256 research outputs found

    An improved lower bound for (1,<=2)-identifying codes in the king grid

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    We call a subset CC of vertices of a graph GG a (1,)(1,\leq \ell)-identifying code if for all subsets XX of vertices with size at most \ell, the sets {cCuX,d(u,c)1}\{c\in C |\exists u \in X, d(u,c)\leq 1\} are distinct. The concept of identifying codes was introduced in 1998 by Karpovsky, Chakrabarty and Levitin. Identifying codes have been studied in various grids. In particular, it has been shown that there exists a (1,2)(1,\leq 2)-identifying code in the king grid with density 3/7 and that there are no such identifying codes with density smaller than 5/12. Using a suitable frame and a discharging procedure, we improve the lower bound by showing that any (1,2)(1,\leq 2)-identifying code of the king grid has density at least 47/111

    Random Convex Hulls and Extreme Value Statistics

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    In this paper we study the statistical properties of convex hulls of NN random points in a plane chosen according to a given distribution. The points may be chosen independently or they may be correlated. After a non-exhaustive survey of the somewhat sporadic literature and diverse methods used in the random convex hull problem, we present a unifying approach, based on the notion of support function of a closed curve and the associated Cauchy's formulae, that allows us to compute exactly the mean perimeter and the mean area enclosed by the convex polygon both in case of independent as well as correlated points. Our method demonstrates a beautiful link between the random convex hull problem and the subject of extreme value statistics. As an example of correlated points, we study here in detail the case when the points represent the vertices of nn independent random walks. In the continuum time limit this reduces to nn independent planar Brownian trajectories for which we compute exactly, for all nn, the mean perimeter and the mean area of their global convex hull. Our results have relevant applications in ecology in estimating the home range of a herd of animals. Some of these results were announced recently in a short communication [Phys. Rev. Lett. {\bf 103}, 140602 (2009)].Comment: 61 pages (pedagogical review); invited contribution to the special issue of J. Stat. Phys. celebrating the 50 years of Yeshiba/Rutgers meeting

    'Education, education, education' : legal, moral and clinical

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    This article brings together Professor Donald Nicolson's intellectual interest in professional legal ethics and his long-standing involvement with law clinics both as an advisor at the University of Cape Town and Director of the University of Bristol Law Clinic and the University of Strathclyde Law Clinic. In this article he looks at how legal education may help start this process of character development, arguing that the best means is through student involvement in voluntary law clinics. And here he builds upon his recent article which argues for voluntary, community service oriented law clinics over those which emphasise the education of students

    Biophysics of Malarial Parasite Exit from Infected Erythrocytes

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    Upon infection and development within human erythrocytes, P. falciparum induces alterations to the infected RBC morphology and bio-mechanical properties to eventually rupture the host cells through parasitic and host derived proteases of cysteine and serine families. We used previously reported broad-spectrum inhibitors (E64d, EGTA-AM and chymostatin) to inhibit these proteases and impede rupture to analyze mechanical signatures associated with parasite escape. Treatment of late-stage iRBCs with E64d and EGTA-AM prevented rupture, resulted in no major RBC cytoskeletal reconfiguration but altered schizont morphology followed by dramatic re-distribution of three-dimensional refractive index (3D-RI) within the iRBC. These phenotypes demonstrated several-fold increased iRBC membrane flickering. In contrast, chymostatin treatment showed no 3D-RI changes and caused elevated fluctuations solely within the parasitophorous vacuole. We show that E64d and EGTA-AM supported PV breakdown and the resulting elevated fluctuations followed non-Gaussian pattern that resulted from direct merozoite impingement against the iRBC membrane. Optical trapping experiments highlighted reduced deformability of the iRBC membranes upon rupture-arrest, more specifically in the treatments that facilitated PV breakdown. Taken together, our experiments provide novel mechanistic interpretations on the role of parasitophorous vacuole in maintaining the spherical schizont morphology, the impact of PV breakdown on iRBC membrane fluctuations leading to eventual parasite escape and the evolution of membrane stiffness properties of host cells in which merozoites were irreversibly trapped, recourse to protease inhibitors. These findings provide a comprehensive, previously unavailable, body of information on the combined effects of biochemical and biophysical factors on parasite egress from iRBCs.Singapore. Agency for Science, Technology and ResearchSingapore-MIT AllianceGlobal Enterprise for Micro-Mechanics and Molecular MedicineNational University of SingaporeNational Institutes of Health (U.S.) (Grant R01 HL094270-01A1)National Institutes of Health (U.S.) (Grant 1-R01-GM076689-01)National Institutes of Health (U.S.) (P41-RR02594-18-24

