382 research outputs found

    Planar Octilinear Drawings with One Bend Per Edge

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    In octilinear drawings of planar graphs, every edge is drawn as an alternating sequence of horizontal, vertical and diagonal (4545^\circ) line-segments. In this paper, we study octilinear drawings of low edge complexity, i.e., with few bends per edge. A kk-planar graph is a planar graph in which each vertex has degree less or equal to kk. In particular, we prove that every 4-planar graph admits a planar octilinear drawing with at most one bend per edge on an integer grid of size O(n2)×O(n)O(n^2) \times O(n). For 5-planar graphs, we prove that one bend per edge still suffices in order to construct planar octilinear drawings, but in super-polynomial area. However, for 6-planar graphs we give a class of graphs whose planar octilinear drawings require at least two bends per edge

    On Smooth Orthogonal and Octilinear Drawings: Relations, Complexity and Kandinsky Drawings

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    We study two variants of the well-known orthogonal drawing model: (i) the smooth orthogonal, and (ii) the octilinear. Both models form an extension of the orthogonal, by supporting one additional type of edge segments (circular arcs and diagonal segments, respectively). For planar graphs of max-degree 4, we analyze relationships between the graph classes that can be drawn bendless in the two models and we also prove NP-hardness for a restricted version of the bendless drawing problem for both models. For planar graphs of higher degree, we present an algorithm that produces bi-monotone smooth orthogonal drawings with at most two segments per edge, which also guarantees a linear number of edges with exactly one segment.Comment: Appears in the Proceedings of the 25th International Symposium on Graph Drawing and Network Visualization (GD 2017

    On the central stellar mass density and the inside-out growth of early-type galaxies

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    [Abridged] In this paper we derive the central stellar mass density within a fixed radius and the effective stellar mass density within the effective radius for a complete sample of 34 ETGs morphologically selected at 0.9<z_{spec}<2 and compare them with those derived for a sample of ~900 local ETGs in the same mass range. We find that the central stellar mass density of high-z ETGs spans just an order of magnitude and it is similar to the one of local ETGs as actually found in previous studies.However, we find that the effective stellar mass density of high-z ETGs spans three orders of magnitude, exactly as the local ETGs and that it is similar to the effective stellar mass density of local ETGs showing that it has not changed since z~1.5, in the last 9-10 Gyr. Thus, the wide spread of the effective stellar mass density observed up to z~1.5 must originate earlier, at z>2. Also, we show that the small scatter of the central mass density of ETGs compared to the large scatter of the effective mass density is simply a peculiar feature of the Sersic profile hence, independent of redshift and of any assembly history experienced by galaxies. Thus, it has no connection with the possible inside-out growth of ETGs. Finally, we find a tight correlation between the central stellar mass density and the total stellar mass of ETGs in the sense that the central mass density increases with mass as M^{~0.6}. This implies that the fraction of the central stellar mass of ETGs decreases with the mass of the galaxy. These correlations are valid for the whole population of ETGs considered independently of their redshift suggesting that they originate in the early-phases of their formation.Comment: 11 pages, 6 figures. Accepted for publication in MNRAS (MNRAS version

    Sequential Array Cytometry: Multi-Parameter Imaging with a Single Fluorescent Channel

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    Heterogeneity within the human population and within diseased tissues necessitates a personalized medicine approach to diagnostics and the treatment of diseases. Functional assays at the single-cell level can contribute to uncovering heterogeneity and ultimately assist in improved treatment decisions based on the presence of outlier cells. We aim to develop a platform for high-throughput, single-cell-based assays using well-characterized hydrodynamic cell isolation arrays which allow for precise cell and fluid handling. Here, we demonstrate the ability to extract spatial and temporal information about several intracellular components using a single fluorescent channel, eliminating the problem of overlapping fluorescence emission spectra. Integrated with imaging technologies such as wide field-of-view lens-free fluorescent imaging, fiber-optic array scanning technology, and microlens arrays, use of a single fluorescent channel will reduce the cost of reagents and optical components. Specifically, we sequentially stain hydrodynamically trapped cells with three biochemical labels all sharing the same fluorescence excitation and emission spectrum. These markers allow us to analyze the amount of DNA, and compare nucleus-to-cytoplasm ratio, as well as glycosylation of surface proteins. By imaging cells in real-time we enable measurements of temporal localization of cellular components and intracellular reaction kinetics, the latter is used as a measurement of multi-drug resistance. Demonstrating the efficacy of this single-cell analysis platform is the first step in designing and implementing more complete assays, aimed toward improving diagnosis and personalized treatments to complex diseases

