A 75° Angle Constraint for Plane Minimal T1 Trees

In this paper it is shown that the minimum angle between any 2 edges of an Euclidean plane minimal T1 tree, or 3-size Steiner tree, is at least 75°.     

Multiethnic Children Portrayed in Children's Picture Books

The portrayal of multiethnic children in picture books provides a unique opportunity for social workers, other helping professionals, and parents to work more effectively with a population of preschool multiethnic children. Twenty-two picture books portraying multiethnic children and their families are identified and evaluated. Their relevance for social work practice with children and families is discussed.     

A marginal regression model for multivariate failure time data with a surviving fraction

A marginal regression approach for correlated censored survival data has become a widely used statistical method. Examples of this approach in survival analysis include from the early work by Wei et al. (J Am Stat Assoc 84:1065–1073, 1989) to more recent work by Spiekerman and Lin (J Am Stat Assoc 93:1164–1175, 1998). This approach is particularly useful if a covariate’s population average effect is of primary interest and the correlation structure is not of interest or cannot be appropriately specified due to lack of sufficient information. In this paper, we consider a semiparametric marginal proportional hazard mixture cure model for clustered survival data with a surviving or “cure” fraction. Unlike the clustered data in previous work, the latent binary cure statuses of patients in one cluster tend to be correlated in addition to the possible correlated failure times among the patients in the cluster who are not cured. The complexity of specifying appropriate correlation structures for the data becomes even worse if the potential correlation between cure statuses and the failure times in the cluster has to be considered, and thus a marginal regression approach is particularly attractive. We formulate a semiparametric marginal proportional hazards mixture cure model. Estimates are obtained using an EM algorithm and expressions for the variance–covariance are derived using sandwich estimators. Simulation studies are conducted to assess finite sample properties of the proposed model. The marginal model is applied to a multi-institutional study of local recurrences of tonsil cancer patients who received radiation therapy. It reveals new findings that are not available from previous analyses of this study that ignored the potential correlation between patients within the same institution.     

Disconnected Geography: A Spatial Analysis of Disconnected Youth in the United States

Since the Great Recession, US policy and advocacy groups have sought to better understand its effect on a group of especially vulnerable young adults who are not enrolled in school or training programs and not participating in the labor market, so called ‘disconnected youth.’ This article distinguishes between disconnected youth and unemployed youth and examines the spatial clustering of these two groups across counties in the US. The focus is to ascertain whether there are differences in underlying contextual factors among groups of counties that are mutually exclusive and spatially disparate (non-adjacent), comprising two types of spatial clusters – high rates of disconnected youth and high rates of unemployed youth. Using restricted, household-level census data inside the Census Research Data Center (RDC) under special permission by the US Census Bureau, we were able to define these two groups using detailed household questionnaires that are not available to researchers outside the RDC. The geospatial patterns in the two types of clusters suggest that places with high concentrations of disconnected youth are distinctly different in terms of underlying characteristics from places with high concentrations of unemployed youth. These differences include, among other things, arrests for synthetic drug production, enclaves of poor in rural areas, persistent poverty in areas, educational attainment in the populace, children in poverty, persons without health insurance, the social capital index, and elders who receive disability benefits. This article provides some preliminary evidence regarding the social forces underlying the two types of observed geospatial clusters and discusses how they differ.     

The potential for mycorrhizae to improve green roof function

The selection of plant species for use on green roofs has been based primarily on their ability to cope with the harsh climatic conditions of the urban rooftop environment. However, green roof plants must also survive in engineered substrates that often lack organic material and beneficial soil microorganisms such as mycorrhizal fungi. We review the literature on mycorrhizae in the context of green roof ecosystems, identifying aspects of green roof functioning that could be enhanced through the integration of mycorrhizal fungi. Although relatively few studies have addressed the influence of mycorrhizal symbiosis on green roof plants specifically, we include information from a variety of naturally occurring habitats with analogous growing conditions. The available literature suggests that the incorporation of mycorrhizal fungi can improve a number of green roof functional attributes, including plant diversity, drought resilience, leachate quality, nutrient use efficiency and carbon sequestration, all while reducing the need for external nutrient inputs. We present evidence that mycorrhizal fungi are of general benefit to green roof ecosystems, and can be effectively integrated into green roof design. We recommend methods for this integration and propose future research directions.     

Automatically Detected Nonverbal Behavior Predicts Creativity in Collaborating Dyads

In the current study we administered a creative task in which two people collaboratively generated novel strategies to conserve resources. During this task, the nonverbal behavior of 104 participants in 52 pairs was tracked and recorded using the Kinect computer vision algorithm. We created a measure of synchrony by correlating movements between the two dyad members, and showed that synchrony occurred—that is, correlations decreased when we increased delay between the recorded movements of pair members. We also demonstrated a link between nonverbal synchrony and creativity, as operationalized by the number of new, valid ideas produced. Linear correlations demonstrated a significant relationship between synchrony and creativity. Finally, models using synchrony scores as input predicted whether dyads were high or low in creativity with a success rate as high as 86.7 % in the more exclusive subsets. We discuss implications for methodological approaches to measuring nonverbal behavior and synchrony, and suggest practical applications which can leverage the current findings.     

Bidirectional longitudinal associations of parent and child health following the BP Deepwater Horizon oil spill

This study (1) assessed whether parent health mediated associations between exposures to the 2010 BP Deepwater Horizon oil spill (BP-DHOS) and child health, and whether child health mediated associations between BP-DHOS exposures and parent health; and (2) assessed bidirectional longitudinal associations between parent health and child health following the BP-DHOS. The study used three waves of panel data (2014, 2016, and 2018) from South Louisiana communities highly impacted by the BP-DHOS. Parents with children (aged 4–18 at the time of the interview) were interviewed based on a probability sample of households. Focal measures included economic and physical BP-DHOS exposures, self-reported parent health, and parent-reported child health. Health measures were gathered at three time points. The analyses included mediation analysis and estimating and comparing effect sizes of longitudinal cross-lagged effects between parent health and child health. Results showed that parent health partly mediated associations between BP-DHOS exposures and child health, and that child health partly mediated associations between BP-DHOS exposures and parent health. Paths from prior waves of parent health to subsequent waves of child health were positive and statistically significant as were paths from prior waves of child health to subsequent waves of parent health. The differences in size of the child-to-parent health effects and the parent-to-child health effects were not statistically significant. This study’s results extend evidence for the post-disaster effect of parent health on child health and the effects of child health on parent health. These findings support the contention that harm to the health of one’s family member following disasters operates as a form of resource loss deleterious to one’s health.

     

Housing services for child welfare-involved families: an initial evaluation using observational data

This study evaluated the impact of housing services among child welfare-involved families using observational data. Propensity score matching with data from the National Survey of Child and Adolescent Well-Being compared intact families (n = 183) who received housing services 12 months after initial investigation to nontreated families balanced on characteristics at the time of investigation. Results suggested that general housing services failed, on average, to effectively address the needs of inadequately housed families.