Search

Hydraulic structures are typically subjected to long-term hydraulic loading, and concrete—the main material of structures—may suffer from cracking damage and seepage failure, which can threaten the safety of hydraulic structures. In order to assess the safety of hydraulic concrete structures and realize the accurate analysis of the whole failure process of hydraulic concrete structures under the coupling effect of seepage and stress, it is vital to comprehend the variation law of concrete permeability coefficients under complex stress states. In this paper, several concrete samples were prepared, designed for loading conditions of confining pressures and seepage pressures in the first stage, and axial pressures in the later stage, to carry out the permeability experiment of concrete materials under multi-axial loading, followed by the relationships between the permeability coefficients and axial strain, and the confining and seepage pressures were revealed accordingly. In addition, during the application of axial pressure, the whole process of seepage–stress coupling was divided into four stages, describing the permeability variation law of each stage and analyzing the causes of its formation. The exponential relationship between the permeability coefficient and volume strain was established, which can serve as a scientific basis for the determination of permeability coefficients in the analysis of the whole failure process of concrete seepage–stress coupling. Finally, this relationship formula was applied to numerical simulation to verify the applicability of the above experimental results in the numerical simulation analysis of concrete seepage–stress coupling.

Context Individuals with type 2 diabetes mellitus (DM) have an increased risk of pneumonia and septic shock. Traditional glucose-lowering drugs have recently been found to be associated with a higher risk of infections. It remains unclear whether sodium-glucose cotransporter 2 inhibitors (SGLT2is), which have pleiotropic/anti-inflammatory effects, may reduce the risk of pneumonia and septic shock in DM. Methods MEDLINE, Embase, and ClinicalTrials.gov were searched from inception up to May 19, 2022, for randomized, placebo-controlled trials of SGLT2i that included patients with DM and reported outcomes of interest (pneumonia and/or septic shock). Study selection, data extraction, and quality assessment (using the Cochrane Risk of Bias Assessment Tool) were conducted by independent authors. A fixed-effects model was used to pool the relative risk (RRs) and 95% CI across trials. Results Out of 4568 citations, 26 trials with a total of 59 264 patients (1.9% developed pneumonia and 0.2% developed septic shock) were included. Compared with placebo, SGLT2is significantly reduced the risk of pneumonia (pooled RR 0.87, 95% CI 0.78-0.98) and septic shock (pooled RR 0.65, 95% CI 0.44-0.95). There was no significant heterogeneity of effect size among trials. Subgroup analyses according to the type of SGLT2i used, baseline comorbidities, glycemic control, duration of DM, and trial follow-up showed consistent results without evidence of significant treatment-by-subgroup heterogeneity (all Pheterogeneity > .10). Conclusion Among DM patients, SGLT2is reduced the risk of pneumonia and septic shock compared with placebo. Our findings should be viewed as hypothesis generating, with concepts requiring validation in future studies.

Introduction: Computational pressure-flow dynamics derived fractional flow reserve (caFFR) is an angiographic-derived index to determine the fractional flow reserve (FFR) in patients with stable coronary artery disease (CAD), without the need of invasive pressure wire and hyperaemic stimulus in FFR. Although the safety of FFR-guided deferral of revascularization in non-ischemic lesions is well-established, clinical events still occur. The aim of the study is to investigate the prognostic implications of caFFR in those without significant ischemia. Methods: 513 stable CAD patients (mean age=64.3±11.1, 57.7% male) with all lesions being nonischemic, defined by caFFR>0.75, without undergoing revascularization were recruited. The study population was divided into high (n=240) and low (n=273) caFFR groups, according to the median value of caFFR (0.89). The primary endpoint was 3-year major adverse cardiac events (MACE), defined as a composite of all-cause mortality, myocardial infarction (MI), target vessel revascularization (TVR) and hospitalization for heart failure. Results: A total of 44 composite events occurred, including 17 all-cause mortality, 2 MI, 8 TVR and 17 hospitalization for heart failure. Following multivariate adjustment, patients in low caFFR group had a significantly higher risk of MACE than those in high caFFR group (adjusted hazard ratio [HR], 3.02; 95% confidence interval [Cl], 1.19-7.71; P=0.02). Every 0.01 decrease in caFFR was associated with a higher risk of MACE (adjusted HR, 1.12; 95%Cl, 1.03-1.21; P Conclusions: In stable CAD patients without significant functional ischemia, caFFR provides valuable prognostic information on adverse cardiac outcomes. This novel index could enhance risk stratification in stable CAD patients with nonischemic lesions.

