Friction stir welding (FSW) of dissimilar welds between ZG61 alloy and AZ91D alloy was investigated. Severe deformation and metal flow occur in the stir zone under high strain rates and high ...temperatures. No distinct reaction layer or intermetallic compounds are observed at the interface of two alloys. When AZ91D was arranged in the advancing side and ZG61 in the retreating side, the joints quality was very poor with all parameters. Microstructure and texture evolution during the FSW and relationship of microstructure, texture and mechanical properties are discussed. The tensile properties of the weld of joints are significantly influenced by the materials positions, grain size and crystallographic orientation. Materials positions and plasticity of base metals is of importance during the FSW of dissimilar alloys. It can be seen that defects cannot be avoided when the heat input were too low to make the metal flow.
A high strength Mg-1.4Gd-1.2Y-0.4Zn (at%) alloy sheet was successfully prepared by the combination of extrusion and corresponding heat treatments. The microstructure, texture and mechanical ...properties were systematically investigated. The results show that the microstructure of the as-extruded alloy is composed of finer recrystallized grains with random orientation, elongated grains, and 14H-LPSO structures which are parallel to the extrusion direction, possessing a modified texture. For the as-aged alloy, the metastable β′ phases dispersively distribute within the grains. The as-extruded alloy already shows high tensile mechanical properties. After aging treatment, the tensile yield strength, ultimate tensile strength, and elongation to failure reach 395 MPa, 461 MPa, and 6.0%, respectively. The solution treatment and extrusion, which give rise to the dissolution of eutectic phases, the grain refinement and the accumulation of dislocations, contribute mainly to the strength of the as-extruded alloy. Aging treatment further strengthens the alloy by precipitating the metaphase β′ at the expense of the rare earth element dissolving into the matrix.
Obstructive sleep apnea (OSA) on its own, as well as its risk factors, have been found to be associated with the outcome of Coronavirus disease 2019 (COVID-19). However, the association between the ...degree of OSA and COVID-19 severity is unclear. Therefore, the aim of the study was to evaluate whether or not parameters to clinically evaluate OSA severity and the type of OSA treatment are associated with COVID-19 severity. Patient data from OSA patients diagnosed with COVID-19 were reviewed from outpatients from the Isala Hospital and patients admitted to the Isala Hospital, starting from March until December 2020. Baseline patient data, sleep study parameters, OSA treatment information and hospital admission data were collected. Apnea hypopnea index (AHI), low oxyhemoglobin desaturation (LSAT), oxygen desaturation index (ODI), respiratory disturbance index (RDI), and the type of OSA treatment were regarded as the independent variables. COVID-19 severity–based on hospital or intensive care unit (ICU) admission, the number of days of hospitalization, and number of intubation and mechanical ventilation days–were regarded as the outcome variables. Multinomial regression analysis, binary logistic regression analysis, and zero-inflated negative binomial regression analysis were used to assess the association between the parameters to clinically evaluate OSA severity and COVID-19 severity. A total of 137 patients were included. Only LSAT was found to be significantly associated with the COVID-19 severity (p<0.05) when COVID-19 severity was dichotomized as non-hospitalized or hospitalized and ICU admission or death. Therefore, our findings showed that LSAT seems to be a significant risk factor for COVID-19 severity. However, the degree of OSA–based on AHI, ODI, and RDI–and OSA treatment were not found to be risk factors for COVID-19 severity when looking at hospital or ICU admission, the number of days of hospitalization, and number of intubation and mechanical ventilation days.
► In this paper, we synthesized Na0.74CoO2 as cathode for rechargeable sodium ion batteries. ► We examined its electrochemical performance. ► A reversible capacity of 107mAh/g with 0.1% capacity ...fading for the first 40 cycles was obtained. ► The deintercalation/intercalation reactions of Na ions from/into Na0.74CoO2 proceeded while Co3+/Co4+ redox.
