Use of Risk Assessment and Likelihood Estimation to Analyze Spatial Distribution Pattern of Respiratory Infection Cases

Obvious spatial infection patterns are often observed in cases associated with airborne transmissible diseases. Existing quantitative infection risk assessment models analyze the observed cases by assuming a homogeneous infectious particle concentration and ignore the spatial infection pattern, which may cause errors. This study aims at developing an approach to analyze spatial infection patterns associated with infectious respiratory diseases or other airborne transmissible diseases using infection risk assessment and likelihood estimation. Mathematical likelihood, based on binomial probability, was used to formulate the retrospective component with some additional mathematical treatments. Together with an infection risk assessment model that can address spatial heterogeneity, the method can be used to analyze the spatial infection pattern and retrospectively estimate the influencing parameters causing the cases, such as the infectious source strength of the pathogen. A Varicella outbreak was selected to demonstrate the use of the new approach. The infectious source strength estimated by the Wells‐Riley concept using the likelihood estimation was compared with the estimation using the existing method. It was found that the maximum likelihood estimation matches the epidemiological observation of the outbreak case much better than the estimation under the assumption of homogeneous infectious particle concentration. Influencing parameters retrospectively estimated using the new approach can be used as input parameters in quantitative infection risk assessment of the disease under other scenarios. The approach developed in this study can also serve as an epidemiological tool in outbreak investigation. Limitations and further developments are also discussed.     

Solving the Multidimensional Assignment Problem by a Cross-Entropy method

The Multidimensional Assignment Problem (MAP) is a higher dimensional version of the linear assignment problem, where we find tuples of elements from given sets, such that the total cost of the tuples is minimal. The MAP has many recognized applications such as data association, target tracking, and resource planning. While the linear assignment problem is solvable in polynomial time, the MAP is NP-hard. In this work, we develop a new approach based on the Cross-Entropy (CE) methods for solving the MAP. Exploiting the special structure of the MAP, we propose an appropriate family of discrete distributions on the feasible set of the MAP that allow us to design an efficient and scalable CE algorithm. The efficiency and scalability of our method are proved via several tests on large-scale problems with up to 5 dimensions and 20 elements in each dimension, which is equivalent to a 0–1 linear program with 3.2 millions binary variables and 100 constraints.     

Parental self‐esteem,parent–child relationships,and authoritative parenting of Chinese migrant parents of left‐behind children: Implications for social policy and services

In this study, we aimed to examine whether and how parental self‐esteem and parent–child relationships interact and associate with the authoritative parenting of Chinese rural‐to‐urban migrant mothers and fathers of left‐behind children. Results from a cross‐sectional survey of 295 Chinese migrant parents living in Shenzhen revealed no statistically significant differences between migrant mothers and fathers in parental self‐esteem, parent–child relationships, and authoritative parenting. Both parental self‐esteem and parent‐child relationships had positive associations with authoritative parenting among two groups of respondents; however, the perceived parent–child relationship quality was a more important predictor than parental self‐esteem. There was also an interaction effect between parental self‐esteem and parent–child relationships on migrant mothers’ authoritative parenting. The findings indicate that migrant parents’ perception of their encounters with their children has a profound influence on their parenting behaviors. Social services should, thus, be provided to strengthen both virtual and face‐to‐face parent–child interactions via mobile phone parenting and periodic visits. New policies should be developed to provide migrant parents with more options regarding family reunion.     

Learning pattern of social work students: a longitudinal study

Research on learning patterns of social work students is scare. This longitudinal study addresses this issue by employing mixed methods of quantitative and qualitative study design to understand the learning pattern of students throughout their undergraduate social work studies. Six rounds of quantitative data collected by structured questionnaires and four rounds of qualitative data collected by focus group interviews have been conducted at an interval of every 6 months to track the learning pattern and to evaluate the continuous impacts of social work education on students. Results indicate that although students’ evaluation on the curriculum was positive and with significant difference in mean scores, paired sample t-tests found no significant difference between time 1 and 6 of all outcome variables. With regard to students’ change in attitude, acquisition of knowledge and skills, results indicate a ‘U-shape’ trend and a fluctuating learning pattern with a rebound in different outcome variables toward the end of the three-year study. Qualitative data echoes the findings and reveals that students go through the confused freshman stage, to disillusioned in practicum and finally with enriching experience upon graduation. The paper discusses meanings and implications of student learning pattern to social work education.     

Parent–child relationships,friendship networks,and developmental outcomes of economically disadvantaged youth in Hong Kong

This research investigates factors conducive to the thriving of economically disadvantaged young people in Hong Kong. In particular, we examine ways in which the parent–child relationship and friendship networks, as the principal sources of support during the transition from childhood to adulthood, influence the developmental outcomes of this group of young people with regard to their mental health, positive identity, behavioral adjustment, resilience and academic achievement. Based on a survey of 479 young people recruited from community-based youth-service centers located in different districts of Hong Kong, the results of the present research support the hypotheses that parent–child relationships and friendship networks have significant positive effects on youth development among low-income young people. Our results also show that, when compared with friendship networks, the parent–child relationship is a stronger predictor of youth development, that is, a stronger parent–child relationship tends to correspond to a better developmental outcome. Moreover, our research provides empirical evidence regarding the influence that parents can have on shaping the quality of young people's friendship networks. The implications of our findings, both for future research and for service delivery to promote the well-being of economically disadvantaged young people, are discussed.     

Corporate Governance und Eigenkapitalkosten - Bestandsaufnahme des Schrifttums unter besonderer Ber��cksichtigung des Informationsaspektes und Forschungsperspektiven

The present paper provides an overview of research concerning the relationship between corporate governance and the cost of equity capital. The purpose is to explore whether and to what extent corporate governance attributes manifest in firms?? cost of capital. Since the separation of ownership and control is seen as the starting point for the academic thinking on this issue, the term of corporate governance from a shareholder perspective is discussed in more detail. Apart from this terminological discussion the emphasis of this paper lies on the critical review of theoretical and empirical literature. In conducting this review, empirical concepts measuring the relevant dimensions and their potential limitations are explained. Based on these limitations I suggest opportunities for expanding research on the relationship between corporate governance and cost of equity capital, thereby showing future research directions.     

On the Hardness of Approximating the Min-Hack Problem

We show several hardness results for the Minimum Hacking problem, which roughly can be described as the problem of finding the best way to compromise a target node given a few initial compromised nodes in a network. We give several reductions to show that Minimum Hacking is not approximable to within where δ = 1− ^c n, for any c < 1/2. We also analyze some heuristics on this problem.