The Stackelberg minimum spanning tree game on planar and bounded-treewidth graphs

The Stackelberg Minimum Spanning Tree Game is a two-level combinatorial pricing problem played on a graph representing a network. Its edges are colored either red or blue, and the red edges have a given fixed cost, representing the competitor’s prices. The first player chooses an assignment of prices to the blue edges, and the second player then buys the cheapest spanning tree, using any combination of red and blue edges. The goal of the first player is to maximize the total price of purchased blue edges. We study this problem in the cases of planar and bounded-treewidth graphs. We show that the problem is NP-hard on planar graphs but can be solved in polynomial time on graphs of bounded treewidth.     

A Spatio‐Temporal Exposure‐Hazard Model for Assessing Biological Risk and Impact

We developed a simulation model for quantifying the spatio‐temporal distribution of contaminants (e.g., xenobiotics) and assessing the risk of exposed populations at the landscape level. The model is a spatio‐temporal exposure‐hazard model based on (i) tools of stochastic geometry (marked polygon and point processes) for structuring the landscape and describing the exposed individuals, (ii) a dispersal kernel describing the dissemination of contaminants from polygon sources, and (iii) an (eco)toxicological equation describing the toxicokinetics and dynamics of contaminants in affected individuals. The model was implemented in the briskaR package (b iological risk a ssessment with R ) of the R software. This article presents the model background, the use of the package in an illustrative example, namely, the effect of genetically modified maize pollen on nontarget Lepidoptera, and typical comparisons of landscape configurations that can be carried out with our model (different configurations lead to different mortality rates in the treated example). In real case studies, parameters and parametric functions encountered in the model will have to be precisely specified to obtain realistic measures of risk and impact and accurate comparisons of landscape configurations. Our modeling framework could be applied to study other risks related to agriculture, for instance, pathogen spread in crops or livestock, and could be adapted to cope with other hazards such as toxic emissions from industrial areas having health effects on surrounding populations. Moreover, the R package has the potential to help risk managers in running quantitative risk assessments and testing management strategies.     

浪漫主义解释学与施莱尔马赫

对西方浪漫主义解释学的分析应该从阿斯特、施莱格尔开始,最后过渡并集中在施莱尔马赫的身上。施莱尔马赫关于误解的普遍性、严格的解释学实践、读者能够比作者更好地理解其作品、解释学的辩证法等思想的重要内涵,暗示了它们之间有一种内在联系。从这些内容上,我们可以具体看到,施莱尔马赫在近代解释学中真正的革命意义之所在,以及以他为代表的浪漫主义的普遍解释学对理性主义的普遍解释学的超越。     

Supermarkets in Low‐income Mediterranean Countries: Impacts on Horticulture Systems

In the past decade, supermarkets have spread rapidly in the low‐income Mediterranean countries. Focusing on a case of advanced supermarket diffusion (Turkey) and of incipient diffusion (Morocco), this article examines this development and its impact on the fresh fruits and vegetable sector, emphasising the level of backward integration by the retailers into the supply chain and the type of retailer‐supplier governance structure. Both countries' food sectors resemble those of Central and Eastern Europe (CEE) transition countries in their shift from a mixed traditional/staterun/owned retail system to a liberalised system. Moreover, Turkey is also on the road to joining the European Union, and is classed in policy discussions with the CEE candidates.     

Adoption in South Africa: trends and patterns in social work practice

This paper reports findings from a research study on adoption in South Africa conducted in 2009. The research included secondary data analysis of the South African National Adoption Register to establish trends and patterns of adoption in South Africa between 2004 and 2009, and primary data collection through qualitative interviews with key informants in public and private social welfare services to explore attitudes, knowledge and experiences of social work practice related to adoption. The quantitative findings report the number of national and international adoptions along with trends and socio‐demographic patterns of national adoptions. Qualitative findings report on social work practice, systemic barriers and social worker attitudes as barriers to improved social work practice around national adoptions. The paper highlights comparisons to adoption literature in the USA, a country with a similar legislative framework and cultural complexities, but significantly more resources for implementation. Recommendations are offered for social work practice, national data collection and policy implementation efforts to support efforts to increase adoption.     

The how and the why: Competences and holistic practice

Social work education and training in the UK was, in the 1990s, restructured on a competence-based model. Drawing on the literature and a survey of students from one Diploma in Social Work programme, this paper offers a critical appraisal of this approach to social work education, placing it in the context of opposing ideological frameworks. It reviews the strengths and limitations of the system and discusses some of the problems and dilemmas arising in training for work involving values conflicts and complex tasks. It argues that there is a need for a new synthesis drawn from the strengths of technical rationalism and holistic reflective practice.