P2-phase Na0.74CoO2 cathode material prepared by a solid-state method exhibits the specific discharge capacity of 107mAhg−1 at 0.1C with good cycling performance for rechargeable sodium ion batteries. The voltage polarization between charging and discharging at 0.1C rate is about 150–250mV and the coulombic efficiency in each cycle is about 89%. The expansion and compression in c-axis of the NaxCoO2 unit cell during the Na intercalation/deintercalation is revealed by ex situ XRD. XPS and in situ XAS data directly confirm that deintercalation/intercalation of Na ions from/into the layered structure proceeds with the Co3+/Co4+ redox reaction.
Summary
Aims: Several epidemiological studies suggested that gamma‐glutamyltransferase (GGT) levels may be associated with risk of Metabolic Syndrome (MetS). However, the exact association between ...them is still not fully clear. We therefore conducted a meta‐analysis of prospective cohort studies to comprehensively evaluate the exact association between GGT and risk of MetS.
Methods: The Pubmed, Embase, Science Citation Index (ISI Web of Science) databases were searched to collect all prospective cohort studies on the association between GGT and MetS. Then, the association between GGT and MetS was analysed in qualitative and quantitative manners.
Results: Nine prospective cohort studies involving 47,499 participants and 5009 cases of MetS were included. When comparing the risk of MetS between the highest versus the lowest category of GGT levels, the pooled RR of MetS was 1.63 (95% CI: 1.43–1.82; p < 0.000). The second dose‐response analysis of GGT levels per 5 U/l increment with risk of MetS showed that the summary RR of MetS was 1.09 (95% CI: 1.06–1.13; p < 0.000). Subgroup analysis suggested that number of adjusted confounding factors may be a potential source of heterogeneity. Sensitivity analyses showed that no single study significantly influenced the pooled RRs.
Conclusions: Our results show that GGT levels are positively associated with risk of MetS independently of alcohol intake. GGT may be a promising marker for predicting MetS. Further studies are needed to confirm our findings and elucidate the underlying mechanisms in future.
The ortho‐nitrophenol (ONP)‐utilizing Alcaligenes sp. strain NyZ215, meta‐nitrophenol (MNP)‐utilizing Cupriavidus necator JMP134 and para‐nitrophenol (PNP)‐utilizing Pseudomonas sp. strain WBC‐3 were ...assembled as a consortium to degrade three nitrophenol isomers in sequential batch reactors. Pilot test was conducted in flasks to demonstrate that a mixture of three mononitrophenols at 0·5 mol l−1 each could be mineralized by this microbial consortium within 84 h. Interestingly, neither ONP nor MNP was degraded until PNP was almost consumed by strain WBC‐3. By immobilizing this consortium into polyurethane cubes, all three mononitrophenols were continuously degraded in lab‐scale sequential reactors for six batch cycles over 18 days. Total concentrations of ONP, MMP and PNP that were degraded were 2·8, 1·5 and 2·3 mol l−1 during this time course respectively. Quantitative real‐time PCR analysis showed that each member in the microbial consortium was relatively stable during the entire degradation process. This study provides a novel approach to treat polluted water, particularly with a mixture of co‐existing isomers.
Significance and Impact of the Study
Nitroaromatic compounds are readily spread in the environment and pose great potential toxicity concerns. Here, we report the simultaneous degradation of three isomers of mononitrophenol in a single system by employing a consortium of three bacteria, both in flasks and lab‐scale sequential batch reactors. The results demonstrate that simultaneous biodegradation of three mononitrophenol isomers can be achieved by a tailor‐made microbial consortium immobilized in sequential batch reactors, providing a pilot study for a novel approach for the bioremediation of mixed pollutants, especially isomers present in wastewater.
Significance and Impact of the Study: Nitroaromatic compounds are readily spread in the environment and pose great potential toxicity concerns. Here, we report the simultaneous degradation of three isomers of mononitrophenol in a single system by employing a consortium of three bacteria, both in flasks and lab‐scale sequential batch reactors. The results demonstrate that simultaneous biodegradation of three mononitrophenol isomers can be achieved by a tailor‐made microbial consortium immobilized in sequential batch reactors, providing a pilot study for a novel approach for the bioremediation of mixed pollutants, especially isomers present in wastewater.
