Horizontal and vertical island biogeography of arthropods on green roofs: a review

From an ecological perspective, urban green roofs can be viewed as green islands embedded in an urban matrix. Island biogeography theory suggests that species richness on an island is the outcome of dynamic equilibrium between immigration and extinction. Immigration is affected by the size of an island and distance of an island from a colonizing source. In the context of green roofs, building height and horizontal distance from green areas can potentially be a limiting factor for many species. Here, we considered two distance components of green roofs - vertical (building height) and horizontal (distance of building from open green areas). Based on island biogeography theory, we would expect species richness or community similarity to be negatively related to horizontal or vertical distances from colonizing sources. The green roof literature addressing such questions is currently sparse. In our review comprised of 10 studies, we were unable to identify consistent statistically significant richness-distance or community similarity-distance (vertical or horizontal) relationships. The absence of statistically significant relationships could be due in large part to low statistical power as a consequence of both the paucity of roofs and limited range of vertical distances in many of the existing studies. In addition, these roofs differ in numerous aspects (e.g. roof size, age, substrate type, plant composition and building height). The low number of replicates, combined with the lack of homogeneity among replicates combines to reduce statistical power and our ability to detect differences.     

Caregiving environment and socio-emotional development of foster-placed FASD-children

The study investigated the role of the postnatal caregiving environment in the socio-emotional development of children under the age of 16 who had been exposed to alcohol in utero and placed in foster family care (n = 38). Quantitative and qualitative methods of analysis were utilized. Based on psychological examinations, most of the children (76%) were reported to have at least one developmental problem; concentration, attention and language/speech problems being the most typical. The critical issues affecting children's development were 1) the range of somatic illnesses and disabilities that had impaired their functional capacity, 2) children's age at the time of the first placement and of entry into long-term foster family care, and 3) the number of traumatic experiences. Placement outside a biological family at an early age decreased, and traumatic experiences, illnesses and disabilities increased socio-emotional problems (including neuropsychological problems). Undiagnosed children had more behavioural problems measured by the Child Behaviour Checklist than children with foetal alcohol syndrome, but in general the differences between the diagnostic categories were small. Damage to the central nervous system by prenatal alcohol exposure together with lack of constructive early interaction seems to launch a process which may make it difficult for the child to form a coherent picture of him-/herself and to control his/her feelings and behaviour.     

Optimal treatment allocation and study duration for trials with discrete-time survival endpoints

Studies on event occurrence may be conducted in experiments, where one or more treatment groups are compared to a control group. Most of the randomized trials are designed with equally sized groups, but this design is not always the best one. The statistical power of the study may be larger with unequal sample sizes, and researchers may want to place more participants in one group relative to the other due to resource constraints or costs. The optimal designs for discrete-time survival endpoints in trials with two groups, where different proportions of subjects in the experimental group are taken into account, can be studied using the generalized linear model. Applying a cost function, the optimal combination of the number of subjects and periods in the study and the optimal allocation ratio can be found. It is observed that the ratio of the recruitment costs in both groups, the ratio of the recruitment cost in the control group to the cost of obtaining a measurement, the size of the treatment effect, and the shape of the survival distribution have the greatest influence on the optimal design.     

Optimizing trial design in pharmacogenetics research: comparing a fixed parallel group,group sequential,and adaptive selection design on sample size requirements

Two‐stage clinical trial designs may be efficient in pharmacogenetics research when there is some but inconclusive evidence of effect modification by a genomic marker. Two‐stage designs allow to stop early for efficacy or futility and can offer the additional opportunity to enrich the study population to a specific patient subgroup after an interim analysis. This study compared sample size requirements for fixed parallel group, group sequential, and adaptive selection designs with equal overall power and control of the family‐wise type I error rate. The designs were evaluated across scenarios that defined the effect sizes in the marker positive and marker negative subgroups and the prevalence of marker positive patients in the overall study population. Effect sizes were chosen to reflect realistic planning scenarios, where at least some effect is present in the marker negative subgroup. In addition, scenarios were considered in which the assumed ‘true’ subgroup effects (i.e., the postulated effects) differed from those hypothesized at the planning stage. As expected, both two‐stage designs generally required fewer patients than a fixed parallel group design, and the advantage increased as the difference between subgroups increased. The adaptive selection design added little further reduction in sample size, as compared with the group sequential design, when the postulated effect sizes were equal to those hypothesized at the planning stage. However, when the postulated effects deviated strongly in favor of enrichment, the comparative advantage of the adaptive selection design increased, which precisely reflects the adaptive nature of the design. Copyright © 2013 John Wiley & Sons, Ltd.     

