Search Results (6,389)

Background: Escherichia coli (E. coli) bacteremia is a significant cause of mortality, particularly in older adults. Limited data exists on clinical outcomes in octogenarians. This study aims to evaluate the clinical outcomes of E. coli bacteremia in octogenarians and determine whether appropriate empirical therapy leads to improved outcomes in this specific population. Methods: We conducted a retrospective cohort study of hospitalized patients with E. coli bacteremia at Beilinson Hospital from January 2012 to December 2022. Clinical characteristics, bacteremia sources, antibiotic resistance patterns, and patient outcomes were analyzed. The primary outcome was 30-day mortality. Multivariate regression was used to assess the impact of empirical antibiotic appropriateness on mortality. Results: The study included 2717 patients, of which 1042 (38%) were 80 years or older. Older patients had more comorbidities with increased rates of ischemic heart disease (20% vs. 14%, p < 0.01) and congestive heart failure (19% vs. 9%, p < 0.01). Patients with 3rd generation cephalosporin resistant strains were more likely to receive inappropriate empiric antibiotic therapy (54% vs. 23%, p < 0.01). Although appropriate empirical therapy was associated with improved survival in univariate analysis (19% vs. 28%, p < 0.01), it was not an independent predictor of 30-day mortality in multivariate analysis [adjusted OR = 1.10, 95% CI (0.64–1.81), p = 0.7]. A lower SOFA score [adjusted OR = 0.17, CI95% (0.01–0.31), p < 0.01] was associated with decreased 30-day mortality. Hypoalbuminemia was significantly associated with increased 30-day mortality [adjusted OR = 2.49, CI95% (0.1.56–3.97), p < 0.01]. Conclusions: E. coli bacteremia in octogenarians is associated with significant mortality. While timely appropriate antibiotic therapy is crucial, mortality appears to be more influenced by overall health status, comorbidities, and infection severity. Future research should focus on addressing these factors and developing personalized care strategies to improve survival in this high-risk group. Full article

Ultra-high-performance concrete (UHPC) has been widely utilised in strengthening and rehabilitating conventional normal concrete (NC) structures due to its exceptional mechanical properties and durability. However, in cold climates, the interfacial bond between UHPC and NC is susceptible to degradation under freeze–thaw cycles, potentially compromising the composite action and long-term performance of strengthened structures. This study systematically investigated the shear behaviour of a UHPC-NC interface with planted reinforcement subjected to various freeze–thaw conditions. The experiments were conducted considering different numbers of freeze–thaw cycles (0, 20, 40, 60, 80, and 100) and salt solution concentrations (0%, 3.5%, and 5%). Direct shear tests were performed to evaluate interfacial failure modes, mass loss, and shear strength degradation. Results identified three characteristic failure modes: adhesive debonding at the interface, mixed failure involving both the interface and the NC substrate, and crushing failure within the NC substrate. Specimens exposed to 3.5% salt solution experienced the most significant deterioration, exhibiting a 35% reduction in shear strength after 100 freeze–thaw cycles. Normally, lower salt concentrations were found to induce greater interfacial damage compared to higher concentrations. The study underscores the importance of increasing the embedment depth of the planted reinforcement to alleviate stress concentration and enhance interfacial durability in freeze–thaw environments. Full article

Mechanical damage to apples that occurs without visible skin rupture represents a significant issue during handling and harvesting. The aim of this study was to evaluate the potential for detecting initial internal tissue failure using parameters derived from the deformation curve obtained during a quasi-static penetration test. Particular attention was given to the parameter Pa, defined as the pressure at the yield point, which indicates the onset of structural failure in the tissue. The occurrence of Pa was monitored across five apple genotypes, and the results demonstrated the parameter’s sensitivity to latent internal damage. The parameter Pc, characterising resistance in the later phase of penetration, also showed a strong correlation with fruit bulk density. Significant differences in all mechanical characteristics were observed between the genotypes. The results highlight the potential of these parameters for assessing varietal suitability for mechanised harvesting and sorting. The proposed methodology is readily applicable in the selection of new genotypes within breeding programmes as well as in post-harvest situations. Full article