In this work, a 316L stainless steel to Inconel 625 functionally graded material (FGM) was built using different deposition strategies (named as direct and smooth-type interfaces) by Twin-Wire and ...Arc Additive Manufacturing (T-WAAM). This combination of materials is of interest in chemical plants, oil & gas, and nuclear applications, where high corrosion and wear resistance are essential requirements. Although these properties are superior in Inconel 625, replacing Inconel with stainless steel in strategic regions of structural components can reduce the overall costs and parts’ weight. Both direct and smooth transition interfaces were tested and characterized. Microscopic analysis revealed that each interface and the as-built samples had an austenitic matrix, and every sample was well bonded and free of defects. Different types of microstructures evolved at the interfaces due to distinct gradients in composition. Synchrotron X-ray diffraction measurements showed that the smooth-gradient produced secondary phases, such as δ-phase (Ni3Nb) and carbides, that were not present with the direct interface strategy. Overall, the properties were superior in the FGM with a direct interface, which experienced higher strengths and elongations upon failure. Moreover, neutron diffraction measurements revealed that lower residual stresses developed in the direct interface FGM than in the smooth gradient FGM.
The SERS performance of Ag-ZnO-NR 3D substrates strongly depends on the radius, length, and density of ZnO NRs as well as the thickness of Ag layer. The refractive index of dielectric materials in ...nanocomposited 3D SERS substrates is capable of tuning the LSPR frequency as well.
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•LSPR frequency is tunable by changing ZnO-NR radius and Ag-layer thickness.•Optimized length of Ag-ZnO-NR is at μn-scale and the density is 83/μm2.•Refractive index is another parameter of optimizing the 3D SERS substrates.•Diploe LSPR of Ag-ZnO-NRs splits into high- and low-frequency two branches.•Low-frequency LSPR is predominant in enhancing Raman signals.
Surface enhanced Raman spectroscopy (SERS) is becoming an effective method of detecting organic molecules, and three-dimensional (3D) SERS substrates are promising in practical applications. To optimizing 3D SERS substrates, the extinction spectra and local electromagnetic fields of Ag-decorated ZnO nanorods (Ag-ZnO-NR) were studied by a finite-difference time-domain (FDTD) method. The diploe local surface plasmonic resonance (LSPR) was found to split into high- and low-frequency two branches, in which the low-frequency mode is predominant in contributing to the Raman enhancement, while the ZnO-NR radius and Ag-layer thickness play important roles in tuning the LSPR frequencies. Both of high- and low-frequency LSPRs were enhanced with the increase in the Ag-ZnO-NR length while the intensity of local electromagnetic field depends on the Ag-ZnO-NR density. The FDTD results were discussed with a comparison to the experimental data obtained from flower-like Ag-ZnO-NR 3D SERS substrates. In addition, the extinction spectra of Ag nanotube and Ag-decorated TiO2 and SiO2 nanorods were calculated and the refractive index of dielectric materials was found to be capable of tuning the LSPR of 3D SERS substrates as well. The principle revealed in this work is helpful for design and optimization of 3D SERS substrates.
Precipitation of Ni4Ti3 plays a critical role in determining the martensitic transformation path and temperature in Ni-Ti shape memory alloys. In this study, the equilibrium shape of a coherent ...Ni4Ti3 precipitate and the concentration and stress fields around it are determined quantitatively using the phase field method. Most recent experimental data on lattice parameters, elastic constants, precipitate-matrix orientation relationship and thermodynamic database are used as model inputs. The effects of the concentration and stress fields on subsequent martensitic transformations are analyzed through interaction energy between a nucleating martensitic particle and the existing microstructure. Results indicate that R-phase formation prior to B19a super(2) phase could be attributed to both direct elastic interaction and stress-induced spatial variation in concentration near Ni4Ti3 precipitates. The preferred nucleation sites for the R-phase are close to the broad side of the lenticular-shaped Ni4Ti3 precipitates, where tension normal to the habit plane is highest, and Ni concentration is lowest.
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