Search Results (244)

Long-term safety assessment of deep geological repositories for spent nuclear fuel requires explicit evaluation of thermo-mechanical (TM) processes induced by decay heat and their influence on fractured host rock. A safety-relevant, though low-probability, scenario concerns shear reactivation of fractures intersecting deposition holes, which could compromise canister integrity if displacement exceeds design limits. This study presents a three-dimensional discrete element modelling approach to analyze the thermal evolution of the Forsmark repository (Sweden) and the associated long-term response of a discrete fracture network (DFN) during the post-closure phase. The model explicitly represents repository panel, deterministic deformation zones, and a stochastically generated fracture network embedded in a bonded particle assembly representing the rock for Particle Flow Code (PFC) numerical simulations. Time-dependent heat release from spent nuclear fuel canisters is implemented using a physically based decay power function. A deposition panel-scale heat-loading formulation accounts for deposition-hole and tunnel spacing. Two emplacement scenarios are analyzed: (a) a simultaneous all-panel heating scenario, used as a conservative bounding case, and (b) a sequential panel heating scenario representing staged emplacement and closure. The simulations show that temperature and thermally induced stress evolution are sensitive to the emplacement and closure sequence. Sequential heating produces a more gradual thermal build-up and lower peak temperatures than simultaneous heating, indicating that thermal and stress perturbations in the host rock can be influenced not only through repository design, but also by operational strategy. Thermally induced fracture shear displacement displays a systematic temporal response. Fractures located within the deposition panel footprint develop shear displacement rapidly during the early post-closure period, reaching peak values at approximately 200 years, followed by gradual relaxation as temperatures decline. The average peak shear displacement on fractures is on the order of 2–3 mm, while fractures outside the panel footprint show smaller early-time displacements and a more prolonged long-term response. All simulated shear displacements remain more than one order of magnitude below the commonly cited canister damage threshold for Forsmark of approximately 50 mm, even for the conservative simultaneous heating case. These results indicate that thermally induced fracture shear is unlikely to cause direct mechanical damage to canisters. At the same time, the persistence of residual shear displacement after heating implies permanent fracture dilation, which may influence long-term hydraulic properties and indirectly affect processes such as groundwater flow and canister corrosion. The modelling framework and results presented here were conducted for review purposes independently from the Swedish safety case, and provide a mechanistic basis for evaluating thermally induced fracture deformation in crystalline rock repositories and contribute to bounding the role of thermo-mechanical processes in the safety assessment of spent nuclear fuel disposal at Forsmark. Full article

Introduction: Intracranial aneurysms (IAs) are focal dilatations of cerebral arteries that carry a significant risk of rupture and subarachnoid hemorrhage (aSAH). Advances in basic science have improved understanding of vascular wall biology, hemodynamic stress, inflammation, and genetic contribution to aneurysm rupture. Rapid progress in neurovascular therapeutics highlights the need to evaluate emerging molecular and pharmacologic strategies targeting IAs. Methodology: This narrative review synthesizes evidence from 2015 to 2025 on the cellular, molecular, and biomechanical mechanisms underlying IA pathophysiology. A structured search of PubMed, Scopus, and Embase identified studies examining molecular pathways, genetic determinants, and therapeutic approaches. Discussion: Aneurysm initiation involves endothelial responses to abnormal shear stress, activating NF-κB, MAPK, and calcium-dependent pathways that promote inflammation, smooth-muscle cell apoptosis, and extracellular matrix degradation. Pharmacologic candidates including MCP-1 antagonists, PPARγ agonists, and IL-6/STAT3 inhibitors reduce inflammatory remodeling, while doxycycline and cathepsin inhibitors preserve matrix integrity. Emerging strategies like microRNA modulation, tyrosine-kinase inhibition, and gene-based delivery offer potential for localized, durable stabilization with minimal systemic toxicity. Conclusions: Integrating surgical and biologic therapies may shift IA management from reactive repair to rupture prevention. Full article