Hydropower is the primary source of electricity in several countries in Latin America. Hydropower provides approximately 80% of Ecuador’s electricity; however, it remains highly vulnerable to climate change, resulting in uncertainties in power generation due to altered precipitation patterns, runoff, and systematic failures. Consequently, Ecuadorians are becoming increasingly reliant on diesel generators during crises, resulting in public health, safety, and economic impacts, as well as social and political disruptions. This study evaluated noise pollution in the central urban area of the city of Loja for the first time during the 2024–2025 electricity crisis in Ecuador. A Type 1 integrating sound-level meter was used to monitor noise pollution (LAeq, 10min) at 20 locations during periods of generator operation and non-operation. At each location, the number of generators, the density of commercial activities along the streets, as well as traffic and other urban characteristics, were recorded. Results revealed that the presence of generators, street width, and the number of generators significantly increased the LAeq, 10min, often exceeding the limits set by the World Health Organization and Ecuador’s environmental regulations. Frequency spectrum analysis revealed that medium frequencies increased with A-weighting, while low frequencies rose with C-weighting, suggesting potential health risks to the local population. The thematic noise map during generator inactivity showed lower noise levels, averaging around 71.5 dBA. Conversely, when the generators were operational, noise levels exceeded 79.6 dBA, indicating a significant increase in environmental noise exposure associated with their use. This highlights an urgent need to implement and expand renewable energy sources, as existing options like wind power, photovoltaic energy, and biomass are insufficient to meet community demands. Full article

Background and Objectives: The use of cementless total knee arthroplasty (TKA) is increasing, but established methods for assessing bone quality to prevent early failure remain undefined. Current preoperative assessments using central bone mineral density (BMD) do not accurately reflect peripheral bone quality, and intraoperative evaluation is subjective. This study aimed to establish objective assessment methods by analyzing the correlations between a novel visual grading system, CT Hounsfield units (HU), and actual bone strength. Materials and Methods: This prospective study included 131 patients undergoing posterior-stabilized TKA. We developed a novel visual grading system (Excellent, Good, Fair, Poor) based on femoral cutting surface characteristics. CT HUs were measured preoperatively by an assisting surgeon in the box bone area. Femoral box specimens underwent indentation testing to determine their actual bone strength. Minimum Required Strength (MRS) was defined at 2.5-fold the patient’s body weight, and Estimated Withstanding Strength (EWS) was determined by scaling first failure load using area ratios. Patients were classified as “cementless suitable” (EWS > MRS) or “cemented mandatory” (EWS < MRS). Correlations were assessed using Spearman’s rank correlation for visual grade and Pearson correlation for Hounsfield units. ROC curve analysis determined diagnostic accuracy. Results: Visual grade exhibited an exceptionally robust relationship to bone strength (Spearman ρ = 0.903, p < 0.01), whereas HU showed substantial correlation (Pearson r = 0.660, p < 0.01, R² = 0.435). Visual grading achieved excellent diagnostic accuracy (AUC = 0.974, sensitivity 95.1%, specificity 95.9%) using “Good” grade as cutoff. HU demonstrated AUC of 0.938 with 92.7% sensitivity and 81.6% specificity at a cutoff value of 65.2. Conclusions: Our novel visual grading system and CT HU demonstrated excellent correlations with actual distal femoral bone strength and outstanding diagnostic performance for identifying cementless TKA candidates. Unlike traditional subjective intraoperative assessments such as the “thumb test”, this system provides objective visual criteria directly correlated with actual bone strength. Preoperative HU screening with intraoperative visual grading can help prevent early failure. Full article

Slate typically contains significant bedding structures and often displays varying mechanical properties under different inclination conditions, with numerous adverse impacts on construction projects. In light of its anisotropic characteristics, a slate foundation pit in Changsha is considered in this study, and uniaxial and triaxial compression tests are initially conducted on slate under various bedding inclination angles. Through these tests, the mechanical parameters of the slate are obtained, and the laws governing the variation in the stress–strain curves and failure modes are analyzed. The results show that the peak strength and elastic modulus present an obvious “U-shaped” variation with the bedding dip angle, reaching the minimum values in the range of 45–60°, and the corresponding failure mode is mainly sliding failure along the bedding plane. The mechanical parameters obtained for slate are input into FLAC3D 6.0 software to simulate a triaxial compressive test of slate, and the calculation results are used to verify the accuracy of the parameters obtained from the tests. Based on these parameters, the foundation pit engineering in the background is simulated in order to analyze the deformation characteristics of the pit under different inclination angles. The simulation results indicate that the foundation pit deformation has significant asymmetry, with larger settlement on the dip side and greater horizontal displacement of the piles. The research findings of this paper can provide a reference for the design and construction of similar slate foundation pit projects. Full article

