Search Results (1,795)

This study systematically explores the structural stability, mechanical properties, elastic anisotropy, fracture toughness, and thermophysical characteristics of Au₃In and Au₃In₂ intermetallic compounds (IMCs) through density functional theory (DFT) simulations. Employing the generalized gradient approximation (GGA) and the Voigt–Reuss–Hill approximation enables precise predictions of polycrystalline elastic behavior, providing critical insights into the intrinsic stability and mechanical anisotropy of these IMCs. Structural optimization identifies the equilibrium lattice parameters and cohesive energies, indicating stronger atomic bonding and superior structural stability in Au₃In relative to Au₃In₂. Elastic constant calculations confirm mechanical stability and reveal pronounced anisotropic elastic behavior; Au₃In exhibits significant stiffness along the [010] crystallographic direction, while Au₃In₂ demonstrates notable stiffness predominantly along the [001] direction. Both Au₃In and Au₃In₂ exhibit ductile characteristics, confirmed by positive Cauchy pressures and elevated bulk-to-shear modulus (K/G) ratios. Fracture toughness analysis further establishes that Au₃In offers greater resistance to crack propagation compared to Au₃In₂, suggesting its suitability in mechanically demanding applications. Thermophysical property evaluations demonstrate that Au₃In possesses higher thermal conductivity, elevated Debye temperature, and superior volumetric heat capacity relative to Au₃In₂, reflecting its enhanced capability for effective thermal management in electronic packaging. Anisotropy assessments, utilizing both universal and Zener anisotropy indices, reveal significantly higher mechanical anisotropy in Au₃In₂, influencing its practical applicability. Full article

Background/Objective: Osteoporotic fractures may be prevalent, as expected, in patients with primary osteoporosis such as menopause-related or age-related bone loss, but a supplementary contribution to the risk may be added by less than common conditions, including a non-functioning adrenal tumor with or without mild autonomous cortisol secretion (MACS). Many of the standard fracture risk-related elements are captured by the FRAX model; yet, novel insights are brought by an improved algorithm, namely, FRAXplus. Our objective was to analyze the fracture risk in menopausal females diagnosed with low bone mineral density (BMD) and MACS-negative adrenal incidentalomas using FRAXplus (lumbar BMD adjustment). Methods: This as a retrospective, multi-center study of 66 menopausal women, where 50% of them had non-MACS adrenal tumors (group A), and 33 were controls (group B). They were put into four sub-groups, either group A1 (N = 14/33 subjects with normal DXA), or A2 (19/33 subjects with lowest T-score < −1), or group B1 (14/33) where subjects had normal DXA, or group B2 (19/33) for subjects with low BMD. Results: The sub-groups were matched on age, body mass index, and years since menopause, as well BMD matched (A versus B, A1 versus B1, A2 versus B2). FRAX analysis showed similar results for 10-year probability between groups A and B, and A2 and B2, while lumbar BMD adjustment showed statistically significant lower risk in group A1 versus B1 (p = 0.013), but not for hip fracture (p = 0.064). Conclusions: we introduced a pilot study in the FRAXplus model regarding adrenal tumors diagnosed in menopausal females with or without low BMD at central DXA assessment, a pilot study that to the best of our knowledge represents the first of this kind due to the novelty of using this fracture risk calculator with lumbar BMD adjustment. FRAXplus algorithm might be a better discriminator for fracture risk in these patients since we found that in age-, BMI-, and years since menopause-matched sub-groups, patients with normal DXA and MACS-free adrenal incidentalomas display a lower 10-year probability of major osteoporotic fractures than controls upon lumbar BMD adjustment. Full article

Accurate characterization of fracture roughness is critical for modeling groundwater flow and solute transport in fractured rock aquifers, where subsurface heterogeneity significantly impacts contaminant migration and water resource management. This study investigates fracture roughness characterization by integrating the Weierstrass–Mandelbrot approach with 3D-printed experimental validation and numerical simulation verification. Specifically, all the related parameters including fractal dimensions (D), frequency density (λ), segmentation accuracy (s), and summation number (n), which control the generation of fracture roughness, along with investigation scales (rs), were initially considered, and their corresponding impacts on the fracture roughness characteristics were examined. The results revealed that D is the primary factor controlling fracture roughness characteristics, while λ shows secondary importance when exceeding 1.3. The roughness remains stable when s ≤ 3 mm, n > 200, and rs ≥ 240 × 240 mm². Two multivariate regression models were established to describe the relationship between fracture roughness and influencing factors. The proposed methodology significantly enhances the precision of groundwater flow and solute transport simulations in fractured media through advanced high-fidelity fracture characterization, offering substantial improvements in groundwater resource management and contaminant remediation strategies. Full article

