesity, dyslipidemia, and cardiovascular disease. However, there is no longitudinal study on whether habitual night eating, regardless of diet quality and energy intake, is associated with arterial stiffness, a major etiological factor in the development of cardiovascular disease.Methods and ResultsThe study included 7771 adult participants without cardiovascular disease, cancer, or diabetes mellitus prior to dietary assessment by a validated food frequency questionnaire in 2014 through 2015. Participants were categorized into 3 groups based on self‐reported night‐eating habits: never or rarely, some days (1–5 times per week), or most days (6+ times per week). Arterial stiffness was assessed by brachial‐ankle pulse wave velocity at baseline and repeatedly during follow‐ups. Mean differences and 95% CIs in the yearly change rate of brachial‐ankle pulse wave velocity across the 3 groups were calculated, adjusting for age, sex, socioeconomic status, total energy intake, diet quality, sleep quality, and other cardiovascular disease risk factors. At baseline, 6625 (85.2%), 610 (7.8%), and 536 (6.9%) participants reported night eating as never or rarely, some days, or most days, respectively. During a mean 3.19 years, we observed a positive association between night‐eating frequency and progression of arterial stiffness (P trend=0.01). The adjusted difference in brachial‐ankle pulse wave velocity change rate between the group that ate at night most days and the group that never or rarely ate at night was 14.1 (95% CI, 0.6–27.5) cm/s per year. This association was only significant in women, but not in men (P interaction=0.03).ConclusionsIn an adult population free of major chronic diseases, habitual night eating was positively associated with the progression of arterial stiffness, a hallmark of arteriosclerosis and biological aging.RegistrationURL: https://www.chictr.org.cn; Unique identifier: ChiCTR‐TNRC‐11001489.

Determination of geological structures by geophysical and geotechnical techniques in Kırklartepe Dam Site (Turkey)

In foundation research of engineering structures, application of geophysics methods before drilling work allows not only more economical studies but also a more detailed determination of underground sections. Especially in pre-feasibility studies on long tunnel routes, dam sites and lake areas, it has a vital importance in terms of structural safety to determine possible underground buried fault lines, lithology changes, anticlinal-synclinal structures and underground openings. By considering these effective factors, the alluvium/bedrock border and the positions of potential buried faults in the dam site and lake area in the Kırklartepe area of the province of Bayburt in northeastern Turkey were determined by comparison with geophysical and geotechnical methods. First of all, the resistivity of the dam axis location and the change of the Vp wave velocity by depth were determined by comparing the results between geophysical methods of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT), respectively. Afterwards, from the foundation boreholes opened in the dam axis location, joint frequency and the other parameters determined by observations were obtained. With these parameters, 2-dimensional zoning profiles of the dam axis location were formed, and the alluvium-bedrock border and the locations of the buried faults were determined. Two potential faults in the NW-SE direction relative to the location of the dam axis were clearly revealed in the zoning profiles obtained in the ERT and SRT measurements. Additionally, the presence of these faults was determined as a result of examining the separation and joint frequency parameters from the drilling core samples collected from the BH_3 and BH_5 boreholes opened in the investigated area based on changes in the vertical and horizontal directions. In addition to these, in the ERT study, two potential faults other than the determined two were also detected. It was seen in the zoning profiles that these faults corresponded to right under the BH_2 borehole and 60 m SW of the BH_6 drilling. Consequently, in the zoning studies conducted at the examined site, the change in the lithology at the dam axis by depth (alluvium-bedrock border), lateral correlations of boreholes and potential faults were determined. It was recommended for the selected dam axis location to be constructed at a more suitable place in the NW direction in terms of engineering. Furthermore, with this study, it was revealed once again that it is highly essential to use geophysical and geotechnical together in conceptualizing large engineering structure projects.

