•Rafting extent of the superalloy was quantitatively characterized by a cross-correlated image processing method.•Rafting behaviour decreases the resistance to plastic deformation and the hardening ...effect of the γ' precipitates, which promote the accumulation of the fatigue damage and reduce the fatigue life.•A fatigue life prediction model considering the microstructural rafting was proposed, which is of good consistence with the experimental data.
Operating under elevated temperature and high stress for long terms, the regularly cubic γ' precipitates of the Ni-based superalloy degrades to plate-like morphology perpendicular to the external stress. This process is called rafting and plays a deteriorated role on the mechanical properties of the alloy. In this study, the quantitative effect of rafting on the low cycle fatigue behaviour of a directionally solidified Ni-based superalloy was investigated. Fatigue tests were conducted at 850 °C with a 1.1% total strain range with six different rafting states. The fatigue life decreased considerably over 90% as the rafting state aggravated. The rafting process increased the width of the matrix channel, which weakened the plastic deformation resistance and the mean stress relaxation of the superalloy. To build a quantitative relationship between the life reduction and rafting state, a life prediction model was proposed based on the strengthening mechanism of Ni-based superalloys by assuming that the rafted alloy suffered a higher loading level compared with the virgin state. Moreover, the scanning electron microscopy was employed to observe fatigue fracture surfaces and the rafted microstructures. The micro-parameters such as the width of the γ' precipitates and the matrix channel were obtained through a cross-correlated image processing method.
This paper was attempted to investigate the microstructure degradation and low cycle fatigue (LCF) performance of a serviced K465 Ni‐based superalloy turbine blade. LCF tests were carried out with ...small‐scale plate specimens sampled from the blades. Relationship between residual LCF life and microstructure state was estimated. The results indicate that the coarsening of γ/γ′ phases was the most significant microstructure degradation mode for the serviced blades. Both the γ matrix width and the γ′ precipitate diameter increased with the increase of service duration, while the γ′ precipitate volume fraction slightly decreased. The most severe microstructure degradation occurred at the leading edge along the chord direction, particularly at 50–70 % airfoil spans. The residual LCF life exhibited an accelerated decrease characteristic as increases of microstructure degradation degree. The coarsened microstructure diminished shear resistance of the superalloy, which resulted in additional accumulated inelastic deformation and a corresponding reduction in LCF life.
Highlights
Service induced microstructure evolution and LCF life decay of a blade were investigated.
Coarsening was identified as the main degradation form of γ/γ' phases in serviced blade.
Accelerated decrease of residual LCF life was identified as increases of coarsening.
Reduced plastic deformation resistance owing to coarsening is crucial to decay LCF life.
A directionally solidified Ni-based superalloy was pre-treated under high temperature with/without the applied stress to obtain different microstructural morphology. Then, strain-controlled low cycle ...fatigue experiments were carried out under 850°C with a 0 strain ratio to measure the reduction in the fatigue resistance. The scanning electron microscopy (SEM) was employed to characterize the microstructures of the alloy with different treatments. The micro-deformation and dislocation movement were investigated via transmission electron microscopy (TEM). The results show that both coarsening and rafting morphology have negative effects on the fatigue properties, which is closely related to the deformation mechanism of the alloys with different γ' morphology. The coarsening morphology decreases the shear resistance of the γ' precipitates, resulting in shearing of γ' particles. More plastic deformation introduces during the cyclic process, leading in the reduction of fatigue life. On the other hand, the wide γ channel promoted the piling up and movement of dislocations in the matrix, also resulting in reduction of plastic deformation resistance and lifespan. Finally, a fatigue life prediction model was proposed based on the continuum damage mechanics (CDM) by introducing the variation of matrix channels’ width, showing a good competency compared with the experimental results.
•Fatigue properties of a Ni-based superalloy with different γ' morphology were investigated.•Both coarsening and rafting morphology decreased the fatigue life of the superalloy.•Coarsening process reduce the shearing resistance of the γ' particles, resulting in the more plastic deformation comparing with the virgin.•A CDM-based fatigue life prediction model was proposed considering the variation of the γ' morphology.
To explore the expression and function of insulin-like growth factor II (IGFII) mRNA binding protein (IMP3) in the Triple Negative Breast Cancer (TNBC).
According to previously reported gene ...expression array, we found that IMP3 had significantly higher expression in the CD44+CD24-ESA+ cell cluster, tumor initiating cell or cancer stem cell (CSCs), compared to other tumor cells. Based on the GEO database (GEO accession No. GSE6883), we detected the mRNA levels of IMP 1,2 and 3 by quantitative polymerase chain reaction (q-PCR) in CD44+CD24-ESA+ cell cluster and other breast tumor cell clusters. Besides, we measured IMP3 expression in microsphere of breast cancer, which exerted more significant tumor stem cell properties. The effects of IMP3 on breast cancer cell stem cell properties were studied by RNA interference and overexpression approaches in vitro. Furthermore, we predicted and identified microRNA, which could target and regulate IMP3 from bioinformatics analysis, and verified the interaction by luciferase assays and rescue experiments.
Previously reported data showed that IMP3 expression was significantly upregulated in CD44+CD24-ESA+ cell cluster from breast cancer tissues. Besides, we found IMP3 had higher expression in mesenchymal cells rather than epithelial cells, which was also significantly elevated in SUM159 and T49D cell lines cultured as microsphere rather than adherent cells or differentiated cells. CD44+CD24-ESA+ cell cluster proportion was significantly decreased after silencing IMP3 in SUM1315, and its ability to develop into microsphere was significantly inhibited. By re-expressing IMP3 in SUM315, we restored the self-renewal capacity and tumorigenesis potential of SUM315. Through relative predicting website, we found several miRNAs which could regulate IMP3. miR-34a with highest score was chosen for further analysis. Mimicking miR-34a significantly downregulated IMP3 expression and inhibited its ability to develop into microsphere, while overexpressing IMP3 could rescue this process.
