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Search Results: 1 - 10 of 5499 matches for " Xavier Golay "
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Supervised Fuzzy Mixture of Local Feature Models  [PDF]
Mingyang Xu, Michael Golay
Intelligent Information Management (IIM) , 2011, DOI: 10.4236/iim.2011.33011
Abstract: This paper addresses an important issue in model combination, that is, model locality. Since usually a global linear model is unable to reflect nonlinearity and to characterize local features, especially in a complex sys-tem, we propose a mixture of local feature models to overcome these weaknesses. The basic idea is to split the entire input space into operating domains, and a recently developed feature-based model combination method is applied to build local models for each region. To realize this idea, three steps are required, which include clustering, local modeling and model combination, governed by a single objective function. An adaptive fuzzy parametric clustering algorithm is proposed to divide the whole input space into operating regimes, local feature models are created in each individual region by applying a recently developed fea-ture-based model combination method, and finally they are combined into a single mixture model. Corre-spondingly, a three-stage procedure is designed to optimize the complete objective function, which is actu-ally a hybrid Genetic Algorithm (GA). Our simulation results show that the adaptive fuzzy mixture of local feature models turns out to be superior to global models.
Crise et sécurité alimentaires : vers un nouvel ordre alimentaire mondial ?
Christophe Golay
International Development Policy/Revue Internationale de Politique de Développement , 2012, DOI: 10.4000/poldev.133
Abstract: En 2007 et 2008 a éclaté la plus importante crise alimentaire depuis 1974. La hausse du prix des denrées alimentaires sur le marché international, en particulier du blé, du riz, du soja et du ma s, a entra né une augmentation sans précédent du nombre de personnes sous-alimentées. Malgré une diminution relative du prix des denrées alimentaires depuis l’été 2008, le nombre de personnes sous-alimentées a continué à augmenter en 2009. Cette crise alimentaire a remis la lutte contre la faim au c ur des préoccupations internationales. Depuis le mois de mars 2008, les Etats, les agences des Nations unies et une grande partie des mouvements sociaux ont pris position sur les causes de la crise et les moyens d’y remédier. Malheureusement, alors que ces acteurs tentent de coordonner leurs activités et de proposer des solutions nouvelles, ce sont souvent des recettes anciennes, visant à augmenter la production alimentaire, qui sont mises en avant. Les propositions faites sont souvent contradictoires et les réflexions sur les causes profondes de la faim et de la crise alimentaire – les exclusions sociales, économiques et politiques et les discriminations – ne semblent pas avoir été entendues. Le premier Objectif du Millénaire pour le développement, qui vise à réduire de moitié la proportion des personnes souffrant de sous-alimentation et vivant dans l’extrême pauvreté d’ici 2015, est devenu clairement inatteignable. Mais la crise alimentaire pourrait être à l’origine de la création d’un nouvel ordre alimentaire mondial, basé sur les trois piliers que sont l’aide alimentaire, la sécurité alimentaire et le droit à l’alimentation.
The Food Crisis and Food Security: Towards a New World Food Order?
Christophe Golay
International Development Policy/Revue Internationale de Politique de Développement , 2010, DOI: 10.4000/poldev.145
Abstract: The worst food crisis since 1974 broke out in 2007-08. Higher world market prices of food commodities (especially wheat, rice, soya and maize) sparked an unprecedented increase in the number of hungry people. Despite moderately lower prices since the summer of 2008, the number of the hungry continued to rise in 2009. This food crisis has placed the fight against hunger on the international agenda. Since March 2008 governments UN agencies and many social movements have adopted positions on the causes of the crisis and the means to address it. Unfortunately, while these parties are trying to coordinate their activities and suggest new approaches, the old recipes for producing more food are often brought up. Contradictory proposals are made and the thought given to the causes underlying hunger and the food crisis (social, economic and political discrimination and exclusion) has gone largely unheeded. The first Millennium Development Goal, which calls for cutting the percentage of hungry people by half by 2015, is clearly out of reach. But the food crisis might lead to a new world food order based on the three pillars of food assistance, food security and the right to food.
Pauvreté et droits humains (Poverty and Human Rights)
Christophe Gironde,Christophe Golay
Ceriscope , 2012,
Abstract: Depuis les années 1980, les questions de droits humains, notamment économiques, sociaux et culturels, se sont progressivement imposées dans l'étude des causes de la pauvreté et des mesures qui permettraient de la réduire. Pourtant, force est de constater que les cas de non-respect, dénis et violations des droits humains n'ont pas sensiblement diminué. Les abus entra nés par le phénomène des acquisitions massives de terres agricoles dans les pays les plus pauvres de la planète en fournissent une bonne illustration. Dans ce contexte, les limites des principes volontaires sautent aux yeux, mais la revendication et la protection d'un droit contraignant, tel le droit à l'alimentation, offre des opportunités plus intéressantes pour les communautés locales et les acteurs qui les soutiennent.(Human rights, particularly economic, social and cultural rights, have, since the 1980s, assumed an important part in the study of the causes of poverty and methods used to reduce it. Nevertheless, there has not been a noticeable decline in human rights abuses. One example is the massive agricultural land grabs in the poorest nations of the world. It is clear that voluntary principles are insufficient. However, imposition of a right to food offers an opportunity for local communities and their supporters).
