偏心搅拌槽内高浓度浆液颗粒的悬浮特性

以直径为0.34 m的无挡板平底圆筒形搅拌槽为研究对象,对偏心搅拌槽内高浓度浆液中颗粒的悬浮特性进行了数值研究,分析了45°的4斜叶开启涡轮式搅拌桨(PBT)和3窄叶整体板式螺旋桨(ZHX)2种桨型在不同偏心率和转速时,搅拌槽内的流型分布、颗粒体积分数分布、完全离底临界悬浮转速以及功率消耗,并与试验结果进行了对比.结果表明:对于高浓度浆液,偏心搅拌打破了中心搅拌时流场结构的对称性,提高了流体的轴向循环能力,颗粒悬浮效果优于中心搅拌;固体颗粒的悬浮效果与搅拌桨在槽内的偏心位置有关,当偏心率E=0.4时颗粒悬浮效果最佳,但偏心搅拌会增大颗粒的完全离底临界悬浮转速和设备的功率消耗,不利于节能降耗.     

Opposite effects of fear conditioning and extinction on dendritic spine remodelling

It is generally believed that fear extinction is a form of new learning that inhibits rather than erases previously acquired fear memories. Although this view has gained much support from behavioural and electrophysiological studies, the hypothesis that extinction causes the partial erasure of fear memories remains viable. Using transcranial two-photon microscopy, we investigated how neural circuits are modified by fear learning and extinction by examining the formation and elimination of postsynaptic dendritic spines of layer-V pyramidal neurons in the mouse frontal association cortex. Here we show that fear conditioning by pairing an auditory cue with a footshock increases the rate of spine elimination. By contrast, fear extinction by repeated presentation of the same auditory cue without a footshock increases the rate of spine formation. The degrees of spine remodelling induced by fear conditioning and extinction strongly correlate with the expression and extinction of conditioned fear responses, respectively. Notably, spine elimination and formation induced by fear conditioning and extinction occur on the same dendritic branches in a cue- and location-specific manner: cue-specific extinction causes formation of dendritic spines within a distance of two micrometres from spines that were eliminated after fear conditioning. Furthermore, reconditioning preferentially induces elimination of dendritic spines that were formed after extinction. Thus, within vastly complex neuronal networks, fear conditioning, extinction and reconditioning lead to opposing changes at the level of individual synapses. These findings also suggest that fear memory traces are partially erased after extinction.     

道家文化影响下的沈从文创作——从尚“三”特征说起

沈从文创作中喜欢用"三"是一个值得引起注意的问题。道家的宇宙模型是"道生一,一生二,二生三,三生万物。"[1]从尚"三"特征出发,探讨沈从文创作的影响,本文考察道家文化从而进一步挖掘沈从文丰富的文化内涵。     

Sn-Zn-Cu/Cu界面反应及剪切强度

为探讨Cu的加入对Sn-Zn钎料性能的影响,研究了Sn-Zn-xCu与Cu箔钎焊界面处金属间化合物(IM C)成分、形貌及剪切强度.试验结果表明,含0~1%Cu时,Sn-Zn-xCu钎料与Cu母材钎焊界面处IM C主要为层状Cu5Zn8相;在含2%~6%Cu时,为Cu6Sn5相和Cu5Zn8相共同组成;在含8%Cu时,为Cu6Sn5相.这是由于合金基体中生成的Cu-Zn化合物阻碍了Zn向Cu界面处扩散,进而使得界面处IM C由层状Cu5Zn8逐渐向扇贝状Cu6Sn5转变.另外,随着Sn-Zn钎料中Cu含量的增加,Sn-Zn-xCu/Cu接头剪切强度因界面IM C类型的变化以及钎料合金自身强度的提高而使得钎焊接头剪切强度明显提高.     

