Monte Carlo Simulation of Rodent Carcinogenicity Bioassays

In this paper we describe a simulation, by Monte Carlo methods, of the results of rodent carcinogenicity bioassays. Our aim is to study how the observed correlation between carcinogenic potency (beta or 1n2/TD50) and maximum tolerated dose (MTD) arises, and whether the existence of this correlation leads to an artificial correlation between carcinogenic potencies in rats and mice. The validity of the bioassay results depends upon, among other things, certain biases in the experimental design of the bioassays. These include selection of chemicals for bioassay and details of the experimental protocol, including dose levels. We use as variables in our simulation the following factors: (1) dose group size, (2) number of dose groups, (3) tumor rate in the control (zero-dose) group, (4) distribution of the MTD values of the group of chemicals as specified by the mean and standard deviation, (5) the degree of correlation between beta and the MTD, as given by the standard deviation of the random error term in the linear regression of log beta on log (1/MTD), and (6) an upper limit on the number of animals with tumors. Monte Carlo simulation can show whether the information present in the existing rodent bioassay database is sufficient to reject the validity of the proposed interspecies correlations at a given level of stringency. We hope that such analysis will be useful for future bioassay design, and more importantly, for discussion of the whole NCI/NTP program.     

Perspective: Risk Apportionment and Disease Intervention Strategies

The ultimate public health objective is the ability to predict and prevent disease, and not necessarily to identify an exhaustive list of potential disease risk factors. For any important public health outcome with multiple and potentially interrelated risk factors, an improved understanding of the contribution of individual and combinations of modifiable risk factors to the disease burden is essential for formulating an appropriate public health strategy. Partitioning techniques that divide the combined impact of multiple risk factors into exposure-specific components while taking into account the potential interrelations among those components, have been described in the epidemiological literature. In this article, we review and compare the available methods and options for such apportionment and apply them in a more general public health context as a method of selecting and prioritizing coronary heart disease (CHD) prevention strategies.     

Russian Influenza in Two University Communities

Abstract

The H1N1 influenza A virus (A/USSR/90/77) appeared first in China, then spread to the United States in January 1978, causing significant outbreaks of influenza among younger age groups. Because college students were particularly affected, epidemiologic investigations were done to define the impact of illness on university populations.

We describe influenza outbreaks involving two college campuses (the Universities of Michigan and Colorado). At both schools, illness attack rates were significantly higher for students than for older faculty and staff members. At the two respective campuses, 25 and 36% of those ill who were surveyed sought medical care. Bed confinement averaged 3.8 days at one school (Michigan). At the other school (Colorado), ill students missed an average of 2.8 days of class. Influenza A (H1N1) virus was isolated from specimens from acutely ill students at both campuses.

These investigations illustrate the practical usefulness of college campuses as sites for monitoring the activity of influenza and other acute respiratory diseases.     

Communication in Nuclear Emergency Preparedness: A Closer Look at Information Reception

Preparedness of the general population plays a key role in the effective implementation of protective actions in case of a nuclear emergency (e.g., evacuation or intake of iodine tablets). In this context, a good communication of emergency management actors with the public along the entire cycle of preparedness–response–recovery is of paramount importance. This article aims at providing a better understanding of the way people process communicated messages and the factors that may influence how they do this. In particular, it investigates information reception as part of the information processing in precrisis communication. As a case study, the precrisis communication context was chosen, as it has been tackled to a lesser extent in the literature. The empirical data used for this study originated from a large‐scale opinion survey in Belgium. One topic in this survey addressed the information campaign for the distribution of iodine tablets, in the context of preparedness for nuclear emergencies. The findings of this study demonstrate that systematic predictors have a stronger influence on information reception, as compared to heuristic predictors. The latter are only to a minor extent involved in the reception of emergency preparedness information. The hypothesized pattern—that more specific knowledge about the field relates to a higher reception of information—was confirmed for precrisis communication. Contrary to expectations, results showed that people with a high perception of radiation risks were less attentive to information about protective actions. People with little confidence in authorities were also more likely to have a low reception of information.     

Algorithms for storage allocation based on client preferences

We consider a packing problem arising in storage management of Video on Demand (VoD) systems. The system consists of a set of video files (movies) and several servers (disks), each having a limited storage capacity, C, and a limited bandwidth (load capacity), L. The goal in the storage allocation problem is to assign the video files to the servers and the bandwidth to the clients. The induced class-constrained packing problem was studied in the past assuming each client provides a single request for a single movie. This paper considers a more general and realistic model—in which each client ranks all the movies in the system. Specifically, for each client j and movie i, it is known how much client j is willing to pay in order to watch movie i. The goal is to maximize the system’s profit. Alternatively, the client might provide a ranking of the movies and the goal is to maximize the lexicographic profile of the solution.     

Exploring Transformational Processes and Meaning in LDS Marriages

For decades, research has shown that religion is correlated with several important aspects of marriage. However, most studies have looked only at distal aspects of a couple's religion, such as church attendance or religious salience, and are therefore hard pressed to explain precisely how religion and marriage correlate. This qualitative study examines the connection Mormon (LDS) couples perceive between their religious faith and their marriage and family relationships. For this study we used a subset of a national sample of 445 individuals from across the United States who were interviewed over several years; this subset consisted of 48 individuals (24 couples) living in seven different states (25% of whom are ethnic minorities) that we interviewed. The interviews specifically sought to understand how these couples connected their faith to five transformational constructs: commitment, sacrifice, coping, conflict resolution, and forgiveness. Each couple shared specific beliefs and practices that impacted their approach to these constructs. Analysis was then made identifying patterns and parallels.     

Hope and activism in the ivory tower: Freirean lessons for critical globalization research

Abstract

This paper uses Freirean theory and field studies of counter-globalist campaigns to add greater lucidity and normative deliberateness to our understanding of resistance to neo-liberal globalism. A difficult tension exists between complete submersion in movement struggles, versus a mythical position of objective analytic detachment. We sketch out the basis for a productive dialogue between these two competing pulls of political engagement and analytic objectivity. To do this, we draw from the writings of Paulo Freire, a Brazilian thinker famous for his theories of popular education. Freire's writings have not seriously entered academic studies of globalization, even though activists in the ‘globalization-from-below’ camp frequently draw on his words for inspiration. We seek to remedy this omission, and construct a dialogue between Freire and social movement struggles on four dualisms centred on epistemology, normativity, methodology and strategy. In each dualism, we outline how Freirean concepts can help redefine these binaries as productive tensions to be developed, rather than conflicts to be suppressed. These insights are not intended as a theoretical injunctive delivered from upon high, but are used in dialogue with examples from global justice campaigns in order to clarify what is already taking place on the ground. Identifying Freirean priorities can also encourage openings for more emancipatory approaches to critical globalization scholarship. While academics cannot engineer resistance to neo-liberal globalism from the top down, they can contribute their research energy and resources, becoming more actively engaged in the process of envisaging alternatives.     

On the approximability of Time Disjoint Walks

Journal of Combinatorial Optimization - We introduce the combinatorial optimization problem Time Disjoint Walks (TDW), which has applications in collision-free routing of discrete objects (e.g.,...