The Structure of Optimal and Near Optimal Target Sets in Consensus Models

We consider the problem of identifying a subset of nodes in a network that will enable the fastest spread of information in a decentralized environment.In a model of communication based on a random walk on an undirected graph, the optimal set over all sets of the same or smaller cardinality minimizes the sum of the mean first arrival times to the set by walkers starting at nodes outside the set. The problem originates from the study of the spread of information or consensus in a network and was introduced in this form by V.Borkar et al. in 2010. More generally, the work of A. Clark et al. in 2012 showed that estimating the fastest rate of convergence to consensus of so-called leader follower systems leads to a consideration of the same optimization problem. The set function $F$ to be minimized is supermodular and therefore the greedy algorithm is commonly used to construct optimal sets or their approximations. In this paper, the problem is reformulated so that the search for solutions is restricted to optimal and near optimal subsets of the graph. We prove sufficient conditions for the existence of a greedoid structure that contains feasible optimal and near optimal sets. It is therefore possible we conjecture, to search for optimal or near optimal sets by local moves in a stepwise manner to obtain near optimal sets that are better approximations than the factor $(1-1/e)$ degree of optimality guaranteed by the use of the greedy algorithm. A simple example illustrates aspects of the method.Comment: arXiv admin note: substantial text overlap with arXiv:1401.696

A randomised controlled pilot study: the effectiveness of narrative exposure therapy with adult survivors of the Sichuan earthquake

Background: Post-Traumatic Stress Disorder (PTSD) is a common psychological reaction after large-scale natural disasters. Given the number of people involved and shortage of resources in any major disaster, brief, pragmatic and easily trainable interventions are needed. The aim of this study is to evaluate the efficacy of Narrative Exposure Therapy (NET) as a short-term treatment for PTSD using Chinese earthquake survivors. Methods: A randomized waiting-list control pilot study was conducted between December 2009 and March 2010, at the site of the Sichuan earthquake in Beichuan County, China. Adult participants with newly diagnosed Post Traumatic Stress Disorder (PTSD) were randomly allocated to Narrative Exposure Therapy (NET) or a Waiting-List (WL) condition. The latter received NET treatment after a two-week waiting period. To compare the effectiveness of NET in traumatised earthquake survivors, both groups were assessed on PTSD symptoms, general mental health, anxiety and depression, social support, coping style and posttraumatic change before and after treatment and two months post treatment. Results: Adult participants (n=22) were randomly allocated to receive NET (n=11) or WL (n=11). Twenty two participants (11 in NET group, 11 in WL) were included in the analysis of primary outcomes. Compared with WL, NET showed significant reductions in PTSD symptoms, anxiety and depression, general mental stress and increased posttraumatic growth. The WL group later showed similar improvements after treatment. These changes remained stable for a two-month follow-up. Measures of social support and coping showed no stable effects. Conclusions: NET is effective in treating post-earthquake traumatic symptoms in adult Chinese earthquake survivors. The findings help advance current knowledge in the management of PTSD after natural disasters and inform future research. Larger sample sizes are needed to extend the present findings

CFD modelling of buoyancy-driven natural ventilation opposed by wind

This paper presents CFD simulations of natural displacement ventilation airflows in which the buoyancy force produced by a heat source is opposed by a wind force. Cases investigated focus on windbuoyancy force relationships for which a two-layer stratification is maintained. CFD predictions of the position of the interface separating the two layers and the change in reduced gravity (temperature difference) between them are compared with the analytical work and salt-bath measurements of Hunt and Linden (2000, 2005). Comparisons are good with only minor discrepancies in the interface position and a small under-prediction of the upper layer reduced gravity

Do men consult less than women? An analysis of routinely collected UK general practice data