    The Science Case for PILOT II: the Distant Universe

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    PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. The atmospheric conditions at Dome C deliver a high sensitivity, high photometric precision, wide-field, high spatial resolution, and high-cadence imaging capability to the PILOT telescope. These capabilities enable a unique scientific potential for PILOT, which is addressed in this series of papers. The current paper presents a series of projects dealing with the distant (redshift >1) Universe, that have been identified as key science drivers for the PILOT facility. The potential for PILOT to detect the first populations of stars to form in the early Universe, via infrared projects searching for pair-instability supernovae and gamma-ray burst afterglows, is investigated. Two projects are proposed to examine the assembly and evolution of structure in the Universe: an infrared survey searching for the first evolved galaxies at high redshift, and an optical survey aimed at characterising moderate-redshift galaxy clusters. Finally, a large-area weak-lensing survey and a program to obtain supernova infrared light-curves are proposed to examine the nature and evolution of dark energy and dark matter

    Large-scale pharmacogenomic study of sulfonylureas and the QT, JT and QRS intervals: CHARGE Pharmacogenomics Working Group

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    Sulfonylureas, a commonly used class of medication used to treat type 2 diabetes, have been associated with an increased risk of cardiovascular disease. Their effects on QT interval duration and related electrocardiographic phenotypes are potential mechanisms for this adverse effect. In 11 ethnically diverse cohorts that included 71 857 European, African-American and Hispanic/Latino ancestry individuals with repeated measures of medication use and electrocardiogram (ECG) measurements, we conducted a pharmacogenomic genome-wide association study of sulfonylurea use and three ECG phenotypes: QT, JT and QRS intervals. In ancestry-specific meta-analyses, eight novel pharmacogenomic loci met the threshold for genome-wide significance (P&lt;5 × 10−8), and a pharmacokinetic variant in CYP2C9 (rs1057910) that has been associated with sulfonylurea-related treatment effects and other adverse drug reactions in previous studies was replicated. Additional research is needed to replicate the novel findings and to understand their biological basis

    How collective action produces psychological change and how that change endures over time: a case study of an environmental campaign

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    Previous research on collective action has suggested that both intra‐ and intergroup interactions are important in producing psychological change. In this study, we examine how these two forms of interaction relate to each other over time. We present results from a longitudinal ethnographic study of participation in an environmental campaign, documenting endurance and prevalence of psychological change. Participants, locals (n = 14) and self‐defined activists (n = 14), connected enduring psychological changes, such as changes in consumer behaviour and attitudes to their involvement in the environmental campaign. Thematic analysis of interviews suggested that participants linked the process of change to categorizing themselves in a new environmental‐activist way that influenced their everyday lives beyond the immediate campaign. This recategorization was a result of a conflictual intergroup relationship with the police. The intergroup interaction produced supportive within‐group relationships that facilitated the feasibility and sustainability of new world views that were maintained by staying active in the campaign. The data from the study support and extend previous research on collective action and are the basis of a model, suggesting that intragroup processes condition the effects of intergroup dynamics on sustained psychological change

    The limited role of galaxy mergers in driving stellar mass growth over cosmic time

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    © The Author(s) 2017. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Published by Oxford University Press on behalf of the Royal Astronomical Society.A key unresolved question is the role that galaxy mergers play in driving stellar mass growth over cosmic time. Recent observational work hints at the possibility that the overall contribution of `major' mergers (mass ratios \gtrsim1:4) to cosmic stellar mass growth may be small, because they enhance star formation rates by relatively small amounts at high redshift, when much of today's stellar mass was assembled. However, the heterogeneity and relatively small size of today's datasets, coupled with the difficulty in identifying genuine mergers, makes it challenging to empirically\textit{empirically} quantify the merger contribution to stellar mass growth. Here, we use Horizon-AGN, a cosmological hydrodynamical simulation, to comprehensively quantify the contribution of mergers to the star formation budget over the lifetime of the Universe. We show that: (1) both major and minor mergers enhance star formation to similar amounts, (2) the fraction of star formation directly attributable to merging is small at all redshifts (e.g. \sim35 and \sim20 per cent at z\sim3 and z\sim1 respectively) and (3) only \sim25 per cent of today's stellar mass is directly attributable to galaxy mergers over cosmic time. Our results suggest that smooth accretion, not merging, is the dominant driver of stellar mass growth over the lifetime of the Universe.Peer reviewedFinal Published versio
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