Importance of Uncertainty and Variability to Predicted Risks from Trophic Transfer of PCBs in Dredged Sediments

Biomagnification of organochlorine and other persistent organic contaminants by higher trophic level organisms represents one of the most significant sources of uncertainty and variability in evaluating potential risks associated with disposal of dredged materials. While it is important to distinguish between population variability (e.g., true population heterogeneity in fish weight, and lipid content) and uncertainty (e.g., measurement error), they can be operationally difficult to define separately in probabilistic estimates of human health and ecological risk. We propose a disaggregation of uncertain and variable parameters based on: (1) availability of supporting data; (2) the specific management and regulatory context (in this case, of the U.S. Army Corps of Engineers/U.S. Environmental Protection Agency tiered approach to dredged material management); and (3) professional judgment and experience in conducting probabilistic risk assessments. We describe and quantitatively evaluate several sources of uncertainty and variability in estimating risk to human health from trophic transfer of polychlorinated biphenyls (PCBs) using a case study of sediments obtained from the New York-New Jersey Harbor and being evaluated for disposal at an open water off-shore disposal site within the northeast region. The estimates of PCB concentrations in fish and dietary doses of PCBs to humans ingesting fish are expressed as distributions of values, of which the arithmetic mean or mode represents a particular fractile. The distribution of risk values is obtained using a food chain biomagnification model developed by Gobas by specifying distributions for input parameters disaggregated to represent either uncertainty or variability. Only those sources of uncertainty that could be quantified were included in the analysis. Results for several different two-dimensional Latin Hypercube analyses are provided to evaluate the influence of the uncertain versus variable disaggregation of model parameters. The analysis suggests that variability in human exposure parameters is greater than the uncertainty bounds on any particular fractile, given the described assumptions.     

Human Interindividual Variability–A Major Source of Uncertainty in Assessing Risks for Noncancer Health Effects

For noncancer effects, the degree of human interindividual variability plays a central role in determining the risk that can be expected at low exposures. This discussion reviews available data on observations of interindividual variability in (a) breathing rates, based on observations in British coal miners; (b) systemic pharmacokinetic parameters, based on studies of a number of drugs; (c) susceptibility to neurological effects from fetal exposure to methyl mercury, based on observations of the incidence of effects in relation to hair mercury levels; and (d) chronic lung function changes in relation to long-term exposure to cigarette smoke. The quantitative ranges of predictions that follow from uncertainties in estimates of interindividual variability in susceptibility are illustrated.     

A variational model of preference under uncertainty

A familiar example devised by Daniel Ellsberg to highlight the effects of event ambiguity on preferences is transformed to separate aleatory uncertainty (chance) from epistemic uncertainty. The transformation leads to a lottery acts model whose states involve epistemic uncertainty; aleatory uncertainty enters into the statedependent lotteries. The model proposes von Neumann-Morgenstern utility for lotteries, additive subjective probability for states, and the use of across-states standard deviation weighted by a coefficient of aversion to variability to account for departures from Anscombe-Aumann subjective expected utility. Properties of the model are investigated and a partial axiomatization is provided.     

从模因论看网络新词语的构词特点

网络的普及导致一些网络词语迅速流行,这些网络流行词语在构词方面具有类比词和谐音词占主流、字母数字和图形符号混用等特点。按照模因论的观点,网络词语的流行相当于语言模因的复制与传播,模因、特别是强势模具有的变异性、时尚性是形成网络流行语构词特点的的内在动因。     

Analytic evaluation of the expectation and variance of different performance measures of a schedule on a single machine under processing time variability

In this paper, we present closed-form expressions, wherever possible, or devise algorithms otherwise, to determine the expectation and variance of a given schedule on a single machine. We consider a variety of completion time and due date-based objectives. The randomness in the scheduling process is due to variable processing times with known means and variances of jobs and, in some cases, a known underlying processing time distribution. The results that we present in this paper can enable evaluation of a schedule in terms of both the expectation and variance of a performance measure considered, and thereby, aid in obtaining a stable schedule. Additionally, the expressions and algorithms that are presented, can be incorporated in existing scheduling algorithms in order to determine expectation-variance efficient schedules.     

Bayesian Spatial Analysis for the Evaluation of Breast Cancer Detection Methods

This study investigated the impact of spatial location on the effectiveness of population‐based breast screening in reducing breast cancer mortality compared to other detection methods among Queensland women. The analysis was based on linked population‐based datasets from BreastScreen Queensland and the Queensland Cancer Registry for the period of 1997–2008 for women aged less than 90 years at diagnosis. A Bayesian hierarchical regression modelling approach was adopted and posterior estimation was performed using Markov Chain Monte Carlo techniques. This approach accommodated sparse data resulting from rare outcomes in small geographic areas, while allowing for spatial correlation and demographic influences to be included. A relative survival model was chosen to evaluate the relative excess risk for each breast cancer related factor. Several models were fitted to examine the influence of demographic information, cancer stage, geographic information and detection method on women's relative survival. Overall, the study demonstrated that including the detection method and geographic information when assessing the relative survival of breast cancer patients helped capture unexplained and spatial variability. The study also found evidence of better survival among women with breast cancer diagnosed in a screening program than those detected otherwise, as well as lower risk for those residing in a more urban or socio‐economically advantaged region, even after adjusting for tumour stage, environmental factors and demographics. However, no evidence of dependency between method of detection and geographic location was found. This project provides a sophisticated approach to examining the benefit of a screening program while considering the influence of geographic factors.     

Confidence Intervals for a New Characteristic of Central Tendency of Distributions

The t-mean is a new characteristic of the central tendency of continuous distributions. In this article, we introduce a t-difference in the sample space, which is used for a construction of confidence intervals for the t-mean.     

Bottom dogs on campus: how subjective age and extrinsic self-esteem relate to affect and stress in first semester of university

The first semester of university can be a difficult transitional period that affects students' psychological well-being, and ultimately, their academic success. Personal resources and vulnerabilities that they bring to the transition may shape their day-to-day experiences. Subjective age (how old one feels) and extrinsic self-esteem (ESE; the extent to which self-worth is based on external sources) were examined as predictors of mean levels of and intraindividual variability in daily affect (positive and negative) and stress in 170 Canadian students tracked for 14 days during their first semester. Consistent with a self-enhancing effect of an older subjective age, regression models found that feeling older predicted higher mean levels of positive affect, and students with higher ESE reported more negative affect unless they felt considerably older than their chronological ages. In addition, an older subjective age and higher ESE predicted higher levels of and more intraindividual variability in daily stress experience. An ESE appears to contribute to negative affect and stress, but an older subjective age might counteract some negative emotion and play a part in positive emotion. As much as an older subjective age is a possible personal resource, its association with stress suggests that it might have some disadvantages for first-year university students, the bottom dogs on campus.     

《土族格赛尔》文本语句的程式化运用

本文将德国学者施劳德先生根据语音记录、经李克郁先生翻译的土族史诗《土族格赛尔》作为分析文本,对其进行语言层面的剖析,试图找出存在于史诗中的程式语言运用。