    How 'universal' is the United Nations' Universal Periodic Review process? An examination of the discussions held on polygamy

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    In 2006, United Nations Human Rights Council was tasked to establish a new human rights monitoring mechanism: Universal Periodic Review process. The primary aim of this process is to promote and protect the universality of all human rights issues and concerns via a dialogical peer review process. The aim of this investigation isto ask the following question: has this claim of promoting and protecting the universality of the human rights been met, or challenged, during state reviews in the UPR process? The issue of polygamy has been selected as the focus for this investigation to be used, primarily, as a tool to undertake an in-depth analysis of the discussions held during state reviews in the review process. In addition, this paper will employ scholarly debates between universalism and cultural relativism, as well as the sophisticated and nuanced approaches that fall in between the polarised opposites, to analyse the discussions held on human rights during state reviews. Ultimately, the findings and discussion of this investigation will provide a unique and valuable insight to the work and operation of the UPR process, so far

    The importance of sedimenting organic matter, relative to oxygen and temperature, in structuring lake profundal macroinvertebrate assemblages

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    We quantified the role of a main food resource, sedimenting organic matter (SOM), relative to oxygen (DO) and temperature (TEMP) in structuring profundal macroinvertebrate assemblages in boreal lakes. SOM from 26 basins of 11 Finnish lakes was analysed for quantity (sedimentation rates), quality (C:N:P stoichiometry) and origin (carbon stable isotopes, d13C). Hypolimnetic oxygen and temperature were measured from each site during summer stratification. Partial canonical correspondence analysis (CCA) and partial regression analyses were used to quantify contributions of SOM, DO and TEMP to community composition and three macroinvertebrate metrics. The results suggested a major contribution of SOM in regulating the community composition and total biomass. Oxygen best explained the Shannon diversity, whereas TEMP had largest contribution to the variation of Benthic Quality Index. Community composition was most strongly related to d13C of SOM. Based on additional d13C and stoichiometric analyses of chironomid taxa, marked differences were apparent in their utilization of SOM and body stoichiometry; taxa characteristic of oligotrophic conditions exhibited higher C:N ratios and lower C:P and N:P ratios compared to the species typical of eutrophic lakes. The results highlight the role of SOM in regulating benthic communities and the distributions of individual species, particularly in oligotrophic systems

    Islet transplantation from a nationally funded UK centre reaches socially deprived groups and improves metabolic outcomes

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    Acknowledgements We thank the transplant nurses involved with the Scottish Islet Transplant Programme (T. McGilvray, J. Davidson, M. Phillips and C. Jansen) for help with participant assessment. We thank the Scottish National Blood Transfusion Services including the Histocompatibility and Immunogenetics Team for HLA typing and antibody screening, and the Tissue and Cells Team (A. Timpson, L. Fraser, L. Irvine and P. Henry) for islet isolation and product release testing. We acknowledge the Departments of Transplantation, Diabetes and Interventional Radiology at NHS Lothian for all aspects of patient care and the organ procurement programme. We thank J. Shaw and A. Brooks from the Department of Regenerative Medicine for Diabetes at the University of Newcastle for advice regarding CGMS. C-peptide assays were performed by the NIHR Cambridge Biomedical Research Centre, Core Biochemical Assay Laboratory. Funding: The Scottish Islet Transplant Programme is funded by the National Services Division. This research was funded by Diabetes UK (Biomedical and Psychosocial Outcomes of Islet Transplantation; Grant no. BDA 06/0003362), Diabetes Research and Wellness Foundation, Diabetes Foundation, Juvenile Diabetes Research Foundation and the Royal Infirmary Diabetes Treatment Trust Fund. Open Access: This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.Peer reviewedPublisher PD
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