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Semisolid rheoforming (SSR) is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry preparation. In this paper, slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method (SIM). Interrupted quenching technology was applied to investigate the primary α-Mg evolution during continuous cooling and isothermal holding. Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains, which becomes ideally globular when the slurry slowly cools to 620 ℃ and isothermally held for at least 30 s. The local solute diffusion leads to dendritic fragmentation and forms separated particles. During prolonged holding, the particle surface gradually becomes smooth because of protuberance melting and groove advancement. Coarsening of α-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory. Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later. The EDS results indicate that a longer holding time leads to Al solute element segregation at the grain boundaries, but Zn distribution within liquid matrix has no obvious change.

One important problem in casting wrought aluminum alloys is the high tendency to the formation of hot tears in the solidification process. By using semi-solid metal (SSM) processing, the hot tearing tendency of alloys can be minimized during casting. In the present research, the semi-solid slurry of wrought aluminum alloy 2024 was firstly prepared with a novel self-inoculation method (SIM), and then the microstructure characteristics of the semi-solid slurry and the rheo-diecastings cast with the semi-solid slurry were investigated. The results indicate that finer and more uniform globular primary α-Al particles can be obtained when the semi-solid slurry are isothermally held for a short period within the semi-solid temperature range, and the primary α-Al particles without entrapped liquid are uniformly fine, globular grains in the rheo-diecastings. The holding temperature and time affect the solid fraction, particle size, and shape factor. After the semi-solid slurry is held at 625 ℃ for 3 min and 5 min, the optimal values for the average equivalent diameter are 70.80 μm and 74.15 μm, and for the shape factor are 1.32 and 1.42, respectively. The solidification process of the rheo-diecastings is composed of the following two distinct stages: primary solidification process and secondary solidification process. The secondary solidification process consists further of the following three stages: (1) direct growth of secondary primary (α2) phase from the surface of the primary α-Al phase particles without re-nucleation, (2) independent nucleation and growth of α3 phase from the residual liquid, and (3) eutectic reaction at the end.

A novel cast processing method, self-inoculation method (SIM), was proposed. The process involves the addition of self-inoculant to melt, then pouring the melt to a mould through a multi-stream mixing cooling channel. In this paper, the process parameters were investigated. Results indicate that the melt treatment temperature, the amount of self-inoculant added, and the slope angle of the cooling channel are the key factors for SIM process. The optimized parameters are that the melt treatment temperature is between 680 and 700°C; the addition of self-inoculant is between 5wt.% and 7wt.%; and the slope angle of the cooling channel is between 30°and 45°. Further analysis reveals that SIM changes the solidification microstructure of slurry by controlling the nucleation and growth of the primary phase in the melt

In an increasingly interconnected world, intercultural competency has become an essential skill for many. It is important for students to learn this skill, but are teachers equipped to instill such knowledge not just adequately, but also objectively and without prejudice? In light of the recent explosion in telecommunications-assisted teaching and learning, this is a timely review on the use of online technology as cognitive tools for enhancing teachers' intercultural competency skills. Though various online platforms for learning and sharing have been developed for and used by students over the years, less attention has been given to teachers' needs; only five well-documented projects pertaining to the upskilling of intercultural competence were found. We focus on these five projects and draw from them best practices, platforms and methods of potential and other insights, which would provide the best benefits in meeting the professional development needs of teachers.

The leptomeningeal collateral status is an independent predictor of stroke outcome. By means of optical coherent tomography angiography to compare two mouse strains with different extent of native leptomeningeal collateralization, we determined the spatiotemporal dynamics of collateral flow and downstream hemodynamics following ischemic stroke. A robust recruitment of leptomeningeal collateral flow was detected immediately after middle cerebral artery (MCA) occlusion in C57BL/6 mice, with continued expansion over the course of seven days. In contrast, little collateral recruitment was seen in Balb/C mice during- and one day after MCAO, which coincided with a greater infarct size and worse functional outcome compared to C57BL/6, despite a slight improvement of cortical perfusion seven days after MCAO. Both strains of mice experienced a reduction of blood flow in the penetrating arterioles (PA) by more than 90% 30-min after dMCAO, although the decrease of PA flow was greater and the recovery was less in the Balb/C mice. Further, Balb/C mice also displayed a prolonged greater heterogeneity of capillary transit time after dMCAO in the MCA territory compared to C57BL/6 mice. Our data suggest that the extent of native leptomeningeal collaterals affects downstream hemodynamics with a long lasting impact in the microvascular bed after cortical stroke.

