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。     

双官能团超分散剂的制备及性能研究

采用溶液聚合法,以水为溶剂、丙烯酸和烯丙醇为功能单体、K2S2O8–NaHSO3氧化还原体系为引发剂,合成了一种双官能团的超分散剂.主要探讨了不同单体配比对超分散剂分散性能的影响.研究结果表明,具有双官能团的超分散剂的分散性能优于常规聚丙烯酸钠分散剂,其中烯丙醇质量分数为55%时的分散性能最优.     

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.     

碱性蛋白酶水解螺旋藻制备抗氧化活性肽的工艺优化

为了提高螺旋藻肽的抗氧化能力与收率,采用单因素实验和响应面法对碱性蛋白酶水解螺旋藻粉制备抗氧化活性肽的工艺条件进行优化。实验结果表明,与木瓜蛋白酶、胰蛋白酶、风味蛋白酶相比,碱性蛋白酶对螺旋藻粉的水解能力最强,其最适水解条件为55.46℃、pH值为 6.71、固(g)液(mL)比为1∶10.83。在此条件下,酶解240min,螺旋藻肽的收率为58.50%,与优化前相比,提高了15.61%。所制备的螺旋藻肽具有较强的抗氧化能力,在质量浓度为0.86g/L时,其DPPH·清除能力为77.60%,与优化前相比,提高了7.62%。     

城市化对旅游的影响及其反馈机制研究进展

结合前人研究工作分析了城市化的概念和特征,总结了城市化对旅游的影响及其评价方法,并对有关旅游对于城市化的影响进行了概括,最后针对旅游城市化这一新兴的现象从概念、特点、影响机制和实证分析等几个方面进行了详细的阐述.结果表明旅游与城市化相互影响机制还尚处在研究初期,研究方法也大多限于定性的方法和简单的统计定量分析,并未形成能广泛应用的基础理论和多学科综合研究方法.此外,旅游城市化的概念还未形成共识,旅游城市化研究也偏向于概念、特征、影响机制及对策等方面的研究,相关研究还处于起步阶段,理论体系还不成熟,还需要大量的研究来加以佐证.     

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.