Venous pulse wave velocity

Central venous pressure and volume status are relevant parameters for the characterization of the patient's haemodynamic condition and for the management of fluid therapy however, their invasive assessment is affected by various risks and complications while non-invasive approaches provide only imprecise and subjective indications. Aim of the present study is to explore the possibility to assess changes in venous pressure from changes in the venous pulse wave velocity (vPWV). In 9 healthy subjects, pressure pulses were generated artificially in the veins by a PC-driven rapid inflation of a pneumatic cuff (300mmHg in

Recovery of small-strain stiffness following blast-induced liquefaction based on shear wave velocity measurements

Changes in soil fabric following liquefaction have been studied using various in situ methods that often return inconclusive or conflicting observations. The time–rate variation of stiffness, when observed, is usually not evaluated over significant periods of time, limiting investigations about aging in post-liquefaction regain of stiffness. Even more uncommon is the application of geophysical techniques to evaluate changes in shear wave velocity (V S) as a proxy for small-strain stiffness. This study uses controlled blasting to examine long-term post-liquefaction regain of stiffness following multiple blast events. The multi-channel analysis of surface waves (MASW) technique was used to observe changes in V S of aged deposits at a test site in South Carolina. Blast-induced liquefaction of the target liquefiable layer resulted in significant reduction to its initial small-strain stiffness owing to the destruction of the aged soil fabric. The time-rate variation in V S indicated that the initial small-strain stiffness was not re-established over many months following liquefaction. Following a second blast event, the small-strain stiffness reduced again, but recovered more quickly, similar to previously reported observations of young sand deposits. This study provides a significant basis for interpreting in situ body and surface wave measurements of aged and young sand deposits densified using blast liquefaction.

On the usage of diffractions in ground-penetrating radar reflection data: Implications for time-lapse gas migration monitoring

Time-lapse ground-penetrating radar (GPR) measurements are used to image/monitor, for example, water infiltration, water table changes, and fluid/gas flow patterns. Although crosshole GPR is often preferred over surface-reflection GPR in such studies, its application is limited by the selected borehole geometry, which may be difficult to define in an optimal way, especially in experiments in which flow pathways are difficult to predict. Surface-reflection GPR data sets are generally faster to collect over relatively large areas and are therefore more efficient for covering the volume when a fast-moving tracer (e.g., gas) may infiltrate a heterogeneous subsurface medium. We have used a diffraction imaging approach on time-lapse surface-reflection GPR data to detect changes in radar wave velocity associated with gas (CO2) injected into a heterogeneous chalk succession. We initially test and evaluate the diffraction imaging approach on synthetic GPR data. Afterward, we apply the methodology to time-lapse GPR field data, and we evaluate the robustness of using information from diffractions in light of the obtained data quality. The synthetic tests indicate that diffractions provide essential information for delimiting the area affected by gas in the heterogeneous chalk section studied. Our field experiment shows that using the diffraction information alone allows for detection of gas-affected zones and, therefore, potential flow characteristics of gas movement. We infer that the CO2 flow patterns in our study most likely are determined by small-scale fractures rather than the porosity/permeability of the rock matrix. Moreover, the approach used may serve as an initial study for future more targeted experiments or for further detail-retrieving full-waveform inversion.

Carotid-femoral pulse wave velocity is significantly increased in newly diagnosed hypertensive patients with primary hyperparathyroidism and significantly related with serum calcium level.

Primary hyperparathyroidism (PHP) is a rare cause of secondary hypertension (HT), but in patients with PHP, HT is very common and 20-80% of patients have HT. The aim of this study was to evaluate the change in carotid-femoral pulse wave velocity (CF-PWV) in hypertensive patients with PHP, and was to determine the clinical, laboratory, and echocardiographic parameters associated with CF-PWV. The study included 83 newly diagnosed hypertensive patients with PHP and 83 patients with newly diagnosed essential HT without PHP. All patients underwent echocardiography and CF-PWV measurements. In patients with PHP, blood urea nitrogen, hs-CRP, uric acid, serum and urine calcium, parathyroid hormone level, CF-PWV value, LV wall thickness, LVMI, aortic and left atrium (LA) diameter, and presence of LVH and CF-PWV > 10m/s were higher, and serum phosphorus levels were lower. Serum calcium, LA diameter, and LVMI values were closely correlated with CF-PWV. In the ROC analysis, the AUROC was calculated as 0.825 for calcium level to determine the patients with increased CF-PWV. When the serum calcium value was taken as 10mg/dL, it was determined with CF-PWV > 10m/s were 79.5% sensitivity and 78.2% specificity. CF-PWV significantly increases in newly diagnosed hypertensive patients with PHP and significantly related to serum calcium level. To protect against target organ damage, high serum calcium levels should be monitored as well as blood pressure in hypertensive patients with PHP.

