1,547 research outputs found

    Up-regulation of aldose reductase activity in cultured mesangial cells overexpressing human aldose reductase gene is associated with increased TGF-beta1 and collagen IV expression

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    Spectral plots and the representation and interpretation of biological data

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    It is basic question in biology and other fields to identify the char- acteristic properties that on one hand are shared by structures from a particular realm, like gene regulation, protein-protein interaction or neu- ral networks or foodwebs, and that on the other hand distinguish them from other structures. We introduce and apply a general method, based on the spectrum of the normalized graph Laplacian, that yields repre- sentations, the spectral plots, that allow us to find and visualize such properties systematically. We present such visualizations for a wide range of biological networks and compare them with those for networks derived from theoretical schemes. The differences that we find are quite striking and suggest that the search for universal properties of biological networks should be complemented by an understanding of more specific features of biological organization principles at different scales.Comment: 15 pages, 7 figure

    Universal Geometric Graphs

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    We introduce and study the problem of constructing geometric graphs that have few vertices and edges and that are universal for planar graphs or for some sub-class of planar graphs; a geometric graph is \emph{universal} for a class H\mathcal H of planar graphs if it contains an embedding, i.e., a crossing-free drawing, of every graph in H\mathcal H. Our main result is that there exists a geometric graph with nn vertices and O(nlogn)O(n \log n) edges that is universal for nn-vertex forests; this extends to the geometric setting a well-known graph-theoretic result by Chung and Graham, which states that there exists an nn-vertex graph with O(nlogn)O(n \log n) edges that contains every nn-vertex forest as a subgraph. Our O(nlogn)O(n \log n) bound on the number of edges cannot be improved, even if more than nn vertices are allowed. We also prove that, for every positive integer hh, every nn-vertex convex geometric graph that is universal for nn-vertex outerplanar graphs has a near-quadratic number of edges, namely Ωh(n21/h)\Omega_h(n^{2-1/h}); this almost matches the trivial O(n2)O(n^2) upper bound given by the nn-vertex complete convex geometric graph. Finally, we prove that there exists an nn-vertex convex geometric graph with nn vertices and O(nlogn)O(n \log n) edges that is universal for nn-vertex caterpillars.Comment: 20 pages, 8 figures; a 12-page extended abstracts of this paper will appear in the Proceedings of the 46th Workshop on Graph-Theoretic Concepts in Computer Science (WG 2020

    A new conceptual approach for systematic error correction in CNC machine tools minimizing worst case prediction error

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    A new artifact-based method to identify the systematic errors in multi-axis CNC machine tools minimizing the worst case prediction error is presented. The closed loop volumetric error is identified by simultaneously moving the axes of the machine tool. The physical artifact is manufactured on the machine tool and later measured on a coordinate measuring machine. The artifact consists of a set of holes in the machine tool workspace at locations that minimize the worst case prediction error for a given bounded measurement error. The number of holes to be drilled depends on the degree of the polynomials used to model the systematic error and the number of axes of the machine tool. The prediction error is also function of the number and location of the holes. The feasibility of the method is first investigated for a two-axis machine to find the best experimental setting. Finally based on the two-axis case study, we extend the results to machine tools with any number of axes. The obtained results are very promising and require only a short time to produce the artifac

    Characterizing the community structure of complex networks

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    Community structure is one of the key properties of complex networks and plays a crucial role in their topology and function. While an impressive amount of work has been done on the issue of community detection, very little attention has been so far devoted to the investigation of communities in real networks. We present a systematic empirical analysis of the statistical properties of communities in large information, communication, technological, biological, and social networks. We find that the mesoscopic organization of networks of the same category is remarkably similar. This is reflected in several characteristics of community structure, which can be used as ``fingerprints'' of specific network categories. While community size distributions are always broad, certain categories of networks consist mainly of tree-like communities, while others have denser modules. Average path lengths within communities initially grow logarithmically with community size, but the growth saturates or slows down for communities larger than a characteristic size. This behaviour is related to the presence of hubs within communities, whose roles differ across categories. Also the community embeddedness of nodes, measured in terms of the fraction of links within their communities, has a characteristic distribution for each category. Our findings are verified by the use of two fundamentally different community detection methods.Comment: 15 pages, 20 figures, 4 table

    Cavernous lymphangioma of the breast

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    <p>Abstract</p> <p>Background</p> <p>Cavernous lymphangioma is a rare lesion in the breast of adults. Only a few cases have been documented in literature.</p> <p>Case presentation</p> <p>We describe a 38-year-old woman who presented with a palpable breast lump, which measured 5 × 4 cm. A local excision of the lump was performed and a diagnosis of cavernous lymphangioma was made. The patient is alive and well, after five years of follow-up, with no complaints or recurrence.</p> <p>Conclusion</p> <p>To the best of our knowledge, this is the first case to be documented in a black African woman. Complete surgical excision seems to be the best modality of treatment of this lesion.</p

    Skeletal growth in class II malocclusion from childhood to adolescence: does the profile straighten?

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    BACKGROUND There is relatively little appreciation of the changes in maxillary-mandibular relationships occurring during adolescence among subjects with normal and increased overjet. The aim of this study was to assess differences in changes in maxillo-mandibular relationships during the adolescent growth period based on the presence of a normal ( 4 mm) overjet in childhood. Our hypothesis was that there is no difference in the change of the A point, nasion, B point (ANB) angle during growth between these two overjet groups. Lateral cephalograms were obtained from 65 subjects taken from the American Association of Orthodontists Foundation (AAOF) Craniofacial Growth Legacy Collections Project. Cephalograms were obtained at ages 7-10 (T0) and 14-17 (T1) with allocation into two groups based on baseline overjet (> 4 mm: group 1, 2-4 mm: group 2). Random effects linear regression was used to account for multiple within -patient measurements with dependent variables including antero-posterior skeletal pattern (based on sella, nasion, A point (SNA); sella, nasion, B point (SNB); and ANB angles). RESULTS We included a similar number of males (n = 34; 52.3%) and females (n = 31; 47.7%). The mean ANB was higher at baseline in group 1 (5.42, SD 2.16°) than in group 2 (3.08, SD 1.91°). The hypothesis was rejected as the ANB angle reduced by 1.92° more in the larger overjet group with the association being statistically significant after accounting for age and gender (P  4 mm overjet group compared to the 2-4 mm group (0.857°, P = 0.271; 95% CI - 0.669 to 2.383). The SNB angle increased by 1.15° more in the higher overjet group but there was only weak evidence of an association (P = 0.086; 95% CI - 2.464 to 0.164). CONCLUSIONS A slight straightening of the facial profile was observed in both groups with a statistically significant greater reduction in ANB arising in the group with larger baseline overjet. This translated into a marginal reduction in the overjet in this group

    Comparative Study of Different Memetic Algorithm Configurations for the Cyclic Bandwidth Sum Problem

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    The Cyclic Bandwidth Sum Problem (CBSP) is an NP-Hard Graph Embedding Problem which aims to embed a simple, finite graph (the guest) into a cycle graph of the same order (the host) while minimizing the sum of cyclic distances in the host between guest’s adjacent nodes. This paper presents preliminary results of our research on the design of a Memetic Algorithm (MA) able to solve the CBSP. A total of 24 MA versions, induced by all possible combinations of four selection schemes, two operators for recombination and three for mutation, were tested over a set of 25 representative graphs. Results compared with respect to the state-of-the-art top algorithm showed that all the tested MA versions were able to consistently improve its results and give us some insights on the suitability of the tested operators
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