Optimal algorithms for sensitivity analysis in associative multiplication problems

We consider efficient ways of determining the sensitivity of a product to changes in individual factors. The task is motivated by several interesting combinatorial and numeric problems which can be given a unified formulation as the problem of finding the (associative) product of N objects. Both deterministic and probabilistic changes to the factors are considered. Algorithms for two kinds of deterministic variation schemes are considered. Nontrivial lower bounds are obtained which demonstrate the algorithms to be optimal. For probabilistic choice of the parameter to be varied, it is shown that optimal ordered binary search trees or Huffman trees determine the optimal strategies. A number of unsolved are posed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24498/1/0000775.pd

Getting farming on the agenda: Planning, policymaking, and governance practices of urban agriculture in New York City

How and why is urban agriculture taken up into local food policies and sustainability plans? This paper uses a case study of urban agriculture policymaking in New York City from 2007 to 2011 to examine the power-laden operation of urban environmental governance. It explores several ‘faces of power,’ including overt authority, institutionalized ‘rules of the game,’ and hegemony. It also investigates how multiple actors interact in policymaking processes, including through the construction and use of broad discursive concepts. Findings draw upon analysis of policy documents and semi-structured interviews with 43 subjects engaged in food systems policymaking. Some municipal decision-makers questioned the significance of urban agriculture, due to the challenges of quantifying its benefits and the relative scarcity of open space in the developed city. Yet, these challenges proved insufficient to prevent a coalition of civic activists working in collaboration with public officials to envision plans on food policy that included urban agriculture. Actors created the ‘local/regional food system’ as a narrative concept in order to build broad coalitions and gain entry to the municipal policy sphere. Tracing the roll-out of plans reveals the way in which both the food systems concept and specific policy proposals were repeated and legitimized.Unpacking the dynamics of this iterative policymaking contributes to an understanding of how urban environmental governance happens in this case

Methodological issues in epidemiological studies of periodontitis - how can it be improved?

Background: This position paper was commissioned by the European Association of Dental Public Health, which has established six working groups to investigate the current status of six topics related to oral public health. One of these areas is epidemiology of periodontal diseases. Methods: Two theses "A systematic review of definitions of periodontitis and the methods that have been used to identify periodontitis" [1] and "Factors affecting community oral health care needs and provision" [2] formed the starting point for this position paper. Additional relevant and more recent publications were retrieved through a MEDLINE search. Results: The literature reveals a distinct lack of consensus and uniformity in the definition of periodontitis within epidemiological studies. There are also numerous differences in the methods used. The consequence is that data from studies using differing case definitions and differing survey methods are not easily interpretable or comparable. The limitations of the widely used Community Periodontal Index of Treatment Need (CPITN) and its more recent derivatives are widely recognized. Against this background, this position paper reviews the current evidence base, outlines existing problems and suggests how epidemiology of periodontal diseases may be improved. Conclusions: The remit of this working group was to review and discuss the existing evidence base of epidemiology of periodontal diseases and to identify future areas of work to further enhance it