Anisotropic Longitudinal Wave Propagation in Swine Skull.

To understand the in-plane elastic character of ultrasonic waves in the skull, longitudinal wave velocities were studied in the MHz range using a conventional pulse technique. Taking advantage of the thickness of swine skulls, anisotropic in-plane wave velocity changes in the outer and diploe layers were experimentally investigated using structural information measured by X-ray computer tomography (CT). The velocities in the thin inner layer were difficult to measure. The main trabecular alignment (MTA) in the thick swine diploe layer was almost perpendicular to the thickness direction and changed with position inside the skull. The degree of anisotropy of in-plane longitudinal wave velocity ranged 1.07-1.33 in both outer and diploe layers, depending on position and swine sample. The angle of the fastest velocity in the outer layer was different from that in most parts of the diploe layer. Anisotropic character in the diploe layer gradually changed with position in the thickness direction.

Analysis of Microwave Thermal Stress Fracture Characteristics and Size Effect of Sandstone under Microwave Heating

Microwave-induced rock fracture is one of the promising approaches of achieving non-blasting continuous mining and assisted mechanical rock breaking. It is of great theoretical and practical significance to study the temperature effect and fracture characteristics of rocks of different sizes under microwave heating; however, there are few studies in this field. Microwave heating of φ 50 × 100 mm, φ 50 × 50 mm, and φ 50 × 25 mm sandstone samples with different heating powers and times was performed to measure the temperature of the sample, the microwave energy absorbed, the mass, and the P-wave velocity before and after heating. The results show suppress that (i) under the same heating conditions, the mass difference and the temperature increase range of φ 50 × 100 mm and φ 50 × 50 mm samples are larger than that of the φ 50 × 25 mm samples; (ii) the wave velocity change rate and the damage factor of samples increase with the increase of heating power and time; (iii) different size specimens have different crack- propagation modes. The main crack of φ 50 × 100 mm specimens usually starts from the middle of the height of the specimen; for the φ 50 × 50 mm specimens, it usually starts from the middle or bottom-end surface of the specimen height; the main crack of φ 50 × 25 mm specimens starts from the vertical surface of the specimen. With an increase in the heating time, the length and width of the main crack continuously increase and secondary cracks are generated. The fracture mode of the sample is also related to the size of the sample. The fracture mode can be divided into three parts: melt fracture, thermal-expansion fracture, and secondary thermal-expansion fracture. The relationship between the sample temperature and the absorbed microwave energy is approximately linear.

Mapping the relationships between joint stiffness, modeled muscle stiffness, and shear wave velocity.

Joint stiffness is often measured to make inferences about the stiffness of muscle groups, but little can be gleaned about individual muscles. Decomposing the muscular origins of joint stiffness may inform treatment targets for conditions like spasticity. To complement joint stiffness, shear wave ultrasound elastography has been used to estimate the material properties of individual muscles. If shear wave measures are to be used to assess the muscular origins of joint stiffness, then changes in shear wave velocity should strongly relate to changes in joint stiffness. Here, we estimated the relationships between shear wave velocity in the primary plantar flexors [soleus (SOL) and medial gastrocnemius (MG)] and ankle joint stiffness. Participants performed isometric plantar flexion tasks at a range of activations (0-40%), while joint stiffness and muscle shear wave velocities were obtained. We observed a strong, linear relationship between plantar flexor shear wave velocities and joint stiffness. Remarkably, the parameter estimates of this stiffness-shear wave relationship strongly agreed with theoretical and literature-based estimates [SOL:MG parameter ratios = 2.83 (observed) vs. 2.85 (expected from theoretical stiffness ratio)]. Finally, a musculoskeletal model of the plantar flexors was able to accurately reproduce joint stiffness estimates, and shear wave velocities could explain 80-95% of the variance in modeled muscle stiffness. These findings suggest that shear wave velocity may be used to infer the muscular origins of changes in joint stiffness.NEW & NOTEWORTHY Shear wave velocity is commonly assessed to infer the muscular origins of changes in joint stiffness, but the exact relationship between shear wave velocity changes in muscle and joint stiffness changes remains unknown. Here, we systematically evaluated and quantified this relationship in the plantar flexors. Our results provide evidence for the ability of shear wave velocity to elucidate the muscular origins of joint stiffness changes.