<p>Objective To examine whether gender differences in primary care consultation rates (1) vary by age and deprivation status and (2) diminish when consultation for reproductive reasons or common underlying morbidities are accounted for.</p> <p>Design Cross-sectional study of a cohort of patients registered with general practice.</p> <p>Setting UK primary care.</p> <p>Subjects Patients (1 869 149 men and 1 916 898 women) registered with 446 eligible practices in 2010.</p> <p>Primary outcome measures Primary care consultation rate.</p> <p>Results This study analyses routinely collected primary care consultation data. The crude consultation rate was 32% lower in men than women. The magnitude of gender difference varied across the life course, and there was no ‘excess’ female consulting in early and later life. The greatest gender gap in primary care consultations was seen among those aged between 16 and 60 years. Gender differences in consulting were higher in people from more deprived areas than among those from more affluent areas. Accounting for reproductive-related consultations diminished but did not eradicate the gender gap. However, consultation rates in men and women who had comparable underlying morbidities (as assessed by receipt of medication) were similar; men in receipt of antidepressant medication were only 8% less likely to consult than women in receipt of antidepressant medication (relative risk (RR) 0.916, 95% CI 0.913 to 0.918), and men in receipt of medication to treat cardiovascular disease were just 5% less likely to consult (RR=0.950, 95% CI 0.948 to 0.952) than women receiving similar medication. These small gender differences diminished further, particularly for depression (RR=0.950, 95% CI 0.947 to 0.953), after also taking account of reproductive consultations.</p> <p>Conclusions Overall gender differences in consulting are most marked between the ages of 16 and 60 years; these differences are only partially accounted for by consultations for reproductive reasons. Differences in consultation rates between men and women were largely eradicated when comparing men and women in receipt of medication for similar underlying morbidities.</p&gt

Open Access Policy: Numbers, Analysis, Effectiveness

The PASTEUR4OA project analyses what makes an Open Access (OA) policy effective. The total number of institutional or funder OA policies worldwide is now 663 (March 2015), over half of them mandatory. ROARMAP, the policy registry, has been rebuilt to record more policy detail and provide more extensive search functionality. Deposit rates were measured for articles in institutions' repositories and compared to the total number of WoS-indexed articles published from those institutions. Average deposit rate was over four times as high for institutions with a mandatory policy. Six positive correlations were found between deposit rates and (1) Must-Deposit; (2) Cannot-Waive-Deposit; (3) Deposit-Linked-to-Research-Evaluation; (4) Cannot-Waive-Rights-Retention; (5) Must-Make-Deposit-OA (after allowable embargo) and (6) Can-Waive-OA. For deposit latency, there is a positive correlation between earlier deposit and (7) Must-Deposit-Immediately as well as with (4) Cannot-Waive-Rights-Retention and with mandate age. There are not yet enough OA policies to test whether still further policy conditions would contribute to mandate effectiveness but the present findings already suggest that it would be useful for current and future OA policies to adopt the seven positive conditions so as to accelerate and maximise the growth of OA.Comment: 49 pages, 21 figures, 15 tables. Pasteur4OA Work Package 3 report: Open Access policies 201

Short form of the changes in outlook questionnaire: translation and validation of the Chinese version

Background: The Changes in Outlook Questionnaire (CiOQ) is a self-report instrument designed to measure both positive and negative changes following the experience of severely stressful events. Previous research has focused on the Western context. The aim of this study is to translate the short form of the measure (CiOQ-S) into simplified Chinese and examine its validity and reliability in a sample of Chinese earthquake survivors. Method: The English language version of the 10-item CiOQ was translated into simplified Chinese and completed along with other measures in a sample of earthquake survivors (n = 120). Statistical analyses were performed to explore the structure of the simplified Chinese version of CiOQ-S (CiOQ-SCS), its reliability and validity. Results: Principal components analysis (PCA) was conducted to test the structure of the CiOQ-SCS. The reliability and convergent validity were also assessed. The CiOQ-SCS demonstrated a similar factor structure to the English version, high internal consistency and convergent validity with measures of posttraumatic stress symptoms, anxiety and depression, coping and social support. Conclusion: The data are comparable to those reported for the original version of the instrument indicating that the CiOQ-SCS is a reliable and valid measure assessing positive and negative changes in the aftermath of adversity. However, the sampling method cannot permit us to know how representative our samples were of the earthquake survivor population

PID and PID-like controller design by pole assignment within D-stable regions

This paper presents a new PID and PID-like controller design method that permits the designer to control the desired dynamic performance of a closed-loop system by first specifying a set of desired D-stable regions in the complex plane and then running a numerical optimisation algorithm to find the controller parameters such that all the roots of the closed-loop system are within the specified regions. This method can be used for stable and unstable plants with high order degree, for plants with time delay, for controller with more than three design parameters, and for various controller configurations. It also allows a unified treatment of the controller design for both continuous and discrete systems. Examples and comparative simulation results are pro-vided to illustrate its merit