27,695 research outputs found

    Dualities and dual pairs in Heyting algebras

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    We extract the abstract core of finite homomorphism dualities using the techniques of Heyting algebras and (combinatorial) categories.Comment: 17 pages; v2: minor correction

    The Complexity of Drawing Graphs on Few Lines and Few Planes

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    It is well known that any graph admits a crossing-free straight-line drawing in R3\mathbb{R}^3 and that any planar graph admits the same even in R2\mathbb{R}^2. For a graph GG and d{2,3}d \in \{2,3\}, let ρd1(G)\rho^1_d(G) denote the minimum number of lines in Rd\mathbb{R}^d that together can cover all edges of a drawing of GG. For d=2d=2, GG must be planar. We investigate the complexity of computing these parameters and obtain the following hardness and algorithmic results. - For d{2,3}d\in\{2,3\}, we prove that deciding whether ρd1(G)k\rho^1_d(G)\le k for a given graph GG and integer kk is R{\exists\mathbb{R}}-complete. - Since NPR\mathrm{NP}\subseteq{\exists\mathbb{R}}, deciding ρd1(G)k\rho^1_d(G)\le k is NP-hard for d{2,3}d\in\{2,3\}. On the positive side, we show that the problem is fixed-parameter tractable with respect to kk. - Since RPSPACE{\exists\mathbb{R}}\subseteq\mathrm{PSPACE}, both ρ21(G)\rho^1_2(G) and ρ31(G)\rho^1_3(G) are computable in polynomial space. On the negative side, we show that drawings that are optimal with respect to ρ21\rho^1_2 or ρ31\rho^1_3 sometimes require irrational coordinates. - Let ρ32(G)\rho^2_3(G) be the minimum number of planes in R3\mathbb{R}^3 needed to cover a straight-line drawing of a graph GG. We prove that deciding whether ρ32(G)k\rho^2_3(G)\le k is NP-hard for any fixed k2k \ge 2. Hence, the problem is not fixed-parameter tractable with respect to kk unless P=NP\mathrm{P}=\mathrm{NP}

    Effects of a Novel Dental Gel on Plaque and Gingivitis: A Comparative Study.

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    ObjectivesThe goal of this prospective, randomized, controlled, double-blinded study was to evaluate the effects of a novel dental gel on plaque and gingival health. The dental gel was designed to (1) break up and prevent re-accumulation of microbial biofilm, and (2) inhibit metal mediated inflammation.Materials and methodsTwenty-five subjects with moderate gingival inflammation (Löe and Silness Gingival Index ≥2) and pocket depths <4 were randomly assigned to brush twice daily for 21 days with the test or the control dental gel. On Days 0, 7, 14 and 21, plaque levels (Quigley-Hein, Turesky Modification Plaque Index), gingival inflammation (Löe and Silness Gingival Index) and gingival bleeding (modified Sulcus Bleeding Index) were determined by one blinded, investigator using a pressure sensitive probe.ResultsAfter 3 weeks, all 3 clinical indices were significantly improved in both groups (P<0.05) and significantly lower in the test group (P<0.05).ConclusionThe novel dental gel formulation was provided effective plaque control and reduced gingival inflammation.Clinical relevanceA novel dentifrice formulation may be an effective tool for plaque removal and maintaining gingival health

    Ethics in the mining of software repositories

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    Research in Mining Software Repositories (MSR) is research involving human subjects, as the repositories usually contain data about developers’ and users’ interactions with the repositories and with each other. The ethics issues raised by such research therefore need to be considered before beginning. This paper presents a discussion of ethics issues that can arise in MSR research, using the mining challenges from the years 2006 to 2021 as a case study to identify the kinds of data used. On the basis of contemporary research ethics frameworks we discuss ethics challenges that may be encountered in creating and using repositories and associated datasets. We also report some results from a small community survey of approaches to ethics in MSR research. In addition, we present four case studies illustrating typical ethics issues one encounters in projects and how ethics considerations can shape projects before they commence. Based on our experience, we present some guidelines and practices that can help in considering potential ethics issues and reducing risks

    Ethical Mining – A Case Study on MSR Mining Challenges

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    Research in Mining Software Repositories (MSR) is research involving human subjects, as the repositories usually contain data about developers’ interactions with the repositories. Therefore, any research in the area needs to consider the ethics implications of the intended activity before starting. This paper presents a discussion of the ethics implications of MSR research, using the mining challenges from the years 2010 to 2019 as a case study to identify the kinds of data used. It highlights problems that one may encounter in creating such datasets, and discusses ethics challenges that may be encountered when using existing datasets, based on a contemporary research ethics framework. We suggest that the MSR community should increase awareness of ethics issues by openly discussing ethics considerations in published articles

    A Twin Study of Early-Childhood Asthma in Puerto Ricans

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    Background:The relative contributions of genetics and environment to asthma in Hispanics or to asthma in children younger than 3 years are not well understood.Objective:To examine the relative contributions of genetics and environment to early-childhood asthma by performing a longitudinal twin study of asthma in Puerto Rican children ≤3 years old.Methods:678 twin infants from the Puerto Rico Neo-Natal Twin Registry were assessed for asthma at age 1 year, with follow-up data obtained for 624 twins at age 3 years. Zygosity was determined by DNA microsatellite profiling. Structural equation modeling was performed for three phenotypes at ages 1 and 3 years: physician-diagnosed asthma, asthma medication use in the past year, and ≥1 hospitalization for asthma in the past year. Models were additionally adjusted for early-life environmental tobacco smoke exposure, sex, and age.Results:The prevalences of physician-diagnosed asthma, asthma medication use, and hospitalization for asthma were 11.6%, 10.8%, 4.9% at age 1 year, and 34.1%, 40.1%, and 8.5% at 3 years, respectively. Shared environmental effects contributed to the majority of variance in susceptibility to physician-diagnosed asthma and asthma medication use in the first year of life (84%-86%), while genetic effects drove variance in all phenotypes (45%-65%) at age 3 years. Early-life environmental tobacco smoke, sex, and age contributed to variance in susceptibility.Conclusion:Our longitudinal study in Puerto Rican twins demonstrates a changing contribution of shared environmental effects to liability for physician-diagnosed asthma and asthma medication use between ages 1 and 3 years. Early-life environmental tobacco smoke reduction could markedly reduce asthma morbidity in young Puerto Rican children. © 2013 Bunyavanich et al

    Predicting Morphologically-Complex Unknown Words in Igbo

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    The effective handling of previously unseen words is an important factor in the performance of part-of-speech taggers. Some trainable POS taggers use suffix (sometimes prefix) strings as cues in handling unknown words (in effect serving as a proxy for actual linguistic affixes). In the context of creating a tagger for the African language Igbo, we compare the performance of some existing taggers, implementing such an approach, to a novel method for handling morphologically complex unknown words, based on morphological reconstruction (i.e. a linguistically-informed segmentation into root and affixes). The novel method outperforms these other systems by several percentage points, achieving accuracies of around 92 % on morphologically-complex unknown words
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