Estimation of the soil parameters in Balçova region using multiple geophysical approach

This study aimed to reveal the soil properties in the research area by using various geophysical methods. Physical parameters determining soil characteristics give us a chance to approach how the soil behaves during an earthquake. Thus, precautions can be taken to minimize earthquake damage. Also, safe construction against earthquake effects is important. The studied area is a tectonically and geothermally active area. Izmir Fault zone is passing through the investigation area and trending E–W direction. To investigate soil parameters at this active tectonic region, microtremor method data were recorded and the multichannel analysis of surface waves (MASW) method at 27 profiles was implemented in the study area. Additionally, these methods were supported by the spatial auto correlation (SPAC) method in center spot. Shear wave velocities up to 30 m, soil classification according to the National Earthquake Hazards Reduction Program (NEHRP), site amplification, predominant site period, amplification factor, ground vulnerability index, and shear wave velocity changes up to 300 m were obtained by evaluating the data collected from the applied geophysical methods. VS30 values varied between 700 and 1100 m/s in the southernmost part of the study area, corresponding to a C and B type as soil classification. While the predominant period values were taken as the lowest value of 0.2 s, it was observed to increase up to 5.5 s on the alluvial unit in the northern parts of the study area. The ground vulnerability index, which is directly related to the probability of earthquake damage, was found to be quite high in some parts of the study area. In this paper, we propose microzonation maps for the Balcova district, based on the variation of the soil dynamic parameters.

SCoda and Rayleigh Waves From a Decade of Repeating Earthquakes Reveal Discordant Temporal Velocity Changes Since the 2004 Sumatra Earthquake

AbstractTemporal changes in the subsurface seismic velocity structure reflect the physical processes that modulate the properties of the media through which seismic waves propagate. These processes, such as healing of the surface damage zone and deep crustal deformation, are described by similar functional forms and operate on similar timescales, making it difficult to determine which process drives the observed changes. We examine earthquake‐induced velocity changes using the measured lag‐time time seriesτ(t) of the repeating earthquake sequences since the 2004Mw9.2 Sumatra and 2005Mw8.6 Nias earthquakes. TheScoda velocity changes (δVS, equivalent to−τS) recover steadily during the 2005–2015 period. The Rayleigh wave velocity changes (δVLR, or−τLR) undergo transient recovery, followed by a strongδVLRreduction in late 2007.δVSrecovery is most likely driven by deep processes, whereas the temporal breaks inδVLRrecovery in 2007 mostly reflect surface damage and healing induced by the strong ground motions of the 2004Mw9.2, 2005Mw8.6, 2007Mw8.4, andMw7.9 Bengkulu and 2008Mw7.3 Simeulue earthquakes. The observed differences between the temporal variations inδVSandδVLRcan distinguish deep processes from healing of the surface damage zone.

