The isothermal oxidation behavior and the microstructure stability was studied at 900 °C, 1000 °C and 1100 °C of the two alloys with and without Ru. The curves of oxidation weight gain show that the ...oxidation resistance decreases sharply with the addition of Ru. A multi-layered scale formed on the alloy surface, and it generally consisted of an external layer of NiO, an intermediate layer of spinel and an Al2O3 inner layer. The oxidation rate at 1100 °C is significantly higher than that at the other two temperatures due to more serious cracking and peeling of oxide scale. Compared with Ru-free alloy, the oxide layer of Ru-containing alloy is thicker and the oxide layer spallation more seriously. The oxide of Ru was found in the spinel layer and the vaporization of the oxide makes the scale spallation. Surprisingly, a large number of TCP phases were found in alloy matrix, especially in 2Ru alloy. This indicates that poor oxidation resistance will lead to a decline in microstructure stability.
DZ951G is a novel developed nickel-based directional solidified superalloy with an incipient high melting point and low density. Compared with DZ417G superalloy, DZ951G superalloy has a higher ...ultimate tensile strength. At intermediate temperatures, the plasticity and strength were both markedly improved, and an obviously anomalous yield behavior could be observed where the yield strength reached its maximum at 760 °C. Below 600 °C, two competitive modes of dislocations shearing γ' particles existed, in which one was the formation of stacking faults and another was a/2 dislocations shearing. At intermediate temperatures, a transitional phase between shearing γ' particles and bypassing appeared, and the fracture translated from brittle fracture into ductile fracture. Exceeding 900 °C, bypassing of dislocations was operated under thermal activation. Moreover, short continuous stacking faults still existed at 760 °C. Finally, the various dislocation configurations were rationally illuminated and explained with the intrinsic connection of mechanical properties.
We propose a tunable narrowband absorber by utilizing a graphene monolayer placed between a dielectric semicylindrical array and a multilayer silica/silicon distributed Bragg reflector (DBR) ...structure. The multi-band perfect absorption can be achieved due to the excitation of multiple resonant modes in the absorber, including the guided mode resonance of the dielectric silica array and BR-based guided mode resonance in the DBR structure. The ultra-high quality factor (Q) is mainly attributed to the low external leakage loss of the resonator and the low intrinsic loss of the graphene monolayer. Moreover, the Q-factor of absorption peaks can be tuned by electrically controlling the Fermi energy of graphene. The sensitivity of a spectral wavelength shift for the refractive index change of the resonator is up to 730 nm/RIU, and the figure of merit is 1043. The proposed graphene-based metamaterial offers potential applications for photodetectors, optical modulators, and sensors in the near infrared frequency regime.
Background
Several studies have explored the association between P wave terminal force in lead V1 (PTFV1) and risk of atrial fibrillation (AF) occurrence, but the results were controversial. This ...meta‐analysis aimed to examine whether abnormal PTFV1 could predict AF occurrence.
Methods
We searched PubMed, Embase, and Cochrane Library databases for articles published before August 25, 2018. Pooled odds ratios (ORs) of AF occurrence were calculated using random‐effects models to explore the significance of PTFV1.
Results
A total of 12 studies examining 51,372 participants were included, with 9 studies analyzing PTFV1 as a categorical variable and 4 studies analyzing PTFV1 as a continuous variable. As a categorical variable, abnormal PTFV1 (>0.04 mm s) was significantly associated with AF occurrence with a pooled OR of 1.39 (95% confidence interval CI 1.08–1.79, p = .01). Subgroup analysis found that ORs of studies in hemodialysis patients (OR = 4.89, 95% CI 2.54–9.90, p < .001) and acute ischemic stroke patients (OR = 1.60, 95% CI 1.14–2.25, p = .007) were higher than general population (OR = 1.15, 95% CI 1.03–1.29, p = .01). Studies from Europe (OR = 1.05, 95% CI 0.91–1.20, p = .51) yielded lower OR of endpoints compared with Asia (OR = 1.89, 95% CI 1.38–2.60, p < .001) and United States (OR = 1.43, 95% CI 1.19–1.72, p < .001). As a continuous variable, PTFV1 was also significantly associated with AF occurrence with a polled OR per 1 standard deviation (SD) change of 1.27 (95% CI 1.02–1.59, p = .03).
