3,990 research outputs found

    Context and Interpretation in Laboratory Experiments: The Case of Reciprocity

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    The existing literature acknowledges that a mismatch between the experimenter's and the subjects' models of an experimental task can adversely affect the interpretation of data from laboratory experiments. We discuss why the two common experimental designs (between-subjects and within-subjects) used to conduct experiments may fail to sufficiently account for this concern. An alternative design for laboratory experiments is proposed which may alleviate this concern especially in studies of social preferences. The proposed design is used to answer some questions that have attracted continued attention in the literature on social preferences in general and reciprocity in particular.Experimental design, Context, Trust game

    Toward an estimation of nadir objective vector using a hybrid of evolutionary and local search approaches

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    A nadir objective vector is constructed from the worst Pareto-optimal objective values in a multiobjective optimization problem and is an important entity to compute because of its significance in estimating the range of objective values in the Pareto-optimal front and also in executing a number of interactive multiobjective optimization techniques. Along with the ideal objective vector, it is also needed for the purpose of normalizing different objectives, so as to facilitate a comparison and agglomeration of the objectives. However, the task of estimating the nadir objective vector necessitates information about the complete Pareto-optimal front and has been reported to be a difficult task, and importantly an unsolved and open research issue. In this paper, we propose certain modifications to an existing evolutionary multiobjective optimization procedure to focus its search toward the extreme objective values and combine it with a reference-point based local search approach to constitute a couple of hybrid procedures for a reliable estimation of the nadir objective vector. With up to 20-objective optimization test problems and on a three-objective engineering design optimization problem, one of the proposed procedures is found to be capable of finding the nadir objective vector reliably. The study clearly shows the significance of an evolutionary computing based search procedure in assisting to solve an age-old important task in the field of multiobjective optimization

    Local search based evolutionary multi-objective optimization algorithm for constrained and unconstrained problems

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    Evolutionary multi-objective optimization algorithms are commonly used to obtain a set of non-dominated solutions for over a decade. Recently, a lot of emphasis have been laid on hybridizing evolutionary algorithms with MCDM and mathematical programming algorithms to yield a computationally efficient and convergent procedure. In this paper, we test an augmented local search based EMO procedure rigorously on a test suite of constrained and unconstrained multi-objective optimization problems. The success of our approach on most of the test problems not only provides confidence but also stresses the importance of hybrid evolutionary algorithms in solving multi-objective optimization problems

    A survey on handling computationally expensive multiobjective optimization problems with evolutionary algorithms

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    This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.Evolutionary algorithms are widely used for solving multiobjective optimization problems but are often criticized because of a large number of function evaluations needed. Approximations, especially function approximations, also referred to as surrogates or metamodels are commonly used in the literature to reduce the computation time. This paper presents a survey of 45 different recent algorithms proposed in the literature between 2008 and 2016 to handle computationally expensive multiobjective optimization problems. Several algorithms are discussed based on what kind of an approximation such as problem, function or fitness approximation they use. Most emphasis is given to function approximation-based algorithms. We also compare these algorithms based on different criteria such as metamodeling technique and evolutionary algorithm used, type and dimensions of the problem solved, handling constraints, training time and the type of evolution control. Furthermore, we identify and discuss some promising elements and major issues among algorithms in the literature related to using an approximation and numerical settings used. In addition, we discuss selecting an algorithm to solve a given computationally expensive multiobjective optimization problem based on the dimensions in both objective and decision spaces and the computation budget available.The research of Tinkle Chugh was funded by the COMAS Doctoral Program (at the University of Jyväskylä) and FiDiPro Project DeCoMo (funded by Tekes, the Finnish Funding Agency for Innovation), and the research of Dr. Karthik Sindhya was funded by SIMPRO project funded by Tekes as well as DeCoMo

    On the number of signals in multivariate time series

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    We assume a second-order source separation model where the observed multivariate time series is a linear mixture of latent, temporally uncorrelated time series with some components pure white noise. To avoid the modelling of noise, we extract the non-noise latent components using some standard method, allowing the modelling of the extracted univariate time series individually. An important question is the determination of which of the latent components are of interest in modelling and which can be considered as noise. Bootstrap-based methods have recently been used in determining the latent dimension in various methods of unsupervised and supervised dimension reduction and we propose a set of similar estimation strategies for second-order stationary time series. Simulation studies and a sound wave example are used to show the method's effectiveness