Introduction: Computational pressure-flow dynamics derived fractional flow reserve (caFFR) has emerged for non-invasive assessment of fractional flow reserve (FFR) in patients with stable coronary artery disease (CAD), without the need for hyperaemic induction and guidewire placement in conventional FFR. The clinical value of caFFR in diabetic patients, who are at risk of microvascular dysfunction, has not been validated. The aim of the study is to evaluate the use of caFFR in diabetic patients with stable CAD. Methods: A total of 212 stable CAD patients with diabetes (mean age=67.6±10.6, 66.5% male) were included. Patients were said to be adherent to caFFR if all ischemic vessels, defined by caFFR≤0.8 were treated with PCI and all nonischemic vessels, defined by caFFR>0.8 were not. Otherwise, they were considered to be non-adherent to caFFR. The primary endpoint was 3-year major adverse cardiac events (MACE), defined as a composite of cardiovascular mortality, non-fatal myocardial infarction (MI), stroke and unplanned revascularization. Results: Among the 212 patients, PCI was performed in 62.3% of them. A total of 26 composite events occurred, including 5 cardiovascular mortality, 5 non-fatal MI, 2 strokes and 14 unplanned revascularization. The incidence rate of MACE was significantly lower in adherent patients than in non-adherent patients (5.4% vs 15.8%; P=0.01). After multivariate adjustment, adherent patients had a significantly lower risk of MACE than non-adherent patients (adjusted hazard ratio [HR], 0.33; 95% confidence interval [Cl], 0.13-0.83; P=0.02). Conclusions: In stable CAD patients with diabetes, caFFR-guided revascularization significantly reduces the risk of MACE in 3 years. The findings support the potential use of caFFR in treatment guidance of diabetic patients.

Introduction: Increasing number of heart failure (HF) patients diagnosed with dementia due to improved treatment and aging population. Data relating to the association of statin use on the risk of dementia incidence among patients with HF are sparse. Hypothesis: The use of statin is associated with lower risk of new- onset dementia in HF population. Methods: Using a previously validated territory-wide clinical information registry, statin use was ascertained among all eligible patients with HF (N=241,995) from 1996 to 2019. Propensity score matching was used to balance baseline covariates between statin nonusers (167,738 patients) with statin users (74,257 patients). Competing risk regression with Cox proportional-hazard models was performed to estimate the risk of incident dementia associated with statin use. Results: Of all eligible subjects, the mean age was 76.5±13.0 years, 115,371(47.7%) was male. Over a median follow-up of 2.7 years (interquartile range [IQR]: 0.6 to 6.7), 13,482 (5.6%) patients were diagnosed with dementia including Alzheimer's disease (N=5,253), senile dementia uncomplicated (N=4,273), arteriosclerotic dementia (N=3,262), and others (N=694). Statin use (vs. none) was associated with a 58% lower risk of dementia incidence (multivariable-adjusted sub-distribution hazard ratio [SHR]=0.42; 95% Confidence Interval [CI], 0.38 to 0.46) after accounting for death as a competing risk. Moreover, the male gender was associated with a 51% lower risk of dementia incidence (multivariable-adjusted SHR=0.59; 95%CI (0.54-0.65) compared with females. Conclusions: Our study suggests that there is substantial sex difference in the incidence of dementia among HF patients. Moreover, statin use is associated with a significantly lower risk of incident dementia in HF.

The mechanical responses of steel fiber–reinforced concrete (SFRC) thermally damaged at high temperature needs a deeper evaluation via a mesoscopic model that explicitly treats the fibers. ...

The mesoscopic thermal cracking behavior in steel fiber reinforced concrete (SFRC) caused by high-temperature load can result in a substantial reduction of effective thermal conductivity (ETC) at macroscale level. In this study, a multiscale homogenization method for identifying the ETC of thermally damaged SFRC is proposed. This new method is characterized by the consideration of crack thermal resistance effect rather than using temperature-dependent thermal conductivities of components in cementitious composite. A series of experiments on thermal conductivity of mortar, plain concrete, and SFRC heated at various temperatures is performed. The method predictions satisfy the experimental results extremely well when the interfacial thermal resistance (ITR) coefficient is assumed to increase linearly with temperature. The numerical and experimental results show that the ITR effect makes approximately 50%, 36%, and 7%–12% contributions to the overall thermal conductivity reductions in the mortar, plain concrete, and SFRC heated up to 600 ∘ C , respectively. Moreover, it is found that the trend and magnitude of ETC reduction caused by heating increase with the increase in particle content and particle-matrix thermal conductivity ratio due to the synergistic effect of heat bridge and ITR.