Conclusions
PTFV1 was significantly associated with the risk of AF and was considered to be a good predictor of AF occurrence in population with or without cardiovascular diseases.
The theoretical development of Schumann Resonances has spanned more than a century as a form of global natural electromagnetic resonances. In recent years, with the development of electromagnetic ...detection technology and the improvement in digital processing capabilities, the connection between Schumann Resonances and natural phenomena, such as lightning, earthquakes, and Earth’s climate, has been experimentally and theoretically demonstrated. This article is a review of the relevant literature on Schumann Resonance observation experiments, theoretical research over the years, and a prospect based on space-based observations. We start with the theoretical background and the main content on Schumann Resonances. Then, observations and the identification of Schumann Resonance signals based on ground and satellite data are introduced. The research and related applications of Schumann Resonances signals are summarized in terms of lightning, earthquakes, and atmosphere. Finally, the paper presents a brief study of Schumann Resonances based on the China Seismo-Electromagnetic Satellite (CSES) and preliminary ideas about how to improve the identification and application of space-based Schumann Resonances signals.
Background:Atrial fibrillation (AF) recurrence remains a tricky problem in patients undergoing ablation. This meta-analysis aimed to summarize the current literature to clarify whether ...renin-angiotensin system inhibitors (RASIs) prevent AF recurrence after ablation.Methods and Results:Relevant studies were searched on Pubmed and EMBASE through December 2019. Pooled relative risk (RR) of AF recurrence was calculated. Subgroup analyses according to study design, race, and follow-up duration were further performed. A total of 15 studies examining 4,300 patients were included, with 3 randomized controlled trials and 12 cohort studies. Overall analysis showed that RASIs significantly reduced AF recurrence after ablation (RR=0.83; 95% confidence interval (CI) 0.70–0.98, P=0.028; I2=68.9%). Subgroup analysis further indicated that positive results were found in randomized controlled trials (RR=0.51, 95% CI 0.37–0.70, P<0.001; I2=4%), studies conducted in Asia (RR=0.59, 95% CI 0.46–0.76, P<0.001; I2=30.7%), and studies with follow-up duration ≥1 year (RR=0.82, 95% CI 0.70–0.95, P=0.01; I2=59.1%); negative results were found in cohort studies, studies conducted in Europe or the USA, and studies with follow-up duration <1 year.Conclusions:RASIs can potentially prevent AF recurrence after ablation under selected conditions. However, more studies are required to confirm this finding due to the variation in current evidence.
Due to natural and external influences in curved channels, ships frequently require adjustments in course and speed, posing challenges for existing control methods. Particularly lacking are speed ...control methods suitable for curved channel navigation. This study initially developed a three-degree-of-freedom MMG model incorporating external interference. It introduced an OP-PID heading controller merging optimal control strategies with traditional PID, adaptable to both external conditions and ship speed, validated through heading control simulations. The study analysed the ship's speed change process, deriving a mathematical expression for advance distance, and proposed a dichotomy-based speed control method to determine speed change points, addressing differential equations with unknown integrands. To mitigate uncertainty errors like parameter inaccuracies in ship maneuvering models and dynamic environmental disturbances, the study proposed a comprehensive control approach. This approach integrates model predictive control, feedback compensation, segment identification, and an enhanced line-of-sight (LOS) guidance method alongside the OP-PID course controller and dichotomy-based speed control. Simulation experiments in the Dongboliao Channel compared the proposed and existing methods. Results demonstrate the proposed method's capability to handle frequent course and speed adjustments effectively, even under model errors and external interference, showcasing superior track deviation and course control accuracy over existing methods.
The objective of this study is to study the effect of
bone flap (ISBF) repositioning, a recently proposed rigid skull base reconstruction technique, on patients diagnosed with pituitary adenoma ...undergoing endoscopic endonasal approach (EEA).
