Exclusion and vulnerability on public transit: experiences of transit dependent riders in Portland,Oregon

In urban areas, the inequitable distribution of transit systems and services has been shown to reproduce safety and environmental risks – potentially exacerbating preexisting inequities. Thus, how vulnerable populations access and utilize public transportation is of critical concern to urban scholars. This paper utilizes focus group data to explore how transit-dependent (particularly low-income) riders engage with the public transit system in Portland, Oregon. We illustrate specific ways in which transit-dependent riders experience marginalization and exclusion. We find that certain groups, particularly mothers with young children and those with disabilities are not well served by a public infrastructure oriented toward an ‘ideal rider’ who is an economically stable, able-bodied, white, male commuter. We conclude that a public infrastructure meant to serve all riders equitably, yet which fails to consider the unique experiences of marginalized transit users risks further amplifying existing social vulnerabilities and reinforcing gender, racial, and class inequalities.     

The impact of mortality development on the number of centenarians in England and wales

The world is ageing both at an individual and a population level, and population ageing is truly a global phenomenon. Life expectancies at birth have increased at the global level from 47 years in the mid-20th century to around 70 years today, and are expected to rise to 76 years by the mid-21st century. The proportion of the world’s population aged 60 years and over has increased from 8 % in the mid-20th century to 12 %, and by 2050 it is expected to reach 21 %. The emergence of large numbers of centenarians has accompanied this development. This paper outlines this emergence historically and the likely growth in the number of centenarians in the 21st century, in particular in England and Wales, analysing mortality trends since 1840 and the rise in the number of centenarians in the 20th and 21st centuries. The number of centenarians in England and Wales increased from around 160 in 1922 to almost 12,500 by 2012, but if mortality at all ages had remained constant from 1912 to 2012, then by 2012 the number of centenarians would only have been around 720. By 2100, the number of centenarians is expected to reach around 1.4 million, but if future mortality at all ages were to remain constant, then by 2100 the number of centenarians would be around 78,000. However, if predicted mortality for those aged 55 years and over was to decrease by an additional 5 % every 5 years until 2100, then the number of centenarians in England and Wales would reach around 1.8 million by the end of the century.     

The Slaughtered and the Survivors: Collaboration Between Social Economy Organizations as a Key to Success in Times of Financial Crisis

The objective of this study is to analyze the aspects that allowed a critical part of Social Economy Organizations (SEOs) to survive a recession period, especially participation in collaborative networks. The financial stress of an SEO will depend on the resources and capabilities available to the organization. To analyze the financial stress of Spanish SEOs, we defined a sample of 714 SEOs. Approximately half of these organizations suffered from financial stress in the analyzed period (2009–2012). The results obtained in this study reveal the existence of three factors that distinguish organizations under financial stress: (a) a high dependence on government funding; (b) changes in the relationship between staff and volunteers; and (c) a lack of access to markets. The combination of these three elements results in an unsustainable situation for the organization. The development of a collaborative profile increases the SEO’s probability of surviving the adverse manifestations of its environment.     

Improved bridge constructs for stochastic differential equations

We consider the task of generating discrete-time realisations of a nonlinear multivariate diffusion process satisfying an Itô stochastic differential equation conditional on an observation taken at a fixed future time-point. Such realisations are typically termed diffusion bridges. Since, in general, no closed form expression exists for the transition densities of the process of interest, a widely adopted solution works with the Euler–Maruyama approximation, by replacing the intractable transition densities with Gaussian approximations. However, the density of the conditioned discrete-time process remains intractable, necessitating the use of computationally intensive methods such as Markov chain Monte Carlo. Designing an efficient proposal mechanism which can be applied to a noisy and partially observed system that exhibits nonlinear dynamics is a challenging problem, and is the focus of this paper. By partitioning the process into two parts, one that accounts for nonlinear dynamics in a deterministic way, and another as a residual stochastic process, we develop a class of novel constructs that bridge the residual process via a linear approximation. In addition, we adapt a recently proposed construct to a partial and noisy observation regime. We compare the performance of each new construct with a number of existing approaches, using three applications.     

Estimating large-scale general linear and seemingly unrelated regressions models after deleting observations

A new numerical method to solve the downdating problem (and variants thereof), namely removing the effect of some observations from the generalized least squares (GLS) estimator of the general linear model (GLM) after it has been estimated, is extensively investigated. It is verified that the solution of the downdated least squares problem can be obtained from the estimation of an equivalent GLM, where the original model is updated with the imaginary deleted observations. This updated GLM has a non positive definite dispersion matrix which comprises complex covariance values and it is proved herein to yield the same normal equations as the downdated model. Additionally, the problem of deleting observations from the seemingly unrelated regressions model is addressed, demonstrating the direct applicability of this method to other multivariate linear models. The algorithms which implement the novel downdating method utilize efficiently the previous computations from the estimation of the original model. As a result, the computational cost is significantly reduced. This shows the great usability potential of the downdating method in computationally intensive problems. The downdating algorithms have been applied to real and synthetic data to illustrate their efficiency.     

Generalizing the standardized hazard ratio to multivariate proportional hazards regression,with an application to clinical~genomic studies

The standardized hazard ratio for univariate proportional hazards regression is generalized as a scalar to multivariate proportional hazards regression. Estimators of the standardized log hazard ratio are developed, with corrections for bias and for regression to the mean in high-dimensional analyses. Tests of point and interval null hypotheses and confidence intervals are constructed. Cohort sampling study designs, commonly used in prospective–retrospective clinical genomic studies, are accommodated.     

Racial/Ethnic Disparities in Mental Health Service Use for Older Foster Youth and Foster Care Alumni

Studies have shown that foster care alumni have disproportionally high rates of poor mental health outcomes compared to the general population. The purpose of this study was to examine differences in mental health service use for Latino, African American, and White youth while in foster care and upon exit from the foster care system. Secondary data were used to identify youth 1 year prior to exiting the foster care system (N?=?934) and 1 year after exit from the foster care system (N?=?433). Racial/ethnic disparities in mental health service use upon exit from the foster care system were found, with Latino youth using the least amount of services after foster care exit. Racial/ethnic service disparities in type of services used were also found. Findings suggest that a lack of support (e.g., mandatory or voluntary) may be significant in overcoming challenges in the continuation or disruption of services.