Shrinkage Estimation in the Random Parameters Logit Model

In this paper, we explore the properties of a positive-part Stein-like estimator which is a stochastically weighted convex combination of a fully correlated parameter model estimator and uncorrelated parameter model estimator in the Random Parameters Logit (RPL) model. The results of our Monte Carlo experiments show that the positive-part Stein-like estimator provides smaller MSE than the pretest estimator in the fully correlated RPL model. Both of them outperform the fully correlated RPL model estimator and provide more accurate information on the share of population putting a positive or negative value on the alternative attributes than the fully correlated RPL model estimates. The Monte Carlo mean estimates of direct elasticity with pretest and positive-part Stein-like estimators are closer to the true value and have smaller standard errors than those with fully correlated RPL model estimator.

Toll样受体4表达对创伤性颅脑损伤后小鼠海马区神经干细胞增殖的影响

目的探讨Toll样受体4表达变化对创伤性颅脑损伤后小鼠海马区髓样分化因子88（MYD88）的影响及其与神经干细胞的关系。方法采用随机数表法将C57BL／6小鼠分为3组，即为CLI-095组、溶剂组、假手术组，使用PCI-3000打击装置建立小鼠颅脑损伤模型，CLI-095组腹腔注射TLR4抑制剂CLI-095，溶剂组和假手术组腹腔注射溶剂，5-溴脱氧尿嘧啶核苷腹腔注射标记神经干细胞，采用免疫荧光染色、Western blot检测海马区MYD88表达变化情况以及神经干细胞变化的特征。结果Western Blotting检测及免疫荧光结果显示：假手术组MYD88表达未见明显变化，溶剂组MYD88表达升高（P〈0．05），CLI-095组MYD88蛋白水平较溶剂组下降（P〈0．05），但仍高于假手术组。免疫荧光结果显示：海马区CLI-095组5-溴脱氧尿嘧啶核苷阳性细胞表达数量较假手术组增多（P〈0．05），溶剂组5-溴脱氧尿嘧啶核苷阳性细胞表达数量相比CLI-095组减少，但仍高于假手术组（P〈0．05）。结论海马区MYD88的表达与神经干细胞变化相反，并证实抑制TLR4可能激活并引起神经干细胞的增殖，从而促进受损神经细胞的修复。