Background/Objectives: Chronic venous disease (CVD) is a prevalent condition marked by valve dysfunction and increased pressure in lower limb veins. The trans-nodal veins in the inguinal region and Scarpa triangle, which connect the superficial and deep venous systems, provide new insight into venous insufficiency pathways. While they function normally in healthy individuals, they can become dilated in chronic venous disease or following surgery. The purpose of this study was to provide an ultrasonographic anatomical description of intranodal varicose veins and to assess possible changes in the stiffness of varicose, dilated inguinal lymph nodes. Methods: The study comprised 92 participants, including 69 women and 23 men, who underwent Doppler ultrasound examinations of the lower-limb venous system, focusing on the groin from both a descriptive morphological and an elastographic perspective. The diagnosis of lymph node varices was made according to established criteria, its severity was assessed using an original classification system, and shear-wave elastography (SWE) values were recorded. Results: More than 83% of patients with operated CVD had lymph node varicose veins. Patients with lymph node varicose veins had larger groin lymph node diameters than patients with CVD without lymph node varicose pathology. The mean shear wave elastography values were significantly lower in the group with lymph node varices compared to the group without (12.2 ± 1.1 kPa vs. 20.1 ± 2.3 kPa; p < 0.05). Elastographic values correlate with lymph node diameter (p = 0.039) and with varicose vein grade (p < 0.001). Conclusions: Intranodal varices may indicate disease progression. These vascular abnormalities impact SWE measurements by altering tissue mechanics. It is imperative to consider the interactions between the lymphatic and venous systems in the management of CVD to improve patient outcomes. Full article

Background: Assessing aortic dissection (AD) in its early stages is crucial for cardiovascular surgeons to improve patient outcomes and avoid complications associated with surgical intervention for type A aortic dissection. Initial evaluations rely on patient referrals for computed tomography (CT) scans, which involve measuring the maximum aortic diameter. Objective: This study aimed to improve current diagnostic thresholds for type A aortic dissection by using computational fluid dynamics (CFD) modeling to correlate hemodynamic factors related to the wall shear stress with maximum aortic diameter growth rate, offering insights into predicting AD progression and reassessing current diameter-based diagnostic criteria. Methods: The pre- and post-AD scan data, with an average duration of three and a half years for the 15 patients, were converted into 3D geometries. These geometries were analyzed using the transitional-turbulent CFD model. Wall shear stress (WSS), its derivatives, and the pressure gradient from the pre-AD CT scans were compared across 15 patients, grouped according to the aortic diameter growth per year. Results: For patients in group 1 (nine patients with normal diagnosis), pre-AD time-average wall shear stress (TAWSS) was mostly 2–4 Pa, above physiologic levels. Post-AD, values dropped below 1.5 Pa (stagnant, thrombus-prone), with oscillatory shear index (OSI) elevated (0.24–0.32). In group 2 (n = 6, abnormal diagnosis), post-AD TAWSS was <3 Pa (thrombosis risk), with OSI 0.1–0.31 near tear sites. These findings confirm a dual-risk profile: low TAWSS promotes thrombosis, while high TAWSS drives dissection progression. Conclusions: WSS parameters, such as TAWSS and OSI, can be utilized to assess the development of a dilated ascending aorta, especially for extreme maximum aortic diameter. Pre-AD analysis for some patients revealed a strong negative correlation, indicating that high shear stress in the true lumen (TL) results in a drop in diastolic pressure post-AD at the upward-going section of the aorta. Full article

The long-term stability of embankments is directly influenced by the stress paths associated with river water level fluctuations. To investigate the anisotropic characteristics of slope soil in embankments under such drainage-induced gradual loading conditions, a series of drained directional shear tests was conducted on slope soil to investigate the coupled effects of the principal stress direction angle α and the intermediate principal stress coefficient b on its strength, deformation, and non-coaxial characteristics. Results showed that radial strain exhibited minimal sensitivity to variations in the principal stress direction angle α at the constant principal stress coefficient b. The circumferential and axial strain directions demonstrated symmetry. Specimens initially contracted then dilated during shearing. Octahedral shear strain anisotropy was more significant at b = 0.5 and 1 than at b = 0. For a constant α, the normalized strength at b = 0.5 exceeded that at b = 0 and 1. Strength showed significant anisotropy across angles α at a constant b. Specimens exhibited significant non-coaxial behavior under axial-torsional shear loading. This study offers theoretical insight into embankment slope behavior under anisotropic stress paths. Full article

Granular materials exhibit complex mechanical behaviors during unloading, yet the underlying micro- and meso-scale mechanisms remain unclear. This study employs a discrete element method to simulate a series of triaxial tests on sand and pebble specimens with varying initial densities under different unloading stress paths. While dense specimens demonstrate strain softening and dilatancy, loose samples exhibit shear contraction. To quantify the underlying fabric evolution, persistent homology (PH) theory is adopted to analyze the particle contact force networks. The results reveal that the average strength of this network correlates strongly with the macroscopic stress–strain response. For dense samples, network strength rapidly increases to a peak coinciding with the deviatoric stress maximum, then gradually decreases with further shear. Crucially, this evolution is path-dependent: the average contact force network strength increases approximately 20% more during unloading in the minor principal stress direction compared to unloading in the major principal stress direction. This quantitative analysis of force chain degradation provides a mechanistic explanation for the observed strain softening, highlighting the dominant role of the unloading stress path. In contrast, loose specimens, which initially lack an obvious force chain network, show negligible microstructural evolution during unloading. Full article

