406 research outputs found

    On the Complexity of Newman's Community Finding Approach for Biological and Social Networks

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    Given a graph of interactions, a module (also called a community or cluster) is a subset of nodes whose fitness is a function of the statistical significance of the pairwise interactions of nodes in the module. The topic of this paper is a model-based community finding approach, commonly referred to as modularity clustering, that was originally proposed by Newman and has subsequently been extremely popular in practice. Various heuristic methods are currently employed for finding the optimal solution. However, the exact computational complexity of this approach is still largely unknown. To this end, we initiate a systematic study of the computational complexity of modularity clustering. Due to the specific quadratic nature of the modularity function, it is necessary to study its value on sparse graphs and dense graphs separately. Our main results include a (1+\eps)-inapproximability for dense graphs and a logarithmic approximation for sparse graphs. We make use of several combinatorial properties of modularity to get these results. These are the first non-trivial approximability results beyond the previously known NP-hardness results.Comment: Journal of Computer and System Sciences, 201

    Extension of graph clustering algorithms based on SCAN method in order to target weighted graphs

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    In this thesis we evaluate current neighbour-based graph clustering algorithms: SCAN, DHSCAN, and AHSCAN. These algorithms possess the ability to identify special nodes in graphs such as hubs and outliers. We propose and extension for each of these in order to support weighted edges. We further implemented two graph generating frameworks to create test cases. In addition we used a graph derived from the ENRON email log. We also implemented a Fast Modularity clustering algorithm, which is considered as one of the top graph clustering algorithms nowadays. One of three sets of experiments showed that results produced by extended algorithms were better than one of the reference algorithms, in other words more nodes were classified correctly. Other experiments revealed some limitations of the newly proposed methods where we noted that they do not perform as well on other types of graphs. Hence, the proposed algorithms perform best on social graphs with pronounced community structure

    Brain Modularity Mediates the Relation between Task Complexity and Performance

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    Recent work in cognitive neuroscience has focused on analyzing the brain as a network, rather than as a collection of independent regions. Prior studies taking this approach have found that individual differences in the degree of modularity of the brain network relate to performance on cognitive tasks. However, inconsistent results concerning the direction of this relationship have been obtained, with some tasks showing better performance as modularity increases and other tasks showing worse performance. A recent theoretical model (Chen & Deem, 2015) suggests that these inconsistencies may be explained on the grounds that high-modularity networks favor performance on simple tasks whereas low-modularity networks favor performance on more complex tasks. The current study tests these predictions by relating modularity from resting-state fMRI to performance on a set of simple and complex behavioral tasks. Complex and simple tasks were defined on the basis of whether they did or did not draw on executive attention. Consistent with predictions, we found a negative correlation between individuals' modularity and their performance on a composite measure combining scores from the complex tasks but a positive correlation with performance on a composite measure combining scores from the simple tasks. These results and theory presented here provide a framework for linking measures of whole brain organization from network neuroscience to cognitive processing.Comment: 47 pages; 4 figure

    I Dissent: The Federal Circuit\u27s Great Dissenter, Her Influence on the Patent Dialogue, and Why It Matters

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    This Article is the first study to comprehensively explore the centrality of the patent dialogue at the Court of Appeals for the Federal Circuit, the nation\u27s principal patent court from empirical, doctrinal, and policy perspectives. It offers several insights into how the Federal Circuit reaches consensus and when it does not, serving as a window into its inner workings, a reference to academics, judges, and attorneys alike. More broadly, this Article provides a template to study the legal dialogue of other judges at the Federal Circuit, those in other Circuits, as well as those in other areas of the law. The Article looks through the lens of one of the Federal Circuit\u27s founders, Judge Pauline Newman, whose opinions have been instrumental in developing patent law over the last thirty years. These opinions reveal the consistency and coherence of her judicial philosophy and a sincere commitment to the mission of the Federal Circuit, a court she helped to create. Moreover, her dissents, particularly over the last twenty years, serve as an institutional record for course correction even as the court continues to navigate new fault lines brought about by the America Invents Act, the globalization of patent litigation, and disruptive technologies that challenge the compact of patent law today. The study involved a review of 1,789 cases and 4,981 law review articles to give 10,461 data points. An in-person interview with Judge Newman, conducted over two sessions, complements the quantitative dimension of this Article. Her frank insights fill the gaps in the facts and quantitative findings. They also provide a fresh and reflective assessment of her dissents. The data confirms that Judge Newman is the Federal Circuit\u27s most prolific dissenter and that her dissents resonate with the Supreme Court, her colleagues, and academic commentators more than those of any other Federal Circuit judge. The data identifies her ideological supporters and detractors on the court, but her influence with those people and the industry is more nuanced than it might appear at first blush. The Article also will paint the nuanced picture of her influence on critical challenges in patent law that the Federal Circuit continues to contend with today

    09081 Abstracts Collection -- Similarity-based learning on structures

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    From 15.02. to 20.02.2009, the Dagstuhl Seminar 09081 ``Similarity-based learning on structures \u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

    Network deconvolution as a general method to distinguish direct dependencies in networks

