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Objective To report on the pathological characteristics of brain tissue in a case of Parkinson's disease (PD) with cerebral small vessel disease (CSVD). Methods and Results The male patient, 69 years old, was suddenly died. His brain tissue was donated and accepted by the Human Brain Tissue Bank of China National Clinical Research Center for Neurological Diseases, Beijing Tiantan Hospital, Capital Medical University, 9.50 h after sudden death. The patient was diagnosed with PD, and had undergone deep brain stimulation (DBS), but there was no clinical diagnosis of CSVD. We processed the brain tissue according to standardized procedure of international brain banks. Gross observation showed there was significant discoloration in the substantia nigra and locus coeruleus. The DBS pathway was also visible. Microscopic observation showed in addition to advanced stage of PD (Braak stage Ⅴ), pathological changes of DBS could also be seen, as well as CSVD pathological changes such as microvascular smooth muscle cell proliferation, thickening and hardening vessel walls, hyaline degeneration, lumen stenosis, severe perivascular dilatation, white matter microinfarction and microhemorrhage in frontal lobe, temporal lobe, cingulate gyrus, basal ganglia, brainstem and other areas. The final pathological diagnosis was PD (Braak stage Ⅴ) after DBS and CSVD. Conclusions This brain tissue was enrolled into the brain bank for the clinical diagnosis of PD. Pathological examination showed that in addition to the pathological changes of PD and DBS, CSVD was also coexisted. This case suggests that attention should be paid to the multiple comorbidities of neurological diseases of the elderly. doi:10.3969/j.issn.1672⁃6731.2021.04.006

Final electromagnetic stirring (F-EMS) is widely used in the billet and bloom continuous casting process because it effectively improves the as-cast quality. Numerous industrial trials on F-EMS have been conducted; however, the real melt flow and heat transfer characteristics at the crater end remain unclear. In this study, based on a round billet special steel continuous casting process, a coupled three-dimensional numerical model was developed to describe the F-EMS phenomenon. The flow and solidification behavior of the melt in the F-EMS region were obtained by a segmentation calculation model, and the Darcy source term method was employed to suppress the velocity within the mushy region. The effect of stirring current intensity and frequency on the electromagnetic field, melt flow, and heat transfer was investigated numerically. The model was validated using the measured data of magnetic flux density in the stirrer center and the strand surface temperature. According to the simulation results, with every 100 A increase in the current intensity, the maximal magnetic flux density increases by 19.05 mT. The electromagnetic force significantly increases with the increase in current intensity. With the increase in current frequency within 20-40 Hz, the magnetic flux density decreases slightly, whereas the electromagnetic force increases. Moreover, a swirling flow field in the stirrer region is observed under the rotary electromagnetic force, and the tangential velocity of melt increases with the increase in current intensity and frequency. Additionally, the swirling flow enhances the local melt heat transfer at the radial direction of the round strand. As the current intensity and frequency increase, the temperature of the melt in the liquid core decreases, and the center solid fraction at the F-EMS-implemented position increases accordingly.

The mushy zone refers to the region of the solid-liquid system where the temperature is between the liquidus and solidus temperatures. In this zone, the turbulence of the interdendritic flow is reduced by blockage of dendrites. The mushy zone coefficient (Amush) is an important calculating parameter in the continuous casting numerical simulation process, which strongly affects the prediction of fluid flow and solidification behavior in the mold zone. However, most researchers have neglected the influence of the mushy zone coefficient, and the correct expression of this coefficient is rarely found in the literature. Generally, the lower default value of 1×105 kg·m-3·s-1 is used in the model, which leads to unrealistic results. In this study, the relationship between the mushy zone coefficient and permeability was analyzed, and the expression of the mushy zone coefficient was proposed. A coupled flow and solidification numerical model was developed to evaluate the effect of the mushy zone coefficient on the melt flow and solidification phenomena in a bloom continuous casting mold. Results show that the higher the value of the mushy zone coefficient, the stronger the damping becomes, and the faster the velocity drops as melt solidifies. A relatively high value of the mushy zone coefficient generates a "banded" form of mushy zone sandwiched between the solid and liquid phases in the mold zone. When the mushy zone coefficient is at a lower value, a wider mushy zone is obtained and the melt cools down rapidly in the mold region. In addition, the temperature at free surface is relatively low with supercooling, and the solidified shell remelts locally. The model is validated through comparison with measurements of shell thickness on a breakout shell. The value of the mushy zone coefficient ranging from 1×108 to 5×108 kg·m-3·s-1 is suggested.