Search Results (35)

Indoxyl sulfate (IS), which is a protein-bound uremic toxin, is involved in vascular dysfunction and cardiovascular risk in subjects with chronic kidney disease (CKD). However, its role in peripheral arterial stiffness (PAS) remains unclear. This cross-sectional study evaluated the relationship between IS and PAS in patients diagnosed with CKD stages 3 through 5 who are not undergoing dialysis. Patients with CKD from a single center were enrolled. High-performance liquid chromatography analyzed the serum IS levels. PAS was evaluated using brachial–ankle pulse wave velocity (baPWV). IS was independently associated with PAS (odds ratio [OR]: 1.389 for 1 μg/mL increase in IS, 95% confidence interval [CI]: 1.086–1.775, p = 0.009) in a multivariable analysis after adjustment for age, hypertension, diabetes mellitus, blood pressure, lipid profiles, renal function, albumin, and proteinuria. Moreover, the mean baPWV (p = 0.010), left baPWV (p = 0.009), and right baPWV (p = 0.015) levels significantly correlated with the log-transformed IS (log-IS) levels. The area under the receiver operating characteristic curve for serum IS as a predictor of PAS was determined to be 0.667 (95% CI: 0.580−0.754; p = 0.0002). IS was associated with PAS in non-dialysis CKD stages 3–5, suggesting that IS may be a possible vascular risk marker. Future studies should address the nature of the relationship between IS and vascular dysfunction and assess therapeutic strategies to reduce IS. Full article

Natural gas hydrates, a promising clean energy resource, hold substantial potential. Porosity plays a crucial role in hydrate systems by influencing formation processes and physical properties. To clarify the effects of porosity on hydrate elasticity, we examined methane hydrate formation and its acoustic characteristics. Experiments were conducted on sediment samples with porosities of 23%, 32%, and 37%. P- and S-wave velocities were measured to assess acoustic responses. Results show that as hydrate saturation increases, sample acoustic velocity also rises. However, high-porosity samples consistently exhibit lower acoustic velocities compared to low-porosity samples and reach a lower maximum hydrate saturation. This behavior is attributed to rapid pore filling in high-porosity samples, which blocks flow pathways and limits further hydrate formation. In contrast, hydrate formation in low-porosity sediments progresses more gradually, maintaining clearer pore channels and resulting in relatively higher hydrate saturation. Higher porosity also accelerates the shift of hydrates from cementing to load-bearing morphologies. These findings underscore porosity’s significant influence on hydrate formation and provide insights into observed variations in hydrate saturation and acoustic velocity across different experimental conditions. Full article

Light element alloying in iron is required to explain density deficit and seismic wave velocities in Earth’s core. However, the light element composition of the Earth’s core seems hard to constrain as nearly all light element alloying would reduce the density and sound velocity (elastic moduli). The alloying light elements include oxidizing elements like oxygen and sulfur and reducing elements like hydrogen and carbon, yet their chemical effects in the alloy system are less discussed. Moreover, Fe-X-ray Absorption Near Edge Structure (Fe-XANES) fingerprints have been studied for silicate materials with ferrous and ferric ions, while not many X-ray absorption spectroscopy (XAS) studies have focused on iron alloys, especially at high pressures. To investigate the bonding nature of iron alloys in planetary interiors, we presented X-ray absorption spectroscopy of iron–nitrogen and iron–carbon alloys at high pressures up to 50 GPa. Together with existing literature on iron–carbon, –hydrogen alloys, we analyzed their edge positions and found no significant difference in the degree of oxidation among these alloys. Pressure effects on edge positions were also found negligible. Our theoretical simulation of the valence state of iron, alloyed with S, C, O, N, and P also showed nearly unchanged behavior under pressures up to 300 GPa. This finding indicates that the high pressure bonding of iron alloyed with light elements closely resembles bonding at the ambient conditions. We suggest that the chemical properties of light elements constrain which ones can coexist within iron alloys. Full article

