The topology aware file distribution problem

We present theoretical results for large-file distribution on general networks of known topology (known link bandwidths and router locations). We show that the problem of distributing a file in minimum time is NP-hard in this model, and we give an O(logn) approximation algorithm, where n is the number of workstations that require the file. We also characterize our method as optimal amongst the class of “no-link-sharing” algorithms.     

Empirically supported ethical research practice: The costs and benefits of research from the participants’ view

Researchers and institutional review boards are routinely called upon to evaluate the cost‐benefit status of proposed research protocols that involve human participants. Often these assessments are based on subjective judgments in the absence of empirical data. This reliance on subjective judgments is of particular concern for studies involving clinical samples where unfounded assumptions may adversely affect research progress or clinical outcomes. The Reactions to Research Participation Questionnaire (RRPQ) was designed to address this shortcoming and to help promote ethical decision making about research practice. The present study describes development of the RRPQ and presents a series of exploratory and confirmatory analyses investigating its structure. Based on these findings, a revised version of the instrument and suggestions for future research are presented. This approach provides a foundation for scientifically informed protection of human subjects.     

A Simple Example Illustrating a Well-Known Property of the Correlation Coefficient

A simple parametrized example is provided to illustrate the well-known fact that correlation near one in magnitude does not imply a relationship that is near perfect linearity.     

Resistance,Space and Political Identities: The Making of Counter-Global Networks

Activists in seven US cities were interviewed about why they thought people in their communities mobilized against alcohol-related problems. The data were analyzed in light of the focus on resource mobilization theory in the social movement literature. In contrast with claims that resources are the primary catalyst for change, informants emphasized the role of grievances, and to a lesser extent, bridging factors that caused residents to be more aware of or frustrated by problems, and thus ready for change. Resources seemed to provide necessary but insufficient conditions for explaining movement participation, suggesting that, to be effective, resources must be channeled to address and be linked to the grievous social conditions of inner city communities.     

Moving college health research forward: Reconsidering our reliance on statistical significance testing

Understanding the unique health needs of college students and establishing best practices to address them depend, heavily, on the inherent quality and contribution of the research identifying these needs. College health-focused publications currently exemplify less than ideal statistical reporting practices. Specifically, college health practitioners and researchers continue to rely heavily upon null hypothesis significance testing (NHST) as the sole standard for effectiveness, validity, and/or replicability of scientific studies, even though NHST itself was not designed for such purposes. Herein we address the following questions: (a) What is NHST? (b) What are the inherent limitations of NHST? (c) What are recommended alternatives to NHST? and (d) How can editorial policies promote adopting NHST alternatives? Using college health data from the CORE 2011 Alcohol and Drug survey, we provide a heuristic example demonstrating how effect sizes do not suffer from the same limitations as NHST.     

Determining an Optimal Penetration Among Weighted Regions in Two and Three Dimensions

We present efficient algorithms for solving the problem of computing an optimal penetration (a ray or a semi-ray) among weighted regions in 2-D and 3-D spaces. This problem finds applications in several areas, such as radiation therapy, geological exploration, and environmental engineering. Our algorithms are based on a combination of geometric techniques and optimization methods. Our geometric analysis shows that the d-D (d = 2, 3) optimal penetration problem can be reduced to solving O(n ^2(d–1)) instances of certain special types of non-linear optimization problems, where n is the total number of vertices of the regions. We also give implementation results of our 2-D algorithms.     

An examination of population changes in Alabama's black belt counties: 1960–1970 and 1970–1980

Population changes in 11 Alabama Black Belt counties are examined by comparing annual average birth, death, and migration rates during the 1960s with those of the 1970s. The specific focus of the study is migration patterns among the nonwhite segment of the population. Data from the 1980 and earlier censuses are utilized, along with birth and death data from Alabama vital statistics reports. Average annual migration rates for each of the two decades are derived. The results indicate that net migration losses among nonwhites declined substantially during the 1970s compared with the 1960s and that in two Black. Belt counties there was a reversal from heavy net losses to moderate net gains. Whites, on a county‐to‐county basis, however, were generally characterized by significantly higher rates of loss during the 1970s than in the 1960s. The substantial reduction in outmigration rates among nonwhites is tentatively attributed to political and economic advances coupled with increased employment opportunities in nonagricultural occupations.     

Approximation algorithms and hardness results for labeled connectivity problems

Let G=(V,E) be a connected multigraph, whose edges are associated with labels specified by an integer-valued function ℒ:E→ℕ. In addition, each label ℓ∈ℕ has a non-negative cost c(ℓ). The minimum label spanning tree problem (MinLST) asks to find a spanning tree in G that minimizes the overall cost of the labels used by its edges. Equivalently, we aim at finding a minimum cost subset of labels I⊆ℕ such that the edge set {e∈E:ℒ(e)∈I} forms a connected subgraph spanning all vertices. Similarly, in the minimum label s – t path problem (MinLP) the goal is to identify an s–t path minimizing the combined cost of its labels. The main contributions of this paper are improved approximation algorithms and hardness results for MinLST and MinLP.     

Are Private Schools Better Than Public Schools? Appraisal for Ireland by Methods for Observational Studies

In observational studies the assignment of units to treatments is not under control. Consequently, the estimation and comparison of treatment effects based on the empirical distribution of the responses can be biased since the units exposed to the various treatments could differ in important unknown pretreatment characteristics, which are related to the response. An important example studied in this article is the question of whether private schools offer better quality of education than public schools. In order to address this question we use data collected in the year 2000 by OECD for the Programme for International Student Assessment (PISA). Focusing for illustration on scores in mathematics of 15-years old pupils in Ireland, we find that the raw average score of pupils in private schools is higher than of pupils in public schools. However, application of a newly proposed method for observational studies suggests that the less able pupils tend to enroll in public schools, such that their lower scores is not necessarily an indication of bad quality of the public schools. Indeed, when comparing the average score in the two types of schools after adjusting for the enrollment effects, we find quite surprisingly that public schools perform better on average. This outcome is supported by the methods of instrumental variables and latent variables, commonly used by econometricians for analyzing and evaluating social programs.