Conservation of Biodiversity: How Are We Doing?

A question rarely raised in discussions on biodiversity conservation, but surely the biggest question of all, is “How much time do we have left before the mass extinction underway surpasses our best efforts to contain it?” This prompts a further prime question because—and unlike all other problems, whether environmental or otherwise—the biotic crisis threatens to leave a severely impoverished planet for millions of years ahead; “Why do we not undertake the necessary actions to get on top of the problem before it gets on top of us?”     

对城市道路交叉口左转专用车道设计的探讨

在参考国内外设计经验的基础上,从左转车道设置的原则、设置左转车道的常用方式、左转车道的长度和宽度等角度对左转车道的设计问题进行了探讨,提出对左转车道进行合理偏移可有助于提高驾驶员的视距.     

混合交通条件下行人左侧通行的安全性研究

听觉是人接受外部刺激的重要信息通道,然而实验表明,行人依靠听觉察觉身后危险的能力很弱,在道路混合交通条件下容易出现行人未及时发现身后驶来的车辆而引发交通事故。由于我国实行车辆靠右侧通行制度,因此,在目前机动车行驶噪声日益受到严格控制的情况下,让行人在混合交通的道路上靠道路的左侧通行,可以使其始终与距离自己最近的车辆保持相互面向,从而充分利用行人视觉对道路危险的良好感知能力,增强行人躲避危险的主动性,减少行人与车辆之间的危险冲突及事故发生。     

左右岸跨界水污染治理演化博弈与政策路径研究

基于流域跨界水污染问题多关注于上下游矛盾而忽视左右岸的"公地悲剧",本研究构建左、右岸地区和流域政府三方演化博弈模型,探索奖惩、补偿及复合机制下的主体决策和演化格局差异,结合仿真实验给出推动左右岸协同治理政策路径.结果显示,实现左右岸地区达标排放的关键在于显化达标排放收益与超标排放损失.流域政府倾向于选择奖惩或补偿的单一机制,奖惩机制在不同政策组合中显示出必要性,补偿机制具有加快达标决策、减缓超标决策的收敛速度的积极意义.政策路径是首先采取"阶梯惩罚政策"并增加严重超标惩罚额;继而依次增加奖励和惩罚额促成"奖惩机制",或依次增加奖励额和左右岸之间的补偿额促成"补偿机制",同时给出了上述额度的量化表达式.     

USING UNCENSORED TRACE-LEVEL MEASUREMENTS TO DETECT TRENDS IN GROUND WATER CONTAMINATION1

ABSTRACT: Environmental decision making involving trace-levels of contaminants can be complicated by censoring, the practice of reporting concentrations either as less than the limit of detection (LOD) or as not detected (ND) when a test result is less than the LOD. Censoring can result in data series that are difficult to meaningfully summarize, graph, and analyze through traditional statistical methods. In spite of the relatively large measurement errors associated with test results below the LOD, simple and meaningful analyses can be carried out that provide valuable information not available if data are censored. For example, an indication of increasing levels of contamination at the fringe of a plume can act as an early warning signal to trigger further study, an increased sampling frequency, or a higher level of remediation at the source. This paper involves the application of nonparametric trend analyses to uncensored trace-level groundwater monitoring data collected between March 1991 and August 1994 on dissolved arsenic and chromium for seven wells at an industrial site in New York.     

吉林省历史文化遗存类科普旅游资源的开发

科普旅游是以游览为目的,在游览过程中普及科学知识,集娱乐性、参与性、知识性、教育性于一体的旅游活动.从吉林省的历史文化遗存出发,分重点城市和专项两个方面探讨了吉林省历史文化遗存的科普旅游开发.     

Prenatal diagnosis of dilated coronary sinus with persistent left superior vena cava in a fetus with trisomy 18

A case of dilated coronary sinus with persistent left superior vena cava diagnosed at 33 weeks in a fetus with trisomy 18 is reported. The features of this cardiac anomaly on prenatal ultrasonography and its association with trisomy 18 are discussed. Published in 2003 John Wiley & Sons, Ltd.     

Difficulties with the lognormal model in mean estimation and testing

A frequent assumption in environmental risk assessment is that the underlying distribution of an analyte concentration is lognormal. However, the distribution of a random variable whose log has a t-distribution has infinite mean. Because of the proximity of the standard normal and t-distribution, this suggests that a distribution such as the gamma or truncated normal, with smaller right tail probabilities, might make a better statistical model for mean estimation than the lognormal. In order to assess the effect of departures from lognormality on lognormal-based statistics, we simulated complete lognormal, truncated normal, and gamma data for various sample sizes and coefficients of variation. In these cases, departures from lognormality were not easily detected with the Shapiro-Wilk test. Various lognormal-based estimates and tests were compared with alternate methods based on the ordinary sample mean and standard error. The examples were also considered in the presence of random left censoring with the mean and standard error of the product limit estimate replacing the ordinary sample mean and standard error. The results suggest that in the estimation of or tests about a mean, if the assumption of lognormality is at all suspect, then lognormal-based approaches may not be as good as the alternative methods.