基于分形理论下的沙漠植被适应性群团抽样技术

以乌兰布和沙漠的白刺沙丘为主要研究对象,采用分形理论将遥感数据和实际调查数据相结合的方法,进行了适应性群团抽样技术的研究。基于分形理论建立描述白刺沙丘周长和面积关系的线性回归方程,利用周长估计了白刺沙丘的面积,估计精度达89.8%。在沙丘面积估计值的基础上,进行了适应性群团抽样分析。研究结果表明：当适应性标准（每个样方内白刺沙丘的面积）等于50 m²时,即接近含有白刺沙丘的样方均值时,适应性群团抽样的估计精度最高达到97.9%,适应性群团抽样效率是简单随机抽样效率的5.56倍。这一研究为沙漠地区具有群团分布特点的植被提供更有效的调查方法。     

乌兰布和沙漠天然白刺适应性群团抽样技术的研究

以乌兰布和沙漠地区天然白刺为具体研究对象,对不同抽样方法获取的数据进行了分析.研究结果表明,当适应性标准大于等于占位单元平均数时,适应性群团抽样比简单随机抽样更有效,并且可以保证估计精度;初始抽样比例越大,总体均值估计值和抽样相对效率越稳定.在该研究区域采用二阶适应性群团抽样,可以达到估计精度,但与简单随机抽样和适应性群团抽样相比效率偏低.     

Multiple Tests for Different Sets of Variables Using a Data‐Driven Ordering of Hypotheses,with an Application to Gene Expression Data

A multiple parametric test procedure is proposed, which considers tests of means of several variables. The single variables or subsets of variables are ordered according to a data‐dependent criterion and tested in this succession without alpha‐adjustment until the first non‐significant test. The test procedure needs the assumption of a multivariate normal distribution and utilizes the theory of spherical distributions. The basic version is particularly suited for variables with approximately equal variances. As a typical example, the procedure is applied to gene expression data from a commercial array.     

Response Adaptive Designs with a Variance‐penalized Criterion

We consider a response adaptive design of clinical trials with a variance‐penalized criterion. It is shown that this criterion evaluates the performance of a response adaptive design based on both the number of patients assigned to the better treatment and the power of the statistical test. A new proportion of treatment allocation is proposed and the doubly biased coin procedure is used to target the proposed proportion. Under reasonable assumptions, the proposed design is demonstrated to generate an asymptotic variance of allocation proportions, which is smaller than that of the drop‐the‐loser design. Simulation comparisons of the proposed design with some existing designs are presented.     

Statistical Inference for a Two‐Stage Outcome‐Dependent Sampling Design with a Continuous Outcome

Summary The two‐stage case–control design has been widely used in epidemiology studies for its cost‐effectiveness and improvement of the study efficiency ( White, 1982 , American Journal of Epidemiology 115, 119–128; Breslow and Cain, 1988 , Biometrika 75, 11–20). The evolution of modern biomedical studies has called for cost‐effective designs with a continuous outcome and exposure variables. In this article, we propose a new two‐stage outcome‐dependent sampling (ODS) scheme with a continuous outcome variable, where both the first‐stage data and the second‐stage data are from ODS schemes. We develop a semiparametric empirical likelihood estimation for inference about the regression parameters in the proposed design. Simulation studies were conducted to investigate the small‐sample behavior of the proposed estimator. We demonstrate that, for a given statistical power, the proposed design will require a substantially smaller sample size than the alternative designs. The proposed method is illustrated with an environmental health study conducted at National Institutes of Health.     

Obesity in 70‐Year‐Old Subjects as a Risk Factor for 15‐Year Coronary Heart Disease Incidence

Objective: To investigate the role of obesity in general and waist circumference (WC) and BMI in particular as risk factors for 15‐year incidence of coronary heart disease (CHD) in the elderly. Research Methods and Procedures: This prospective study was based on 1597 (737 males and 860 females) 70‐year‐olds free from CHD and participants of three birth cohorts examined in 1971 to 1972 (Cohort I), 1976 to 1977 (Cohort II), and 1981 to 1982 (Cohort III) at Göteborg, Sweden. Fifteen‐year incidence of CHD (fatal and nonfatal) was ascertained from follow‐up examinations and registers. Relative risk (RR) for first ever CHD in reference to the lowest quartiles of WC and BMI was calculated from Cox regression. Results: In males, RRs for CHD in the highest WC and BMI quartiles were 1.36 [95% confidence interval (CI) 1.00 to 1.85] and 1.42 (95% CI 1.04 to 1.92), respectively, after adjustment for cohorts, smoking habits, diabetes, systolic blood pressure, and total cholesterol. In men, the risk associated with WC was independent of BMI. Neither WC nor BMI was related to CHD risk in females. After exclusion of first 5‐year all‐cause deaths, the adjusted RRs in the highest WC and BMI quartiles in males were 1.47 (95% CI 1.06 to 2.04) and 1.42 (1.04 to 1.92), respectively. In females, a significantly higher RR of 1.41 (95% CI 1.02 to 1.94) was observed in the second BMI quartile only after such exclusions. Discussion: WC, an indicator of both central and general obesity, appears to be a stronger predictor of CHD than BMI in elderly males, but in females, obesity was not a risk factor for CHD.     

