We report acute antibody responses to SARS-CoV-2 in 285 patients with COVID-19. Within 19 days after symptom onset, 100% of patients tested positive for antiviral immunoglobulin-G (IgG). ...Seroconversion for IgG and IgM occurred simultaneously or sequentially. Both IgG and IgM titers plateaued within 6 days after seroconversion. Serological testing may be helpful for the diagnosis of suspected patients with negative RT-PCR results and for the identification of asymptomatic infections.
Mechanical properties play a key role in the failure of dental implants. Dental implants require fatigue life testing before clinical application, but this process takes a lot of time. This study ...investigated the effect of various loading angles and implant lengths on the static fracture and fatigue life of dental implants. Implants with lengths of 9 mm and 11 mm were prepared. Static fracture tests and dynamic fatigue life tests were performed under three loading angles (30°, 40°, and 50°), and the level arm and bending moment were measured. After that, the fracture morphology and fracture mode of the implant were observed. The results showed that 9 mm length implants have a higher static failure load and can withstand greater bending moments, while 11 mm length implants have a longer fatigue life. In addition, as the loading angle increases, the static strength and bending moment decrease linearly, and the fatigue life shows an exponential decrease at a rate of three times. Increasing the loading angle reduces the time of the implant fatigue test, which may be an effective method to improve the efficiency of the experiment.
Seismic performance of rectangular underground structures as a hot topic was studied systematically for decades. However, less attention was paid to the functionalities of the structural components. ...This paper presents a detailed numerical investigation of the seismic responses of rectangular underground structures and aims to explore the functionalities of the structural components. A three-dimensional numerical model for nonlinear dynamic responses simulations of underground structures was built, and the seismic responses of a rectangular underground structure under multiple ground motions were simulated. Dynamic response data, including internal forces, drifts of the columns and walls were obtained and analysed. Results of the proportions of seismic loads undertaken by the structural components explicitly illustrated the functionalities of the structural components before and during earthquakes. Then the failure process of Daikai station during the Great Hanshin earthquake was simulated, and the loading and deformation capacities of the slabs, as well as the intermediate columns and lateral walls, were presented. In terms of the load carrying capacities and functionalities of the structural components, the failure mechanism of the structures was better to understand, and the intermediate columns as the supporting components for the rectangular underground structures were proposed. The conclusions are beneficial to the seismic design of underground structures.
•Proportions of the seismic loads carried by the structural components of the rectangular underground structures.•Functionalities and loading carrying capacities of the structural components.•Collapse procedure and failure mechanism of the rectangular underground structures.
To assess the diagnostic accuracy of 1,3-β- d -glucan (BDG) assay for diagnosing invasive fungal infections (IFI), we searched the Medline and Embase databases, and studies reporting the performance ...of BDG assays for the diagnosis of IFI were identified. Our analysis was mainly focused on the cutoff level. Meta-analysis was performed using conventional meta-analytical pooling and bivariate analysis. Our meta-analysis covered 28 individual studies, in which 896 out of 4214 patients were identified as IFI positive. The pooled sensitivity, specificity, diagnostic odds ratio, and area under the summary receiver operating characteristic (AUC-SROC) curve were 0.78 95% confidence interval (CI), 0.75–0.81, 0.81 (95% CI, 0.80–0.83), 21.88 (95% CI, 12.62–37.93), and 0.8855, respectively. Subgroup analyses indicated that in cohort studies, the cutoff value of BDG at 80 pg/mL had the best diagnostic accuracy, whereas in case–control studies the cutoff value of 20 pg/mL had the best diagnostic accuracy; moreover, the AUC-SROC in cohort studies was lower than that in case–control studies. The cutoff value of 60 pg/mL has the best diagnostic accuracy with the European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria as a reference standard. The 60 pg/mL cutoff value has the best diagnostic accuracy with the Fungitell assay compared to the BDG detection assay. The cutoff value of 20 pg/mL has the best diagnostic accuracy with the Fungitec G-test assay, and the cutoff value of 11 pg/mL has the best diagnostic accuracy with the Wako assay. Serum BDG detection is highly accurate for diagnosing IFIs. As such, 60 pg/mL of BDG level can be used as the best cutoff value to distinguish patients with IFIs from patients without IFI (mainly due to Candida and Aspergillus ).
