Estimation of Population Regression Coefficient in Successive Sampling

An attempt has been made to derive the theory of successive sampling for estimation of regression coefficient. The situations considered are estimation of regression coefficient for current occasion, estimation of change of regression coefficients over two occasions and estimation of average of regression coefficients over two occasions. The expressions of optimum estimators along with their variances have been worked out. On comparing their efficiencies empirically, it has been observed that similar to the estimation of mean, successive sampling can also be used with advantage for estimation of regression coefficient.     

Response of ecosystem services to socioeconomic development in the Yangtze River Basin,China

The provision of ecosystem services from multifunctional landscapes has contributed to human well-being. However, a general tendency exists to consider only marketed ecosystem services and to ignore non-marketed services, which has become more common when evaluating multiple-ecosystem services at the local level. In this study, we present an integrative index of multiple-ecosystem services (IMES) that avoids this tendency. Our main objective is to evaluate how socioeconomic factors interact with the spatial differences between the supply of and demand for multiple-ecosystem services. GlobCover data and a modified ecosystem service “matrix” are used to quantify and map ecosystem service supply and demand at the municipality level in the Yangtze River Basin, China. We used multiple regression analysis to detect relationships between ecosystem services and socioeconomic factors in municipalities to identify the main drivers of change in the supply of and demand for multiple-ecosystem services at the local level, respectively. The results revealed that 111 municipalities in the Yangtze River Basin (84.7% of the area) had an oversupply of multiple-ecosystem services; these municipalities were primarily situated in the western part of the upper reach and the southeast parts of the middle reach. Undersupplied areas were mainly situated in densely populated municipalities in the northern part of the lower reach and in agricultural municipalities in the northeastern part of the middle reach. The driving factors of changes in multiple-ecosystem services are significantly different not only in terms of the supply, demand and balance between the two but also among the three reaches. These differences in the driving factors among the three reaches can produce incorrect conclusions if an entire basin is considered, particularly for large basins. This information may be of interest to policymakers. The first principal component for the supply of and demand for multiple-ecosystem services exhibits a good correlation with the IMES in the Yangtze River Basin. Additionally, the integrative index of multiple-ecosystem services (including IMES_s and IMES_d) in the study area is relatively reliable according to the sensitivity analysis. Therefore, IMES is an effective tool for aggregating the value of multiple-ecosystem services at local scales. This tool can be used to identify the drivers of changes in multiple-ecosystem services based on the relationships between IMES and socioeconomic factors at the municipality scale. IMES should be useful for policymakers and stakeholders because it can provide important information for local decision-making.     

Long-term study of litter decomposition on a Pennine peat bog: which regression?

It is estimated that in the northern hemisphere one-third of the world pool of soil carbon is contained in peat resulting from an incomplete decomposition of plant remains. The time course for the decomposition of the predominant plant litters on a Pennine moorland in northern England is reported for a study extending over 23 years. Spatial variation of the weight remaining of decomposing litters increased with time. This experimental study gave an age for the upper layers of the bog and a curve for long-term decay based on direct observation rather than inferred from profile samples or from short-term observations. It showed that short-term observations can give misleading results in the long term, with a variety of litters with differing early decay rates ultimately making a similar contribution to accumulation. Spatial variation of the weight remaining of the decomposing litters increased with time, so that variation within micro-environments, or within apparantly uniform substrates, may contribute significantly to organic matter accumulation. An asymptotic curve best described the long-term course of decomposition leading to the accumulation of peat. The use of the model for the three litter types, Calluna vulgaris, Eriophorum vaginatum and Rubus chamaemorus, is described and the implication of the results for modelling of organic matter accumulation are then discussed. Received: 20 October 1996 / Accepted: 27 July 1997     

A parametric study of occupational radiation dose in interventional radiology by Monte-Carlo simulations

This paper presents the results of a parametric study on the occupational exposure in interventional radiology to explore the influence of various variables on the staff doses. These variables include the angiography beam settings: x-ray peak voltage (kVp), added copper filtration, field diameter, beam projection and source to detector distance. The study was performed using Monte-Carlo simulations with MCNPX for more than 5600 combinations of parameters that account for different clinical situations. Additionally, the analysis of the results was performed using both multiple and random forest regression to build a predictive model and to quantify the importance of each variable when the variables simultaneously change. Primary and secondary projections were found to have the most effect on the scatter fraction that reaches the operator followed by the effect of changing the x-ray beam quality. The effect of changing the source to image intensifier distance had the lowest effect.     

Goodness-of-Fit Testing for the Logistic Regression Model when the Estimated Probabilities are Small

The distribution of the Hosmer-Lemeshow chi-square type goodness-of-fit tests (?_g, ?_g) for the logistic regression model are examined via simulations designed to examine their behavior when most of the estimated probabilities are small or are expected to fall in a few deciles. The results of the simulations show statistic ?_g should be used when the two outcome groups (y = 0, 1) are not well separated, Δ≤2, where Δ² is the Mahalanobis distance. Statistic ?_g should be used when Δ ≥ 8. Either statistic may be used when 2 ≦ Δ ≦ 8. All tests should be used with caution when the proportion in the sample with y = 1 is less than 0.1.     

Regression analysis of four physical characteristics—stature,length of thigh,length of leg and length of foot of the male population in Sichuan Province

Using four physical characteristics of 394 adult male individuals in the Sichuan Province of China — stature, length of thigh, length of leg and length of foot, a series of linear regression equations and ternary regression equations have been established. Meanwhile three stepwise regression equations also have been established including a quarternary regression equation. Generally speaking, the established multiple equations in this study should be applied as much as possible, where there are two or three independent variables, because they predict more effectively in the individual identification of forensic practice.     

高致病性猪繁殖与呼吸综合征病毒感染性克隆的构建

目的 确定"猪高热综合征"的主要病原是否为猪繁殖与呼吸综合征病毒(PRRSV),为探寻高致病性病毒基因组结构和功能、高致病性蓝耳病发病机制,以及进一步研制针对后者的基因工程疫苗奠定基础。方法 根据PRRSV基因组序列设计特异性引物,分5段扩增了高致病性PRRSV JX143株的全长cDNA,将各cDNA片段克隆到pBlueScriptⅡSK(+)载体中,进而利用重叠区中的单酶切位点将其连接成JX143株的全长cDNA克隆pJX143和含有遗传标记MluⅠ限制性内切酶的基因组全长cDNA克隆pJX143-M。结果全长cDNA克隆经体外合成RNA后转染MA-104细胞,均获得稳定的拯救病毒。通过比较亲本病毒与拯救病毒的病毒滴度、多步生长曲线和利用拯救病毒vJX143进行动物回归试验,结果 发现病毒学及生物学特性没有显著差异。结论 PRRSV的JX143株病毒确实是引起"猪高热综合征"的主要病原;建立了首个高致病性PRRSV的感染性cDNA克隆,证明拯救病毒与亲本病毒生物学特性相同。