Search Results (21,462)

Carbonate reservoirs, characterized by extensive fractures and cavities, are prone to gravity displacement during drilling when the bottom-hole pressure approaches equilibrium. This phenomenon, driven by density differences between drilling and formation fluids, can result in simultaneous overflow and leakage, posing significant well control risks such as kicks or blowouts. The occurrence of gravity displacement downhole makes its timely detection through conventional annular flow monitoring techniques challenging. This study investigates the triggering conditions and safe density window for gravity displacement in fractured and cavernous formations. Through theoretical analysis and experimental simulation, we examined the displacement mechanisms in both fractured and cavernous conditions. Computational fluid dynamics (CFDs) simulations were used to validate critical fluid column heights for fractured formations and the proposed safe density window. Based on these findings, practical methods to mitigate the hazards associated with gravity displacement overflow are proposed. The results offer valuable guidance for the field identification and mitigation of such incidents, contributing to managed pressure drilling and enhancing drilling safety in complex carbonate reservoirs. Full article

Polypropylene fibers provide an innovative solution for enhancing the crack resistance of tunnel lining segments. However, existing macro-models obscure the distinct effects of fibers on the mortar and ITZ, while explicit meso-modeling remains computationally prohibitive. This study develops a multi-scale modeling framework to investigate PFRC segment fracture under bending. The framework integrates a 3D meso-scale module for calibrating fracture-related material properties, a 3D macro-scale module for predicting global displacements, and a 2D meso-scale module for resolving local fracture processes. A full-scale bending test was performed to validate the framework and to examine the effects of fiber content at both scales. Both the full-scale test and numerical simulations show that the segment response exhibits three stages: elastic, damage development, and cracking at the design load. Numerical simulations further reveal that an optimal fiber content of 0.4% reduces the vertical displacement at the load point by 9.8% and the horizontal displacement at the edge point by 2.9% relative to the fiber-free case. Meso-scale simulations show that 0.4% fibers decrease the bottom crack width from 0.0868 to 0.0770 mm (−11.29%) and limit internal crack connectivity. Although fibers may locally promote ITZ cracking due to reduced mortar–aggregate bonding, a strengthened mortar matrix suppresses crack penetration and connected crack networks. A pronounced high-damage peak in the ITZ near the failure threshold confirms the ITZ as the governing weak link; therefore, further improvements may require ITZ-strengthening strategies. Full article

This study systematically investigates the reaction characteristics of laminated shale oil reservoirs in the 7₃ sub-member of the Yanchang Formation, Heshui area, Ordos Basin, under exposure to CNI-I nanoviscous fracturing fluid. The reservoir matrix comprises 84.85% brittle minerals and 15.15% clay minerals. Fluid–rock interactions significantly dissolve calcite and dolomite, releasing Ca²⁺ and Mg²⁺ ions, while clay mineral reactions liberate substantial amounts of Na⁺. Post-reaction, fluid system stability is markedly reduced, elevating the risk of precipitate formation and pore-throat plugging. Exposure to fracturing fluid reduces the T₂ cutoff value of core samples from 3.29 ms to 1.72 ms, indicating a densification of the micro-pore-throat network and a decline in mobile fluid saturation, while fracture apertures exhibit widening. Based on empirical data, a discriminant criterion (R value) defined as the ratio of fracture aperture increment rate to pore-throat diameter reduction rate is established at 1.25, confirming that fracture propagation dominates over pore constriction. Dual-medium modeling yields a net permeability enhancement of 19.35%. Fluid–rock interactions induce overall degradation of rock mechanical properties with pronounced anisotropy: rock strength along the direction perpendicular to bedding declines by 37.546%, Young’s modulus decreases by 1.81%, and Poisson’s ratio increases by 0.02%—all significantly exceeding the degree of degradation parallel to bedding. This anisotropic mechanical degradation predisposes the near-wellbore region to shear slip and wall spalling, prompting the development of targeted engineering mitigation strategies. Full article

