Applications of Centrality Measures and Extremal Combinatorics

Centrality measures assign numbers or rankings to network nodes that reflect their importance. There are many types of centrality measures, each suitable for different types of networks and applications. In Chapter 2, we consider a model of astronaut health during a space mission. Katz centrality is commonly used to measure the influence of nodes in social and biological networks. We motivate its use in this application to estimate the expected quality time lost due to the progression of medical conditions. In Chapter 3, we find dominating sets in satellite networks. To do this, we use the Shapley value, a centrality measure that originates in game theory and is computed based only on local network information. We demonstrate that the Shapley value is an effective and time-efficient tool for finding small dominating sets in various random graph families and a set of real-world networks. In Chapter 4, we introduce a novel algorithm for categorizing which nodes are nearest the boundary, called boundary nodes, in a network that uses Chvátal’s definition of a line in a graph. We test this algorithm on random geometric graphs and compare its effectiveness to other known methods for boundary node detection. In Chapter 5, for certain sets S and equations eq, we look for the smallest number of colors rb(S, eq) such that for every surjective rb(S, eq)-coloring of S, there exists a solution to eq where every element of the solution set is assigned a distinct color. We show that rb([n], x_1 + x_2 = x_3) = ⌊log_2(m) + 2⌋ and rb([m] × [n], x_1 + x_2 = x_3) = m + n + 1 for m, n \u3e 1. In Chapter 6, a graph G is H-semi-saturated if adding an edge e to G that is not currently in G causes H to appear as a subgraph in G that contains e. We say that G is H-saturated if G does not contain H as a subgraph before adding e. The smallest number of edges in an H-semi-saturated (H-saturated) graph is called the semi-saturation number of H (saturation number of H). We show that the saturation and semi-saturation numbers differ by at least 1 for a disjoint union of paths called a linear forest. Additionally, we find graph families for which the saturation number is monotonic with respect to the subgraph relation

The psychosocial determinants of the intention to test for HIV among young men in KwaZulu-Natal province, South Africa

: Voluntary counselling and testing is one of the effective prevention strategies against the HIV/AIDS epidemic. This study investigated the psychosocial determinants of the intention to be tested for HIV among young men in South Africa’s KwaZulu-Natal province using the theory of planned behaviour as the guiding framework. A facilitator-administered questionnaire was used to collect data among 350 isiZulu-speaking men between the ages of 18 and 35. Results show that 24% reported ever having tested. Intention to test showed strong positive correlations with subjective norm to test (r = 0.67), intention to use condoms (r = 0.65), intention to reduce alcohol use (r = 0.60), subjective norm to reduce alcohol use (r = 0.54), and subjective norm to use condoms (r = 0.51). For multiple regression, attitude, subjective norm and perceived behavioural control explained 43% of the variance in intention to test, with subjective norm and perceived behavioural control making significant unique contributions. An additional 12% of the variance was explained by intention to reduce alcohol and drug use, and use condoms

A protocol for whole-exome sequencing in newborns with congenital deafness: a prospective population-based cohort

Introduction: The aetiology of congenital hearing loss is heterogeneous, and in many infants a genetic cause is suspected. Parents face a diagnostic odyssey when searching for a cause of their infant’s hearing loss. Through the Melbourne Genomics Health Alliance, a prospective cohort of infants will be offered whole-exome sequencing (WES) with targeted analysis in conjunction with chromosome microarray to determine the genetic causes of congenital hearing loss. Parents will also be offered the opportunity to receive additional results from their infant’s WES. Methods: Eligible infants will be identified through the Victorian Infant Hearing Screening Program and offered an appointment in a paediatrician-run clinic, a genetics assessment and enrolment in the Victorian Childhood Hearing Impairment Longitudinal Databank. If parents consent to WES, genes causing deafness will be analysed and they can choose to obtain additional findings. For the additional results component, a modified laboratory protocol has been designed for reporting of results in the absence of a relevant phenotype. Parents’ experience of being offered WES will be evaluated using surveys. Discussion This project will provide descriptive analysis of the genetic aetiology of congenital hearing loss in this cohort and may provide data on genotype–phenotype correlations. Additionally, choices regarding additional findings will be analysed. Participants will represent a diverse cross section of the population, increasing the ability to generalise results beyond the study group. Evaluation surveys will allow analysis of preferences around counselling, usefulness of a decision aid and adequacy of information provision

Social Class

Discussion of class structure in fifth-century Athens, historical constitution of theater audiences, and the changes in the comic representation of class antagonism from Aristophanes to Menander

Motivation to reduce alcohol consumption and subsequent attempts at reduction and changes in consumption in increasing and higher-risk drinkers in England:a prospective population survey