A Co-based composite powder, doped with rare earth Y, was crafted through a series of processes involving spray-drying, calcination, and low-temperature reduction. This powder was then blended with tungsten carbide (WC) powder and subjected to ball-milling. The resultant mixture was consolidated into a robust Y-doped WC-Co cemented carbide via the process of spark plasma sintering (SPS). The outcomes demonstrate that incorporating rare earth Y into Co powder to form a Co-Y₂O₃ composite powder via an innovative spray-drying, calcination, and low-temperature reduction process ensures uniform distribution of Y in the Co matrix. This uniform distribution refines the alloy’s grain structure during subsequent sintering, leading to enhanced performance. Within a specific range, increasing the Y content improves the overall alloy properties. It is notable that at a Y content of 1.5%, the alloy’s properties reach a state of stability, characterized by a density of 98.91%, a maximum hardness of 2120 Hv₃₀, and a fracture toughness of 8.24 MPa·m^1/2. The novel Y incorporation method has been shown to enhance the strength of the binder phase, impede the growth of WC grains, and thereby lead to a substantial improvement in the overall performance of the cemented carbide. Full article

Spontaneous counter-current imbibition is a crucial recovery mechanism in water-wet fractured reservoirs, especially in unconventional formations like tight and shale reservoirs. The geometric characteristics of microscale fractures require further clarification regarding their impact on imbibition. In this paper, the numerical simulation method is used to study the influence of fracture aperture, length, density, and relative position between fracture and imbibition open face on the counter-current imbibition process of a matrix block. For fractures perpendicular to the imbibition surface and in contact with water, the embedded discrete fracture model is utilized to simulate the impact of varying fracture apertures on counter-current imbibition. For fractures parallel to the imbibition surface, considering the impact of fracture on the capillary discontinuity of the matrix, the effects of varying fracture lengths and densities on counter-current imbibition are simulated. The results show that when fractures are perpendicular to the imbibition surface and in contact with water, the imbibition rate can be increased, and as the fracture aperture decreases, the imbibition rate first increases and then decreases. On the other hand, fractures parallel to the imbibition surface inhibit the imbibition process, with the imbibition rate decreasing as fracture length or density increases. This paper proposes an empirical shape factor considering the geometric characteristics of fractures, which can effectively characterize the influence of microfractures on matrix block imbibition, thus improving the dual-medium numerical simulation model. Full article

Pore–fracture carbonate gas reservoirs exhibit complex pore–throat structures and significant heterogeneity. Formation water can easily migrate along fractures, leading to extensive water-sealed gas accumulation, which severely limits the recovery rate of such reservoirs. To further investigate the water invasion process and the distribution characteristics of water-sealed gas in these reservoirs, a microscopic visualization model was developed using core CT scanning and laser etching technologies, incorporating the actual fracture sizes. The effects of fracture size, fracture density, and permeability heterogeneity on the microscopic distribution of water-sealed gas were analyzed in detail. The results indicate the following findings: (1) Homogeneous fracture size leads to a smaller extent of water-sealed gas accumulation. The ultimate gas saturation in the homogeneous fracture model is 5.79% lower than that in the heterogeneous model. (2) An increase in fracture density helps reduce the volume of water-sealed gas. The ultimate gas saturation in the high-density fracture model is 2.58% lower than in the low-density model. (3) The presence of seepage channels at the reservoir boundary with significant permeability heterogeneity exacerbates the accumulation of water-sealed gas and accelerates water invasion. Full article