The scroll vacuum pump is a dry vacuum pump with a wide range of applications. The radiated noise of a multi-stage scroll vacuum pump under different suction pressures is tested. The discharge ...velocity field is measured by the PIV technique. When the suction pressure changes from 101 kPa to 5 Pa, the average sound pressure level of the scroll pump decreases from 80.37 dB to 58.13 dB, which is reduced by 22.24 dB. The maximum and minimum sound power levels are 97 dB and 74.76 dB, respectively. The spectrum characteristics and the distribution law of radiated noise are analyzed. The measured noises at the rear of all operating conditions are the smallest, followed by the positions above the front part, and the next is the directly above position. Aeroacoustics is the main noise source in the scroll pump. Based on the CFD method, the simulation calculation is carried out at different suction pressures and the maximum simulation error is −5.7%. The location and formation mechanism of the aeroacoustics source are analyzed. In different working processes, the main excitation sources of aeroacoustics are different. The results are helpful to the noise source identification and aeroacoustics improvement of the scroll vacuum pump.
•The radiated noise of the scroll pump is experimentally investigated.•The discharge velocity field of the scroll vacuum pump is measured by PIV.•The aeroacoustics sources of the scroll pump are analyzed by CFD.•Other noises of the scroll pump are analyzed.
The dry scroll vacuum pump is a kind of variable capacity dry vacuum pump that is applied in chemical, pharmaceutical, semiconductor, and scientific instruments. Analyzing the thermodynamic ...characteristics of the scroll vacuum pump and studying the impact of operating temperature on its consistent performance are necessary for the design and application of the cooling system of the scroll vacuum pump. Based on the dynamics mesh method, the computational fluid dynamics (CFD) simulation model of a multi-stage dry scroll vacuum pump is established in this study. Under the suction pressure of 1000 Pa, the simulation calculation is carried out at different operating temperatures of fixed scrolls (25 °C, 45 °C, and 65 °C). The results show that the pumping speed, the gas compression power, and the energy efficiency ratio are significantly affected by different temperatures. The operating temperature of the pump has been reduced from 65 °C to 25 °C, the pumping speed is increased by approximately 5.97%, the gas compression power is increased by approximately 4.32%, and the energy efficiency ratio is increased by approximately 1.745%. This research provides a transient simulation method using dynamic mesh technology for the study of the dry scroll vacuum pump, and the results can provide a theoretical basis for the design and application of the cooling system of the dry scroll vacuum pump.
Medulloblastoma (MB) is the most common malignant pediatric brain tumor arising in the cerebellum or the 4
ventricle. Cerebellopontine angle (CPA) MBs are extremely rare tumors, with few cases ...previously described. In this study, we sought to describe the clinical characteristics, molecular features and outcomes of CPA MB. We retrospectively reviewed a total of 968 patients who had a histopathological diagnosis of MB at the Beijing Neurosurgical Institute between 2002 and 2016. The demographic characteristics, clinical manifestations and radiological features were retrospectively analyzed. Molecular subgroup was evaluated by the expression profiling array or immunohistochemistry. Overall survival (OS) and progression-free survival (PFS) were calculated using Kaplan-Meier analysis. In this study, 15 patients (12 adults and 3 children) with a mean age at diagnosis of 25.1 years (range 4-45 years) were included. CPA MBs represented 1.5% of the total cases of MB (15/968). Two molecular subgroups were identified in CPA MBs: 5 WNT-MBs (33%) and 10 SHH-MBs (67%). CPA WNT-MBs had the extracerebellar growth with the involvement of brainstem (P = 0.002), whereas CPA SHH-MBs predominantly located within the cerebellar hemispheres (P = 0.004). The 5-year OS and PFS rates for CPA MB were 80.0% ± 10.3% and 66.7% ± 12.2%, respectively. Pediatric patients with CPA MBs had worse outcomes than adult patients (OS: P = 0.019, PFS: P = 0.078). In conclusion, CPA MB is extremely rare and consists of two subgroups. Adult patients with CPA MB had a good prognosis. Maximum safe surgical resection combined with adjuvant radiotherapy and chemotherapy can be an effective treatment strategy for this rare tumor.