Vascular ageing is a complex process marked by progressive endothelial dysfunction, chronic low-grade inflammation (“inflammageing”), and reduced regenerative capacity, driven in part by an imbalance between protective endothelial autophagy and cellular senescence characterized by a proinflammatory senescence-associated secretory phenotype (SASP). Disruption of this autophagy–senescence axis accelerates vascular inflammation, arterial stiffening, and atherogenesis. High-intensity interval training (HIIT), consisting of repeated bouts of near-maximal anaerobic effort with recovery periods, is widely used by both elite and recreational athletes and is increasingly recognized as an effective nonpharmacological strategy to enhance endothelial function, arterial elasticity, and mitochondrial biogenesis. However, excessively intense or poorly structured HIIT, particularly in the absence of adequate recovery or in individuals with underlying cardiometabolic or vascular vulnerability, may induce endothelial stress and promote maladaptive vascular remodelling, including calcification and plaque instability. These considerations underscore the need for refined individualized exercise prescription strategies that balance performance benefits with endothelial protection. Based on these observations, here, we introduce a novel conceptual framework, “shear dose–calibrated HIIT,” designed to understand and define an optimal shear dose capable of maximizing autophagic flux while minimizing SASP activation. Experimental and clinical evidence of HIIT-induced effects on flow-mediated dilation (FMD), pulse wave velocity (PWV), and redox biomarkers is presented, followed by the proposal of a biomarker panel for assessing autophagic flux and cellular senescence in peripheral samples (peripheral blood mononuclear cells (PBMCs), extracellular vehicles (EVs), and plasma). This integrative approach, which combines vascular mechanotransduction, redox biology, and autophagic signalling, provides a novel translational perspective on how individually calibrated HIIT can promote vascular longevity and reduce cardiometabolic risk associated with aging and metabolic syndrome. Full article

Strike-slip faults and their associated fractures in the ultra-deep marine carbonate reservoirs of the Fuman Oilfield, Tarim Basin, hold significant petroleum geological importance, with the developmental characteristics of fractures being a key factor controlling reservoir productivity. This study targets the F_I17 strike-slip fault zone within the oilfield, where a comprehensive evaluation of fracture effectiveness was performed by integrating geological methods, including core and thin section observation, fluid inclusion thermometry, geophysical fracture identification approaches using imaging logging and seismic data, and geomechanical simulations. The results showed that: (1) structural fractures were developed in at least three stages, predominantly high-angle fractures with their strikes obliquely intersecting the main fault at a small angle, and were affected by multiple episodes of fluid activity, while early-phase fractures exhibited severe filling whereas late-phase fractures had good effectiveness; (2) ultra-deep carbonate rocks contained well-developed stylolites, with extensive horizontal stylolites reducing fracture effectiveness; (3) mechanical effectiveness evaluation parameters were proposed by integrating normal stress, shear stress, and formation pressure, with slip tendency as the dominant indicator, and referenced to the leakage factor and dilation tendency to characterize fracture effectiveness; (4) dynamic effectiveness was assessed using closure/opening pressures, defining a reasonable formation pressure range for hydrocarbon exploitation. The findings of this study can provide theoretical guidance for the further exploration and development of ultra-deep reservoirs in the Fuman Oilfield. Full article

The rheological behavior of a 9.5 °API extra-heavy dead crude oil produced in the southern Gulf of Mexico is experimentally investigated over the temperature range $30 °\mathrm{C}\le T\le 100 °\mathrm{C}$. Steady-shear measurements are used to characterize the stress–strain-rate response and apparent viscosity under controlled laboratory conditions representative of surface transport. Statistical analyses show that the oil exhibits a Bingham plastic behavior at 30 °C, transitions to a Herschel–Bulkley-type response at 50 °C, and displays a predominantly dilatant behavior at 100 °C. Existing dead oil viscosity correlations commonly used in field applications are evaluated against the experimental data and are found to systematically underpredict the viscosity by approximately one order of magnitude within the studied temperature range. Motivated by the observed exponential dependence of viscosity on temperature, a crude-specific viscosity–temperature correlation is proposed for this specific crude oil. The new correlation provides a significantly improved representation of the experimental data and leads to substantially more accurate pressure drop predictions in a representative pipeline transport scenario. The results highlight the importance of crude-oil-specific rheological characterization and viscosity modeling for reliable flow assurance analyses involving extra-heavy crude oils. Full article