Variations in the groundwater chemical environment are a critical factor affecting the mechanical property degradation and structural alteration of coal measure strata. Addressing the engineering challenges commonly encountered in coal mining areas of Northwest China, where groundwater with varying pH leads to difficulties in controlling surrounding rock in underground spaces, this study established a comprehensive experimental methodology integrating mechanical loading, nuclear magnetic resonance (NMR) quantitative pore analysis, and scanning electron microscopy (SEM) microstructural characterization. The study revealed the mechanical degradation mechanisms and microstructural evolution characteristics of coal measure coarse sandstone under groundwater environments with different pH values (6–10). With prolonged immersion time, the peak strength and elastic modulus of the coarse sandstone exhibited exponential decay across all pH environments. NMR analysis revealed that the porosity evolved through a path of “increase–decrease–re-increase,” while the macroscopic mechanical failure mode shifted from brittle to brittle-ductile and finally to ductile characteristics. Micropores continuously transformed into medium and large pores, and the macroscopic failure mode exhibited a transition from brittle to brittle-ductile. The findings indicate that groundwater with varying acidity/alkalinity systematically alters the integrity and load-bearing capacity of coal measure coarse sandstone through the complex mechanism of “mineral dissolution (acidic H⁺ corrosion, alkaline OH⁻ hydrolysis)—structural damage—pore/fracture evolution—mechanical degradation.” This mechanism not only reveals the essence of progressive rock damage in weak acid to moderately strong alkaline environments but also provides important insights for the integrity, sealing capacity, and permeability modification of various underground engineering applications, such as CO₂ geological storage, unconventional natural gas development, and underground space utilization. Full article

Background: Sport participation has been shown to have a positive impact on bone mineral density (BMD) in children and adolescents. In fact, the type, intensity, and duration of sports activities may influence the magnitude of the effect on BMD. The aim of this study was to examine the effect of different sports on BMD in children and adolescents. Methods: We studied 90 children and adolescents (age 10.21 ± 2.96 years): 43 soccer players, 27 vocational dancers, and 20 active controls. In all subjects, bone mineral density at the lumbar spine (BMD-LS), at the femoral neck (BMD-FN), and at the total femur (BMD-TH) was measured. Moreover, their daily dietary calcium intake was assessed, and the presence of prior fractures was reported. Results: The values of the BMD-LS Z-score adjusted for height did not differ between the three groups: controls (BMD-LS Z-score values were 0.41 ± 1.26, 0.16 ± 0.94, and −0.14 ± 0.96 for soccer players, vocational dancers, and active controls, respectively). On the contrary, BMD-FN and BMD-TH were significantly higher in the soccer players group compared to the vocational dancers and active controls groups (BMD-FN Z-score values, adjusted for height, were 0.49 ± 1.35, −0.04 ± 0.84, and −0.63 ± 1.25 for soccer players, vocational dancers, and active controls, respectively). Soccer players with a history of fractures showed no reduced BMD values compared to those without previous fractures, whereas vocational dancers and active controls with fracture history had reduced BMD values. Conclusions: Consistent athletic involvement during the pre-pubertal and pubertal years significantly enhances bone mineral acquisition. Specifically, youth soccer players demonstrate superior BMD at the proximal femur compared to less active peers, underscoring the site-specific osteogenic effect of sport-related mechanical strain. Full article

Background/Objectives: Rigid interfragmentary compression is essential for primary bone healing following fractures, osteotomies, and arthrodeses of the foot and ankle. Evidence on the clinical performance of the MAX Variable Pitch Compression (VPC) Screw System (Zimmer Biomet, Warsaw, IN, USA) remains limited. This post-market, retrospective cohort study evaluated its safety, performance, and patient-reported outcomes. Methods: A single-center, consecutive series of patients treated with the MAX VPC Screw System for foot or ankle fractures, osteotomies, or arthrodeses between March 2018 and October 2023 was analyzed. The primary endpoint was radiographic and clinical bone union or joint fusion at 6–8 weeks and ≥18 months. Secondary endpoints included adverse events and functional outcomes using the Foot and Ankle Ability Measure (FAAM). Results: A total of 214 procedures were included (27 fractures, 80 osteotomies, 107 arthrodeses). Union was assessed in 209 procedures (97.7%) at 6–8 weeks and in 82 procedures (38.3%) at ≥18 months. Union rates were 86.1% at 6–8 weeks and 98.8% at ≥18 months. Early union was higher in arthrodeses (91.5%) than in fractures/osteotomies (80.6%). Adverse events occurred in 13.1% of procedures, 67.9% of which were device-related; no recurrent mechanical failures were observed. Mean FAAM scores were 92.3 (ADL) and 78.8 (Sports) for arthrodeses and 94.3 and 85.8, respectively, for fractures/osteotomies, at a mean FAAM follow-up of 2.9 years. Conclusions: The MAX VPC Screw System demonstrated high bone-union rates, favorable functional outcomes, and a moderate number of device-related complications. These results support its clinical use in foot and ankle surgery. However, the retrospective, single-center design limits generalizability, and prospective multicenter trials are warranted to confirm these findings. Full article