Confidence Intervals of the Attributable Risk under Cross‐Sectional Sampling with Confounders

Since it can account for both the strength of the association between exposure to a risk factor and the underlying disease of interest and the prevalence of the risk factor, the attributable risk (AR) is probably the most commonly used epidemiologic measure for public health administrators to locate important risk factors. This paper discusses interval estimation of the AR in the presence of confounders under cross‐sectional sampling. This paper considers four asymptotic interval estimators which are direct generalizations of those originally proposed for the case of no confounders, and employs Monte Carlo simulation to evaluate the finite‐sample performance of these estimators in a variety of situations. This paper finds that interval estimators using Wald's test statistic and a quadratic equation suggested here can consistently perform reasonably well with respect to the coverage probability in all the situations considered here. This paper notes that the interval estimator using the logarithmic transformation, that is previously found to consistently perform well for the case of no confounders, may have the coverage probability less than the desired confidence level when the underlying common prevalence rate ratio (RR) across strata between the exposure and the non‐exposure is large (≥4). This paper further notes that the interval estimator using the logit transformation is inappropriate for use when the underlying common RR ≐ 1. On the other hand, when the underlying common RR is large (≥4), this interval estimator is probably preferable to all the other three estimators. When the sample size is large (≥400) and the RR ≥ 2 in the situations considered here, this paper finds that all the four interval estimators developed here are essentially equivalent with respect to both the coverage probability and the average length.     

Multiple Comparisons of Treatments with Stable Multivariate Tests in a Two‐Stage Adaptive Design,Including a Test for Non‐Inferiority

The application of stabilized multivariate tests is demonstrated in the analysis of a two‐stage adaptive clinical trial with three treatment arms. Due to the clinical problem, the multiple comparisons include tests of superiority as well as a test for non‐inferiority, where non‐inferiority is (because of missing absolute tolerance limits) expressed as linear contrast of the three treatments. Special emphasis is paid to the combination of the three sources of multiplicity – multiple endpoints, multiple treatments, and two stages of the adaptive design. Particularly, the adaptation after the first stage comprises a change of the a‐priori order of hypotheses.     

Five Confidence Intervals of the Closed Population Size in the Capture‐recapture Problem under Inverse Sampling with Replacement

In the capture‐recapture problem for two independent samples, the traditional estimator, calculated as the product of the two sample sizes divided by the number of sampled subjects appearing commonly in both samples, is well known to be a biased estimator of the population size and have no finite variance under direct or binomial sampling. To alleviate these theoretical limitations, the inverse sampling, in which we continue sampling subjects in the second sample until we obtain a desired number of marked subjects who appeared in the first sample, has been proposed elsewhere. In this paper, we consider five interval estimators of the population size, including the most commonly‐used interval estimator using Wald's statistic, the interval estimator using the logarithmic transformation, the interval estimator derived from a quadratic equation developed here, the interval estimator using the χ²‐approximation, and the interval estimator based on the exact negative binomial distribution. To evaluate and compare the finite sample performance of these estimators, we employ Monte Carlo simulation to calculate the coverage probability and the standardized average length of the resulting confidence intervals in a variety of situations. To study the location of these interval estimators, we calculate the non‐coverage probability in the two tails of the confidence intervals. Finally, we briefly discuss the optimal sample size determination for a given precision to minimize the expected total cost. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Molecular Identification of a 16SrII‐A Group‐Related Phytoplasma Associated with Cinnamon Yellow Leaf Disease in China

Chinese cinnamon (Cinnamomum cassia Presl), an evergreen tree native to China, is a multifaceted medicinal plant. The stem bark of cinnamon is used worldwide in traditional and modern medicines and is one of the most popular cooking spices. In recent years, cinnamon with pronounced yellow leaf symptoms has been observed in their natural habitat in Hainan, China. Phytoplasmas were detected from symptomatic cinnamon trees via polymerase chain reaction using phytoplasma universal primers P1/P7 followed by R16F2n/R16R2. No amplification products were obtained from templates of asymptomatic cinnamon trees. These results indicated a direct association between phytoplasma infection and the cinnamon yellow leaf (CYL) disease. Sequence analysis of the CYL phytoplasma 16S rRNA gene determined that CYL phytoplasma is a ‘Candidatus Phytoplasma australasiae’‐related strain. Furthermore, virtual restriction fragment length polymorphism pattern analysis and phylogenetic studies showed that CYL phytoplasma belongs to the peanut witches’‐broom (16SrII) group, subgroup A. This is the first report of a 16SrII group phytoplasma infecting cinnamon under natural conditions.     

