809 research outputs found

    Streaming Kernelization

    Full text link
    Kernelization is a formalization of preprocessing for combinatorially hard problems. We modify the standard definition for kernelization, which allows any polynomial-time algorithm for the preprocessing, by requiring instead that the preprocessing runs in a streaming setting and uses O(poly(k)logx)\mathcal{O}(poly(k)\log|x|) bits of memory on instances (x,k)(x,k). We obtain several results in this new setting, depending on the number of passes over the input that such a streaming kernelization is allowed to make. Edge Dominating Set turns out as an interesting example because it has no single-pass kernelization but two passes over the input suffice to match the bounds of the best standard kernelization

    Simultaneous Embeddings with Few Bends and Crossings

    Full text link
    A simultaneous embedding with fixed edges (SEFE) of two planar graphs RR and BB is a pair of plane drawings of RR and BB that coincide when restricted to the common vertices and edges of RR and BB. We show that whenever RR and BB admit a SEFE, they also admit a SEFE in which every edge is a polygonal curve with few bends and every pair of edges has few crossings. Specifically: (1) if RR and BB are trees then one bend per edge and four crossings per edge pair suffice (and one bend per edge is sometimes necessary), (2) if RR is a planar graph and BB is a tree then six bends per edge and eight crossings per edge pair suffice, and (3) if RR and BB are planar graphs then six bends per edge and sixteen crossings per edge pair suffice. Our results improve on a paper by Grilli et al. (GD'14), which proves that nine bends per edge suffice, and on a paper by Chan et al. (GD'14), which proves that twenty-four crossings per edge pair suffice.Comment: Full version of the paper "Simultaneous Embeddings with Few Bends and Crossings" accepted at GD '1

    Use Of open Access Journals By Librarians In Ghana

    Get PDF
    Introduction: This study examined the use of open access journals by librarians in Ghana. The objectives were to establish the familiarity, attitude and benefits of open access journals among librarians in Ghana. Method: This study uses a survey research design. A web-based questionnaire was used to seek information on respondents’ demographics, awareness, use, attitudes and benefits of open access journals. Analysis: Descriptive statistics was used to analyze survey results. The Statistical Package for the Social Sciences (SPSS) was used for the analysis of data collected from 103 librarians who are members of the Ghana Library Association. Results: All the respondents were aware of open access journals and to a greater extent, they showed positive attitude towards open access journals. Many of them, however, are not fully committed to publishing their articles in open access journals. It is recommended that librarians should be willing to publish more of their research works in open access journals for them to be ambassadors and advocate for open access. Conclusion: Knowledge of open access journals and related content among librarians is crucial not only in disseminating research quality but also in weeding out poor content

    Leveraging Accelerometer Data for Lameness Detection in Dairy Cows: A Longitudinal Study of Six Farms in Germany

    Get PDF
    Lameness in dairy cows poses a significant challenge to improving animal well-being and optimizing economic efficiency in the dairy industry. To address this, employing automated animal surveillance for early lameness detection and prevention through activity sensors proves to be a promising strategy. In this study, we analyzed activity (accelerometer) data and additional cow-individual and farm-related data from a longitudinal study involving 4860 Holstein dairy cows on six farms in Germany during 2015–2016. We designed and investigated various statistical models and chose a logistic regression model with mixed effects capable of detecting lameness with a sensitivity of 77%. Our results demonstrate the potential of automated animal surveillance and hold the promise of significantly improving lameness detection approaches in dairy livestock

    Clinical phenotype of adolescent and adult patients with extracranial vascular malformation.

    Get PDF
    BACKGROUND In recent years, genotypic characterization of congenital vascular malformations (CVM) has gained attention; however, the spectrum of clinical phenotype remains difficult to attribute to a genetic cause and is rarely described in the adult population. AIM The aim of this study is to describe a consecutive series of adolescent and adult patients in a tertiary center, where a multimodal phenotypic approach was used for diagnosis. METHODS We analyzed clinical findings, imaging, and laboratory results at initial presentation, and set a diagnosis according to the International Society for the Study of Vascular Anomalies (ISSVA) classification for all consecutively registered patients older than 14 years of age who were referred to the Center for Vascular Malformations at the University Hospital of Bern between 2008 and 2021. RESULTS 457 patients were included for analysis (mean age 35 years; females 56%). Simple CVMs were the most common (n=361, 79 %), followed by CVM associated with other anomalies (n=70, 15%), and combined CVM (n=26, 6%). Venous malformations (n=238) were the most common CVM overall (52%), and the most common simple CVM (66%). Pain was the most frequently reported symptom in all patients (simple, combined and vascular malformation with other anomalies). Pain intensity was more pronounced in simple venous and arteriovenous malformation. Clinical problems were related to the type of CVM diagnosed, with bleeding and skin ulceration in arteriovenous malformations, localized intravascular coagulopathy in venous malformations and infectious complications in lymphatic malformations. Limb length difference occurred more often in patients with CVM associated with other anomalies as compared to simple or combined CVM (22.9 vs 2.3%, p< 0.001). Soft tissue overgrowth was seen in one quarter of all patients independent of the ISSVA group. CONCLUSIONS In our adult and adolescent population with peripheral vascular malformations, simple venous malformations predominated, with pain as the most common clinical symptom. In a quarter of cases, patients with vascular malformations presented with associated anomalies on tissue growth. The differentiation of clinical presentation with or without accompanying growth abnormalities need to be added to the ISSVA classification. Phenotypic characterization considering vascular and non-vascular features remains the cornerstone of diagnosis in adult-as well as pediatric patients

    Constraints on Pluto’s H and CH₄ profiles from New Horizons Alice Lyα observations

    Get PDF
    The Alice spectrograph on New Horizons performed several far-ultraviolet (FUV) airglow observations during the July 2015 flyby of Pluto. One of these observations, named PColor2, was a short (226 s) scan across the dayside disk of Pluto from a range of ∼34,000 km, at about 40 minutes prior to closest approach. The brightest observed FUV airglow signal at Pluto is the Lyman alpha (Lyα) emission line of atomic hydrogen, which arises primarily through the resonant scattering of solar Lyα by H atoms in the upper atmosphere, with a brightness of about 30 Rayleighs. Pluto appears dark against the much brighter (∼100 Rayleigh) sky background; this sky background is likewise the result of resonantly scattered solar Lyα, in this case by H atoms in the interplanetary medium (IPM). Here we use an updated photochemical model and a resonance line radiative transfer model to perform detailed simulations of the Lyα emissions observed in the Alice PColor2 scan. The photochemical models show that H and CH₄ abundances in Pluto’s upper atmosphere are a very strong function of the near-surface mixing ratio of CH₄, and could provide a useful way to remotely monitor seasonal climate variations in Pluto’s lower atmosphere. The morphology of the PColor2 Lyα emissions provides constraints on the current abundance profiles of H atoms and CH₄ molecules in Pluto’s atmosphere, and indicate that the globally averaged near-surface mixing ratio of CH₄ is currently close to 0.4%. This new result thus provides independent confirmation of one of the primary results from the solar occultation, also observed with the New Horizons Alice ultraviolet spectrograph
    corecore