This study investigates the synergistic effect of functionalized carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibers (CFs) on the mechanical performance of cement-based composites through a multivariate optimization approach. All carbon allotropes were covalently functionalized via acid treatment to enhance dispersion and interfacial bonding with the cement matrix. A face-centered central composite design (FCCD) combined with response surface methodology (RSM) was employed to systematically evaluate the influence of the three reinforcements, each varied between 0.033 wt.% and 0.067 wt.%, with a total carbon content not exceeding 0.2 wt.% of cement. The statistical analysis revealed a negligible correlation between reinforcement content and flexural strength (explained variance ≈ 1%), whereas fracture energy and compressive strength showed stronger dependencies, with explained variances of 25% and 66%, respectively. The maximum experimental fracture energy reached 18.1 J, corresponding to an increase of nearly 800% compared to plain cement, obtained at the highest combined reinforcement content. Compressive strength improved up to 48 MPa (≈32% higher than the reference), with the model predicting potential enhancements up to 40% under optimized compositions. The regression analysis highlighted the dominant role of quadratic and interaction terms, indicating that mechanical performance is governed more by synergistic effects than by the linear contribution of individual components. These findings demonstrate that controlled co-dispersion of multiple functionalized carbon allotropes enables significant enhancement of cement mechanical properties at very low total carbon contents, providing a cost-effective strategy for the design of high-performance cementitious composites. Full article

The development and utilization of unconventional shale oil and gas have enhanced the resilience of global energy security. Hydraulic fracturing is the primary method for enhancing unconventional shale oil and gas extraction. Previous studies have predominantly employed homogenized geomechanical models to simulate fracture propagation in rock masses. However, bedding planes and inhomogeneous mineral distributions introduce mechanical anisotropy in shale, rendering conventional homogenized models insufficient for accurately representing hydraulic fracturing in real reservoirs. For this, millimeter-scale indentation testing was employed to systematically quantify the depth-dependent distribution of mechanical parameters across varying bedding orientations, using fragmented shale samples obtained from the Qingshankou Formation of the Songliao Basin, northern China. Then, hydraulic fracturing simulations were performed using the mechanical properties derived from the indentation tests. The key findings include: (1) The elastic modulus of the Qingshankou Formation shale reservoir exhibits significant anisotropic properties in both the depth and bedding orientations. The elastic modulus measured parallel to bedding (10.23–65.08 GPa) is 28% higher than that measured perpendicular to bedding (9.60–47.24 GPa) due to shale bedding anisotropy. The mineralogical composition predominantly governs the depth-dependent anisotropy, with an elevated brittle mineral content increasing the elastic modulus and a higher clay content reducing it. (2) The simulation results reveal that the depth-dependent anisotropy of elastic modulus induces asymmetric hydraulic fracture propagation, with the fractures preferentially extending along the orientations exhibiting a higher elastic modulus. This behavior arises due to the enhanced brittleness and reduced deformation resistance of high-modulus rocks, facilitating fracture advancement. The study offers critical insights for hydraulic fracturing design and operational implementation in bedded shale reservoirs. Full article

The morphology and connectivity of subsurface fracture networks are critical factors controlling wellbore stability and hydraulic fracturing efficiency. Accurate characterization of the three-dimensional complexity of fractures holds significant importance for engineering safety and performance enhancement. A novel image segmentation model is established in this study. It enhances the iterative threshold method by incorporating simple linear iterative clustering superpixels, ResNet50, and a Gaussian mixture model. The model first divides complex computed tomography images into numerous superpixel images using simple linear iterative clustering superpixel segmentation. Subsequently, ResNet50 is employed to classify these superpixel images. Based on the classification results, the iterative threshold segmentation method is applied to segment different categories of superpixel images accordingly. Following preliminary image segmentation, Gaussian mixture module is used for denoising the segmented fracture images, resulting in high-precision segmented images. The two-dimensional segmented images are then reconstructed in three-dimensional space, and the three-dimensional distribution characteristics of fractures are analyzed. This study concludes that the new fracture segmentation method enables high-precision extraction of fracture regions. Compared with threshold segmentation, the morphological analysis noise value in the two-dimensional images segmented by the method proposed in this study was reduced from 0.21% to 0.08%. Fracture distribution in three-dimensional space is complex, and areas with larger fracture networks exhibit greater complexity in their three-dimensional distribution. Full article