Multiscale Adaptive Marginal Analysis of Longitudinal Neuroimaging Data with Time‐Varying Covariates

Summary Neuroimaging data collected at repeated occasions are gaining increasing attention in the neuroimaging community due to their potential in answering questions regarding brain development, aging, and neurodegeneration. These datasets are large and complicated, characterized by the intricate spatial dependence structure of each response image, multiple response images per subject, and covariates that may vary with time. We propose a multiscale adaptive generalized method of moments (MA‐GMM) approach to estimate marginal regression models for imaging datasets that contain time‐varying, spatially related responses and some time‐varying covariates. Our method categorizes covariates into types to determine the valid moment conditions to combine during estimation. Further, instead of assuming independence of voxels (the components that make up each subject’s response image at each time point) as many current neuroimaging analysis techniques do, this method “adaptively smoothes” neuroimaging response data, computing parameter estimates by iteratively building spheres around each voxel and combining observations within the spheres with weights. MA‐GMM’s development adds to the few available modeling approaches intended for longitudinal imaging data analysis. Simulation studies and an analysis of a real longitudinal imaging dataset from the Alzheimer’s Disease Neuroimaging Initiative are used to assess the performance of MA‐GMM. Martha Skup, Hongtu Zhu, and Heping Zhang for the Alzheimer’s Disease Neuroimaging Initiative.     

Application of Two‐Way Hierarchical Cluster Analysis for the Identification of Similarities between the Individual Lipid Fractions of Lucilia sericata

The composition of the cuticular and internal lipids of larvae and pupae of Lucilia sericata was studied using chromatographic techniques. The lipids from both stages of L. sericata had similar free fatty acid (FFA) profiles and also contained alcohols and cholesterol. The range of the number of C‐atoms detected for these classes of compounds was to some extent similar in larvae and pupae, but the relative amounts of each class differed between stages. Saturated as well as unsaturated FFAs with even and odd numbered C‐atom chains were present in both cuticular and internal lipids. The alcohol fractions of L. sericata were represented by free, straight‐chain primary alcohols containing an even number of C‐atoms. The lipid composition of male and female L. sericata adults and the hydrocarbon composition of all stages of L. sericata had previously been analyzed. To have a full overview of the lipid composition and to identify similarities or dissimilarities between the individual lipid fractions in this insect species, two‐way hierarchical cluster analysis (HCA) was performed using also the data from these previous publications. The content of FFA 18 : 1 (n‐9) was noticed to be very high in the cuticular fractions of larvae and pupae as well as in all internal fractions (male, female, larvae, and pupae) and low in the cuticular fractions of male and female imago. The contents of FFAs 16 : 0 and 16 : 1 (n‐9), cholesterol, and the n‐alkanes n‐C₃₁, n‐C₂₉, n‐C₂₇, n‐C₂₅, and n‐C₂₃ varied between particular fractions, whereas the amounts of other compounds were similar in all fractions.     

Poisson Regression with Change‐Point Prior in the Modelling of Disease Risk around a Point Source

Bayesian estimation of the risk of a disease around a known point source of exposure is considered. The minimal requirements for data are that cases and populations at risk are known for a fixed set of concentric annuli around the point source, and each annulus has a uniquely defined distance from the source. The conventional Poisson likelihood is assumed for the counts of disease cases in each annular zone with zone‐specific relative risk and parameters and, conditional on the risks, the counts are considered to be independent. The prior for the relative risk parameters is assumed to be piecewise constant at the distance having a known number of components. This prior is the well‐known change‐point model. Monte Carlo sampling from the posterior results in zone‐specific posterior summaries, which can be applied for the calculation of a smooth curve describing the variation in disease risk as a function of the distance from the putative source. In addition, the posterior can be used in the calculation of posterior probabilities for interesting hypothesis. The suggested model is suitable for use in geographical information systems (GIS) aimed for monitoring disease risks. As an application, a case study on the incidence of lung cancer around a former asbestos mine in eastern Finland is presented. Further extensions of the model are discussed.     