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    Recognizing direct relationships between variables connected in a network is a pervasive problem in biological, social and information sciences as correlation-based networks contain numerous indirect relationships. Here we present a general method for inferring direct effects from an observed correlation matrix containing both direct and indirect effects. We formulate the problem as the inverse of network convolution, and introduce an algorithm that removes the combined effect of all indirect paths of arbitrary length in a closed-form solution by exploiting eigen-decomposition and infinite-series sums. We demonstrate the effectiveness of our approach in several network applications: distinguishing direct targets in gene expression regulatory networks; recognizing directly interacting amino-acid residues for protein structure prediction from sequence alignments; and distinguishing strong collaborations in co-authorship social networks using connectivity information alone. In addition to its theoretical impact as a foundational graph theoretic tool, our results suggest network deconvolution is widely applicable for computing direct dependencies in network science across diverse disciplines.National Institutes of Health (U.S.) (grant R01 HG004037)National Institutes of Health (U.S.) (grant HG005639)Swiss National Science Foundation (Fellowship)National Science Foundation (U.S.) (NSF CAREER Award 0644282

    Help-seeking by older wife caregivers of demented husbands: a grounded theory approach

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    The purpose of this study was to gain an understanding of patterns of help seeking by older wife caregivers of demented husbands. Essential to an understanding of service utilization is an understanding of the more basic process of help-seeking.Research to date has largely concentrated on help-seeking as a variable, rather than as an independent entity.Grounded theory methodology with a nursing perspective of health as expanding consciousness, was used to explore interactions, thoughts and feelings associated with patterns of help-seeking by eleven older wife caregivers and allowed for a more holistic view of the process of help-seeking by these older women. This methodology led to discovery of a new substantive theory entitled Help-seeking choices: Taking one day at a time which was grounded in reality as experienced by the participants and illuminates help-seeking for this group of caregivers. The core category of reaching out/reaching within described the main phenomena of wives reaching out to involve both informal and formal sources and reaching within themselves to manage care and seek help on a day-to-day basis. Wives made choices to employ strategies of avoiding,shouldering and facing to accomplish continuing to provide care at home for the husbands. These choices were influenced by a myriad of facilitating and hindering intervening conditions.Understanding obtained from the study indicates that earlier screening and intervention are essential to assisting with identification of dementia and to help caregivers realize that a problem exists. Further suggestion is for more comprehensive case management across health care settings for this group, and a recognition of the impact of previous experiences on future health choices by these caregivers. The Importance of pattern recognition which enables caregivers to view, seek, and manage their husbands\u27 health care in creative ways is also indicated. Understanding gained may lead ultimately to the development of interventions which can increase the effectiveness of help-seeking patterns, result in more appropriate utilization of formal and informal resources, reduce burden and stress associated with the caregiving role, and assist women to sustain the caregiving role

    (Attenuated) hallucinations join basic symptoms in a transdiagnostic network cluster analysis

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    Producción CientíficaHallucinations are considered characteristic symptoms of psychosis and part of the ‘psychosis superspectrum’ of the Hierarchical Taxonomy Of Psychopathology (HiTOP) initiative. To gain insight into their psychopathological relevance, we studied their dimensional placement within a single dense transdiagnostic network constituting of basic symptoms as well as of attenuated and frank psychotic, and related symptoms. Newman's modularity analysis was used to detect symptom clusters in an earlier generated network (Jimeno, N., et al., 2020. Main symptomatic treatment targets in suspected and early psychosis: New insights from network analysis. Schizophr. Bull. 46, 884–895. https://doi.org/10.1093/schbul/sbz140). The constituting 86 symptoms were assessed with the Schizophrenia Proneness Instrument, Adult version (SPI-A), the Structured Interview for Psychosis-Risk Syndromes (SIPS), and the Positive And Negative Syndrome Scale (PANSS) in three adult samples of an early detection service: clinical high-risk (n = 203), first-episode psychosis (n = 153), and major depression (n = 104). Three clusters were detected: “subjective disturbances”, “positive symptoms and behaviors”, and “negative and anxious-depressive symptoms”. The predominately attenuated hallucinations of both SIPS and PANSS joined the basic symptoms in “subjective disturbances”, whereas other positive symptoms entered “positive symptoms and behaviors”. Our results underline the importance of insight in separating true psychotic hallucinations from other hallucinatory experiences that, albeit phenomenologically similar are still experienced with some insight, i.e., are present in an attenuated form. We conclude that, strictly, hallucinations held with any degree of insight should not be used to diagnose transition to or presence of frank psychoses and, relatedly, to justify antipsychotic medication.Deutsche Forschungsgemeinschaft (grants KL970/3-1 and KL970/3-2)Koeln Fortune Program / Faculty of Medicine of the University of Cologne (projects 8/2005 and 27/2006)Ministerio de Ciencia e Innovación - Fondo Europeo de Desarrollo Regional (projects PGC2018-098214-A-I00 and DPI2017-84280-R)Unión Europea (grant 602152)German Research Foundation (grant KA 4413/1-1
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