AIMS: To assess how far motivation to reduce alcohol consumption in increasing and higher-risk drinkers in England predicts self-reported attempts to reduce alcohol consumption and changes in alcohol intake during the following 6 months. METHODS: This study used self-reported data from 2928 higher-risk drinkers in the Alcohol Toolkit Study (ATS): a series of monthly cross-sectional household surveys of adults aged 16+ years of age in England. Alcohol consumption was measured in an initial survey and in a 6-month telephone follow-up interview using the Alcohol Use Disorders Identification Test (AUDIT)-C questionnaire. Motivation was measured in the initial survey using the Motivation to Reduce Alcohol Consumption (MRAC) scale. Attempts to reduce alcohol consumption during the past 6 months were recorded at follow-up. Data were analysed using repeated-measures difference-in-differences and logistic regression models. RESULTS: Participants with higher initial motivation to reduce alcohol consumption were more likely to report that they had made an attempt to reduce consumption at follow-up [adjusted odds ratio (ORadj ) = 2.39, 95% confidence interval (CI) = 1.75-3.29]. There was an overall reduction in alcohol consumption between initial survey and follow-up (ORadj  = 0.72, 95% CI = 0.65-0.79), but there was insufficient evidence of an additional effect of motivation to reduce consumption on subsequent changes in alcohol consumption, with the difference-in-differences effect instead suggesting an average increase (ORadj  = 1.37, 95% CI = 1.00-1.88). CONCLUSIONS: Increasing and higher-risk drinkers in England who report greater motivation to reduce their consumption are more likely to report making an attempt to reduce during the next 6 months, but this may not be associated with a reduction in alcohol consumption

Substance abuse, treatment needs and access among female sex workers and non-sex workers in Pretoria, South Africa

<p>Abstract</p> <p>Background</p> <p>This study examined cross-sectional data collected from substance-using female sex workers (FSW) and non-sex workers (non-SW) in Pretoria, South Africa, who entered a randomized controlled trial.</p> <p>Methods</p> <p>Women who reported alcohol use and recently engaging in sex work or unprotected sex were recruited for a randomized study. The study sample (N = 506) comprised 335 FSW and 171 female non-SW from Pretoria and surrounding areas. Self-reported data about alcohol and other drug use as well as treatment needs and access were collected from participants before they entered a brief intervention.</p> <p>Results</p> <p>As compared with female non-SW, FSW were found to have a greater likelihood of having a past year diagnosis of alcohol or other drug abuse or dependence, having a family member with a history of alcohol or other drug abuse, having been physically abused, having used alcohol before age 18, and having a history of marijuana use. In addition, the FSW were more likely to perceive that they had alcohol or other drug problems, and that they had a need for treatment and a desire to go for treatment. Less than 20% of participants in either group had any awareness of alcohol and drug treatment programs, with only 3% of the FSW and 2% of the non-SW reporting that they tried but were unable to enter treatment in the past year.</p> <p>Conclusion</p> <p>FSW need and want substance abuse treatment services but they often have difficulty accessing services. The study findings suggest that barriers within the South African treatment system need to be addressed to facilitate access for substance-using FSW. Ongoing research is needed to inform policy change that fosters widespread educational efforts and sustainable, accessible, woman-sensitive services to ultimately break the cycle for current and future generations of at-risk South African women.</p

Opportunistic screening for alcohol use problems in adolescents attending emergency departments: an evaluation of screening tools

Objective To estimate and compare the optimal cut-off score of Alcohol Use Disorders Identification Test (AUDIT) and AUDIT-C in identifying at-risk alcohol consumption, heavy episodic alcohol use, ICD-10 alcohol abuse and alcohol dependence in adolescents attending ED in England. Design Opportunistic cross-sectional survey. Setting 10 emergency departments across England. Participants Adolescents (n = 5377) aged between their 10th and 18th birthday who attended emergency departments between December 2012 and May 2013. Measures Scores on the AUDIT and AUDIT-C. At-risk alcohol consumption and monthly episodic alcohol consumption in the past 3 months were derived using the time-line follow back method. Alcohol abuse and alcohol dependence was assessed in accordance with ICD-10 criteria using the MINI-KID. Findings AUDIT-C with a score of 3 was more effective for at-risk alcohol use (AUC 0.81; sensitivity 87%, specificity 97%), heavy episodic use (0.84; 76%, 98%) and alcohol abuse (0.98; 91%, 90%). AUDIT with a score of 7 was more effective in identifying alcohol dependence (0.92; 96%, 94%). Conclusions The 3-item AUDIT-C is more effective than AUDIT in screening adolescents for at-risk alcohol use, heavy episodic alcohol use and alcohol abuse. AUDIT is more effective than AUDIT-C for the identification of alcohol dependence