Increased Humoral Immune Responses of Pigs to Foot‐and‐Mouth Disease Vaccine Supplemented with Ginseng Stem and Leaf Saponins

Vaccination is a conventional approach against foot‐and‐mouth disease (FMD) in pigs. However, failure to elicit an immune response to vaccine has been reported. Our previous investigation showed that ginseng stem and leaf saponins (GSLS) and mineral oil acted synergistically to promote Th1/Th2 immune responses to FMD vaccine in mice. This study was designed to i) find the optimal doses of GSLS in oil‐emulsified FMD vaccines to induce immune responses in mice and pigs and ii) to evaluate the effect of oil‐emulsified FMD vaccine supplemented with GSLS on the immune responses in pigs, by measuring the serum indirect hemagglutination (IHA) titer and IgG and IgG subclass levels. The GSLS‐enhanced immune response to FMD oil‐emulsion vaccine depended on the dose of GSLS added to the vaccine. Addition of GSLS at a dose of 40 μg to 2 ml of FMD oil‐emulsified vaccine significantly enhanced the humoral immune responses in pigs, when compared to the vaccine without GSLS (P<0.05). The increased antibodies included IgG1 and IgG2. Hence, GSLS and oil adjuvant synergistically promoted the immune responses to vaccination against FMD in pigs, and GSLS could be a promising vaccine additive to improve oil‐emulsified veterinary vaccines.     

Plasticity and constraint in response to early‐life stressors among late/final jomon period foragers from Japan: Evidence for life history trade‐offs from incremental microstructures of enamel

This study evaluates two hypotheses that address how Late/Final Jomon period people responded to early‐life stress using linear enamel hypoplasia (LEH) and incremental microstructures of enamel. The first hypothesis predicts that Jomon people who experienced early‐life stressors had greater physiological competence in responding to future stress events (predictive adaptive response). The second hypothesis predicts that Jomon people traded‐off in future growth and maintenance when early investment in growth and survival was required (plasticity/constraint). High resolution tooth impressions were collected from intact, anterior teeth and studied under an engineer's measuring microscope. LEH were identified based on accentuated perikymata and depressions in the enamel surface profile. Age of formation for each LEH was estimated by summing counts of perikymata and constants associated with crown initiation and cuspal enamel formation times. The relationship between age‐at‐first‐defect formation, number of LEH, periodicity between LEH, and mortality was evaluated using multiple regression and hazards analysis. A significant, positive relationship was found between age‐at‐death relative to age‐at‐first‐defect formation and a significant, negative relationship was found between number of LEH relative to age‐at‐first‐defect formation. Individuals with earlier forming defects were at a significantly greater risk of forming defects at later stages of development and dying at younger ages. These results suggest that Late/Final Jomon period foragers responded to early‐life stressors in a manner consistent with the plasticity/constraint hypothesis of human life history. Late/Final Jomon period individuals were able to survive early‐life stressors, but this investment weakened responses to future stress events and exacerbated mortality schedules. Am J Phys Anthropol 155:537–545, 2014. © 2014 Wiley Periodicals, Inc.     

Potential Role of Interleukin‐18 in Liver Disease Associated with Insulin Resistance

Objective: Interleukin (IL)‐18 has been associated with obesity and insulin resistance, both risk factors for the development of liver disease, but the role of IL‐18 in liver disease associated with insulin resistance is presently unknown. We hypothesized that circulating IL‐18 would be related to serum concentrations of liver chemistry tests (LCTs) in apparently healthy subjects and wished to study whether this correlation was dependent on insulin sensitivity (S_I). Research Methods and Procedures: One hundred six apparently healthy white men consecutively enrolled in a cross‐sectional, population‐based study dealing with S_I in men were studied, and S_I (minimal model analysis), LCTs (colorimetry), and IL‐18 serum concentrations (immunoassay) were assessed. Results: Compared with subjects in the lowest quartile for serum IL‐18, subjects in the highest quartile exhibited increased serum triglycerides and decreased S_I, in addition to higher serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) (all p < 0.05). The direct association between both ALT and AST and IL‐18 was further confirmed by examining the distribution of serum IL‐18 by quartiles of ALT and AST. Subjects in the highest quartile for serum ALT and AST had higher IL‐18 concentrations compared with subjects in the lowest quartile for these LCTs (both p = 0.01). In multiple regression analysis, IL‐18, but not S_I, was an independent predictor of serum concentrations of ALT and AST, explaining 7% and 4% of their variance, respectively. Discussion: In summary, IL‐18 serum concentrations are associated in apparently healthy humans with plasma concentrations of various LCTs. IL‐18 could contribute to the development of liver disease associated with insulin resistance.     

Experimental Design and Statistical Inference for Cluster Point Processes – with Applications to the Fruit Dispersion of Anemochorous Forest Trees

This paper deals with experimental design and statistical inference for cluster point processes. The results are applied to fruit dispersion models of forest trees where the corresponding design of experiments is given by the positions of the traps containing the collected fruits. It is shown that consideration of anisotropic behaviour can lead to more realistic models. Modelling interactivity effects between trees seems to be of great interest. It is shown that an approach based on ordered weighted averages yields an notable improvement of model quality. The mathematical background of such models (Choquet integral, fuzzy measures) is sketched in the appendix. Finally, results for choosing a D‐optimal sub‐design are presented.