Soil–steel interface shear governs load transfer and long-term serviceability in piles, retaining systems, and buried infrastructure; yet the large-displacement interface mechanics of fibre-reinforced sands remain poorly resolved, limiting sustainable design. This study couples large-displacement ring-shear testing with physics-guided hybrid AI to quantify and predict the peak and residual resistance of sand–polypropylene fibre mixtures sliding on smooth and rough steel. Two quartz sands with contrasting particle morphology were tested under 25–200 kPa normal stress and 0–1.0% fibre content, producing a design-oriented database that captures post-peak evolution and residual states. The experiments reveal a strongly nonlinear reinforcement law: an optimum fibre range enhances dilation, stabilises the shear band, suppresses post-peak softening, and increases residual strength, whereas excessive fibres disrupt the granular skeleton and reduce mobilisation efficiency. Roughness and confinement act as amplifiers, intensifying fibre-driven dilation and asperity interlock. To translate mechanisms into prediction, three strategies were benchmarked: a deep neural network (DNN), the Physics-Guided Neural Additive Model (PG-NAM++), and the physics-anchored Residual-DNN that learns only the correction to a mechanical baseline. Residual-DNN achieved the tightest agreement and the highest physical consistency for both peak and residual strength, enabling robust parameter selection with reduced uncertainty and overdesign. The combined experimental–AI framework advances the United Nations Sustainable Development Goals (SDGs) by supporting SDG 9 through resilient, innovation-led infrastructure design and contributing to SDG 12 by enabling optimised (rather than maximal) use and reuse of reinforcement materials within circular ground-improvement practice. Full article

Cemented paste backfill (CPB) is widely adopted in underground mines, where the shear resistance of the CPB–rock interface critically governs the integrity of backfill–rock systems. This study investigates the effects of polypropylene fiber reinforcement, surface roughness (Joint Roughness Coefficient, JRC = 0 and 1.76), and curing time (1, 3, and 7 days) on the shear strength and deformation characteristics of CPB–rock interfaces. Direct shear tests were performed under normal stresses of 50, 100, and 150 kPa, with synchronous measurements of shear and vertical displacements. Results show that increasing roughness markedly strengthens the interface, with the peak shear stress rising by up to 45% due to enhanced mechanical interlocking and dilation. In contrast, adding 0.5 vol.% PP fibers slightly reduces peak shear capacity but consistently improves post-peak deformability, indicating a transition from brittle interfacial fracture to a more ductile, progressive failure mode. A three-stage mechanical model was established to describe the shear stress–displacement relationship, incorporating elastic, bond degradation, and frictional sliding phases. The model parameters, including the shear stiffness ($K_s$), bond degradation coefficient ($\eta$), and residual strength (${\tau }_r$), were calibrated using the experimental data. Mohr–Coulomb analysis further quantifies the curing-dependent evolution of interfacial strength parameters, highlighting a marked increase in cohesion from 1 to 7 days alongside roughness-governed peak strengthening. This research provides insights into the optimization of the CPB–rock interface design for enhanced geomechanical performance in underground applications. Full article

Based on true triaxial loading experiments and particle flow numerical simulations (PFC3D), this study systematically analyzes the mechanical behavior and failure mechanisms of granite under the influence of stress difference (deviatoric stress). The experimental results indicate that increasing deviatoric stress reduces peak strength, axial strain, and lateral strain, promoting rock failure with less deformation and dilatancy. An energy analysis reveals that higher deviatoric stress suppresses peak energy accumulation, with a greater proportion of energy being dissipated through crack initiation and propagation. Macroscopic observations show that failure surfaces develop combined tensile-shear cracks, evolving into distinct “V” shapes as deviatoric stresses increase. Numerical simulations demonstrate that intermediate principal stress plays a dual role, initially facilitating, then inhibiting, and finally promoting rock failure with its continuous increase. Microscopically, tensile cracks dominate during pre-peak stages, while rapid crack coalescence in the post-peak stage leads to the formation of throughgoing V-shaped failure zones. Particle displacement analysis reveals that deformation concentrates along the minimum principal stress direction, with the displacement vectors ultimately forming a V-shaped boundary that delineates the failure zone. The research provides comprehensive insights into the macro-meso failure characteristics of hard rock under true triaxial conditions, offering valuable guidance for stability prediction and control in underground rock engineering projects such as water-sealed storage caverns. Full article