A retrospective analysis was conducted on 188 patients with pituitary adenomas who underwent EEA from February 2018 to September 2022. Patients were divided into the ISBF group and non-ISBF group, according to whether ISBF was used during skull base reconstruction.
Of the 75 patients in the non-ISBF group, 6 had postoperative cerebrospinal fluid (CSF) leakage (8%), while only 1 of 113 patients in the ISBF group (0.8%) had postoperative CSF leakage, indicating that the incidence of postoperative CSF leakage in the ISBF group was significantly lower than that in the non-ISBF group (
= 0.033). In addition, we also found that the postoperative hospitalization days of patients in the ISBF group (5.34 ± 1.24) were significantly less than those in the non-ISBF group (6.83 ± 1.91,
= 0.015).
ISBF repositioning is a safe, effective, and convenient rigid skull base reconstruction method for patients with pituitary adenoma treated by EEA, which can significantly reduce the rate of postoperative CSF leakage and shorten postoperative hospital stays.
Abstract Objective This study aims to review the recent literatures on the diagnostic accuracy of 320-slice computed tomography angiography (CTA) for detection of coronary artery stenosis, with ...invasive coronary angiography (ICA) as the reference standard. Methods A PubMed and EMBASE cross-search of the literatures on use of 320-slice CTA compared with ICA for detection of coronary artery stenosis, with publication date limited to January 1, 2008 to December 31, 2012. Individual and pooled sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated at the patient-, vessel- and segment-level. A positive result was defined as greater than or equal to 50%-diameter stenosis. Results A total of ten studies were included in the present meta-analysis, examining 1088 patients, 1629 vessels and 12,406 segments. The meta-analysis at the patient-level indicated a pooled sensitivity of 93% (95%CI: 91%–95%), specificity of 86% (95%CI: 82%–89%), PPV of 90% (95%CI: 87%–92%) and NPV of 90% (95%CI: 87%–93%). At the vessel-level, the pooled sensitivity was 92% (95%CI: 89%–94%), specificity 95% (95%CI: 94%–96%), PPV 87% (95%CI: 83%–90%), and NPV 97% (95%CI: 96%–98%). At the segment-level, the pooled sensitivity was 78% (95%CI: 76%–80%), specificity 98% (95%CI: 97%–98%), PPV 82% (95%CI: 80%–84%), and NPV 97% (95%CI: 97%–97%). Conclusions 320-CTA can effectively identify the majority of patients with coronary artery disease (CAD). The high NPV makes it as an effective noninvasive alternative to ICA for the exclusion of stenosis.
The T2 mapping of magnetic resonance imaging (MRI) in endometrial cancer (EC), benign endometrial lesions (BELs), and normal endometrium (NE) has rarely been reported. This study aimed to determine ...the T2 values of MRI in EC, BELs, and NE to investigate whether the T2 values can differentiate them and to assess the aggressiveness of EC.
In total, 73 patients EC, 51 (age, 57.4 ± 5.4 years); BELs, 22 (age, 57.8 ± 11.8 years) and 23 normal volunteers (age, 56.1 ± 6.6 years) were included. The T2 values of MRI of the EC (type I and II), BEL, and NE groups were described and compared. The relationships between the T2 values of MRI in EC and the pathological characteristics International Federation of Gynecology and Obstetrics (FIGO) stage and grade were analyzed.
The median T2 values of NE, BEL, and EC were 197.5 (142.9-324.0) ms, 131.1 (103.2-247.9) ms, and 103.0 (71.6-243.5) ms (
< 0.001), respectively. The median T2 values of type I and type II EC were 100.8 (71.62-130.44) ms and 125.7 (119.7-243.5) ms, respectively. There were significant differences in the T2 values among the NE, BEL, type I EC, and type II EC groups (
< 0.001) except for between the type II EC and BEL groups (
= 0.938). The T2 value of MRI in type I EC was significantly lower than that in type II EC (
= 0.001). There were no significant differences in patients with type I EC having different FIGO stages (
= 0.273) or tumor grades (
= 0.686).
T2 mapping of MRI has the potential to quantitatively differentiate between EC, BELs, and NE as well as between type I and type II EC.
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