卧式搅拌釜气液流动数值模拟及多目标参数优化

采用双欧拉模型、SST k-ω湍流模型和多重参考系法对搅拌釜内气液两相流动行为进行数值模拟。结果表明:在所有影响因素中,转速对搅拌釜性能的影响最大,其次是挡板宽度。通过正交试验和矩阵分析,发现最优工况为桨叶离底高度950 mm、桨叶间距1300 mm、挡板宽度525 mm和转速123 r/min。在优化工况下,保证气含率和相对功耗基本不变时,混匀时间从31.620 s缩短至25.845 s。

Parametric study of gas−liquid two-phase flow field in horizontal stirred tank

Based on Fluent software,the gas−liquid two-phase flow in the horizontal stirred tank was simulated with SST k−ωturbulence model,Eulerian−Eulerian two-fluid model,and multi-reference flame method.The mixing process in the tank was calculated by tracer method.The results show that increasing the rotating speed or gas flow is conducive to a more uniform distribution of the gas phase and accelerates the mixing of the liquid phase.When the rotating speed exceeds 93 r/min,the relative power demand remains basically constant.The change in the inclination angle of the upper impeller has minimal effect on the gas phase distribution.When the inclination angle is 50°,the relative power demand reaches the maximum.An appropriate increase in the impeller distance from the bottom improves the gas holdup and gas phase distribution but increases the liquid phase mixing time.

Influence of simvastatin on dopaminergic neurons of lipopolysaccharide—induced rat model of Parkinson's disease

Objective::To investigate the neuroprotective effects of simvastatin on lipopolysaccharide(LPS)-indueed rat model of Parkinson's disease(PD) and the mechanisms involved.Methods:Hemiparkinsonian rat models were induced by stereotaxieal injection of LPS in the right substantia nigra compacts.After 2 weeks of simvastatin treatment,rotational behavior test was performed after the intraperitoneal injection of apomorphine.Expression of tyroxine hydroxylase(TH) and glial fibrillan acidic protein were analyzed through immunohistochemical staining of substantia nigra and striatum,and the level of TNF-α was evaluated using enzyme-linked immunosorbent assay.Results:Comparing with untreated group,behavioral symptoms of the rats were significantly less in the rats that received simvastatin treatment.The TH positive cell count in substantia nigra and striatum were significantly increased(P<0.05) and TNF- α expression was significantly decreased(P<0.05) in simvastatin group compared to untreated group.Conclusions:Simvastatin could effectively inhibit the activation of astrocytes,reduce TNF-α expression,and exert anti-inflammatory effects,and thus protect the dopaminergic neurons in substantia nigra and striatum of the rat model of PD.

Expressions of SOCS-1 and SOCS-3 in the myocardium of patients with sudden cardiac death

BACKGROUND：As the regulators of cytokines, suppressors of cytokine signaling （SOCS） play an important role in the inflammation reaction. Some studies found that SOCS-1 and SOCS-3 were involved in the pathogenesis of some inflammatory diseases such as rheumatoid arthritis, inflammatory bowel disease. But the expressions of SOCS in coronary heart disease have not yet been reported. This study aimed to investigate the expression and clinical significance of SOCS-1 and SOCS-3 in the myocardium of patients with sudden cardiac death （SCD）.METHODS： Myocardial autopsy specimens were collected from 24 patients at the Forensic Medicine Department of Sun Yat-Sen University, Guangzhou, China between 2005 and 2006. Of them, 9 patients had autopsy findings consistent with coronary atherosclerosis （non-myocardial infarction） leading to SCD （non-MI group）, 7 died of acute myocardial infaction （MI group）, and 8 died from traffic accidents and trauma （control group）. The expressions of SOCS-1 mRNA and SOCS-3 mRNA in the myocardium of the non-MI, MI and control groups were detected using RT-PCR. The levels of SOCS-1 and SOCS-3 proteins were detected using immunohistochemistry. Statistical analyses were performed using SPSS version 13.0 sottware and the data were analyzed by ANOVA.RESULTS： The expressions of SOCS-1 mRNA and SOCS-3 mRNA in the non-MI and MI groups were significantly higher than those in the control group[（0.788±0.101）, （0.741±0.111） vs. （0.436±0.044）, （P〈0.01）; （0.841±0.092）, （0.776±0.070） vs. （0.454±0.076）, （P〈0.01）] respectively. The antibody-positive cells of SOCS-1 protein in the myocardium of the non-MI and MI groups were significantly higher than those in the myocardium of the control group[（320.00±48.48）, （347.14±70.88） vs. （42.50±10.35）, （P〈0.01）] respectively. The antibody-positive cells of SOCS-3 protein in the myocardium of the non-MI and MI groups were significantly higher than those in the myocardium of the control group[（381.11 ±59.25） vs. （40.00±10.69）, （P〈0.01）] and[（332.86±111.91） vs. （40.00±10.69）, （P=0.001）].CONCLUSION： The expressions of SOCS-1 and SOCS-3 in the myocardium of patients with SCD from coronary heart disease are significantly increased and contribute to the pathogenesis of SCD.

