Embryonic exposure to hyper glucocorticoids suppresses brown fat development and thermogenesis via REDD1

Maternal stress during pregnancy is prevailing worldwide,which exposes fetuses to intrauterine hyper glucocorticoids (GC),programming offspring to obesity and m...     

浅评我国生态环境监测现状

生态环境监测是环境监测中一个全新的概念,是环境生态建设的技术保证和支持体系.本文阐释了生态环境监测的基本内涵,并结合我国生态环境监测现状,提出了不断完善生态环境监测的一些建议.     

Model averaging estimation for conditional volatility models with an application to stock market volatility forecast

This paper is concerned with model averaging estimation for conditional volatility models. Given a set of candidate models with different functional forms, we propose a model averaging estimator and forecast for conditional volatility, and construct the corresponding weight-choosing criterion. Under some regulatory conditions, we show that the weight selected by the criterion asymptotically minimizes the true Kullback–Leibler divergence, which is the distributional approximation error, as well as the Itakura–Saito distance, which is the distance between the true and estimated or forecast conditional volatility. Monte Carlo experiments support our newly proposed method. As for the empirical applications of our method, we investigate a total of nine major stock market indices and make a 1-day-ahead volatility forecast for each data set. Empirical results show that the model averaging forecast achieves the highest accuracy in terms of all types of loss functions in most cases, which captures the movement of the unknown true conditional volatility.     

Modeling eBay price using stochastic differential equations

Online auctions have become increasingly popular in recent years. There is a growing body of research on this topic, whereas modeling online auction price curves constitutes one of the most interesting problems. Most research treats price curves as deterministic functions, which ignores the random effects of external and internal factors. To account for the randomness, a more realistic model using stochastic differential equations is proposed in this paper. The online auction price is modeled by a stochastic differential equation in which the deterministic part is equivalent to the second‐order differential equation model proposed in Wang et al. (Journal of the American Statistical Association, 2008, 103, 1100–1118). The model also includes a component representing the measurement errors. Explicit expressions for the likelihood function are also obtained, from which statistical inference can be conducted. Forecast accuracy of the proposed model is compared with the ODE (ordinary differential equation) approach. Simulation results show that the proposed model performs better.     

Antennae and the role of olfaction and contact stimulation in mate recognition by males of the pollinating fig wasp Ceratosolen gravelyi (Hymenoptera: Agaonidae)

Finding a mate is a crucial step in sexual reproduction. The mutualism between figs and their pollinators is exploited by many figwasps that develop within their galls and attain sexual maturity simultaneously. Male pollinators carry the specific burden of detecting and opening mating holes in galls containing conspecific females before mating with them. The mating behaviourand antennal sensilla of male pollinators associated with Ficus semicordata was investigated to understand mate recognition. Male Ceratosolen gravelyi located female-containing galls from a distance, but only attempted to chew a mating hole after antennal contact with the gall surface was made. They showed similar responses to females and body extracts but failed to respond to washed female bodies. This behaviour indicates that unidentified chemicals present on the body surfaces of females are sufficient to elicit olfactory attraction and tactile confirmation. Multiporous plate sensilla are candidates for olfactory reception from a distance while basiconic sensilla may be involved in contact chemoreceptor. All of the sensilla are highly localised, on the distal part of the terminal flagellomere, suggesting a response to selection for strong directionality in the complex odour environment of the fig in which messages produced by hundreds of females may confuse precise mate localisation.     

禁牧前与禁牧后畜牧业成本差异对比——以宁夏盐池县为例

以宁夏盐池县为例,采用偶遇抽样法随机取得30份有效问卷.在对数据进行统计整理的基础上,分析了禁牧前与禁牧后畜牧业成本的差异.结果表明,禁牧前畜牧业成本为60.68元/只(山羊)或61.68元/只(绵羊),禁牧后则达到了204.17元/只;禁牧后劳动力投入费用增加了123.47%,集中体现在饲喂用工投入加大;禁牧后饲草料的投入增加了309.68%,主要由圈养后饲草来源变化引起;禁牧前在圈舍、机械购买方面投入很少,禁牧后机械购买率达到64.29%,禁牧前不存在附加投入,而禁牧后普遍存在.禁牧后畜牧业成本增加,提高了畜牧业的门槛,在一定程度上使部分农户放弃畜牧业,不利于畜牧业的发展,由此提出必须调整畜牧业结构,改良品种,提高养殖效率等建议.     

Engineering of multiferroic BiFeO3 grain boundaries with head-to-head polarization configurations

Confined low dimensional charges with high density such as two-dimensional electron gas (2DEG) at interfaces and charged domain walls in ferroelectrics show gre...     

Sm3+掺杂纳米晶ZrO2材料的制备及表征

用化学沉淀法制备纳米晶ZrO2∶Sm3 发光粉体,用X射线衍射谱对材料的粒径和晶体结构进行了表征,探讨了制备条件对样品粒径和晶体结构的影响.用荧光激发和发射光谱对材料的发光性质进行了表征,合理地归属了各谱项和跃迁.     

Optimal design and experiment research of an orthogonal-parallel six-axis force/torque sensor

A novel orthogonal-parallel six-axis force/torque sensor is studied based on a modified Stewart platform architecture,and the optimal design and experiment rese...