This study investigates the natural gas hydrates within the Qiongdongnan Basin by integrating well-log and seismic data. Through pre-stack inversion and rock physics analysis, key parameters such as P-wave and S-wave impedances were utilized to distinguish hydrate-bearing formations from other geological bodies. A low-frequency model was constructed using the Inverse Distance Weighting (IDW) algorithm to improve the precision of parameter inversion. This study employs a multi-constraint inversion strategy, incorporating hard constraints from multiple wells and soft constraints from geological frameworks, ensuring reliable inversion results. Findings indicate that hydrate reservoirs are characterized by increased wave velocity and density due to hydrate accumulation, providing insights into the spatial distribution and characteristics of hydrates. This research enhances the understanding of hydrate reservoirs and offers valuable data for exploration in the Qiongdongnan Basin. Full article

The effective utilization of medium-high temperature geothermal energy is pivotal in reducing carbon emissions and plays a crucial role in developing clean energy technologies. The MiDu geothermal field, situated in the southeastern region of Dali Prefecture, Yunnan Province, lies within the Mediterranean–Himalayan high-temperature geothermal belt and is characterized by abundant geothermal resources. However, due to its considerable depth, exploration poses significant risks, resulting in a total utilization rate of less than 0.5% of the total reserves. This study employs natural seismic data to perform a tomographic analysis of the geothermal system in the Midu basin. By examining the P-wave velocity (Vp) and the velocity ratio of P-waves and S-waves (Vp/Vs) at various depths, the findings reveal that the basin comprises two distinct structural layers: the thrust basement of the Mesozoic and Paleozoic eras and the strike–slip extensional sedimentary layer of the Cenozoic era. A low-velocity anomaly in the central basin corresponds to the loose Cenozoic sedimentary layer. In contrast, high-velocity anomalies at the basin edges correlate with boundary faults and the Mesozoic–Paleozoic strata. Below a depth of 4 km, the Red River Fault and MiDu Fault continue to dominate the basin’s structure, whereas the influence of the Malipo Fault diminishes. The MiDu Fault exhibits higher thermal conductivity than the Yinjie Fault. It interfaces with multiple carbonate and basalt formations characterized by well-developed pores and fractures, making it a crucial conduit for water and a control point for geothermal storage. Consequently, the existence of medium-high temperature (>90 °C) geothermal resources for power generation should be concentrated around the Midu fault on the western side of the basin, while the Yinjie fault area is more favorable for advancements in heating and wellness. Full article

Cultural heritage assets face significant threats from climate change and land subsidence, leading to extensive social, economic, and environmental losses, and damage to artistic and monumental heritage in Italian coastal cities. In particular, addressing these challenges in the Venetian context necessitates the development of an adaptation plan for the lagoon area and the identification of targeted intervention strategies to preserve cultural and territorial heritage. To address these objectives, a systematic study was conducted to investigate the deterioration patterns exhibited by the most representative lithologies used in Venetian buildings. Thirty samples of five carbonate stone varieties subjected to natural aging were monitored in six different areas of Venice’s historic center and on Torcello Island, selected based on altimetry relative to tidal zero and exposure to environmental forces. An integrated multi-analytical approach was employed to identify and map macro- and micro-morphologies of stone surfaces related to chemical weathering and physical decay. Stones underwent evaluation during nine monitoring periods using various tests (ultrasound P-wave velocity and colorimetric measures) and analyses (µX-Ray Fluorescence, X-ray powder diffraction, stereomicroscope observations, and recognition of biological patinas). Data processing aimed to elucidate how microclimate and intrinsic stone features influence the occurrence and progression of deterioration phenomena. From the experimental findings, a Stone Deterioration Index and Intervention Procedures (SDIi) were proposed to estimate deterioration rates and assess the need for targeted intervention through conservative actions. Full article