The accurate real-time delineation of overburden failure zones, specifically the caved and water-conducted fracture zones, remains a significant challenge in longwall mining, as conventional monitoring methods often lack the spatial continuity and resolution for precise, full-profile strain measurement. Based on the hydrogeological data of the E9103 working face in Hengjin Coal Mine, a numerical calculation model for the overburden strata of the E9103 working face was established to simulate and analyze the stress distribution, failure characteristics, and development height of the water-conducting fracture zones in the overburden strata of the working face. To address this problem, this study presents the application of a distributed optical fiber sensing (DOFS) system, centering on an innovative fiber installation technology. The methodology involves embedding the sensing fiber into boreholes within the overlying strata and employing grouting to achieve effective coupling with the rock mass, a critical step that restores the in situ geological environment and ensures measurement reliability. Field validation at the E9103 longwall face successfully captured the dynamic evolution of the strain field during mining. The results quantitatively identified the caved zone at a height of 13.1–16.33 m and the water-conducted fracture zone at 58–60.6 m. By detecting abrupt strain changes, the system enables the back-analysis of fracture propagation paths and the identification of potential seepage channels. This work demonstrates that the proposed DOFS-based monitoring system, with its precise spatial resolution and real-time capability, provides a robust scientific basis for the early warning of roof hazards, such as water inrushes, thereby contributing to the advancement of intelligent and safe mining practices. Full article

This study assesses the flexural performance of concrete beams repaired with externally bonded carbon-fiber-reinforced polymer (CFRP) patches under controlled damage conditions. Prismatic beams (7 × 7 × 28 cm) underwent three-point bending tests in four configurations: uncracked, uncracked-reinforced, cracked-unrepaired, and cracked-repaired. Pre-existing damage was caused by mid-span notches at a = 7, 21, and 35 mm. CFRP patches were placed on the tension face, and the ultimate load and failure mode were recorded. Repairing CFRP beams increased maximum load by up to 240% compared to unrepaired counterparts, and the failure characteristic changed from brittle shear to ductile flexural. Strengthening uncracked beams also yielded significant benefits. These findings show that patch-type CFRP reinforcement effectively recovers and enhances flexural performance across a wide range of crack severity, and they provide quantitative guidelines for determining repair levels depending on original crack depth. Full article

Ensuring the safe operation of large hydro-generators is essential for energy supply and economic development. Stator-winding single-phase grounding faults are among the most common failures in such generators. Conventional protection methods—such as fundamental voltage protection, third-harmonic voltage saturation, and low-frequency injection—lack fault location capability and cannot assess the fault severity. This paper proposes a stepwise variable-frequency pulse injection method for fault diagnosis and location in large hydro-generator stator windings. A finite element model of a salient-pole hydro-generator is established to analyze magnetic flux density and electromotive force distributions under normal and fault conditions, from which fault characteristics are derived. Equivalent circuit models suitable for low- and high-frequency pulse injection are developed. A bidirectional pulse injection circuit and algorithm are designed to identify the fault phase via terminal current vector characteristics, diagnose the faulty branch based on leakage loop equivalent inductance, and locate the fault point using voltage–current signal slopes. Simulation results validate the effectiveness of the proposed diagnostic approach. Full article

During sand cleanout operations in shale oil horizontal wells, severe wellbore leakage occurs due to incompatibility between plugging particles and the formation, resulting in a failure to establish circulation. This study determined the optimal plugging theory for the target formation characteristics through laboratory leakage sealing tests and numerical simulations such as fluid–discrete element coupling (CFD-DEM). The results show the following: Plugging experiments indicated that the Vickers criterion achieved the best performance, with an invasion depth of 9 mm, followed by the Ideal Packing Theory, at 12 mm, while the D90 rule performed the worst, with an invasion depth of 13 mm. The simulations results from the CFD-DEM coupling model demonstrated that the Vickers criterion achieves the most effective plugging performance, followed by the Ideal Packing Theory, with the D90 rule exhibiting the least effectiveness. This indirectly validates the rationality and effectiveness of the Vickers criterion in configuring particle sizes for plugging materials. Finally, sand-packed-tube displacement experiments demonstrate that the Vickers criterion yields the lowest permeability and optimal plugging performance, further validating its rationality and effectiveness in configuring particle sizes for plugging materials. This research provides crucial technical support for the safe and efficient development of shale oil horizontal wells, effectively reduces operational costs, and holds significant importance for advancing technological progress in shale oil extraction. Full article

