The density maximization problem in graphs

We consider a framework for bi-objective network construction problems where one objective is to be maximized while the other is to be minimized. Given a host graph G=(V,E) with edge weights w _e ∈? and edge lengths ? _e ∈? for e∈E we define the density of a pattern subgraph H=(V′,E′)?G as the ratio ?(H)=∑ _e∈E′ w _e /∑ _e∈E′ ? _e . We consider the problem of computing a maximum density pattern H under various additional constraints. In doing so, we compute a single Pareto-optimal solution with the best weight per cost ratio subject to additional constraints further narrowing down feasible solutions for the underlying bi-objective network construction problem. First, we consider the problem of computing a maximum density pattern with weight at least W and length at most L in a host G. We call this problem the biconstrained density maximization problem. This problem can be interpreted in terms of maximizing the return on investment for network construction problems in the presence of a limited budget and a target profit. We consider this problem for different classes of hosts and patterns. We show that it is NP-hard, even if the host has treewidth 2 and the pattern is a path. However, it can be solved in pseudo-polynomial linear time if the host has bounded treewidth and the pattern is a graph from a given minor-closed family of graphs. Finally, we present an FPTAS for a relaxation of the density maximization problem, in which we are allowed to violate the upper bound on the length at the cost of some penalty. Second, we consider the maximum density subgraph problem under structural constraints on the vertex set that is used by the patterns. While a maximum density perfect matching can be computed efficiently in general graphs, the maximum density Steiner-subgraph problem, which requires a subset of the vertices in any feasible solution, is NP-hard and unlikely to admit a constant-factor approximation. When parameterized by the number of vertices of the pattern, this problem is W[1]-hard in general graphs. On the other hand, it is FPT on planar graphs if there is no constraint on the pattern and on general graphs if the pattern is a path.     

Estimating percentile-specific treatment effects in counterfactual models: a case-study of micronutrient supplementation, birth weight and infant mortality

Summary.  Clinical trials of micronutrient supplementation are aimed at reducing the risk of infant mortality by increasing birth weight. Because infant mortality is greatest among the low birth weight (LBW) infants (2500 g or under), an effective intervention increases the birth weight among the smallest babies. The paper defines population and counterfactual parameters for estimating the treatment effects on birth weight and on survival as functions of the percentiles of the birth weight distribution. We use a Bayesian approach with data augmentation to approximate the posterior distributions of the parameters, taking into account uncertainty that is associated with the imputation of the counterfactuals. This approach is particularly suitable for exploring the sensitivity of the results to unverifiable modelling assumptions and other prior beliefs. We estimate that the average causal effect of the treatment on birth weight is 72 g (95% posterior regions 33–110 g) and that this causal effect is largest among the LBW infants. Posterior inferences about average causal effects of the treatment on birth weight are robust to modelling assumptions. However, inferences about causal effects for babies at the tails of the birth weight distribution can be highly sensitive to the unverifiable assumption about the correl-ation between the observed and the counterfactuals birth weights. Among the LBW infants who have a large causal effect of the treatment on birth weight, we estimate that a baby receiving the treatment has 5% less chance of death than if the same baby had received the control. Among the LBW infants, we found weak evidence supporting an additional beneficial effect of the treatment on mortality independent of birth weight.     

A Comparison of South-East Asian and Australian First-Year Students' Views on University

A questionnaire study was carried out with Asian and Australian university entrants in order to ascertain their differential attitudes as to the purposes of an ideal university, and their expectations as to the milieu of an actual university. The implications of the significant culturally based differences between the two groups are discussed in terms of relative value systems, culture-shock effects, and the ramifications for both academic policy and inter-racial relations.     

Book Review: Peter Frumkin,On Being Nonprofit: A Conceptual and Policy Primer,Harvard University Press,Cambridge, MA, 2002, 213 pp., preface,notes, index, $35.00

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -     

Domestic Violence,Children's Agency and Mother–Child Relationships: Towards a More Advanced Model

Although domestic violence research increasingly recognises children's agency, this awareness has not extended to our understanding of children's relationships with their abused mothers. Findings suggesting that some children actively support their mother, and encourage her to leave the perpetrator, have been consistently under‐discussed. This article argues that the model of parent–child relationships used by most domestic violence research sees children as passive and contributes to mother‐blaming discourses. Analysing key quantitative and qualitative research, I suggest that a more sophisticated model of parent–child relationships is needed to understand how children's agency affects them, their mothers and the domestic violence situation.     

Seeing Clinical Attention Anew: Results from an Exploratory Study of Attention in Clinical Practice

Attention is an acknowledged component of the therapeutic relationship that forms the heart of clinical work. Yet it is rarely studied. This study explored the structure of clinical attention with a focus on internal processes occurring within the clinician, not on actions or interventions taken in sessions. Fourteen experienced clinicians participated in an elicitation interview. Data analysis followed a modified phenomenological methodology. The structure of clinical attention was discovered to consist of a dynamic and iterative process of intention and intuition based in distinct, recursive and iteratively related attentional levels. Attention is a process grounded in inner psycho-physiological awareness providing clinicians with abilities to reflect on practice and regulate affective experience.     

Amnestic Heterosexism and Bystander Responses to Anti-Gay Bullying

Amnestic heterosexism (AH) reflects the belief that, in contemporary society, people who are lesbian, gay, or bisexual (LGB) no longer experience discrimination related to sexual orientation. We investigated potential associations between individuals’ AH beliefs and their responses to anti-gay bullying. Heterosexual undergraduates (N = 238) completed a measure of AH before responding to a scenario in which a man accuses another man of being a “fag.” As expected, those with greater AH beliefs perceived the situation as less severe/dangerous, felt less personally responsible to intervene, and were more blaming toward the target of bullying. In multivariate analyses, AH was indirectly associated with intent to confront the perpetrator via a path of reduced personal responsibility. Our results indicate that beliefs denying the existence of discrimination based on sexual orientation reduce feelings of personal responsibility to address anti-gay bullying. In turn, low personal responsibility inhibits confrontation of those who perpetrate bullying behaviors.     

Armor for Ethnographers

As its public readership has vastly increased, ethnography has entered a new world of social interaction, at once rewarding and dangerous. Among social researchers, ethnographic fieldworkers are unusually exposed to pressures to both make and break promises of confidentiality to subjects because they work to expose subjects to readers in a relatively transparent way. By showing individuals in their individuality, ethnographers draw the attention of nonacademic readers, which can be motivating but also terrifying because sources might be questioned and subjects sought out in ways the ethnographer may not be able to control. Tracking the schizophrenia that now threatens to pervade ethnographic work, I describe overlooked risks that all practitioners face and point to an as‐yet unexplored collective strategy for resisting pressures to breach promises of confidentiality. I then switch from a collective to an individual focus and review ethnography as a multiphased research act, suggesting ways to minimize personal and ethical risks at each stage.