With the rapid development of the subway rail transit, tunnels are buried at an increasing depth, raising the requirements of bearing capacity and waterproofness for linings. Functionally graded ...materials are introduced into the design of linings to save costs, and concrete with different elastic moduli is equipped at different positions to reduce the waste of materials, compared to the homogeneous lining. The significance of this study includes that the functionally graded lining for the buried subway tunnel is under the non-uniform confining pressure and the calculation model of internal force and deformation for the functionally graded lining is established. The elastic modulus of the lining is set to vary with the angle in the form of a power function, and the function parameters are analyzed on the basis of this model. The results show that the radial displacement of the lining axis decreases with the increase in a and b, but the deformation mode remains the same, and the reduction in deformation is smaller and smaller. With the increase in a and b, the distribution trend of the moment remains the same. The lateral pressure coefficient λ has a great impact on the safety of the structure, which exceeds the influence of the function parameters on the safety of the structure. The displacement of the lining axis and the section moment change linearly with the increase in λ. With the increase in λ, the shape of the lining changes significantly, which shows that the side with larger pressure deforms to the inside and the side with smaller pressure expands to the outside. When the maximum deformation occurs at 0°, the parameter a should be larger than b. When the maximum deformation occurs at 90°, the parameter b should be larger than a, so as to minimize the cost of materials and reduce the structural deformation. Finally, the numerical simulation is conducted to verify the theoretical results, showing that the calculation model of internal force and deformation is suitable for the cylinder with t/R≤0.2, and there is a certain gap between the theoretical calculation and numerical simulation, but the largest gap of the displacement is within 8%. Compared with Function I, Function II has some advantages in reducing the maximum deformation of the structure, but the advantages are relatively low. The analysis results have significant reference value for designers and relevant scholars.
With the mining depth of coal resources increasing, the thickness of traditional lining for deep mines becomes large. The bearing capacity of the outer lining cannot be fully utilized, so a new type ...of functionally graded lining structure (FGL) with radial Young’s modulus varying in gradient is proposed. In this study, through theoretical analysis and numerical simulation, the mechanical properties of the functionally graded lining were studied, including the characteristics of the elastic working state and the ultimate bearing state. The influences of the structural parameters of the functionally graded lining, including the inner radius, the thickness, Young’s modulus, the compressive strength of the concrete, Poisson’s ratio, and the number of layers on the mechanical properties were analyzed. The calculation formula of the ultimate bearing capacity of the lining and the calculation formula of the maximum tangential strain at the time of lining failure were put forward. The accuracy of the formula was verified by comparing with the numerical simulation results. The research results provide the basis for the construction of the design theory of a functionally graded lining structure and have great engineering significance for the construction of the kilometer-deep mines in the future.
Type-2 diabetes not only causes gray matter injury but also induces widespread white matter damages, which may contribute the cognitive impairments. This study aimed to assess the structural ...alterations of the gray and white matter in 20-week-old diabetic db/db mice using magnetic resonance imaging including T2-weighted imaging (T2WI) and diffusion tensor imaging (DTI), and to correlate them with the cognitive performance detected by Morris water maze (MWM). The results revealed impaired spatial learning and memory in db/db mice. T2WI detected severe brain atrophy involving the hippocampus and cortex after diabetes. DTI showed reduced fractional anisotropy (FA) in the cortex, hippocampus, corpus callosum/external capsule, and increased radial diffusivity in the corpus callosum/external capsule of the db/db mice. The immunostaining confirmed the MRI findings showing decreased cell density in the cortex, hippocampus, and reduced integrated optical density of Luxol fast blue staining in the corpus callosum/external capsule. The correlational analysis revealed that the T2WI-derived tissue atrophy and DTI-derived FA in the relevant gray matter and white matter significantly correlated with the behavior performance in the MWM test. Collectively, the present in vivo MRI detected varying degrees of structural abnormalities in the gray and white matter of db/db mice, which might be favorable predictors of diabetic cognitive dysfunction. Our findings might provide new clues for identifying gray and white matter damages associated with cognitive decline, which is imperative for the evaluation of potential pharmacological therapies in preclinical phase.
•Twenty-week-old db/db mice exhibit spatial learning and memory impairments.•T2WI demonstrates brain atrophy in the hippocampus and cortex of db/db mice.•DTI detects microstructural injuries in the gray and white matter of db/db mice.•Brain atrophy and FA correlates well with the cognitive performance.
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