A New Estimator of Intrinsic Dimension Based on the Multipoint Morisita Index
Jean Golay,Mikhail Kanevski
Physics , 2014,
Abstract: The size of datasets has been increasing rapidly both in terms of number of variables and number of events. As a result, the empty space phenomenon and the curse of dimensionality complicate the extraction of useful information. But, in general, data lie on non-linear manifolds of much lower dimension than that of the spaces in which they are embedded. In many pattern recognition tasks, learning these manifolds is a key issue and it requires the knowledge of their true intrinsic dimension. This paper introduces a new estimator of intrinsic dimension based on the multipoint Morisita index. It is applied to both synthetic and real datasets of varying complexities and comparisons with other existing estimators are carried out. The proposed estimator turns out to be fairly robust to sample size and noise, unaffected by edge effects, able to handle large datasets and computationally efficient.
A Comparison of Imaging Techniques to Monitor Tumor Growth and Cancer Progression in Living Animals
Anne-Laure Puaux,Lai Chun Ong,Yi Jin,Irvin Teh,Michelle Hong,Pierce K. H. Chow,Xavier Golay,Jean-Pierre Abastado
International Journal of Molecular Imaging , 2011, DOI: 10.1155/2011/321538
Abstract: Introduction and Purpose. Monitoring solid tumor growth and metastasis in small animals is important for cancer research. Noninvasive techniques make longitudinal studies possible, require fewer animals, and have greater statistical power. Such techniques include FDG positron emission tomography (FDG-PET), magnetic resonance imaging (MRI), and optical imaging, comprising bioluminescence imaging (BLI) and fluorescence imaging (FLI). This study compared the performance and usability of these methods in the context of mouse tumor studies. Methods. B16 tumor-bearing mice ( for each study) were used to compare practicality, performance for small tumor detection and tumor burden measurement. Using RETAAD mice, which develop spontaneous melanomas, we examined the performance of MRI ( mice) and FDG-PET ( mice) for tumor identification. Results. Overall, BLI and FLI were the most practical techniques tested. Both BLI and FDG-PET identified small nonpalpable tumors, whereas MRI and FLI only detected macroscopic, clinically evident tumors. FDG-PET and MRI performed well in the identification of tumors in terms of specificity, sensitivity, and positive predictive value. Conclusion. Each of the four methods has different strengths that must be understood before selecting them for use. 1. Introduction Studies in living animals are critical to oncology research, and many experimental models have been exploited for drug development and basic studies [1, 2]. Fast-growing tumors can be generated in mice by orthotopic or ectopic implantation of tumor cell lines. However, models exhibiting spontaneous oncogenesis better mimic human disease therefore, oncogene-driven or chemically induced tumor models have come into use more recently [3, 4]. In both spontaneous and transplanted tumor models, the most common readouts are primary tumor growth and metastatic spread, but accurate measurement of these parameters is challenging. Unlike necropsy, noninvasive imaging techniques could offer an ideal solution as they allow measurement of tumor burden in the whole body without the need to sacrifice the animal. This makes longitudinal studies possible, simultaneously reducing the number of animals required and producing more robust data. These technologies are also sensitive and accurate enough to detect microscopic nodules, whose importance in human disease prognosis is increasingly recognized [5, 6]. Several imaging techniques have recently become available for small animals [7]. These include 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography (FDG-PET) [8], T2-weighted
MS Cortical Lesions on DIR: Not Quite What They Seem?
Varun Sethi, Nils Muhlert, Maria Ron, Xavier Golay, Claudia A. Wheeler-Kingshott, David H. Miller, Declan T. Chard, Tarek A. Yousry
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0078879
Abstract: Objective Accurate identification and localization of cortical gray matter (CGM) lesions in MS is important when determining their clinical relevance. Double inversion recovery (DIR) scans have been widely used to detect MS CGM lesions. Phase sensitive inversion recovery (PSIR) scans have a higher signal to noise, and can therefore be obtained at a higher resolution within clinically acceptable times. This enables detection of more CGM lesions depicting a clearer cortical and juxtacortical anatomy. In this study, we systematically investigated if the use of high resolution PSIR scans changes the classification of CGM lesions, when compared with standard resolution DIR scans. Methods 60 patients [30 RR(Relapsing remitting) and 15 each with PP(Primary progressive) and SP(Secondary progressive) MS] were scanned on a 3T Philips Achieva MRI scanner. Images acquired included DIR (1×1×3 mm resolution) and PSIR (0.5×0.5×2 mm). CGM lesions were detected and classified on DIR as intracortical (IC) or leucocortical (LC). We then examined these lesions on corresponding slices of the high resolution PSIR scans and categorized them as IC, LC, Juxtacortical white matter (JC-WM, abutting but not entering cortex) and other white matter (WM, not juxtacortical). Classifications using both scans were noted. Results 282 IC and 483 LC were identified on DIR. Of the IC lesions, 61% were confirmed as IC on PSIR, 35.5% were reclassified as LC and 3.5% as JC-WM or other WM only. Of the LC DIR lesions, 43.9% were confirmed at LC on PSIR, 16.1% were reclassified as IC and 40% as JC-WM or other WM only. Overall, 50% (381/765) of CGM lesions seen on DIR were reclassified, and 26.5% (203/765) affected WM only. Conclusions When compared with higher resolution PSIR, a significant proportion of lesions classified as involving CGM on DIR appear to either contain more white matter than expected or to not involve CGM at all.