To address the pronounced productivity heterogeneity among different well intervals of coalbed methane (CBM) wells in the Weizhou Syncline, as well as the lack of quantitative clarity regarding the respective contributions of geological and engineering factors to well productivity, a systematic analysis of the main productivity-controlling factors of CBM wells was conducted based on geological data from producing wells, hydraulic fracturing treatment parameters, and production dynamic data in the study area. On this basis, a coupled coal reservoir–fracture numerical simulation model was established to quantitatively evaluate the response of CBM productivity to key geological parameters, including porosity, permeability, coal seam thickness, and Langmuir parameters, as well as fracture geometric and flow parameters. Furthermore, multiple machine learning methods were employed to rank and cross-validate the relative importance of factors influencing CBM well productivity. The results indicate that within the parameter ranges representative of the study area, coal seam thickness, permeability, and Langmuir pressure exert a dominant control on cumulative gas production, constituting the primary controlling factors for CBM well productivity. The number of fractures and porosity are secondary influencing factors, and, under the combined effects of multiple factors, fracture geometry, fracture flow parameters, and reservoir pressure make relatively limited contributions to well productivity. These findings provide a quantitative basis and methodological reference for favorable target selection, fracturing parameter optimization, and efficient development of CBM blocks in the Weizhou Syncline and other regions with similar geological conditions. Full article

Albumen transparency is an important quality trait of pigeon eggs that directly influences consumer preference and market value; however, its molecular basis remains unclear. This study aimed to characterize the key molecular differences between transparent and opaque pigeon egg albumen from an N-glycoproteomic perspective and to explore their associations with macroscopic textural properties. Transparent and opaque pigeon eggs were selected, and N-glycoproteomic analysis combined with texture profile analysis was conducted to compare glycosylation modifications and textural characteristics between the two groups. The results showed that transparent pigeon egg albumen exhibited significantly lower hardness, fracturability, gumminess, and chewiness than opaque albumen. Comparative glycoproteomic analysis revealed that the abundance of 122 glycopeptides was significantly lower in the transparent group, primarily originating from ovalbumin-related proteins and transferrin. Functional enrichment and protein–protein interaction analyses indicated that these proteins are closely associated with the extracellular space and serine-type endopeptidase inhibitor activity, and form a functional interaction module dominated by ovalbumin family proteins and transferrin. Overall, reduced N-glycosylation of key egg white proteins may influence protein aggregation behavior and gel network formation during heating, thereby contributing to differences in albumen textural properties and transparency. These findings provide glycoproteomic insights into the molecular mechanisms underlying transparency differences in pigeon egg albumen and identify specific glycosylation-related targets that may be exploited to modulate gel properties during thermal processing. This knowledge may support precision quality control of pigeon eggs and facilitate the development of transparent protein-based foods and functional gel products in the food industry. Full article

This narrative review summarizes current evidence on the molecular and cellular effects of low-dose methotrexate (LD-MTX) on bone tissue. In addition, it critically examines the limited and heterogeneous data on LD-MTX-associated osteopathy, a rare and incompletely understood condition that may be underrecognized in clinical practice. Finally, the review highlights key knowledge gaps and outlines future research directions aimed at improving diagnosis, management, and prevention. In total, 451 relevant articles were retrieved, and 71 studies were included in our review. Methotrexate (MTX) has been shown to prevent bone loss associated with inflammatory rheumatic diseases, primarily through its anti-inflammatory properties. However, current evidence highlights a variety of negative effects on bone associated with LD-MTX therapy, including osteoblast dysfunction, increased osteoclastogenesis, and endothelial damage. Collectively, these effects may result in deterioration of microarchitecture, impaired bone healing and insufficiency fractures. Despite the long and successful use of MTX in rheumatology, our knowledge of its effects on bone and awareness of LD-MTX osteopathy remain limited, potentially leading to delayed or missed diagnoses. Recent clinical studies highlight the potential underestimation of this condition and emphasize the need for further research to establish clear diagnostic criteria and treatment guidelines, as well as to achieve a more comprehensive understanding of the complex pathophysiology underlying LD-MTX osteopathy. Full article

