On the Price of Anarchy of Highly Congested Nonatomic Network Games

We consider nonatomic network games with one source and one destination. We examine the asymptotic behavior of the price of anarchy as the inflow increases. In accordance with some empirical observations, we show that, under suitable conditions, the price of anarchy is asymptotic to one. We show with some counterexamples that this is not always the case. The counterexamples occur in very simple parallel graphs.Comment: 26 pages, 6 figure

Spatial and environmental drivers of macrophyte diversity and community composition in temperate and tropical calcareous rivers

The hypothesis was examined that sources of variation in macrophyte species richness (alpha-diversity: S) and community composition (“species-set”), attributable to spatial and environmental, variables, may differ in importance between tropical and temperate calcareous rivers (>10 mg CaCO3 L−1). To test this hypothesis geographic, environmental, and aquatic vegetation data was acquired for 1151 sites on calcareous rivers within the British Isles, supporting 106 macrophyte species (mean S: 3.1 species per sample), and 203 sites from Zambian calcareous rivers, supporting 255 macrophyte species (mean S: 8.3 species per sample). The data were analysed using an eigenfunction spatial analysis procedure, Moran’s Eigenvector Maps (MEM), to assess spatial variation of species richness and community composition at large regional scale (>105 km2: British Isles and Zambia); and at medium catchment scale (104–105 km2: British Isles only). Variation-partitioning was undertaken using multiple regression for species richness data, and partial redundancy analysis (pRDA) for community data. For the British Isles, spatial and environmental variables both significantly contributed to explaining variation in both species richness and community composition. In addition, a substantial amount of the variation in community composition, for the British Isles as a whole and for some RBUs, was accounted for by spatially-structured environmental variables. In Zambia, species richness was explained only by pure spatial variables, but environmental and spatially-structured environmental variables also explained a significant part of the variation for community composition. At medium-scale, in the British Isles, species richness was explained by spatial variables, and only for four of the six RBUs

A survey of agent-oriented methodologies

This article introduces the current agent-oriented methodologies. It discusses what approaches have been followed (mainly extending existing object oriented and knowledge engineering methodologies), the suitability of these approaches for agent modelling, and some conclusions drawn from the survey

Can sacrificial feeding areas protect aquatic plants from herbivore grazing? Using behavioural ecology to inform wildlife management

Effective wildlife management is needed for conservation, economic and human well-being objectives. However, traditional population control methods are frequently ineffective, unpopular with stakeholders, may affect non-target species, and can be both expensive and impractical to implement. New methods which address these issues and offer effective wildlife management are required. We used an individual-based model to predict the efficacy of a sacrificial feeding area in preventing grazing damage by mute swans (Cygnus olor) to adjacent river vegetation of high conservation and economic value. The accuracy of model predictions was assessed by a comparison with observed field data, whilst prediction robustness was evaluated using a sensitivity analysis. We used repeated simulations to evaluate how the efficacy of the sacrificial feeding area was regulated by (i) food quantity, (ii) food quality, and (iii) the functional response of the forager. Our model gave accurate predictions of aquatic plant biomass, carrying capacity, swan mortality, swan foraging effort, and river use. Our model predicted that increased sacrificial feeding area food quantity and quality would prevent the depletion of aquatic plant biomass by swans. When the functional response for vegetation in the sacrificial feeding area was increased, the food quantity and quality in the sacrificial feeding area required to protect adjacent aquatic plants were reduced. Our study demonstrates how the insights of behavioural ecology can be used to inform wildlife management. The principles that underpin our model predictions are likely to be valid across a range of different resource-consumer interactions, emphasising the generality of our approach to the evaluation of strategies for resolving wildlife management problems

Bandgaps in the propagation and scattering of surface water waves over cylindrical steps