Crosstalk of protein kinase C ε with Smad2/3 promotes tumor cell proliferation in prostate cancer cells by enhancing aerobic glycolysis

Protein kinase C ε (PKCε) has emerged as an oncogenic protein kinase and plays important roles in cancer cell survival, proliferation, and invasion. It is, however, still unknown whether PKCε affects cell proliferation via glucose metabolism in cancer cells. Here we report a novel function of PKCε that provides growth advantages for cancer cells by enhancing tumor cells glycolysis. We found that either PKCε or Smad2/3 promoted aerobic glycolysis, expression of the glycolytic genes encoding HIF-1α, HKII, PFKP and MCT4, and tumor cell proliferation, while overexpression of PKCε or Smad3 enhanced aerobic glycolysis and cell proliferation in a protein kinase D- or TGF-β-independent manner in PC-3M and DU145 prostate cancer cells. The effects of PKCε silencing were reversed by ectopic expression of Smad3. PKCε or Smad3 ectopic expression-induced increase in cell growth was antagonized by inhibition of lactate transportation. Furthermore, interaction of endogenous PKCε with Smad2/3 was primarily responsible for phosphorylation of Ser213 in the Samd3 linker region, and resulted in Smad3 binding to the promoter of the glycolytic genes, thereby promoting cell proliferation. Forced expression of mutant Smad3 (S213A) attenuated PKCε-stimulated protein overexpression of the glycolytic genes. Thus, our results demonstrate a novel PKCε function that promotes cell growth in prostate cancer cells by increasing aerobic glycolysis through crosstalk between PKCε and Smad2/3.     

FD-3022四道γ能谱仪测量过程及常见问题浅谈

FD-3022能谱仪是铀资源勘查和核技术应用领域常见的一种γ能谱仪,广泛用于放射性矿床和其他金属和非金属矿床(如金矿、石油等)的野外普查找矿工作,也可做填图等其他地质研究、水文地质调查和环境监测等工作.仪器经标定后还可进行天然石材放射性测量.随着铀资源勘查任务的增加和核技术应用领域的拓展,仪器数量和使用人数不断增加,一些仪器故障、使用注意事项等困扰新手的问题也随之出现.错误的操作不仅影响了仪器的使用寿命,也耽误了项目进度.针对该仪器在计量检定和野外测量使用过程中常见的一些问题,进行了分析和归纳,并给出了参考的解决方法.     

Intraday volume percentages forecasting using a dynamic SVM-based approach

This paper proposes a dynamic model to forecast intraday volume percentages by decomposing the trade volume into two parts: The average part as the intraday volume pattern and the residual term as the abnormal changes. An empirical test on data spanning half-a-year gold futures and S&P 500 futures reveals that a rolling average of the previous days’ volume percentages shows great predictive ability for the average part. An SVM approach with the input pattern consisting of two categories is employed to forecast the residual term. One is the previous days’ volume percentages in the same time interval and the other is the most recent volume percentages. The study shows that this dynamic SVM-based forecasting approach outperforms the other commonly used statistical methods and enhances the tracking performance of a VWAP strategy greatly.     

An improvement to multiple criteria ABC inventory classification using Shannon entropy

This paper extends the Ng-model [Ng, 2007] for multiple criteria ABC inventory classification based upon Shannon entropy. The proposed approach determines the common weights associated with all criteria importance rankings, and provides a comprehensive scoring scheme by aggregating all rankings of the criteria importance. A numerical illustration is presented to compare the model with previous studies.     

A study on transport costs and China’s Exports: An extended gravity model

This paper suggests an extending conventional gravity model design to empirically analyze the effect of transport costs and port efficiency on China’s export flows. It shows that factor endowment and transport costs variables affect export trade value in directions that New Trade Theory (NTT) predicted. Also, the evidence indicates that, controlling for the effects of transport costs on trade, variables in traditional gravity model are consistent with previous empirical studies in both magnitudes and directions. Moreover, more than 22% of the variation in Chinese export trade can be explained by those three variables alone. The findings reported in this paper empirically explains how seriously transport costs and port efficiency affect China’s export growth by comparing effects of labour production factor costs on external trade. It suggests that the improvement of port efficiency and reduction of road transport costs play a vital role in China’s export competitiveness in the global market.