Cortical and subcortical anatomy of chronic spatial neglect following vascular damage
Laetitia Golay, Armin Schnider, Radek Ptak
Behavioral and Brain Functions , 2008, DOI: 10.1186/1744-9081-4-43
Abstract: We examined the anatomical basis of spatial neglect in a sample of patients examined in the post-acute stage following right-hemispheric vascular brain damage. Lesions of 28 patients with chronic spatial neglect were contrasted to lesions of 22 control patients without neglect using lesion subtraction techniques and voxel-wise comparisons.The comparisons identified the temporo-parietal junction (TPJ) with underlying white matter, the supramarginal gyrus, the posterior STG, and the insula as brain regions damaged significantly more often in neglect compared to non-neglect patients. In a subgroup of neglect patients showing particularly large cancellation bias together with small errors on line bisection damage was prevalent deep in the frontal lobe while damage of patients with the reverse pattern was located in the white matter of the TPJ.Considering our results and the findings of previous studies, spatial neglect appears to be associated with a network of regions involving the TPJ, inferior IPL, posterior STG, the insular cortex, and posterior-frontal projections. Frontal structures or projections may be of particular relevance for spatial exploration, while the IPL may be important for object-based attention as required for line bisection.Damage to the right cerebral hemisphere may lead to a severe impairment in spatial orienting towards the left side of space: spatial neglect [1,2]. The exact locus of damage leading to this striking and debilitating disorder is currently intensely discussed [3-6]. Early investigations, based on visual inspection of computerized tomography (CT) scans, suggested that the inferior parietal lobule (IPL) and the temporo-parietal junction (TPJ) are the brain regions most often damaged in patients with spatial neglect [7,8]. However, these studies may be criticized on the ground of their inclusion criteria – in particular, neglect may have been confounded with visual field loss – as well as the absence of a comparison between patients
Against coefficient of variation for estimation of intraindividual variability with accuracy measures
Philippe Golay,Delphine Fagot,Thierry Lecerf
Tutorials in Quantitative Methods for Psychology , 2013,
Abstract: Previous studies have shown that intraindividual variability (iV) in performance is an important indicator of individual s cognitive functioning and neurological integrity. While most experiments have examined iV of performance using Reaction Time data (RTs), few studies have considered it with accuracy measures (e.g. number or percentage of correct responses). For these two types of measures, intraindividual standard deviation (iSD) or intraindividual coefficient of variation (iCV; intraindividual standard deviation divided by the individual mean) were used as indicators of iV in performance. However, because accuracy data have a lower and an upper bound (in contrast to RTs), we illustrate both formally and with simulated data, that the iCV cannot be used with accuracy measures. We also show that the coefficient iCV is influenced by the number of items which is an issue when dealing with missing data. We further provide formulas that may help researchers to visualize and correctly interpret their data using any spreadsheet software. The current article finally proposes an alternative coefficient (zeta) to examine iV in performance with accuracy measures that shows similar behaviour as does iCV with RTs data.
The Multipoint Morisita Index for the Analysis of Spatial Patterns
J. Golay,M. Kanevski,C. Vega Orozco,M. Leuenberger
Physics , 2013, DOI: 10.1016/j.physa.2014.03.063
Abstract: In many fields, the spatial clustering of sampled data points has many consequences. Therefore, several indices have been proposed to assess the level of clustering affecting datasets (e.g. the Morisita index, Ripley's K-function and R\'enyi's generalized entropy). The classical Morisita index measures how many times it is more likely to select two measurement points from the same quadrats (the data set is covered by a regular grid of changing size) than it would be in the case of a random distribution generated from a Poisson process. The multipoint version (k-Morisita) takes into account k points with k greater than or equal to 2. The present research deals with a new development of the k-Morisita index for (1) monitoring network characterization and for (2) the detection of patterns in monitored phenomena. From a theoretical perspective, a connection between the k-Morisita index and multifractality has also been found and highlighted on a mathematical multifractal set.
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