The Information Structure of the Covariances between Financial Returns

本文应用随机矩阵理论及方法解析资产组合协方差矩阵的信息结构。实证发现,我国股票组合的协方差矩阵存在市场因素、行业因素的信息结构。最大特征值携带着反映市场因素的信息,影响程度非常高,是股票资产间相关性的主导因素。最大特征值偏离rMT上界的倍数远远高于其他市场。偏离rMT上界的特征值,携带着反映行业因素的信息,影响同一行业或者主营业务相同的公司,但随着特征值与rMT上界靠近,信息特征减弱。We use the methods of random matrix theory(RMT)to investigate the information structure of the covariance matrix between stock returns.The largest eigenvalue are found to represent the market information.Chinese stock portfolio has a particularly high value of largest eigenvalue,which is about 175 times larger than the RMT upper bound.Market information is the dominate factor determining the correlations between stock returns.The other eigenvalues deviating from the RMT upper bound represent information affecting stocks belonging to similar or related industries.国家社会科学基金资助项目(09CJY013;11CJY098); 教育部人文社会科学研究资助项目(08JC790038); 广东省哲学社会科学“十一五”规划青年资助项目(08YE-02); 中央高校科研业务费资助项目(x2jmD2117980;x2jmD2118000

An Empirical Analysis of China Price Transmission Mechanism After 2008 Financial Crisis

本文采用扩展SOP模型的方法,分析金融危机发生以来我国rMPI、PPI、CgPI和CPI物价传导机制的特征。结果发现,生产环节的PPI对上游投入环节的rMPI和下游批发环节的CgPI传导不畅,生产厂商在价格传递链处于夹心地位;金融危机后,消费环节的CPI不能回馈传导上游的任何环节,居民的需求拉动能力和作用发挥不明显。The post-financial crisis price transmission mechanism between RMPI,PPI,CGPI,and CPI is investigated by using extended stage of processing model.The empirical evidence shows that,changes in RMPI transmit to PPI,not vice versa,and PPI response to the changes in CGPI.After the financial crisis,the changes in CPI do not feedback to any stage in the price chain,the consumer demand is not the key factor in driving prices.国家社会科学基金资助项目(09CJY013;11CJY098); 中央高校基本科研业务费专项资金资助项目(2014ZM0082;2014GD03

Effects of Trichoderma on nitrogen absorption and use efficiency in Lycium chinense roots under saline stress

To clarify the mechanisms underlying the improvement of Trichoderma on Chinese wolfberry (Lycium chinense) growth under saline stress,we analyzed the effects of application of organic fertilizer,Trichoderma agent and fertilizer on nitrogen uptake,assimilation,accumulation and use efficiency in Chinese wolfberry,based on a pot experiment with coastal saline soil.The organic fertilizer was the sterilization substance of Trichoderma fertilizer without viable Trichoderma,without any difference in the content of nutrients (such as nitrogen,phosphorus and potassium) between them.The results showed that the application of organic fertilizer,Trichoderma agent and fertilizer significantly increased NO_3~- and NH_4~+ influx rate in meristematic zone and NO_3~- influx rate in maturation zone of roots.The magnitude of such enhancement was greater in the application with Trichoderma fertilizer than organic fertilizer.Compared with the control,the application of Trichoderma agent and fertilizer significantly increased root,stem and leaf biomass and nitrogen content as well as plant nitrogen accumulation,strengthened root and leaf nitrate reductase,nitrite reductase and glutamine synthetase activities,and elevated nitrogen uptake efficiency,photosynthetic rate,stable carbon isotope abundance and photosynthetic nitrogen use efficiency.For all those variables,the beneficial effect was obviously stronger in the application with Trichoderma fertilizer than organic fertilizer.Therefore,Trichoderma facilitated nitrogen uptake,assimilation and accumulation in Chinese wolfberry under saline stress,improved photosynthetic carbon fixation ability and nitrogen use efficiency,and ultimately promoted plant growth