Osteoporosis is a prevalent metabolic bone disorder characterized by decreased bone mineral density and increased fracture risk, particularly among aging populations. While conventional pharmacological treatments exist, they often have adverse effects, necessitating the search for alternative therapies. Resveratrol, a naturally occurring polyphenol, has gained significant attention for its potential osteoprotective properties through various molecular mechanisms. This systematic review aims to comprehensively analyze the molecular pathways through which resveratrol protects against osteoporosis. Using an advanced search strategy in the Scopus, PubMed, and Web of Science databases, we identified 513 potentially relevant articles. After title and abstract screening, followed by full-text review, 28 studies met the inclusion criteria. The selected studies comprised 14 in vitro studies, 8 mixed in vitro and in vivo studies, 6 in vivo studies, and 1 cross-sectional study in postmenopausal women. Our findings indicate that resveratrol exerts its osteoprotective effects by enhancing osteoblast differentiation through the activation of the Phosphoinositide 3-Kinase/Protein Kinase B (PI3K/Akt), Sirtuin 1 (SIRT1), AMP-Activated Protein Kinase (AMPK), and GATA Binding Protein 1 (GATA-1) pathways while simultaneously inhibiting osteoclastogenesis by suppressing Mitogen-Activated Protein Kinase (MAPK) and TNF Receptor-Associated Factor 6/Transforming Growth Factor-β-Activated Kinase 1 (TRAF6/TAK1). Additionally, resveratrol mitigates oxidative stress and inflammation-induced bone loss by activating the Hippo Signaling Pathway/Yes-Associated Protein (Hippo/YAP) and Nuclear Factor Erythroid 2-Related Factor 2 (NRF2) pathways and suppressing Reactive Oxygen Species/Hypoxia-Inducible Factor-1 Alpha (ROS/HIF-1α) and NADPH Oxidase 4/Nuclear Factor Kappa-Light-Chain-Enhancer of Activated B Cells (Nox4/NF-κB). Despite promising preclinical findings, the low bioavailability of resveratrol remains a significant challenge, highlighting the need for novel delivery strategies to improve its therapeutic potential. This review provides critical insights into the molecular mechanisms of resveratrol in bone health, supporting its potential as a natural alternative for osteoporosis prevention and treatment. Further clinical studies are required to validate its efficacy and establish optimal dosing strategies. Full article

Thermal shock testing has long been employed to assess thermal barrier coatings (TBCs), with crack formation and propagation on TBC surfaces serving as important indicators of fracture toughness. In this study, the influence of preexisting cracks within TBC coatings was investigated. These cracks can help alleviate stress concentrations at the interface and within the thermally grown oxide (TGO) layers of the TBC model. In other words, surface crack propagation may eventually intersect the interface, leading to delamination and spallation. This research focused on modifying the volume fraction of functionally graded materials (FGMs) and optimizing preexisting surface cracks in TBCs to extend their lifespan before delamination occurs. The accuracy of the J-integral and displacement correlation technique (DCT) methods was evaluated for use in thermal shock testing simulations. The results showed that both the stress intensity factor (SIF) and interface tensile stress of preexisting cracks were significantly reduced when the volume fraction was set at N = 3. Furthermore, the SIF values demonstrated strong agreement with calculations using the J-integral and DCT methods. The SIF for preexisting cracks dropped to below 62.42% of the fracture toughness when the crack length was approximately 50% of the TBC coating thickness in FGM structures, with a crack density of 10 cracks per inch (CPI). Full article

To investigate the mechanism of ground hydraulic fracturing technology in preventing mine earthquakes induced by hard–thick roof (HTR) breakage in coal mines, this study established a Timoshenko beam model on a Winkler foundation incorporating the elastoplasticity and strain-softening behavior of coal–rock masses. The following conclusions were drawn: (1) The periodic breaking step distance of a 15.8 m thick HTR on the 61,304 Workface of Tangjiahui coal mine was calculated as 23 m, with an impact load of 15,308 kN on the hydraulic support, differing from measured data by 4.5% and 4.8%, respectively. (2) During periodic breakage, both the bending moment and elastic deformation energy density of the HTR exhibit a unimodal distribution, peaking 1.0–6.5 m ahead of cantilever endpoint O, while their zero points are 40–41 m ahead, defining the breaking position and advanced influence area. (3) The PBSD has a cubic relationship with the peak values of bending moment and elastic deformation energy density, and the exponential relationship with the impact load on the hydraulic support is $F_{ZJ}=5185.2e^{0.00431L_p}$. (4) Theoretical and measured comparisons indicate that reducing PBSD is an effective way to control impact load. The hard–thick roof ground hydraulic fracturing technology (HTRGFT) weakens HTR strength, shortens PBSD, effectively controls impact load, and helps prevent mine earthquakes. Full article