The mechanical response of geomembranes in hydraulic structures is strongly influenced by temperature variations, which alter both material stiffness and interface shear strength behavior. This study develops a non-linear, temperature-dependent tensile behavior constitutive model for a polyvinyl chloride (PVC) geomembrane and evaluates its implications for the stability of geomembrane-lined reservoir slopes. The empirical relationship was calibrated using tensile tests reported in literature for temperatures between 10 °C and 60 °C, reproducing the observed non-linear softening and modulus reduction with increasing temperature. A classical thermal dilation formulation was incorporated to simulate cyclic thermal expansion and contraction. The constitutive and thermal formulations were implemented in FLAC2D and applied to a 2H:1V covered geomembrane slope representative of dam lining systems. The results show that temperature-induced softening significantly increases tensile strain within the geomembrane. The model also shows that the lower surface interface friction angle of the geomembrane plays a significant role in the slope stability. Thermal cycle analysis demonstrates the accumulation of efforts resulting from the fatigue of the geomembrane. The proposed model provides a practical framework for incorporating thermo-mechanical coupling in design analyses and highlights the necessity of accounting for realistic thermal conditions in assessing the long-term stability of geomembrane-lined reservoirs. Full article

This study aimed to elucidate the impact of Persian Gum (PG; Amygdalus scoparia Spach) on the heat-induced aggregation and interfacial behavior of whey protein isolate (WPI). To achieve this, pure WPI and mixed WPI-PG systems were subjected to thermal treatments between 25 and 85 °C, and their structural and functional changes were characterized using fluorescence spectroscopy, UV-vis absorption, turbidity and bulk viscosity measurements, interfacial shear and dilatational rheology, and foaming assessments. The presence of PG altered the aggregation pathway of WPI in a temperature-dependent manner, producing smaller, more soluble complexes with lower turbidity, particularly at higher temperatures. Both pure WPI and WPI-PG mixtures exhibited increased surface hydrophobicity upon heating; however, PG generally reduced the dilatational elastic modulus except at 85 °C, where the mixed system showed a higher modulus than WPI alone. In contrast, the interfacial shear modulus increased over time in all samples, with consistently higher values observed for WPI-PG mixtures at both 25 °C and 85 °C. Notably, three complementary methods were employed to evaluate foaming properties and interfacial behavior in this study, revealing that factors such as concentration, measurement time, and methodological approach strongly influence the observed responses, highlighting the complexity of interpreting protein-polysaccharide interactions. The ability of PG to modulate WPI unfolding and limit the formation of large aggregates during heating demonstrates a previously unreported mechanism by which PG tailors heat-induced protein network formation. These findings underscore the potential of Persian Gum as a functional polysaccharide for designing heat-treated food systems with controlled aggregation behavior and optimized interfacial performance. Full article

Deep-sea-resource development and marine engineering represent cutting-edge global research priorities. As a typical deep-sea region in the Western Pacific, the physical–mechanical properties of the South China Sea’s deep-sea sediments have critical implications for regional and global deep-sea engineering design and the safety assessments of resource exploitation. However, due to extreme environmental conditions and sampling technology limitations, studies on the mechanical behavior and microstructural control mechanisms of sediments in complex marine environments exceeding 2000 m in depth remain insufficient worldwide, hindering precise engineering design and risk management. This study systematically investigates the physical–mechanical properties, microstructure, and mechanical behavior of intact sediments acquired at a depth of 2060 m in the South China Sea. Through physical property tests, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), one-dimensional consolidation, and triaxial shear tests, combined with comparisons with nearshore soft soils and other deep-sea sediments, we acquired the following results: The sediments primarily consist of muscovite, quartz, and calcite. Triaxial shear tests revealed initial dilation followed by shear consolidation, reaching critical conditions with an effective cohesion of 19.58 kPa and an effective internal friction angle of 27.32°. One-dimensional consolidation tests indicated a short principal consolidation time, wherein the consolidation coefficient first decreased under loading before slowly increasing, while the secondary consolidation coefficient stabilized after vertical pressure exceeded 400 kPa. The research results not only provide a direct reference for designing deep-sea engineering projects in the South China Sea, calculating the penetration resistance of deep-sea drilling rigs, and predicting the foundation settlement of offshore wind power but also furnish typical cases and key data support for the study of the mechanical properties of global deep-sea high-organic-matter sediments and engineering applications. Full article