Cardiovascular (CV) morbidity and mortality have been associated with rheumatoid arthritis (RA) and ankylosing spondylitis (AS). Natural autoantibodies (nAAb) are involved in innate immunity, as well as autoimmunity, inflammation, and atherosclerosis. There have not been any studies assessing the effects of biologics on nAAbs in RA and AS, also in relation to vascular pathophysiology. Fifty-three anti-TNF-treated RA and AS patients were included in a 12-month follow-up study. Anti-citrate synthase (CS) and anti-topoisomerase I fragment 4 (TOPO-F4) IgM and IgG levels were determined by ELISA. Ultrasonography was performed to assess brachial artery flow-mediated vasodilation (FMD), common carotid intima-media thickness (ccIMT), and arterial pulse-wave velocity (PWV). Other variables were also evaluated at baseline and 6 and 12 months after treatment initiation. Anti-TNF therapy improved FMD in RA and PWV in AS and stabilized ccIMT. TNF inhibition increased anti-CS IgM and IgG, and possibly also anti-TOPO-F4 IgG levels. Various correlation analyses revealed that nAAbs might be independently involved in autoimmunity as well as changes in inflammation and vascular pathology over time in biologic-treated patients (p < 0.05). We also found associations between anti-TOPO-F4 IgG and anti-Hsp60 IgG (p < 0.05). Baseline nAAb levels or nAAb level changes might determine changes in CRP, disease activity, FMD, PWV, and ccIMT over time (p < 0.05). The interplay between arthritis and inflammatory atherosclerosis, as well as the effects of anti-TNF biologics on these pathologies, might independently involve nAAbs. Full article

In physical engineering, a rock surface, whether naturally or artificially formed, is rough. When irradiating rocks, microwaves produce reflections and diffractions on the surface of rough rocks, which significantly affect the absorption of microwave energy by rocks, thus influencing the result of microwave irradiation. In order to explore the influence of rough rock surfaces on the effect of microwave-assisted rock breaking, microwave irradiation tests were carried out on basalt samples with different values of roughness to test the temperature and P-wave velocity of the samples before and after microwave irradiation. Numerical test methods were used to systematically study the influence of rough rock surfaces on microwave irradiation. The results show that, under the same microwave irradiation conditions, the effect of microwave irradiation on rough surface basalt is more significant than that of flat surface basalt. The surface temperature distribution range of flat surface specimens is narrow, the surface temperature range of rough surface specimens is wider and more inhomogeneous, and the maximum surface temperatures of rough surface specimens are much higher than those of flat surface specimens. After irradiation, new macroscopic cracks were generated on the surface of the samples, and the crack propagation of the rough surface samples was more obvious. The decrease in P-wave velocity before and after the irradiation of flat surface samples is small, and that of rough surface samples is larger. The main factors affecting the effect of microwave irradiation on the rough surface are the refraction and reflection of electromagnetic waves, heat conduction, and stress concentration on the surface. Full article

The investigation of arterial stiffening is a promising approach to estimating cardiovascular risk. Despite the widespread use of different methods, the dynamic nature of measured and calculated stiffness parameters is marginally investigated. We aimed to determine the stability of large artery elasticity parameters assessed via commonly used, ultrasound-based and oscillometric methods in relation to peripheral resistance modulation. A human experimental environment was composed, and fifteen young males were investigated at rest after extremity heating and external compression. Functional vascular parameters were monitored in each session, and several arterial stiffness parameters were analysed. The distensibility coefficient (DC) did not show significant changes during heat provocation and extremity compression, while DC’s stability seemed to be acceptable. The same stability of carotid–femoral pulse wave velocity (PWV) was detected with ultrasound measurement (5.43 ± 0.79, 5.32 ± 0.86 and 5.28 ± 0.77, with p = 0.38, p = 0.27 and p = 0.76, respectively) with excellent intersession variability (intraclass correlation coefficient of 0.90, 0.88 and 0.91, respectively). However, the oscillometric PWV (oPWV) did change significantly between the heating and outer compression phase of the study (7.46 ± 1.37, 7.10 ± 1.18 and 7.60 ± 1.21, with p = 0.05, p = 0.68 and p < 0.001, respectively), the alteration of which is closely related to wave reflection, represented by the changes in reflection time. Our results indicate the good stability of directly measured elastic parameters such as DC and PWV, despite the extreme modulation of peripheral resistance. However, the oscillometric, indirectly detected PWV might be altered by physical interventions, which depend on wave reflection. The effective modulation of wave reflection was characterized by changes in the augmentation index, detected using both oscillometry and applanation tonometry. Thus, the environment during oscillometric measurement should be rigorously standardized. Furthermore, our results suggest the dynamic nature of the reflection point, rather than being a fixed anatomical point, proposed previously as aortic bifurcation. Full article