Here we investigate the propagation and scattering of surface water waves by arrays of bottom-mounted cylindrical steps. Both periodic and random arrangements of the steps are considered. The wave transmission through the arrays is computed using the multiple scattering method based upon a recently derived formulation. For the periodic case, the results are compared to the band structure calculation. We demonstrate that complete band gaps can be obtained in such a system. Furthermore, we show that the randomization of the location of the steps can significantly reduce the transmission of water waves. Comparison with other systems is also discussed.Comment: 4 pages, 3 figure

Blood Mercury Reporting in NHANES: Identifying Asian, Pacific Islander, Native American, and Multiracial Groups

INTRODUCTION: Asians, Pacific Islanders, and Native Americans are a potentially high-risk group for dietary exposure to methylmercury through fish consumption. However, blood mercury levels in this group have not been identified in recent reports of the National Health and Nutrition Examination Survey (NHANES) for the years 1999–2002. METHODS: We used NHANES data from 1999–2002 to obtain population estimates of blood mercury levels among women of childbearing age classified as belonging to the “other” racial/ethnic group (Asian, Pacific Islander, Native American, and multiracial; n = 140). Blood mercury levels in this group were compared with those among all other women participants, classified as Mexican American, non-Hispanic black, non-Hispanic white, and “other” Hispanic. RESULTS: An estimated 16.59 ± 4.0% (mean ± SE) of adult female participants who self-identified as Asian, Pacific Islander, Native American, or multiracial (n = 140) had blood mercury levels ≥5.8 μg/L, and 27.26 ± 4.22% had levels ≥3.5 μg/L. Among remaining survey participants (n = 3,497), 5.08 ± 0.90% had blood mercury levels ≥5.8 μg/L, and 10.86 ± 1.45% had levels ≥3.5 μg/L. CONCLUSIONS: Study subjects in NHANES who self-identified as Asian, Pacific Islander, Native American, or multiracial had a higher prevalence of elevated blood mercury than all other racial/ethnic participants in the survey. Future studies should address reasons for the high mercury levels in this group and explore possible interventions for lowering risk of methylmercury exposure in this population

The asialoglycoprotein receptor in human hepatocellular carcinomas: its expression on proliferating cells

The expression of the asialoglycoprotein receptor (ASGP-R) on human hepatocellular carcinoma (HCC) cells might be exploited to reduce the extrahepatic toxicity of DNA synthesis inhibitors by their conjugation with galactosyl-terminating peptides. In the present study we first assessed the frequency of ASGP-R expression in 60 HCCs. Secondly, we investigated whether the receptor was maintained on the plasma membranes of DNA synthesizing cancer cells. Needle biopsies of HCC were evaluated. Diagnosis and grading of HCC were performed on routine haematoxylin and eosin-stained sections according to Edmondson and Steiner (1953). Thirty-five tumours were grade I and II and were classified as well differentiated, while 25 tumours were grade III and IV and were classified as poorly differentiated. Sections from formalin-fixed, paraffin-embedded samples were incubated, after antigen retrieval, with an anti-ASGP-R monoclonal antibody revealed by secondary biotinylated antibody and streptavidin–biotin–peroxidase–diaminobenzidine reaction. A clear immunolabelling of plasma membranes of HCC cells was observed in 28 out of 35 (80%) well differentiated (grade I and II) and in five out of 25 (20%) poorly differentiated (grade III and IV) HCCs. The presence of the ASGP-R on the surface of DNA synthesizing cancer cells was also investigated after in vitro bromodeoxyuridine (BrdU) labelling of HCC samples by immunohistochemical visualization of both the ASGP-R and incorporated BrdU on the same section. The results obtained clearly demonstrated that DNA synthesizing cancer cells expressed the ASGP-R on their surface. The presence of ASGP-R on cell plasma membrane in the majority of differentiated HCCs and its maintenance on proliferating cells encourages studies in order to restrict the action of the inhibitors of DNA synthesis of HCC cells by their conjugation with galactosyl-terminating carriers internalized through this receptor. © 1999 Cancer Research Campaig