Thermal deterioration of high-temperature granite after cooling shock: multiple-identification and damage mechanism

Cooling shock has a significant thermal deterioration (TD) on the physical and mechanical properties of rocks in high-temperature conditions, which is a critical concern for the engineering application of the cyclic hydraulic fracturing technique in an enhanced geothermal system (EGS). In this work, cooling shock tests were carried out on granite samples to evaluate the actual TD of high-temperature rocks by cooling shocks, and multiple test methods were used to explore the effect of TD on the corresponding physical and mechanical properties of high-temperature granite. Some core conclusions from the study are as follows: (1) The wave velocity and apparent resistivity (AR) can reflect the thermal damage effect of cooling shocks on high-temperature granite. Notably, the higher the temperature of granite, the more significant change in wave velocity and AR. (2) The stress-strain curve tends to be smooth with the granite temperature increases and the cooling shocks intensify, the quiet period of acoustic emission (AE) events is lengthened, and the number is gradually reduced. (3) The TD effect of the cooling shock tends to be more significant for the samples at temperatures above 550 °C, and the peak stress continues to decrease with cooling shock strengthen. Furthermore, thermal stress is the main cause of TD to high-temperature granite. This study has the potential to guide the use of the cooling shock effect in extraction applications of geothermal engineering.

The effect of low-volume high-intensity interval training on cardiovascular health outcomes in type 2 diabetes: A randomised controlled trial

BackgroundLow-volume high-intensity interval training (HIIT) may be a time-efficient strategy that leads to similar or superior improvements in cardiorespiratory fitness (CRF) and cardiovascular disease (CVD) risk factors when compared with moderate-intensity continuous training (MICT). Our study investigated the effect of low-volume HIIT or MICT versus sham placebo-control (PLA) on central arterial stiffness, hemodynamic responses, and CVD risk factors in adults with obesity and type 2 diabetes (T2D). MethodsEligible participants were previously inactive adults with obesity and T2D. Individuals were randomly allocated to: i) HIIT (1 × 4 min cycling at 90% peak oxygen consumption [V̇O2peak]); ii) MICT (45 min of cycling at 60% VO2peak); or PLA. Training groups exercised thrice weekly for 12 weeks. Central arterial stiffness, hemodynamics and CVD risk factors were assessed at baseline and post-intervention. Analysis of covariance (ANCOVA) was used to examine changes following HIIT, MICT and PLA. ResultsThirty-five participants (age: 55.1 ± 1.4 years, BMI: 36.1 ± 0.8 kg/m2) completed the study. A significant intervention effect was found for changes in pulse wave velocity (PWV) (p = .03), which reduced with HIIT (−0.3 ± 0.9 m/s) and MICT (−0.1 ± 1.1 m/s) but increased with PLA (0.8 ± 1.6 m/s). There was a significant intervention effect for changes in V̇O2peak (p < .01), glycosylated hemoglobin (p = .03), systolic blood pressure (p < .01), and waist circumference (p = .03), which all improved following MICT or HIIT but not PLA; there was no difference between MICT and HIIT. ConclusionsTwelve minutes of low-volume HIIT per week leads to improvements in central arterial stiffness and cardiovascular health in inactive individuals with obesity and T2D.

Changes in aortic pulse wave velocity in peritoneal dialysis do not mirror changes in extracellular water measured by bioimpedance.

Pulse wave velocity is a measurement of arterial stiffness and associated with increased cardiovascular mortality. Previous reports in peritoneal dialysis have linked increased pulse wave velocity with an expansion in extracellular water. As cardiovascular mortality is increased in peritoneal dialysis patient, we wished to determine whether changes in pulse wave velocity mirrored changes in extracellular water. We repeated aortic pulse wave velocity and bioimpedance-derived extracellular water measurements in peritoneal dialysis patients attending for assessment of peritoneal membrane function. Sixty-six patients, 41 males (62.1%), mean age of 66.2 ± 13.9 years, median duration of peritoneal dialysis treatment (14.3 (3.1-31.9) months) had repeated measurement 6.4 (5.8-10.2) months apart, with no significant change in aortic pulse wave velocity (10.1 ± 3.2 to 9.9 ± 2.8 m/s). In univariate analysis, the initial aortic pulse wave velocity was associated with extracellular water (r = 0.26, p = 0.034) and serum N-terminal pro brain-type natriuretic peptide (r = 0.25, p = 0.04), and on follow-up, aortic pulse wave velocity with N-terminal pro brain-type natriuretic peptide (r = 0.31, p = 0.01). Aortic pulse wave velocity increased in 50% of patients, and these patients had greater serum C-reactive protein 3(2-10) versus 2(1-4) mg/L, and ferritin (778(444-1099) versus 585(313-811), p < 0.05), but there were no differences in either absolute or adjusted extracellular water. Both log C-reactive protein (odds ratio 4.7 (95% confidence limits 1.3-17.1), p = 0.019) and prescription of calcium channel blockers (odds ratio 4.9 (95% confidence limits 1.2-19.1), p = 0.024) were independently associated with an increase in aortic pulse wave velocity. We did not find an independent association between a change in aortic pulse wave velocity and extracellular water, suggesting that changes in aortic stiffness in peritoneal dialysis patients are more complex than simply following changes in extracellular water.