To develop liner materials with improved toughness, this study combines molecular dynamics simulations and experimental testing to investigate the effect of different mass ratios (10/0, 7/3, 6/4, 4/6, 3/7, and 0/10) of high-density polyethylene (HDPE)/polyamide 6 (PA6) on their fracture toughness of the composites. The fracture toughness was quantitatively assessed using the J-integral method, while the material’s behavior in terms of crack propagation during tensile deformation was examined at the molecular level. The results reveal that as the HDPE mass ratio increases, the fracture toughness of the composites also gradually improves. Furthermore, the fracture toughness of four materials (PA6, 4HDPE/6PA6, 7HDPE/3PA6, and HDPE) was tested using the essential work of the fracture method. The trend observed in the simulation results was in agreement with the experimental results, validating the reliability of the molecular dynamics simulation. Full article

Deep coalbed methane (CBM) reservoirs hold substantial resource potential and play a crucial role in China’s unconventional natural gas development. However, the vertical propagation behavior of hydraulic fractures in deep CBM formations remains inadequately understood, posing challenges for optimizing fracturing parameters to control fracture height growth and enhance fracture development within the coal seam. To address this, this study establishes numerical simulation models to investigate hydraulic fracture propagation in directional wells, incorporating three typical lithological combinations representative of deep CBM reservoirs. Through these models, the influence mechanisms of bedding density, stress ratio, rock friction coefficient, and fracturing parameters on vertical fracture propagation and post-fracture productivity were systematically analyzed. The results reveal that the fracture propagation characteristics vary significantly with lithological combinations. Initially, hydraulic fractures penetrated adjacent formations near the wellbore while simultaneously generating branched fractures, leading to the formation of a complex fracture network. As propagation continues, branch fractures exhibited reduced width compared to the primary fracture. Well-developed bedding planes in the roof or floor, combined with lower stress ratios and friction coefficients, effectively constrained vertical fracture growth. Furthermore, optimizing fracturing fluid volume, reducing injection rate, and lowering proppant concentration promoted fracture development within the coal seam, thereby enhancing post-fracture well productivity. These findings provide a theoretical foundation for the optimization of hydraulic fracturing strategies in deep CBM reservoirs, contributing to more effective reservoir stimulation and resource recovery. Full article

Osteoporosis, the most common bone disorder, profoundly impacts women’s health, especially during postmenopausal phases. Characterised by diminished bone mineral density (BMD), it increases the risk of fractures, affecting mobility, quality of life, and potentially mortality. The present review analyses the intricate interactions among physiological alterations, diseases, and medications that lead to bone mineral density reduction in women. It underscores the importance of gynaecologists in the prevention, diagnosis, and management of osteoporosis via early risk assessment, suitable hormone treatment, and lifestyle modifications. Essential considerations encompass the categorisation of osteoporosis into primary (age-related) and secondary (attributable to diseases or pharmacological treatments) types, with particular emphasis on predisposing conditions such as premature menopause, hormone deficits, and cancer therapies. The significance of diagnostic instruments such as DXA and novel methodologies like trabecular bone score and quantitative ultrasonography is emphasised for precise evaluation and surveillance. The review also addresses nutritional methods, physical exercise, and pharmaceutical interventions, including hormone replacement therapy (HRT), selective oestrogen receptor modulators (SERMs), and other anti-resorptive drugs, to preserve bone health. This review highlights the important role of gynaecologists in maintaining women’s bone health, promoting a proactive strategy to avert osteoporosis-related complications and enhance long-term results. Full article