Background: Intravascular lithotripsy (IVL) has emerged as a safe and effective modality for treating severely calcified coronary lesions. While the Shockwave™ system is well-established, clinical data on newer IVL platforms such as the Shunmei ShockFast™ system remain limited. Objectives: To evaluate the safety, feasibility, and procedural outcomes of the ShockFast IVL device in patients with heavily calcified de novo coronary artery disease. Methods: We conducted a prospective, single-center case series of 16 patients undergoing percutaneous coronary intervention (PCI) with the ShockFast IVL system between June and December 2025. Inclusion required angiographic or optical coherence tomography (OCT) evidence of severe coronary calcification. The primary efficacy endpoint was acute procedural success and absence of in-hospital MACE. Secondary endpoints included, among others, device deliverability, presence of calcium fracture and post-stent expansion metrics. Results: All patients underwent successful lithotripsy delivery with the ShockFast IVL system. Acute procedural success was 100%, with no intraprocedural complications, abrupt closure, or in-hospital MACE. OCT was performed in 50% of cases and demonstrated calcium fractures in all imaged lesions, with ≥2 fractures in 63% of cases. Median stent expansion was 90% [IQR 9], with no major malapposition or edge dissections. Quantitative coronary analysis showed a median acute lumen gain of 1.86 mm [0.62]. Conclusions: The ShockFast IVL system showed excellent safety and procedural performance in this first-in-center experience. Outcomes were encouraging and consistent with those reported in early-stage studies of other IVL platforms. These findings support the clinical feasibility of ShockFast as a novel tool for calcium modification in complex PCI. Full article

To address the problems of strong roof integrity, severe energy accumulation, and difficult caving in thick and hard roofs, a three-dimensional numerical study on fracture propagation and pressure-relief control durisng segmented hydraulic fracturing was carried out based on the engineering geological conditions of the 6125-1 working face at the Haishiwan Coal Mine, Shaanxi Province, China. using the ABAQUS finite element platform coupled with Ins-coh cohesive elements. A systematic analysis was conducted to elucidate the effects of elastic modulus, Poisson’s ratio, injection rate, and fluid viscosity on fracture initiation, stress evolution, and fractured volume. The results show that for every 10 GPa increase in elastic modulus, the average fractured volume decreases by 8%, and the fracture width exhibits a marked reduction; increasing Poisson’s ratio enhances the lateral deformation compatibility of the rock mass, raising the fracture width and volumetric growth rate by approximately 3% and 5%, respectively, although an excessively high Poisson’s ratio induces stress diffusion and reduces fracture stability. When the injection rate increases from 0.01 m³/s to 0.025 m³/s, the fractured volume increases by about 160%, and the maximum fracture width increases by 43%, whereas increasing fluid viscosity exerts a limited influence on volumetric growth but is conducive to stabilizing fracture morphology. Field observations via borehole imaging and seepage confirm full fracture connectivity within the roof and the formation of a continuous rupture zone, promoting timely roof breakage and caving along the dip direction and thereby creating favorable conditions for reducing rockburst hazards at the working face. This study clarifies the mechanical mechanisms and multi-parameter coupling laws governing hydraulic fracture propagation in thick and hard roofs, providing a theoretical basis and engineering reference for roof pressure-relief control and rockburst-resistant design under similar geological conditions. Full article

Fracture healing is a multistage regenerative process requiring the coordinated regulation of inflammation, osteogenesis, and bone remodeling, yet pharmacological agents that effectively modulate these processes remain limited. Adenophorae Radix (AR), a traditional medicinal herb used for tissue repair, has not been mechanistically investigated in skeletal regeneration. In this study, a mouse femoral fracture model was employed to evaluate the effects of short-term (7 days) and long-term (5 weeks) oral administration of AR. Bone regeneration was assessed using micro-computed tomography, histological staining, and quantitative real-time polymerase chain reaction. Network pharmacology and molecular docking were applied to predict bioactive AR constituents and their target pathways, followed by in vivo validation. Short-term AR treatment significantly upregulated osteogenic markers, including RUNX2 and osteocalcin, in the bone marrow, indicating early activation of osteoblast differentiation. Long-term administration enhanced bone mineral density, trabecular organization, and callus maturation. Network pharmacology analysis identified cycloartenol acetate, β-sitosterol, and mandenol as major active compounds targeting osteogenesis- and osteoclast-related pathways, converging on HIF1A, PTGS2, and PPARG. Molecular docking demonstrated strong binding affinities between these compounds and their predicted targets, which was supported by increased expression of HIF1A, PTGS2, and PPARG in AR-treated femora. Collectively, these findings suggest that AR promotes fracture healing by regulating osteogenic differentiation and bone remodeling through multi-target transcriptional networks. Full article