Nachruf auf Prof. Dr. Achim Schrader

Ohne Zusammenfassung     

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.     

Financial insecurity and risk experiences of justice involved persons with severe mental illness

More information is needed about the financial experiences of justice-involved persons with severe mental illness. Qualitative and quantitative methods were used to examine the financial resources, financial risk experiences, and financial literacy of a random sample of 12 mental health court participants. Mental health court participants had limited financial resources, frequently ran out of money, and had engaged very few financial tools to manage their money. Justice-involved persons with severe mental illness need financial management interventions to help develop strategies for managing depleted resources and to develop the financial resources needed to live in community settings.     

Changes in inequality and unemployment over the 1980s: comparative cross-national responses

This paper reviews the research evidence regarding high and persistent unemployment in the western European nations and widening inequality in the United States and selected European countries. It has been suggested that both of these problems are due to fundamental economic shifts in labor demand within the more industrialized world that have led to declines in the demand for less skilled workers: The effect on countries with more regulated labor markets was rising unemployment, while in less regulated labor markets it was rising wage inequality. The paper considers the evidence for this hypothesis, as well as the research questions and policy issues that it raises.The author thanks Rebecca London and Leslie Moscow for research assistance.     

The effects of poverty on sleep problems in Sweden

Does relative poverty measured as low disposable household income or the presence of personal financial crisis affect health measured in terms of self-reported sleep problems? If so, is this effect modified by macroeconomic conditions or life changes such as unemployment experience, divorce or limiting illness, and it is buffered by social networks or coping behavior such as smoking? These questions are studied on a representative sample of employed people aged 20-65 who participated in the Survey of Living Conditions conducted by Statistics Sweden for the years 1980-1981 (7180 people) and 1986-1989 (13,376 people). The results reveal a conditional relationship between poverty and sleep problems. Among men it is modified, in particular, by previous experience of unemployment. Among women strong social networks buffers the effect but smoking aggravates it. Men's sleep was affected more by poverty and unemployment in the late 1980s than in the earlier period.     

Inventory control in hospital blood banks

The delicate relationship between donors and the Transfusion Service in the U.K. implies a clear duty to make the best possible use of the limited blood supplies, and this turns attention upon the stocking policies adopted by Hospital Blood Banks. Whereas Blood Bank staff can obtain an intuitive grasp of the effects of various stock levels for the common bloods, this is not usually the case for the rare bloods which are more difficult to control. A policy decision has to be made which balances the conflicting stock requirements of maintaining a high availability and also low out-dating rates. A Markovian structure is exploited in this paper for this purpose and the effects of the key variables are shown to be interrelated. In any particular instance the form of the probability distribution of demand between replenishments, the scale of the throughput, the blood life in relation to the ordering interval, the fraction of blood transfused and the fraction of the replenishment order which is supplied to the Bank will together determine the form of the operating characteristics.     

Combinatorial analysis for route first-cluster second vehicle routing

Two Route first-cluster second vehicle routing algorithms are contrasted in the first section of the paper. Next, the ‘large’ number of feasible solutions to a multiple travelling salesman problem is established given that each salesman can visit any number of customers in a stated range. An approximate expression is given for the ‘small’ fraction of this solution space searched by a route first-cluster second vehicle routing heuristic. Nevertheless, this heuristic is seen to be a very efficient means of searching its solution space.