Seismic response assessment requires reliable information about subsurface conditions, including soil shear wave velocity $(V_s)$. To properly assess seismic response, engineers need accurate information about $V_s$, an essential parameter for evaluating the propagation of seismic waves. However, measuring $V_s$ is generally challenging due to the complex and time-consuming nature of field and laboratory tests. This study aims to predict $V_s$ using machine learning (ML) algorithms from cone penetration test (CPT) data. The study utilized four ML algorithms, namely Random Forests (RFs), Support Vector Machine (SVM), Decision Trees (DT), and eXtreme Gradient Boosting (XGBoost), to predict $V_s$. These ML models were trained on 70% of the datasets, while their efficiency and generalization ability were assessed on the remaining 30%. The hyperparameters for each ML model were fine-tuned through Bayesian optimization with k-fold cross-validation techniques. The performance of each ML model was evaluated using eight different metrics, including root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), coefficient of determination ($R^2$), performance index ($PI$), scatter index ($SI$), $A10-I$, and $U_{95}$. The results demonstrated that the RF model consistently performed well across all metrics. It achieved high accuracy and the lowest level of errors, indicating superior accuracy and precision in predicting $V_s$. The SVM and XGBoost models also exhibited strong performance, with slightly higher error metrics compared with the RF model. However, the DT model performed poorly, with higher error rates and uncertainty in predicting $V_s$. Based on these results, we can conclude that the RF model is highly effective at accurately predicting $V_s$ using CPT data with minimal input features. Full article

The influence of saturation on the Poisson’s ratio v of reservoir sediments has an engineering significance in the field of oil and nature gas exploration. Based on a self-developed combined (BE-EE-RC) test system, under the dehydration path, the Poisson’s ratio variation of reservoir silty-fine sand in Hangzhou Bay, China, was investigated. Results show that the P- and S-wave velocities vary non-monotonically with decreasing saturation at different net stresses, and reach a maximum at the optimum saturation S_r(opt); Biot’s theory with respect to variation in V_p with S_r matches well with the measured e data. With a small amount of gas intrusion, Poisson’s ratio of saturated sand shows a sudden drop and gradually stabilizes; then, it attenuates slowly and reaches the minimum value at S_r(opt). Once the saturation degree decreases to the level lower than S_r(opt), it rapidly increases. Based on the soil–water characteristic curve (SWCC) and mesoscopic evolution of internal pore water morphology, the variation in Poisson’s ratio v can be divided into four segments of saturation: the boundary effect stage, the primary transition stage, the secondary transition stage, and the unsaturated residual stage. Ultimately, a prediction model for Poisson ratio’s v of the silty-fine sand was proposed to consider the saturation variation. Full article

Rock mechanics parameters control the distribution of in situ stress and natural fractures, which is the key to sweet spot evaluation in reservoir engineering. Combined with the distribution of in situ stress, an experimental scheme of stress on rock physical parameters was designed. The results show that rock sonic velocity is extremely sensitive to water saturation under overburden pressure. At ultrasonic frequencies, when the water saturation increases from 0% to 80%, the P-wave velocity increases first and then decreases. When the water saturation continues to increase to 100%, the P-wave velocity increases. This is due to the effect of water saturation on the shear modulus. Saturation is negatively correlated with shear wave velocity and resistivity. Different minerals have different control effects on the rock P-S wave velocity ratio. Quartz content plays a dominant role, and the two are negatively correlated, followed by feldspar and clay, and the two are positively correlated with the P-S wave ratio. The confining pressure, axial compression, stress ratio and burial depth are positively correlated with the P-S wave and negatively correlated with the P-S wave ratio; in descending order, the influencing factors of stress on the petrophysical parameters are maximum stress ratio > confining pressure > axial pressure. Full article