This study examines the flexural behavior of reinforced concrete (RC) beams that utilize steel, glass fiber-reinforced polymer (GFRP), and hybrid steel–GFRP longitudinal bars. It considers variations in stirrup material (steel or GFRP) and stirrup spacing (100 mm or 200 mm). Nine beam specimens were subjected to three-point bending tests until failure. Their performance was assessed based on ultimate load, deflection, stiffness, ductility, energy absorption, and failure mode. The experimental program aimed to isolate the effects of transverse reinforcement detailing and to elucidate the role of stirrup characteristics in governing the transition between flexure and shear-controlled behavior. The findings indicated that both the type of reinforcement and the configuration of stirrups significantly influenced structural performance. Steel-reinforced beams demonstrated stable and ductile flexural behavior, whereas GFRP-reinforced beams supported loads up to 18% higher but experienced abrupt failure in brittle shear with restricted ductility. Hybrid beams effectively integrated the benefits of both materials: The HS100 specimen, which featured closely spaced steel stirrups, achieved the highest ultimate load (162.5 kN), maximum deflection (19.7 mm), and greatest energy absorption (2450 kN·mm). In contrast, beams utilizing GFRP stirrups exhibited early diagonal cracking and abrupt failure, even with closely spaced stirrups. The study indicates that hybrid steel–GFRP reinforcement can enhance the strength, ductility, and toughness of reinforced concrete beams, contingent upon the application of sufficient steel confinement. The findings provide practical recommendations for enhancing hybrid RC design by positioning steel in tension and utilizing steel stirrups for confinement, while effectively employing GFRP in compression zones or in corrosive environments. Full article

Roof instability in coal mines is one of the primary causes of mining disasters, casualties, and environmental damage. Accurately assessing its reliability is crucial for achieving safe production and sustainable development in coal mining. Based on 192 small measured samples from multiple domestic coal mines (including Anhui, Shanxi, Shaanxi, and Inner Mongolia), this study constructs multidimensional Gaussian Copula and t Copula models to characterize the complex correlation structure of mechanical parameters. The hybrid adaptive multi-method data augmentation (HAMDA) method with three distinct weighting strategies is proposed. Through Monte Carlo Simulation (MCS), systematic reliability assessments are conducted for different roof locations. The results indicate that multidimensional elliptical Copulas effectively simulate the correlation structure of highly variable multidimensional coal mine roof mechanical parameters. Roof system instability is primarily triggered by failure in the bottom zone, accompanied by sidewall instability in approximately 60% of cases, while the top zone remains relatively secure. This provides crucial insights for optimizing support design. The HAMDA method significantly overcomes the limitations of small sample data, with its expanded statistical characteristics closely matching measured data. Failure probability estimates vary across different HAMDA schemes: conservative programs may underestimate risks, while diverse programs tend toward conservatism in lateral zones. These results provide theoretical support for refined roof support design in coal mines, holding significant theoretical and practical value for advancing safety, environmental sustainability, and sustainable development in the coal industry. Full article