Study on the surface crack propagation mechanism of coal and sandstone subjected to cryogenic cooling with liquid nitrogen

Conventional hydraulic fracturing often causes problems such as reservoir damage, water consumption, and pollution. Recently, liquid nitrogen (LN2) fracturing, an environmentally friendly fracturing technology, has attracted more attention. In this paper, the mechanism of surface crack propagation in coal and sandstone induced by LN2 is explored through laboratory tests and numerical simulations. An ultrasound detection analyser is employed to investigate the longitudinal wave velocity (Vp) changes in specimens before and after LN2 cooling. The micromorphology of specimens is observed through scanning electron microscopy (SEM). Furthermore, the heat transfer characteristics and damage zone of specimens induced by LN2 are determined. The experimental results indicate that LN2 cooling is more effective for improving coal permeability than it is for improving sandstone permeability. After LN2 cooling, a complex fracture network is observed from the coal surface. However, limited damage to the sandstone surface is observed. Vp decreases by 24.7%–38.1% for coal specimens after cooling but by less than 0.06% for sandstone. The simulation results indicate that the low-temperature region and the tensile area gradually expand into the interior of the specimens with time. However, the temperature of sandstone drops faster than coal when specimens contact LN2. The maximum tensile stress induced by the instantaneous contact between the specimens and LN2 can be generated at the outer surface of the specimens. Moreover, the maximum damage area of coal extends 3.3 mm from the outer surface, while the damage zone of the sandstone is almost zero.

Determination of acoustic nonlinearity parameters using thermal modulation of ultrasonic waves

This study presents a test method and its theoretical framework to determine the acoustic nonlinearity parameters (α, β, δ) of material using thermal modulation of ultrasonic waves. Temperature change-induced thermal strain excites the nonlinear response of the material and modulates the ultrasonic wave propagating in it. Experimental results showed a strong correlation between the relative wave velocity change and the temperature change. With a quadratic polynomial model, the acoustic nonlinearity parameters were obtained from the polynomial coefficients by curve fitting the experimental data. Their effects on thermal-induced velocity change were discussed. The parameters α, β, and δ govern the hysteretic gap, average slope, and curvature of the correlation curve, respectively. The proposed theory was validated on aluminum, steel, intact and damaged concrete samples. The obtained nonlinear parameters show reasonable agreement with values reported in the literature. Compared to other nonlinear acoustic methods using vibration or acoustic excitation, the thermal modulation method generates more uniform, slow changing, and larger strain field in the test sample. Employing the thermal effect as the driving force for nonlinearity instead of an undesired influencing factor, this method can measure the absolute values of α, β, and δ with good accuracy using a simple ultrasonic test setup.

Acoustic Radiation Force Impulse Elastography May Predict Acute Rejection in Kidney Transplantation