The freeze–thaw process plays a dominant role as far as the exploration and development of natural resources in cold regions are concerned. Freeze–thaw cycles can cause frost heaving pressure in the rock matrix and result in micro cracking, which influences its physical and mechanical properties. A series of physical and mechanical tests are performed on red sandstone to investigate the fracture behavior and mechanical properties induced by freeze–thaw cycles. The testing results show that after being treated by freeze–thaw cycles, the mass, density, and P-wave velocity of rocks decrease, while the volume of rocks increases. The peak stress and elastic modulus decrease with the increase in freeze–thaw cycles, while peak strain and Poisson’s rate increase. When 30 MPa confining pressure is applied, the peak stress and elastic modulus of untreated samples reach the maximum values of 92.49 MPa and 12.84 GPa, respectively. However, after being treated by 30 freeze–thaw cycles, the peak strain and Poisson’s rate reach the maximum values of 0.631 % and 0.18, respectively. The development of micro-cracks and the growth of pores induced by frost heaving stress are the main reasons for the deterioration of the mechanical properties of rocks. Confining pressure and freeze–thaw cycles can transfer the rock’s failure mode from tensile to shear and make red sandstone show more ductility features. Full article

The Urumqi area in China is a seasonally cold region, and the rock structures in the region are susceptible to freeze-thaw (F-T) weathering. Therefore, this study investigated the effect of F-T on the physical, mechanical, and fracture behavior of sandstone from Urumqi. The acoustic emission method (AE) was used to determine the stress thresholds for the initiation and development of cracks in the samples under cyclic F-T action. The results suggested that parameters such as P-wave velocity, elastic modulus, and peak stress presented a significant negative correlation with F-T damage, while porosity exhibited a close positive correlation. The elastic modulus of the sample was more sensitive to the F-T action with the smallest half-life (27 cycles) and the largest decay factor (0.0254). In addition, the stress threshold for micro-cracks development and macro-cracks initiation in the samples decreased with increasing F-T damage. After 30 F-T cycles, the stress threshold for micro-cracks propagation in the samples decreased from 20.73 MPa to 5.02 MPa by approximately 76%. The normalized stress threshold for the macro-cracks initiation was also decreased from 0.93 to 0.71. Moreover, the macro-cracks damage zone of the samples showed an increasing trend with F-T damage, from 7% under natural conditions to 29% after 30 cycles. It is concluded that F-T action lowers the stress thresholds for cracks development in sandstone in the Urumqi area, posing serious safety concerns for mass rock engineering in this area. Full article

The Young’s modulus and Poisson’s ratio, parameters reflecting the elastic response of a rock to stress, are the key parameters used in many engineering activities, such as hard coal mining and natural gas extraction. The objective of this paper was to present the results of complex laboratory measurements of the static and dynamic Young’s modulus and Poisson’s ratio for Upper Carboniferous hard coals from the Upper Silesian Coal Basin. The coals differed in geologic age (Mudstone Series—younger coals; Upper Silesian Sandstone Series—older coals) and petrographic structure (vitrain, clarain, and durain lithotype). Elastic parameters of the coals were determined following compression tests under a complex state of stress, as well as using the ultrasonic method in reservoir conditions. On this basis, linear functional dependences between parameters such as UCS, differential stress, confining pressure, strain rate, P- and S-wave velocities, and the static and dynamic Young’s modulus and Poisson’s ratio were determined. These dependences turned out to be linear, with strong and very strong correlation, as indicated by the high coefficients of determination, R². These new results significantly broaden the knowledge of elastic properties of Carboniferous hard coals, especially in the field of geoengineering, underground coal gasification, and reservoir stimulation for coal bed methane extraction. Full article