The ultra-high-frequency (UHF) detection method is highly accurate and has a fault localization function. At present, most gas-insulated switchgear (GIS) installations are equipped with online UHF monitoring devices to detect partial discharges. In order to ensure the accuracy of the detection results, UHF sensors need to be verified regularly. UHF sensors used for online monitoring are usually installed at the handhole of the GIS and cannot be removed. Measuring the laboratory verification indexes (e.g., equivalent height, dynamic range, etc.) of the sensors directly is very difficult. However, it is easier to measure S₁₁ of the sensor for verification and S₂₁ between it and the neighboring sensors by injecting power signals. Accordingly, this paper proposes a degradation identification method for GIS UHF sensors using a cross-comparison of S-parameters. When sensor sensitivity decreases, S₁₁ increases while S₂₁ decreases, both serving as effective indicators of performance degradation. In this study, the equivalent S-parameter network and the variation mechanisms of S₁₁ and S₂₁ during sensor verification were first analyzed. Normal and typically degraded sensor models were then constructed and coupled in different GIS structures for electromagnetic simulation. The simulation and on-site verification results show that S₁₁ is mainly affected by the sensor’s intrinsic performance and installation conditions at the inspection port, whereas S₂₁ is predominantly influenced by sensor performance and the propagation characteristics of the GIS structure. Through cross-comparison of S₁₁ and S₂₁ at corresponding positions across three phases, sensor aging or failure can be effectively identified, enabling rapid on-site verification without removing the sensors. The proposed method was successfully validated on actual GIS equipment at the China Southern Power Grid Research Institute. It exhibits high accuracy, efficiency, and strong engineering applicability, enabling the early detection of degraded sensors and providing valuable support for condition assessment and maintenance decision-making in GIS online monitoring systems. Full article

In deep coal mines characterized by high temperature, high humidity, high-salinity water, and elevated ground stress, stress corrosion cracking (SCC) of bolts is widespread, causing frequent instability of roadway surrounding rock and hindering long-term stability. This study systematically examines the failure characteristics of anchorage materials in highly corrosive roadways and clarifies the effects of deep-mine temperature and humidity on material corrosion. Long-term corrosion tests on bolts reveal changes in mechanical properties and macroscopic morphology and elucidate the intrinsic mechanisms of SCC. The results show that with the increase in corrosion time, the yield strength, ultimate load and elongation of the anchor rod decrease by up to 11.8%, 13.6%, and 7.08%, respectively. Under high stress, localized corrosion pits form on bolt surfaces, rupturing the oxide film and initiating rapid anodic dissolution and cathodic hydrogen evolution. Interaction between corroded surfaces and microcracks produced by internal impurities leads to progressive damage accumulation and ultimate fracture of the bolts. These findings provide guidance for corrosion protection of coal mine roadway support materials and for improving the long-term performance of roadway supports. Full article

Background: Coronary artery bypass grafting (CABG) remains a standard revascularization strategy for patients with advanced coronary artery disease (CAD). However, a considerable proportion of patients experience recurrent ischemia requiring repeat revascularization. Residual platelet reactivity (RPR) and dyslipidemia are recognized as key factors contributing to graft failure and disease progression. Methods: This observational study was conducted at a tertiary cardiology center in Kazakhstan. A total of 195 post-CABG patients who underwent repeat coronary angiography between 2023 and 2024 recruitment period for recurrent ischemic symptoms within 6–36 months after surgery were included. Clinical characteristics, comorbidities, lipid profiles, and antiplatelet response were analyzed. RPR was measured using the VerifyNow P2Y12 assay when available. Dyslipidemia was defined according to the 2019 and 2021 European guidelines. Results: Elevated RPR was identified in 45% of patients (n = 90) despite dual antiplatelet therapy (p < 0.01). Poor lipid control was frequent among those who underwent repeat percutaneous coronary intervention (PCI), particularly elevated levels of low-density lipoprotein cholesterol (LDL-C) and total cholesterol (p < 0.05). Both elevated RPR and dyslipidemia were independently associated with native coronary disease progression and graft failure (RPR: OR = 2.8; 95% CI 1.4–5.6; p = 0.003; dyslipidemia: OR = 2.2; 95% CI 1.1–4.3; p = 0.02). The use of ezetimibe was independently associated with a significantly lower risk of repeat stenting (OR = 0.12; 95% CI 0.02–0.75; p = 0.023). Smokers were younger, had lower blood pressure, and less frequently presented with diabetes or chronic kidney disease, demonstrating a pattern consistent with the “smoker’s paradox.” Conclusions: Residual platelet reactivity and dyslipidemia are common and clinically relevant predictors of repeat revascularization after CABG. Optimization of antiplatelet and lipid-lowering therapy should be prioritized in secondary prevention for this high-risk population. These findings are particularly important in Kazakhstan, where post-CABG management strategies warrant further improvement. Full article