Image segmentation using voronoi polygons and MCMC, with application to muscle fibre images

We investigate a Bayesian method for the segmentation of muscle fibre images. The images are reasonably well approximated by a Dirichlet tessellation, and so we use a deformable template model based on Voronoi polygons to represent the segmented image. We consider various prior distributions for the parameters and suggest an appropriate likelihood. Following the Bayesian paradigm, the mathematical form for the posterior distribution is obtained (up to an integrating constant). We introduce a Metropolis-Hastings algorithm and a reversible jump Markov chain Monte Carlo algorithm (RJMCMC) for simulation from the posterior when the number of polygons is fixed or unknown. The particular moves in the RJMCMC algorithm are birth, death and position/colour changes of the point process which determines the location of the polygons. Segmentation of the true image was carried out using the estimated posterior mode and posterior mean. A simulation study is presented which is helpful for tuning the hyperparameters and to assess the accuracy. The algorithms work well on a real image of a muscle fibre cross-section image, and an additional parameter, which models the boundaries of the muscle fibres, is included in the final model.     

American families: trends and correlates

Discussion focused on the nature of the roles of the family, a review of the major demographic changes (marriage, cohabitation, nonfamily households, remarriage, fertility, teenage pregnancy, and female employment) affecting the American family in the past decades, and the nature of the impact on women, men, and children. There were four major trends identified: 1) increased proportions of children living in single-parent families due to high rates of divorce and increased childbearing outside of marriage; 2) increased proportions of adults in nontraditional living arrangements; 3) increased female labor force participation during all stages of the life cycle; and 4) decreased proportions of children and increased proportions of older people out of total population due to declining mortality and fertility rates. Family formation arises out of childbearing and childrearing roles, the need for companionship and emotional support, and the opportunities for specialization and trade, and the economies of scale. The costs of family living may include the potential for disagreement, conflict, loss of privacy, and time and money. There were a number of reasons identified for not maintaining traditional families consisting of a married couple with children. The trends were for later age at marriage: 24.4 years in 1992 for women, increased cohabitation (almost 50% cohabiting prior to first marriage in 1985-86), decreased number of married couple households, and increased number of adults in non-family households. The divorce rate has risen over the past 100 years with peaks in the 1970s; the reasons were identified as increased baby boomers and new marriages, increased labor participation of women, and changes in gender roles. The stabilization and slight decline in rates may be due to a natural leveling, the likelihood of greater stability within new marriages, and the aging of the baby boomers. An anticipated increase in divorce rates in the future was also justified. Remarriage rates varied by gender, age at separation/divorce, presence of children, race/ethnicity, and education. Fertility remained stable at 1.8 during the late 1970s and early 1980s and increased slightly to 2.0 in 1989. IN 1990, there were 25% out-of-wedlock births compared to 5% in 1960. About 12% of births in 1989 were to teenagers. There has been an increase in female-headed households, the median income of which in 1992 was $13,012, or 33% of married couple income.     

Senior Services that Support Housing First in Metro Vancouver

Housing First is a model and philosophy for housing homeless people in immediate and permanent housing. In order to implement and deliver Housing First, research is essential to understand the system of support services as they currently exist. Guided by principles of community-based participatory research, this paper presents the findings from a senior-focused deliberative dialogue workshop in Metro Vancouver, Canada. Participants (16 service providers and 1 service recipient) identified services and resources available to support seniors in maintaining housing and barriers and facilitators for accessing services. Broadly, data were organized into seven themes: (1) Housing; (2) Home support; (3) Transportation; (4) Information availability, accessibility, and navigation; (5) Cultural diversity; (6) Discrimination; and (7) Funding and financial support. Results found that affordable housing that adapts to changing health conditions, income supports, health services, homecare, transportation, and culturally appropriate and nondiscriminatory informational resources are among the supports most needed for persons as young as 50 years old to succeed under the Housing First model in Metro Vancouver. Barriers to Housing First service provision, including rigid eligibility criteria for chronically and episodically homeless, should be revised to better support the growing number of older adults who are newly entering homelessness in Metro Vancouver.     

How does paid work affect who does the childcare? An analysis of the time use of Australian couples

This paper analyzes the effect of paid work by coupled parents of young children on the joint decisions to spend time engaged in childcare. We explore this using Australian Time-Use Survey data from 2006. We examine the effect of paid work in terms of the effect that total work time on a given day has on the amount of time spent on childcare; the allocation of time on activities across work and non-work days; and the effect of non-traditional work hours. The results show that mothers perform a large share of childcare, irrespective of their earning power or their partner’s availability to take on some of these tasks. The use of formal and informal childcare by others allows the mother to balance the competing demands of work and her own childcare; an effect that does not hold for fathers. These effects on childcare are also almost solely concentrated in the routine component of childcare (e.g. preparing meals, changing nappies), with each parent ‘protecting’ interactive childcare from the effect of both paid work and the relative availability of their partner to take on some of this childcare.     