    Microbiology of Bartholin's Duct Abscess

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    Objective: The aim of the study was to determine the currently most frequent microbial findings in Bartholin's duct abscess

    Pareto optimality in multilayer network growth

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    We model the formation of multi-layer transportation networks as a multi-objective optimization process, where service providers compete for passengers, and the creation of routes is determined by a multi-objective cost function encoding a trade-off between efficiency and competition. The resulting model reproduces well real-world systems as diverse as airplane, train and bus networks, thus suggesting that such systems are indeed compatible with the proposed local optimization mechanisms. In the specific case of airline transportation systems, we show that the networks of routes operated by each company are placed very close to the theoretical Pareto front in the efficiency-competition plane, and that most of the largest carriers of a continent belong to the corresponding Pareto front. Our results shed light on the fundamental role played by multi-objective optimization principles in shaping the structure of large-scale multilayer transportation systems, and provide novel insights to service providers on the strategies for the smart selection of novel routes

    Elucidation of the secoiridoid pathway in Catharanthus roseus

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    The (seco)iridoids and their derivatives, the monoterpenoid indole alkaloids (MIAs), form two large families of plant-derived bioactive compounds with a wide spectrum of high-value pharmacological and insect-repellent activities. Vinblastine and vincristine, MIAs used as anti-cancer drugs, are produced by Catharanthus roseus in extremely low levels, leading to high market prices and poor availability. Their biotechnological production is hampered by the fragmentary knowledge of their biosynthesis. Here we report the discovery of the last four missing steps of the (seco)iridoid biosynthesis pathway. Expression of the eight genes encoding this pathway together with two genes boosting precursor formation and two downstream alkaloid biosynthesis genes in an alternative plant host allowed the heterologous production of the complex MIA strictosidine. This confirms the functionality of all enzymes of the pathway and highlights their utility for synthetic biology programs towards a sustainable biotechnological production of valuable (seco)iridoids and alkaloids with pharmaceutical and agricultural applications.UBL - phd migration 201

    Rannikkotykistön teknillinen kehitys toisen maailmansodan jälkeen

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    Artikkelin aluksi esitellään toisesta maailmansodasta saadut kokemuksen rannikon puolustamisessa ja maihinnousun torjunnassa. Kirjoittaja toteaa, että "nykyaikaisen maihinnousu- ja maahanlaskutekniikan suomat mahdollisuudet yhdessä kiinteän tykistön käyttöön perustuvan puolustuksen joustamattomuuden kanssa ovat aiheuttaneet liikkuvien rannikkopuolustusjoukkojen muodostamisen". Artikkelissa esitellään sotien kokemusten perustella tykkikalustossa, ampumatarvikkeissa sekä mittaus- ja johtokalustossa tapahtuneet muutokset. Ohjuksien osalta esitellään muun muassa toiminnallisia vaatimuksia sekä esimerkkinä ajatus niiden ohjausjärjestelmästä. Kirjoittaja on sitä mieltä, että ohjukset eivät tule lähitulevaisuudessa syrjäyttämään aktiotykistöä. Suojaa käsitellään uusien uhkien asettamien vaatimusten pohjalta

    Identification of transcriptional and metabolic programs related to mammalian cell size

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    SummaryBackgroundRegulation of cell size requires coordination of growth and proliferation. Conditional loss of cyclin-dependent kinase 1 in mice permits hepatocyte growth without cell division, allowing us to study cell size in vivo using transcriptomics and metabolomics.ResultsLarger cells displayed increased expression of cytoskeletal genes but unexpectedly repressed expression of many genes involved in mitochondrial functions. This effect appears to be cell autonomous because cultured Drosophila cells induced to increase cell size displayed a similar gene-expression pattern. Larger hepatocytes also displayed a reduction in the expression of lipogenic transcription factors, especially sterol-regulatory element binding proteins. Inhibition of mitochondrial functions and lipid biosynthesis, which is dependent on mitochondrial metabolism, increased the cell size with reciprocal effects on cell proliferation in several cell lines.ConclusionsWe uncover that large cell-size increase is accompanied by downregulation of mitochondrial gene expression, similar to that observed in diabetic individuals. Mitochondrial metabolism and lipid synthesis are used to couple cell size and cell proliferation. This regulatory mechanism may provide a possible mechanism for sensing metazoan cell size
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