IMP3 plays a vital role in maintaining stem cell properties of breast cancer cells, which could be regulated by mir-34a.
During the last several years, the HL-2A experiment has made significant progress in the following areas: (1) lower-hybrid wave (LHW) heating and current drive, (2) plasma confinement and turbulent ...transport, (3) magnetohydrodynamic (MHD) instabilities and energetic particle physics and (4) H-mode and edge localized mode (ELM) control. The results show that the LHW system working in the co-current mode can reach higher driving efficiency and full non-inductive lower-hybrid current drive (LHCD) has been achieved. The intrinsic poloidal torque characterized by the divergence of the residual stress is deduced from synthesis for the first time. The dynamics of spectral symmetry breaking in drift wave turbulence is in good agreement with the development of the poloidal torque to drive the edge poloidal flow. The influence of the cross-phase dynamics on turbulent stress was also investigated. The ion internal transport barrier has been observed in the NBI-heated plasma, and inside the barrier the ion thermal transport is reduced to the neoclassical level. Besides, micro-turbulence is modulated by the rotation frequency of the magnetic island, and this modulation effect is related to a critical island width. Strong E × B shear is found at the island boundary. Three kinds of axisymmetric modes, beta-induced Alfven eigenmode (BAE), toroidal Alfven eigenmode (TAE) and the ellipticity-induced Alfven eigenmode (EAE), are found to be driven unstable by nonlinear mode coupling between Alfven eigenmodes and tearing mode which is well explained by the nonlinear gyrokinetic theory. The fishbone and tearing modes were actively controlled by the electron cyclotron resonance heating (ECRH). The dynamics of the edge plasma flows and turbulence during the L–I–H transition have been dedicatedly investigated. The geodesic acoustic mode (GAM) and limit cycle oscillation (LCO) coexist for a short time and disappear in the H-mode plasma with the increasing of E × B shear flow before the I–H transition, which plays an important role in the turbulence suppression. Different techniques, such as LHW, ECRH, resonant magnetic perturbation (RMP), and impurity seeding by the laser blow-off (LBO) and supersonic molecular beam injection (SMBI), have been successfully applied to control the large ELMs. It has been found that pedestal turbulence enhancement might be responsible for the observed mitigation effect.
Hand, foot and mouth disease (HFMD) is an acute contagious condition caused by a spectrum of human enteroviruses. HFMD reinfection is common in the absence of cross-protection from other virus ...subtypes. This study focused on reinfection in children in Anhui province, China between 2008 and 2013 using surveillance system data. We classified 8960 cases as reinfected, corresponding to a rate of 2·02%. The reinfection rate was higher in boys than in girls odds ratio (OR) 1·27, 95% confidence interval (CI) 1·21–1·32, P < 0·001, children aged < 3 years (OR 3·82, 95% CI 3·58–4·07, P < 0·001), and children living in rural areas (OR 1·09, 95% CI 1·04–1·14, P = 0·001). The reinfection rate in children who were originally infected with non-enterovirus A71 (non-EVA71) enteroviruses was higher than those infected with EVA71 (OR 1·36, 95% CI 1·02–1·80, P = 0·034). Influential factors of reinfection rate included annual incidence (β coefficient = 0·715, P = 0·002) and the proportion of EVA71 in patients with mild HFMD (β coefficient = −0·509, P = 0·018). These results demonstrate that boys aged <3 years, especially those in rural areas or regions with a lower EVA71 proportion are more prone to reinfection, and specific health education programmes should be developed to protect these susceptible populations.
Abstract Introduction There are many reports concerning the fondaparinux prophylaxis of deep vein thrombosis (DVT) after surgery, but little is known about the usefulness of diagnosing DVT by the ...thrombotic markers such as soluble fibrin (SF) and D-dimer in patients treated with fondaparinux. The main purpose of this study was to evaluate the accuracy of SF and D-dimer tests for DVT screening in patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA) treated with fondaparinux. Materials and methods A total of 519 patients who underwent THA or TKA were evaluated. SF and D-dimer levels were evaluated on postoperative days 1, 4, 7, 14 and 21. DVT was confirmed by ultrasonography 4 days after surgery. Results The incidence of DVT in patients treated with fondaparinux was significantly lower than in patients without fondaparinux. The SF test on postoperative day 1, and the D-dimer test on postoperative days 1, 4, and 7 were useful in untreated patients. However, in the patients treated with fondaparinux, the D-dimer test on postoperative day 7 only was useful for DVT screening. Conclusion The accuracy of SF and D-dimer test for the diagnosis of DVT was decreased by administration of fondaparinux. A new strategy for diagnosing DVT might be required for patients receiving fondaparinux.
We measure the lifetime of the $D^+_s$ meson using a data sample of 207 fb-1 collected by the Belle II experiment running at the SuperKEKB asymmetric-energy e+e- collider. The lifetime is determined ...by fitting the decay-time distribution of a sample of 116 × 103 $D^+_s$ → φπ+ decays. Our result is τ$D^+_s$ = (499.5 ± 1.7 ± 0.9) fs, where the first uncertainty is statistical and the second is systematic. This result is significantly more precise than previous measurements.
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