A SAEM algorithm for the estimation of template and deformation parameters in medical image sequences

This paper is about object deformations observed throughout a sequence of images. We present a statistical framework in which the observed images are defined as noisy realizations of a randomly deformed template image. In this framework, we focus on the problem of the estimation of parameters related to the template and deformations. Our main motivation is the construction of estimation framework and algorithm which can be applied to short sequences of complex and highly-dimensional images. The originality of our approach lies in the representations of the template and deformations, which are defined on a common triangulated domain, adapted to the geometry of the observed images. In this way, we have joint representations of the template and deformations which are compact and parsimonious. Using such representations, we are able to drastically reduce the number of parameters in the model. Besides, we adapt to our framework the Stochastic Approximation EM algorithm combined with a Markov Chain Monte Carlo procedure which was proposed in 2004 by Kuhn and Lavielle. Our implementation of this algorithm takes advantage of some properties which are specific to our framework. More precisely, we use the Markovian properties of deformations to build an efficient simulation strategy based on a Metropolis-Hasting-Within-Gibbs sampler. Finally, we present some experiments on sequences of medical images and synthetic data.     

New public management and professionals in the public sector. What new patterns beyond opposition?

The proliferation of reforms in public administration based on the principles and instruments of the “New Public Management” (NPM) have triggered protest from and collective action by many professional groups in various sectors (healthcare, education, justice, social work, research…) and raised questions about the future of professionals working in the public service, particularly as concerns their autonomy. However, after analyzing the situation, it seems that the opposition between NPM and certain professional groups is not the last word in the debate. Should changes be seen as the decline of professional groups and of their autonomy or as a transformation of professional models, an overhaul of professionalism, etc.? Such questions, which current events in France and Europe have brought to the fore, are food for ongoing sociological thought. They are broached here empirically, from the field, applying varied levels of analysis and research. The contributors to this dossier explore the different forms of tension existing between professional groups and NPM.     

From Geneva to San José: The ILO standards and the Inter-American System for the protection of human rights

This article analyses how the Inter-American System for the protection of human rights has used ILO standards as a reference on matters relating to freedom of association and the rights of indigenous peoples. Having established the limits to their use, the authors also analyse how these standards have influenced recent Inter-American jurisprudence in relation to certain economic, social and cultural rights. They argue that such cross-referencing is both desirable and useful, since it allows the Inter-American bodies to base their arguments on the interpretation of specialized authorities, thereby reinforcing the credibility, normative legitimacy and universality of their decisions.     

Anisotropy of Hölder Gaussian random fields: characterization,estimation, and application to image textures

The characterization and estimation of the Hölder regularity of random fields has long been an important topic of Probability theory and Statistics. This notion of regularity has also been widely used in image analysis to measure the roughness of textures. However, such a measure is rarely sufficient to characterize textures as it does not account for their directional properties (e.g., isotropy and anisotropy). In this paper, we present an approach to further characterize directional properties associated with the Hölder regularity of random fields. Using the spectral density, we define a notion of asymptotic topothesy which quantifies directional contributions of field high-frequencies to the Hölder regularity. This notion is related to the topothesy function of the so-called anisotropic fractional Brownian fields, but is defined in a more generic framework of intrinsic random fields. We then propose a method based on multi-oriented quadratic variations to estimate this asymptotic topothesy. Eventually, we evaluate this method on synthetic data and apply it for the characterization of historical photographic papers.     

Influence and sensitivity measures in correspondence analysis

Since correspondence analysis appears to be sensitive to outliers, it is important to be able to evaluate the sensitivity of the data on the results. This article deals with measuring the influence of rows and columns on the results obtained with correspondence analysis. To establish the influence of individuals on the analysis, we use the notion of influence curve and we propose a general criterion based on the mean square error to measure the sensitivity of the correspondence analysis and its robustness. A numerical example is presented to illustrate the notions developed in this article.     

Joint Estimation of Intersecting Context Tree Models

We study a problem of model selection for data produced by two different context tree sources. Motivated by linguistic questions, we consider the case where the probabilistic context trees corresponding to the two sources are finite and share many of their contexts. In order to understand the differences between the two sources, it is important to identify which contexts and which transition probabilities are specific to each source. We consider a class of probabilistic context tree models with three types of contexts: those which appear in one, the other, or both sources. We use a BIC penalized maximum likelihood procedure that jointly estimates the two sources. We propose a new algorithm which efficiently computes the estimated context trees. We prove that the procedure is strongly consistent. We also present a simulation study showing the practical advantage of our procedure over a procedure that works separately on each data set.     

Various Approaches for Predicting Land Cover in Mountain Areas

Using former maps, geographers intend to study the evolution of the land cover in order to have a prospective approach on the future landscape; predictions of the future land cover, by the use of older maps and environmental variables, are usually done through the GIS (Geographic Information System). We propose here to confront this classical geographical approach with statistical approaches: a linear parametric model (polychotomous regression modeling) and a nonparametric one (multilayer perceptron). These methodologies have been tested on two real areas on which the land cover is known at various dates; this allows us to emphasize the benefit of these two statistical approaches compared to GIS and to discuss the way GIS could be improved by the use of statistical models.     

The Well-Being of the Canadian Arctic Inuit: The Relevant Weight of Economy in the Happiness Equations

Which of the three dimensions of Allardt’s model, “having, loving, and being”, best predicts the incidence of subjective feeling of well-being among the Canadian Arctic Inuit adults? To answer this question, two logistic regression equations have been constructed, one based on a negative assessment of well-being (feeling of despair), and the other on a positive assessment (satisfaction with life in the community). Each of them took first the form of a global model, and then of three scale models, one for each dimension of the Allardt’s model. The equations are likely to be more effective for predicting the incidence of Inuit’s feeling of satisfaction than for anticipating their feeling of despair. Furthermore, the “being” scale model is the one that will have contributed most to the predictive performance of the global model. In other words, what the Inuit “ARE” contributes more to the incidence of their satisfaction with life than what they “HAVE” or what they “LOVE”.     

Objective measures of well-being and the cooperative production problem

 The concern for measuring well-being objectively (as opposed to subjectively, that is, relying only on preferences) is found in modern political philosophy, especially in J. Rawls’s, A. Sen’s and G. Cohen’s writings. This paper explains the implications of using an objective well-being index as equalisandum or, close to the so-called “safety net preoccupation”, to guarantee a well-being lower bound. In the simple production model studied here, five characterization results and two related theorems prove the convergence of both approaches. We come to the conclusion that the Proportional Solution is the dominant solution according to “objectivist” axioms. Received: 5 September 1994/Accepted: 29 June 1996