1,721,012 research outputs found
A Game perspective to complex adaptive systems
Full text linkUnderstanding the behaviour of a system through the properties of the elements of the system is a central problem in several fields of contemporary research. Appealing approaches for gaining such understanding have been proposed in complex systems studies. One particular approach is based on the scheme of agent-based modelling, in which the elements of the system are described by a set of precise rules which are implemented by computer programs. This dissertation is focused on topics related to two types of agent-based models: minority games and spatial two player games.
The first part of the thesis deals with minority games that have been extensively studied in the physics literature during the past eight years. A minority game describes a society of adaptive individuals with bounded rationality competing for scarce resources. Questions arising from such a model are associated with the efficiency of the system and the success of its individuals in utilizing the scarce resources. Previous studies have indicated that in case the individuals are allowed to evolve, they tend to evolve such that the efficiency of the system improves. However, the actual level of efficiency substantially depends on the type of evolution present in the system. We have applied genetic algorithms to make the system evolving. Our results indicate that natural selection and genetic algorithms can lead the system perform optimally and increase the success of individuals remarkably.
The second part of the thesis describes aspects of games that model strategic interaction situations between individuals. Especially, the focus of this part of the thesis is on models that aim at explaining the emergence and persistence of cooperative behaviour in an animal or human society. Previous studies have indicated that spatial structure of the society largely contributes to the maintenance of cooperation in these models. However, much of the research has been carried out by relying on evolutionary dynamics of the society associated with changes occurring in long times. We have explored a spatial game by allowing the individuals in the system be adaptive and act on short times, and our results show that the characteristic behaviour of the system is different from that observed in studies using evolutionary dynamics.reviewe
Plasma ceramides predict cardiovascular death in patients with stable coronary artery disease and acute coronary syndromes beyond LDL-cholesterol
Full text linkAims The aim was to study the prognostic value of plasma ceramides (Cer) as cardiovascular death (CV death) markers in three independent coronary artery disease (CAD) cohorts.
Methods and results Corogene study is a prospective Finnish cohort including stable CAD patients (n = 160). Multiple lipid biomarkers and C-reactive protein were measured in addition to plasma Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/24:0), and Cer(d18:1/24:1). Subsequently, the association between high-risk ceramides and CV mortality was investigated in the prospective Special Program University Medicine—Inflammation in Acute Coronary Syndromes (SPUM-ACS) cohort (n = 1637), conducted in four Swiss university hospitals. Finally, the results were validated in Bergen Coronary Angiography Cohort (BECAC), a prospective Norwegian cohort study of stable CAD patients. Ceramides, especially when used in ratios, were significantly associated with CV death in all studies, independent of other lipid markers and C-reactive protein. Adjusted odds ratios per standard deviation for the Cer(d18:1/16:0)/Cer(d18:1/24:0) ratio were 4.49 (95% CI, 2.24–8.98), 1.64 (1.29–2.08), and 1.77 (1.41–2.23) in the Corogene, SPUM-ACS, and BECAC studies, respectively. The Cer(d18:1/16:0)/Cer(d18:1/24:0) ratio improved the predictive value of the GRACE score (net reclassification improvement, NRI = 0.17 and ΔAUC = 0.09) in ACS and the predictive value of the Marschner score in stable CAD (NRI = 0.15 and ΔAUC = 0.02).
Conclusions Distinct plasma ceramide ratios are significant predictors of CV death both in patients with stable CAD and ACS, over and above currently used lipid markers. This may improve the identification of high-risk patients in need of more aggressive therapeutic interventions.All authors:Reijo Laaksonen, Kim Ekroos, Marko Sysi-Aho, Mika Hilvo, Terhi Vihervaara, Dimple Kauhanen, Matti Suoniemi, Reini Hurme, Winfried März, Hubert Scharnagl, Tatjana Stojakovic, Efthymia Vlachopoulou, Marja-Liisa Lokki, Markku S. Nieminen, Roland Klingenberg, Christian M. Matter, Thorsten Hornemann, Peter Jüni, Nicolas Rodondi, Lorenz Räber, Stephan Windecker, Baris Gencer, Eva Ringdal Pedersen, Grethe S. Tell, Ottar Nygård, Francois Mach, Juha Sinisalo, Thomas F. Lüsch
A mathematical model of metabolism and autoimmune response in progression to type 1 diabetes
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A regression subset-selection strategy for fat-structure data
No full textA strategy is proposed for finding the most significant linear regression submodel for fat-structure data, that is when the number of variables n exceeds the number of available observations m. The method consists of two stages. First, a heuristic is employed to preselect a number of variables nS such that nS ≤m. The second stage performs an exhaustive search on the reduced list of variables. It employs a regression tree structure that generates all possible subset models. Non-optimal subtrees are pruned using a branch-and-bound device. Cross validation experiments on a real biomedical dataset are presented and analyzed
Bioinformatics and computational methods for lipidomics
No full textLarge amounts of lipidomics data are rapidly becoming available. However, there is a lack of tools capable of taking the full advantage of the wealth of new information. Lipid bioinformatics is thus an emerging need as well as challenge for lipid research. Lipid concentration changes in biological systems reflect regulation at multiple spatial and dynamic scales, e.g., biochemical reactions in the cells, intercellular lipid trafficking, changes in cell membrane composition, systemic lipid metabolism or lipid oxidation. In order to address the complexity of lipids and their regulation, four areas of bioinformatics need to be developed: (1) data processing and lipid identification, (2) statistical data analysis, (3) pathway analysis, and (4) lipid modeling in systems and biophysical contexts. In this paper we overview the current state of the lipid bioinformatics field as well as suggest few potential new areas of research.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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