BackgroundAllograft biopsy that is done as indicated by clinical and laboratory clues about graft rejection provides a definitive diagnosis. Noninvasive methods that may be useful for predicting or diagnosing rejection are important for early diagnosis of possible rejection. PurposeThe aim of this study is to investigate the relationship between changes in shear wave velocity (SWV) values and renal allograft kidney biopsy findings. Material and MethodsThirty-four end-stage renal failure patients who underwent living donor renal transplantation between January 2015 and July 2015 were enrolled in this prospective cohort study. Implantation, sixth-month protocol, and biopsies that were performed with suspicion of acute rejection were evaluated with renal Doppler ultrasound and elastography findings of recipients’ preimplantation donor ultrasonography findings. ResultsComparison of renal ultrasound and elastography findings of 2 groups revealed a significant elevation in the resistive index (0.81 vs 0.63, P = .005) and pulsatility index (2.08 vs 1.20, P = .008) values in the rejection group, and no significant difference in the SWV values between the 2 groups. Delta (Δ)-SWV was calculated using the difference between acute rejection values and preimplantation, implantation, and sixth-month values showed a positive correlation between acute rejection (Δ-sixth month, r = 0.498, P = .030), tubulitis (Δ-pretransplant, r = 0.509, P = .037), and inflammation (Δ-pretransplant, r = 0.657, P = .004) scores. However, there were no correlations between Δ-SWV values and glomerulitis and peritubular capillaritis score. ConclusionChanges in SWV may predict acute rejection in kidney transplantation patients if the reference measurements were done at a more stable time after the transplantation.

Using Velocities, Density, and Bulk Modulus to Predict the Permeability Evolution of Microfractured Rocks

Thermal fracturing in reservoir rocks can cause significant increase in permeability. The change in permeability due to fracturing was predicted using the change in elastic wave velocity, density, and elastic moduli. Westerly granite samples were thermally treated to 250, 450, 650 and 850 °C. Increasing the temperature produces an increase in fracture length, aperture and density that is isotropically distributed. The permeability was measured at 10, 30 and 50 MPa effective pressure using deionized water as the pore fluid. The permeability was correlated to P- and S-wave velocities, bulk density, and static bulk modulus that were measured at similar effective pressures on the same suite of samples. Kachanov’s (Elastic solids with many cracks and related problems, in: John, Theodore (eds) Advances in applied mechanics, Elsevier, pp 259–445, 1994) model was used to calculate the evolution of fracture density. Closure of fracture, due to increasing effective pressure, caused the permeability and fracture density to decrease, and the other parameters to increase. Thermal treatment caused a systematic increase in permeability and fracture density, and a decrease in the other parameters. Empirical relationships with high correlation coefficient exist between permeability and the other parameters for both dry and saturated conditions, which vary with effective pressure. Overall, we conclude that the elastic wave velocity, density and bulk modulus can be used to predict the change in permeability due to isotropic fracturing. However, a reliable method would be required to upscale these laboratory measurements for modelling and describing the permeability within a granitic reservoir.

Endothelium function dependence of acute changes in pulse wave velocity and flow-mediated slowing.

Flow-mediated slowing (FMS), defined as the minimum pulse wave velocity (PWVmin) during reactive hyperemia, is potentially a simple, user-objective test for examining endothelial function. The purpose of the current study was to determine the effects of a known endothelial dysfunction protocol on arm PWV and PWVmin. Complete data were successfully collected in 22 out of 23 healthy adults (23.8 years [SD 4.1], 16 F, 22.8 kg/m2 [SD 2.8]). Local endothelial dysfunction was induced by increasing retrograde shear stress in the upper arm, through inflation of a distal (forearm) tourniquet to 75 mmHg, for 30 min. Pre- and post-endothelial dysfunction, PWV was measured followed by simultaneous assessment of PWVmin and flow-mediated dilation (FMD). PWV was measured between the upper arm and wrist using an oscillometric device, and brachial FMD using ultrasound. FMD (%) and PWVmin (m/s) were calculated as the maximum increase in diameter and minimum PWV during reactive hyperemia, respectively. Endothelial dysfunction resulted in a large effect size (ES) decrease in FMD (∆ = −3.10%; 95% CI: –4.15, –2.05; ES = −1.3), and a moderate increase in PWV (∆ = 0.38 m/s; 95% CI: 0.07, 0.69; ES = 0.5) and PWVmin (∆ = 0.16 m/s; 95% CI: 0.05, 0.28; ES = 0.6). There was a large intra-individual (pre- vs post-endothelial dysfunction) association between FMD and PWVmin (r = −0.61; 95% CI: –0.82, –0.24). In conclusion, acute change in PWV and PWVmin are at least partially driven by changes in endothelial function.