Dealing with separation or near-to-separation in the model for multinomial response with application to childhood health seeking behavior data from a complex survey

Separation or monotone-likelihood can be observed in fitting process of a multinomial logistic model using maximum likelihood estimation (MLE) when sample size is small and/or one of the outcome categories is rare and/or there is one or more influential covariates, resulting in infinite or biased estimate of at least one regression coefficient of the model. This study investigated empirically to identify the optimal data condition to define both ‘separation’ and ‘near-to-separation’ (partial separation) and explored their consequences in MLE and provided a solution by applying a penalized likelihood approach, which has been proposed in the literature, by adding a Jeffreys prior-based penalty term to the original likelihood function to remove the first-order bias in the MLEs of the multinomial logit model via equivalent Poisson regression. Furthermore, the penalized estimating equation (PMLE) is extended to a weighted estimating equation allowing for survey-weight for analyzing data from a complex survey. The simulation study suggests that the PMLE outperforms the MLE by providing smaller amount of bias and mean squared of error and better coverage. The methods are applied to analyze data on choice of health facility for treatment of childhood diseases.     

Which factors explain the decline in infant and child mortality in Matlab,Bangladesh?

Infant and child mortality rates have decreased substantially in Matlab, Bangladesh, as they have in many developing areas. We use data from the Matlab Demographic Surveillance System on nearly 94,000 singleton live births that occurred between 1987 and 2002 to investigate the extent to which the change in mortality over this period can be explained by changes in reproductive patterns and socio-economic characteristics. We estimate Cox proportional hazards models for four subperiods of infancy and childhood. Changes over time in reproductive patterns (maternal age, parity, and pregnancy spacing) and in the socio-economic characteristics we consider (e.g. maternal education, SES) explain between 10 and 40% of the decline in mortality rates. Changes in maternal education explain the largest portion of the reduction in infant and child mortality over time that we are able to explain, followed by reductions in the incidence of short interpregnancy intervals. In the other direction, decreases in fertility over time led to increases in the proportion of births that were first births, putting upward pressure on mortality.

Convention on the Elimination of Discrimination Against Women and the Prospect of Development of Muslim Personal Law in Singapore

This paper examines Singapore's partial reservations to Articles 2 and 16 of the United Nations Convention on the Elimination of Discrimination against Women (CEDAW). It contends that the reservations justified on the basis of protecting the rights of the Muslim minority community to practice its personal law has unwittingly impeded the potential of reviewing and addressing significant gaps and limitations in the ways in which the laws are conceived and administered. More pertinently, the policy reinforces the dominance of traditionalism in the thinking of dominant stakeholders of the law. Taking the standpoint that the values of equality and non-discrimination on the basis of gender espoused by CEDAW are compatible with the objectives of Muslim law, this paper maintains that ratifying the relevant Articles of CEDAW will strengthen the process of the development of the Muslim personal law and address essentialist presumptions of the law. This perspective departs from the dominant discourse on the Muslim law and CEDAW which is framed in terms of conflict and polarity between the law and human rights, religious law and women's rights, and universal values versus cultural relativism.     

A model-based concordance-type index for evaluating the added predictive ability of novel risk factors and markers in the logistic regression models

ABSTRACT

The Concordance statistic (C-statistic) is commonly used to assess the predictive performance (discriminatory ability) of logistic regression model. Although there are several approaches for the C-statistic, their performance in quantifying the subsequent improvement in predictive accuracy due to inclusion of novel risk factors or biomarkers in the model has been extremely criticized in literature. This paper proposed a model-based concordance-type index, C_K, for use with logistic regression model. The C_K and its asymptotic sampling distribution is derived following Gonen and Heller's approach for Cox PH model for survival data but taking necessary modifications for use with binary data. Unlike the existing C-statistics for logistic model, it quantifies the concordance probability by taking the difference in the predicted risks between two subjects in a pair rather than ranking them and hence is able to quantify the equivalent incremental value from the new risk factor or marker. The simulation study revealed that the C_K performed well when the model parameters are correctly estimated for large sample and showed greater improvement in quantifying the additional predictive value from the new risk factor or marker than the existing C-statistics. Furthermore, the illustration using three datasets supports the findings from simulation study.     

Nonparametric Bayes estimation of gap-time distribution with recurrent event data

Nonparametric Bayes (NPB) estimation of the gap-time survivor function governing the time to occurrence of a recurrent event in the presence of censoring is considered. In our Bayesian approach, the gap-time distribution, denoted by F, has a Dirichlet process prior with parameter α. We derive NPB and nonparametric empirical Bayes (NPEB) estimators of the survivor function F?=1?F and construct point-wise credible intervals. The resulting Bayes estimator of F? extends that based on single-event right-censored data, and the PL-type estimator is a limiting case of this Bayes estimator. Through simulation studies, we demonstrate that the PL-type estimator has smaller biases but higher root-mean-squared errors (RMSEs) than those of the NPB and the NPEB estimators. Even in the case of a mis-specified prior measure parameter α, the NPB and the NPEB estimators have smaller RMSEs than the PL-type estimator, indicating robustness of the NPB and NPEB estimators. In addition, the NPB and NPEB estimators are smoother (in some sense) than the PL-type estimator.     

Integration policy in Singapore: a transnational inclusion approach

A number of models of integration have been developed to highlight the experiences of immigration and integration in the Western world. However, the existing models do not adequately capture the complexities of contemporary international immigration and integration, especially the integration process in the light of migrant transnationalism in Asia. This study examines the models of integration through a case study of Singapore. This paper introduces a new concept ‘transnational inclusion’ to conceptualize Singapore's initiative to embrace its transnational global Singaporeans as well as its transnational immigrants, estimated to make up one-fourth of the total population. The paper shows that a transnational inclusion model of integration can provide better insights into the dynamics of transnationalism and integration in today's complex migration scenario. We point to Singapore's integration approach that regards integrating migrants into the different spheres of the society as a process rather than an end.