Numerical analysis of supersonic jet flow and dust transport induced by air ingress in a fusion reactor

During a loss of vacuum accident(LOVA),the air ingress into a vacuum vessel(VV)may lead to radioactive dust resuspension,migration,and even explosion,thereby posing a great threat to the safe operation of future fusion reactors;thus,it is crucial to understand the flow characteristics and radioactive dust transport behavior induced by LOVA.However,only a few studies have identified the characteristics of the highly under-expanded jet flow at a scale of milliseconds during LOVA.Particularly,the occurrence and behavior of a Mach disk is yet to be captured in existing studies.In this study,we used a more advanced model with a finer mesh and adaptive mesh strategies to capture the Mach disk in a VV during LOVA.In detail,a computational fluid dynamics–discrete phase model one-way coupled multiphase approach was established using the computational fluid dynamics code ANSYS FLUENT and applied to the analysis during the first seconds of LOVA.The results showed that air ingress into the VV behaved like a highly free under-expanded jet at the initial stage and Mach disk was formed at~6 ms.Moreover,the flow field dramatically changed at the position of the Mach disk.The jet core before the Mach disk had a maximum velocity of~8 Mach with the corresponding lowest static pressure(~100 Pa)and temperature(few tens of K).The friction velocities in the lower part of the VV,which is an area of concern due to dust deposition,were generally larger than 15 m/s near the inlet region.Lastly,the crude prediction of the particle trajectories demonstrated the spiral trajectories of the dust following the air motion.Therefore,this study provided a basis for further safety analysis and accident prevention related to dust transport and explosion in future fusion reactors.

Research progress on the correlation between ion channel and excitability of striatum neurons in Parkinson's disease

Parkinson's disease(PD)is a neurodegenerative disorder due to gradual loss of dopaminergic neurons in the substantia nigra in the midbrain,however the pathogenesis is unclear.There is a correlation between the excitability of striatal neurons and PD.Ion channels are important to maintain membrane potential and regulate excitability of neurons,while ionic mechanisms for modulation of neurons excitability are not fully understood.This article reviews the relationship between ion channels and excitability of striatal neurons in PD and ion channel changes in the pathogenesis of PD.In order to find new targets to treatment PD by intervening ion channels.

Meta-analysis of efficacy and safety of Donepezil in treating cognitive decline of Parkinson's disease

Objective:To systematically evaluate the efficacy and safety of Donepezil in treating the cognitive decline in patients with Parkinson's disease(PD).Methods:Nine literature databases in domestic and abroad were searched by computer,and the search deadline was November 2,2020.The randomized controlled trials(RCT)using donepezil to treat the cognitive decline in patients with PD were screened.The MMSE(Mini-Mental State Exam)scores,MoCA(Montreal Cognitive Assessment)scores and adverse events of the included RCTs were extracted.Meta-analysis was implemented with RevMan 5.3 software,and the subgroup analyses were conducted to evaluate the effects of mean age and mean course of disease on the MMSE scores.Results:14 RCTs with 1263 patients were selected,including 646 cases in the experimental group and 617 cases in the control group.There were 1209 effective patients who completed MMSE score,including 612 in the experimental group and 597 in the control group.Meta-analysis results showed that MMSE scores in the experimental group were higher than that in the control group after using donepezil intervention,and the difference was statistically significant[SMD=0.55,95%CI(0.24,0.87),P=0.0006].It was also found that the MoCA scores of experimental group were higher than that of control group after using donepezil intervention,and the difference was statistically significant[SMD=1.25,95%CI(0.79,1.72),P<0.00001].Subgroup analysis showed that donepezil improved MMSE scores in different subgroups,and the difference between each group was statistically significant.There was no heterogeneity in the subgroup of mean age lower than 65 years,and the heterogeneity existed between the subgroup of mean course of disease lower than 3 years and the subgroup of mean course of disease larger than or equal to 3 years.For adverse events,the incidence of adverse events in the experimental group was 22.18%.There was no heterogeneity between the included studies(I2=0%),and the difference was not statistically significant[RR=1.18,95%CI(0.95,1.47),P=0.14].Conclusion:The results of meta-analysis showed that donepezil can improve the cognitive decline in patients with Parkinson's disease significantly,and it has good safety.

Polar Dependence of Threading Dislocation Density in GaN Films Grown by Metal-Organic Chemical Vapor Deposition

We investigate the threading dislocation(TD)density in N-polar and Ga-polar GaN films grown on sapphire substrates by metal-organic chemical vapor deposition.X-ray diffraction results reveal that the proportion of screw type TDs in N-polar GaN is much larger and the proportion of edge type TDs is much smaller than that in Ga-polar.Transmission electron microscope results show that the interface between the AlN nucleation layer and the GaN layer in N-polar films is smoother than that in Ga-polar films,which suggests different growth modes of GaN.This observation explains the encountered difference in screw and edge TD density.A model is proposed to explain this phenomenon.

THE BLOSSOM APPROACH TO THE DIMENSION OF THE BIVARIATE SPLINE SPACE

Presents information on a study which outlined the blossom approach to the dimension count of bivariate spline space. Smoothness conditions in blossoming form; Application of the approach to the case of Morgan-Scott partition.