Aneuploidy in the normal and diseased brain

The brain is remarkable for its complex organization and functions, which have been historically assumed to arise from cells with identical genomes. However, recent studies have shown that the brain is in fact a complex genetic mosaic of aneuploid and euploid cells. The precise function of neural aneuploidy and mosaicism are currently being examined on multiple fronts that include contributions to cellular diversity, cellular signaling and diseases of the central nervous system (CNS). Constitutive aneuploidy in genetic diseases has proven roles in brain dysfunction, as observed in Down syndrome (trisomy 21) and mosaic variegated aneuploidy. The existence of aneuploid cells within normal individuals raises the possibility that these cells might have distinct functions in the normal and diseased brain, the latter contributing to sporadic CNS disorders including cancer. Here we review what is known about neural aneuploidy, and offer speculations on its role in diseases of the brain. Received 13 April 2006; received after revision 2 June 2006; accepted 13 July 2006     

油茶林生草栽培对地表径流及氮磷流失特征的影响

目的 研究间种草本植物对油茶林地表径流以及随径流流失的溶解态氮磷的影响,以期降低油茶林面源污染风险并改善下游水体环境,为油茶高效生态经营提供参考。方法 选取林下植被覆盖度低的5年生油茶幼林,设计3个试验处理:无间种对照、间种百喜草和间种金鸡菊,每个试验处理面积600 m²,3次重复,同时,在每个试验样地建设水平投影为16 m×7 m的标准径流监测小区,共计9个径流监测区。经过2年的生草处理后,间种百喜草和金鸡菊的油茶林下植被覆盖度从对照的31.13%分别提高到90.47%和80.40%。在此基础上,通过土壤理化性质测定、多场次的地表径流及其氮磷含量的监测,比较各处理样地的地表径流量、土壤侵蚀量、径流溶解态氮(DN)和溶解态磷(DP)流失量的变化特征,分析南方油茶幼林生草栽培对地表径流及氮磷流失的影响。结果 油茶林下间种百喜草和金鸡菊2年后,土壤有机质、全氮及全磷含量均比对照有增加趋势。2020年6—7月,在试验区共观测到5场侵蚀性降雨事件。与对照处理相比,间种百喜草和金鸡菊的处理在5场侵蚀性降雨事件中均显著降低了地表径流量和土壤侵蚀量(P<0.05)。与对照相比,间种百喜草和金鸡菊处理的地表总径流量分别减少了35.04%和33.56%,土壤累积侵蚀量分别减少了83.89%和79.85%。不同场次径流中DN和DP浓度变化趋势不一致,第1和第2场径流中DN浓度较低而DP浓度较高,第4和第5场径流中DN浓度较高而DP浓度较低。所有观测场次的径流DN和DP浓度均值超过了GB 3838—2002《地表水环境质量标准》中总氮、总磷Ⅴ类标准限值。与对照相比,间种百喜草能够显著降低径流中DN和DP浓度(P<0.05),减少量分别为4.67%和16.88%;而间种金鸡菊后径流DP浓度显著降低了16.88%(P<0.05),但DN浓度却增加了5.14%(P<0.05)。总体上,与对照处理相比,间种百喜草和金鸡菊分别降低了径流DN流失量26.66%和21.49%、径流DP流失量63.06%和50.57%。结论间种百喜草和金鸡菊的油茶林地显著降低了地表径流量和土壤侵蚀量,显著减少了径流溶解态氮磷流失量,相较而言,油茶幼林间种百喜草对林地地表径流及其可溶性氮磷流失的阻控效果比间种金鸡菊的好。     

输气管道泄漏模型不确定性因素敏感性分析

输气管道泄漏模型中不确定性因素的分析是影响管道泄漏风险评价不确定的主要原因.为此,在确定起点压力、泄漏孔面积、气体温度和泄漏点距起点距离4项为影响输气管道泄漏速率计算的主要不确定性因素基础上,考虑多因素相互关联、共同影响模型计算精度的问题,采用多因素敏感度整体分析方法分别抽取数量为500,1 000,2 000和3 0...     