The net asset value and stock prices of European real estate companies

The frequently large divergences between share price and net asset value (NAV) of listed real estate companies have been a key topic in real estate research for many years. However, previous research has mainly focused on the U.S. market, concentrating on companies’ performance ratios related to information from balance sheet statements and/or income statements as well as information from the stock market, and its results are not satisfying. This study, on the other hand, focuses on the European real estate market and presents a semi-rational model for explaining NAV spreads, taking into account performance ratios and market sentiment simultaneously. It appears that market sentiment in particular substantially improves the model, which explains more than 76% of the NAV spread. Thus, the developed model constitutes a significant improvement over previous studies on the explanation of NAV spreads.     

Stakeholder Knowledge and Behavioral Integration in Boards of Social Enterprises: A Team Production Approach

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - The social entrepreneurship literature increasingly acknowledges that the board of directors is of major importance in...     

Practices of Dual Earner Couples Successfully Balancing Work and Family

Researchers have long explored conflict and strain in dual-career couples. Recently, the focus has begun to shift toward documenting the adaptive strategies of dual-earner couples in balancing family and work. The current study investigates workplace practices perceived as supportive in balancing work and family. Respondents were middle-class, dual-earner couples (N=47) who described themselves as successful in balancing family and work. These supportive practices include: flexible work scheduling, non-traditional work hours, professional/job autonomy, working from home, supportive supervisors, supportive colleagues and supervisees, and the ability to set firm boundaries around work. Additionally, many participants describe their efforts to actively secure employment at workplaces that offered family–friendly alternatives, and describe the tradeoffs they are willing to make.     

Peer Contacts of 15-Month-olds in Childcare: Links With Child Temperament, Parent–Child Interaction and Quality of Childcare

Seventy 15‐month‐old children were observed during 90 minutes of free play with their peers in childcare centers. The study aimed to describe individual differences in the children's contacts with peers and to explain the individual differences in relation to: (1) child temperament, (2) the quality of parental behavior toward the child and (3) the quality of the professional childcare environment. Three distinct peer contact factors emerged from our analyses; one reflects children's involvement in peer contacts initiated by peers and two reflect the positive and negative contacts initiated by the target children themselves. Children in groups with more children per caregiver were found to be involved in more contacts initiated by peers. Children with a relatively difficult temperament were less involved in contacts initiated by peers although only in cases of lower quality childcare, as assessed using the infant/toddler environment rating scale. Boys initiated significantly more negative contacts with peers than girls. In addition, more peer‐directed negative initiatives were observed in lower quality childcare.     

Bandwidth selection for kernel density estimation: a review of fully automatic selectors

On the one hand, kernel density estimation has become a common tool for empirical studies in any research area. This goes hand in hand with the fact that this kind of estimator is now provided by many software packages. On the other hand, since about three decades the discussion on bandwidth selection has been going on. Although a good part of the discussion is about nonparametric regression, this parameter choice is by no means less problematic for density estimation. This becomes obvious when reading empirical studies in which practitioners have made use of kernel densities. New contributions typically provide simulations only to show that the own selector outperforms some of the existing methods. We review existing methods and compare them on a set of designs that exhibit few bumps and exponentially falling tails. We concentrate on small and moderate sample sizes because for large ones the differences between consistent methods are often negligible, at least for practitioners. As a byproduct we find that a mixture of simple plug-in and cross-validation methods produces bandwidths with a quite stable performance.