Background: Denosumab, a receptor activator of nuclear factor kappa-Β ligand (RANKL) inhibitor, demonstrates therapeutic effects beyond traditional osteoporosis management through the RANK/RANKL/osteoprotegerin pathway. Methods: This narrative review analyzed 37 studies (2018–2024) examining denosumab’s broader physiological effects and clinical applications. Results: Long-term safety data spanning 10 years showed sustained fracture prevention efficacy with a favorable benefit/risk profile. Compared to bisphosphonates, denosumab demonstrated superior outcomes in bone mineral density improvement and fracture risk reduction, particularly in elderly and frail populations. It enhanced muscular function by improving appendicular lean mass and grip strength while reducing fall risk. The drug showed potential cardiovascular benefits through its effects on cardiac and smooth muscle function. Notably, denosumab use was associated with reduced Type II diabetes mellitus risk through improved glucose metabolism. Additionally, it demonstrated promise in osteoarthritis treatment by suppressing osteoclast activity and chondrocyte apoptosis. While there are multisystem benefits, vigilance is required regarding adverse events, including hypocalcemia, infection risk, cutaneous reactions, and osteonecrosis of the jaw. Conclusions: Denosumab exhibits potential benefits in bone and systemic metabolism. Further research is needed to fully understand its therapeutic potential beyond osteoporosis and optimize clinical applications across different populations. Full article

(1) Background: Dual-energy X-ray absorptiometry (DXA)-based parameters such areal bone mineral density (aBMD) and Trabecular Bone Score (TBS) are routinely used to evaluate participants at risk for fragility fractures (FFs). We compared the accuracy of lumbar spine aBMD and TBS to that of volumetric BMD (vBMD) by quantitative computed tomography (QCT). (2) Methods: We conducted a retrospective analysis of participants who received both a DXA scan and a chest/abdomen CT scan. BMD and TBS values were obtained from lumbar DXA and vBMD values from QCT (three vertebrae from L1 to L4). T-score values were used for DXA diagnosis; the American College of Radiology ranges were used to diagnose bone status with QCT. (3) Results: We included 105 participants (87 women, mean age 69 ± 11 years). Among them, n = 49 (46.6%) presented at least one major FF. QCT diagnosis was as follows: osteoporosis = 59 (56.2%); osteopenia = 36 (34.3%); and normal status = 10 (9.5%). DXA diagnosis was osteoporosis = 25 (23.8%); osteopenia (33.3%) = 35; and normal status = 45 (42.9%). A total of 38 participants (36.2%) showed a TBS degraded microarchitecture. Correlation was moderate between aBMD and vBMD (r = 0.446), as well as between TBS and vBMD (r = 0.524). A good correlation was found between BMD and TBS (r = 0.621). ROC curves to discriminate between participants with/without FFs showed the following areas under the curve: 0.575 for aBMD, 0.650 for TBS, and 0.748 for QCT BMD. (4) Conclusions: QCT detected a higher prevalence of osteoporosis compared to DXA. TBS performed better than aBMD from DXA in discriminating between subjects with and without FFs. Full article

Objectives: The BsmI polymorphism of the VDR gene (vitamin D receptor) is one of the important genetic variants influencing the development of osteoporosis. Measurement and evaluation of the 25-hydroxyvitamin D (25(OH)D) concentration in individuals with reduced bone mineral density are essential because deficiency of this hormone causes impaired bone mineralization, leads to low BMD (bone mineral density), and influences fracture formation. The aim of the study was to investigate the relationship between the VDR gene BsmI polymorphism and 25(OH)D levels in Slovak postmenopausal women. Materials and Methods: The study population consisted of 287 untreated postmenopausal women, who were divided into three groups based on T-scores: normal (CG = 65), osteopenia (OPE = 126), and osteoporosis (OPO = 96). DNA isolation was performed using a standard protocol. Genetic analyses of the BsmI (rs1544410) polymorphism of the VDR gene were performed using the TaqMan SNP genotyping assays. Biochemical analysis of total 25(OH)D was performed in blood serum using the electrochemiluminescence method. Results: The chi-square test confirmed that the mutant T allele was not associated with the development of osteoporosis (p = 0.419). Through Kruskal–Wallis analysis, we found significant differences (p < 0.05, p < 0.01) in total 25(OH)D concentrations in individual genotypes of the BsmI variant of the VDR gene between the groups of women studied. Conclusions: It can be concluded that the VDR gene and its variant BsmI as well as 25(OH)D total may be relevant markers in the etiology of the search for individuals at risk of osteoporosis. Full article