国有资产流失的现状及对策

介绍了国有资产的涵义,分析了国有资产流失的原因,提出了防止国有资产流失的对策。     

浅议高速公路建设项目的水土保持

分析了高速公路建设项目水土流失的成因及危害,结合公路项目建设的特点,对新增水土流失防治应根据不同防治分区、地表扰动情况和工程布局、施工特点等,结合高速公路综合防护和道路沿线绿化美化的特殊要求及其防治目标,提出了可行性较强的综合治理措施。     

Are Analysts' Loss Functions Asymmetric?

Despite displaying a statistically significant optimism bias, analysts' earnings forecasts are an important input to investors’ valuation models. Understanding the possible reasons for any bias is important if information is to be extracted from earnings forecasts and used optimally by investors. Extant research into the shape of analysts' loss functions explains optimism bias as resulting from analysts minimizing the mean absolute forecast error under symmetric, linear loss functions. When the distribution of earnings outcomes is skewed, optimalforecasts can appear biased. In contrast, research into analysts' economic incentives suggests that positive and negative earnings forecast errors made by analysts are not penalized or rewarded symmetrically, suggesting that asymmetric loss functions are an appropriate characterization. To reconcile these findings, we exploit results from economic theory relating to the Linex loss function to discriminate between the symmetric linear loss and the asymmetric loss explanations of analyst forecast bias. Under asymmetric loss functions optimal forecasts will appear biased even if earnings outcomes are symmetric. Our empirical results support the asymmetric loss function explanation. Further analysis also reveals that forecast bias varies systematically across firm characteristics that capture systematic variation in the earnings forecast error distribution. Copyright © 2011 John Wiley & Sons, Ltd.     

江汉平原耕地变化的经济损失分析

对江汉平原2000～2003年耕地流失的基本态势及其经济损失进行定量分析,为缓解耕地流失形势、确定耕地流失的经济补偿提供决策依据.估算表明,2000～2003年江汉平原耕地资源净减少28 968.69hm2,耕地流失所带来的经济损失达82.07亿元,年均损失20.52亿元.其中,耕地资源的市场价值损失72.61亿元,占88.47%;目前无法通过市场价格机制体现的非市场价值流失9.46亿元,占11.53%.耕地流失经济损失的货币化计量,是有效解决农地生态补偿机制构建的一个技术难题,为确定农地生态补偿标准、规范人类活动的性质和干扰程度、限制土地的过度开发和优化农地景观格局提供决策依据.图1,表6,参14.     

考虑漏失的抽油泵示功图的计算机仿真模型

综合考虑柱塞的运动规律、泵筒内流体的可压缩性、柱塞与泵筒之间的间隙漏失量,建立了泵筒内流体流动的连续流方程。根据改进的连续流方程,建立了泵筒内液体压力、柱塞运动规律与柱塞泵筒间隙之间相互关系的数学模型,从而建立了泵筒内液体瞬时压力与泵示功图的仿真模型。仿真分析了柱塞与泵筒之间不同间隙时,泵筒内液体压力变化规律的时间历程曲线和泵示功图。仿真分析结果表明,柱塞与泵筒之间的间隙漏失不仅会导致固定阀滞后打开,而且会导致游动阀提前关闭。当间隙增大到一定程度时,会出现固定阀无法打开而导致抽油泵完全失效的状态。所建立的数学模型为完善漏失状态抽油机井动态参数的计算机仿真技术提供了理论基础。     

基于PD-效用函数的预期行为描述与特征分析

以偏尾分布为基础,提出了预期行为的一种新型效用函数--PD效用函数.利用PD-效用函数反映行为人对赢利与亏损的风险偏好特征,描述预期与赢利效用的关系特征,揭示赢利效用与亏损效用的若干重要关系.用数量方式解释Daniel Kahneman预期理论中的许多重要结论,将"理性"与"非理性"假设纳入到同一理论框架下.