Fe‐based sulfate materials have attracted much attention in the cathode of sodium‐ion batteries (SIBs) due to their low cost and high operating voltage, as well as possessing application prospects comparable to hard carbon in the anode based on Fe0/Fe2+/Fe3+ redox properties. However, the poor conductivity and the tendency to agglomerate have limited their further application. Herein, the study constructs a dual‐conductive structure that the Na2.31Fe1.72(SO4)3 particles with amorphous carbon in situ‐coated embedded in ketjen black (KB) conducting carbon networks (NFS/KB) via a solid phase ball‐milling strategy, which effectively enhanced inherent conductivity and electron transfer efficiency among particles of the Fe‐based sulphate. The NFS/KB can provide a reversible capacity of 92 mAh g−1 at 0.1 C and stable cycling stability at high current (85% retention after 500 cycles at 20 C) as cathode of SIBs. Surprisingly, as anode of SIBs, the NFS/KB delivers a rate performance (149 mAh g−1 at 10 C) that is superior to that of hard carbon. Notably, further application of the material to symmetric SIBs also achieves favorable results. This work effectively enhances the performance of Fe‐based sulphate materials in SIBs with a low‐cost carbon modification method, providing a new approach for the low‐cost symmetric SIBs. [ABSTRACT FROM AUTHOR]

As the Nairobi–Malaba Railway traverses the East African Rift Valley, it has complex engineering geological conditions due to the development of its geological formations. Since March 2018, four large ground fissures have occurred in the East African Rift Valley area crossed by the Nairobi–Malaba Railway engineering construction, posing a significant threat to the safety of the railway engineering. According to the field investigation, it is initially considered that the ground fissures are caused by the loss of strength of the lower soil layers. In view of the fact that the settlement occurred during the rainy season and no earthquake events were recorded in the local and nearby areas during that period, it is inferred that the ground fissures originated from the subduction of the underlying soil layer by the submerged erosion of groundwater. For this reason, a further field investigation was conducted and a geological trench was directly excavated to the underlying rock for the uneven ground settlement, which revealed that the overlying soil layers are mainly silty clay layers and volcanic ash layers, and there are some deep and long cracks of a certain width on the underlying volcanic rock layer and there is gas flow spilling from the cracks. The field investigation also found the existence of some penetrating holes in the volcanic rock layer and caves beneath the volcanic rock layer. Based on the field investigation and phenomenological analysis, it is concluded that during the rainy season, the alternating action phenomenon of downward seepage of water in the surface soil layer and upward reflux of water beneath the volcanic rock layer happened through the cracks and penetrating holes on the volcanic rock layer, and the alternating effect of groundwater flow causes some silty clay and volcanic ash particles to flow into the caves and cracks beneath the volcanic rock layer, which leads to the generation of ground fissures. In addition, to further confirm the reliability of this interpretation of the generative mechanism of ground fissures, related results of conventional geotechnical tests on the overlying soil were studied, which verified the conclusion obtained. [ABSTRACT FROM AUTHOR]

Normal aging is associated with significant alterations in brain's vascular structure and function, which can lead to compromised cerebral circulation and increased risk of neurodegeneration. The in vivo examination of cerebral blood flow (CBF), including capillary beds, in aging brains with sufficient spatial detail remains challenging with current imaging modalities. In the present study, we use 3-dimensional (3-D) quantitative optical coherence tomography angiography (OCTA) to examine characteristic differences of the cerebral vasculatures and hemodynamics at the somatosensory cortex between old (16 months old) and young mice (2 months old) in vivo. The quantitative metrics include cortical vascular morphology, CBF, and capillary flow velocity. We show that compared with young mice, the pial arterial tortuosity increases by 14%, the capillary vessel density decreases by 15%, and the CBF reduces by 33% in the old mice. Most importantly, changes in capillary velocity and heterogeneity with aging are quantified for the first time with sufficiently high statistical power between young and old populations, with a 21% (p < 0.05) increase in capillary mean velocity and 19% (p ≤ 0.05) increase in velocity heterogeneity in the latter. Our findings through noninvasive imaging are in line with previous studies of vascular structure modification with aging, with additional quantitative assessment in capillary velocity enabled by advanced OCTA algorithms on a single imaging platform. The results offer OCTA as a promising neuroimaging tool to study vascular aging, which may shed new light on the investigations of vascular factors contributing to the pathophysiology of age-related neurodegenerative disorders.