Algorithms for Computing Abelian Periods of Words

Constantinescu and Ilie (Bulletin EATCS 89, 167--170, 2006) introduced the notion of an \emph{Abelian period} of a word. A word of length $n$ over an alphabet of size $\sigma$ can have $\Theta(n^{2})$ distinct Abelian periods. The Brute-Force algorithm computes all the Abelian periods of a word in time $O(n^2 \times \sigma)$ using $O(n \times \sigma)$ space. We present an off-line algorithm based on a \sel function having the same worst-case theoretical complexity as the Brute-Force one, but outperforming it in practice. We then present on-line algorithms that also enable to compute all the Abelian periods of all the prefixes of $w$.Comment: Accepted for publication in Discrete Applied Mathematic

Fast Computation of Abelian Runs

Given a word $w$ and a Parikh vector $\mathcal{P}$, an abelian run of period $\mathcal{P}$ in $w$ is a maximal occurrence of a substring of $w$ having abelian period $\mathcal{P}$. Our main result is an online algorithm that, given a word $w$ of length $n$ over an alphabet of cardinality $\sigma$ and a Parikh vector $\mathcal{P}$, returns all the abelian runs of period $\mathcal{P}$ in $w$ in time $O(n)$ and space $O(\sigma+p)$, where $p$ is the norm of $\mathcal{P}$, i.e., the sum of its components. We also present an online algorithm that computes all the abelian runs with periods of norm $p$ in $w$ in time $O(np)$, for any given norm $p$. Finally, we give an $O(n^2)$-time offline randomized algorithm for computing all the abelian runs of $w$. Its deterministic counterpart runs in $O(n^2\log\sigma)$ time.Comment: To appear in Theoretical Computer Scienc

The role of space-time activity patterns in the exposure assessment of residents

International audienceIndustrial development can generate hazardous situations – in particular, when there is a need to deal with dangerous substances, such as those in chemical or petrochemical plants. Too often, these industries are located in the heart of urbanized areas with high-density populations, as urbanization intrudes on the hazardous sites (originally established outside of cities). Protecting civil populations from these risks – either through precautionary measures or special crisis management plans, if a catastrophe occurs – is a key issue. To better protect citizens, identifying the risks to which they are exposed and also how they perceive the risks in their area can help authorities and stakeholders better understand the risks (Glatron & Beck, 2008). Adequate knowledge of these risks can also dissuade populations from settling in certain zones and thus lower their vulnerability. Finally, authorities need to assess the exposure of populations to hazards – through modelling – to set up appropriate and efficient risk management plans based on land planning. The present chapter – founded on responses to a questionnaire-based investigation (see the Annex) carried out in the Milazzo–Valle del Mela area of Sicily, in 2008 – explores two main aspects of exposure assessment: space-time-pattern methodological challenges and results of individual space-time activity data extracted from the investigation in the Milazzo–Valle del Mela area

Robust calibration of numerical models based on relative regret

Classical methods of parameter estimation usually imply the minimisation of an objective function, that measures the error between some observations and the results obtained by a numerical model. In the presence of random inputs, the objective function becomes a random variable, and notions of robustness have to be introduced. In this paper, we are going to present how to take into account those uncertainties by defining a family of calibration objectives based on the notion of relative-regret with respect to the best attainable performance given the uncertainties and compare it with the minimum in the mean sense, and the minimum of variance

To make LUTI models operationnal tools for planning

International audienceLand Use and Transport Integrated models (LUTIs) are promising tools for urban planning. Although a large literature is dedicated to these models, little attention has been paid to them as operational tool for planners and few efforts have been made by academics to fill the gap between lab application and operational use for planning practice. We shed light on what would make them accepted and more used by planners to evaluate urban and transport policies. In addition to a literature review and reflection on our own experience, we carried out a survey of end users in France to identify their motivations and barriers to using LUTI models. Our analysis shows a need for a far more bottom-up oriented approach. Only a closer collaboration between modelers and end users, and more efforts to integrate modeling into urban planning will make LUTIs considered as relevant approaches

Modélisation numérique : Quel développement durable ?

National audienceSi tout le monde, ou presque, s'accorde sur la nécessité d'un développement durable, une certaine cacophonie règne dès qu'il s'agit de rendre des arbitrages sur des solutions concrètes. Des outils d'aide à la décision pourraient faciliter la tâche des acteurs institutionnels

A surface registration approach for video-based analysis of intraoperative brain surface deformations.

Anatomical intra operative deformation is a major limitation of accuracy in image guided neurosurgery. Approaches to quantify these deforamations based on 3D reconstruction of surfaces have been introduced. For accurate quantification of surface deformation, a robust surface registration method is required. In this paper, we propose a new surface registration for video-based analysis of intraoperative brain deformations. This registration method includes three terms: the first term is related to image intensities, the second to Euclidean distance and the third to anatomical landmarks continuously tracked in 2D video. This new surface registration method can be used with any cortical surface textured point cloud computed by stereoscopic or laser range approaches. We have shown the global method, including textured point cloud reconstruction, had a precision within 2 millimeters, which is within the usual rigid registration error of the neuronavigation system before deformations

Severe hepatopathy and neurological deterioration after start of valproate treatment in a 6-year-old child with mitochondrial tryptophanyl-tRNA synthetase deficiency

Background: The first subjects with deficiency of mitochondrial tryptophanyl-tRNA synthetase (WARS2) were reported in 2017. Their clinical characteristics can be subdivided into three phenotypes (neonatal phenotype, severe infantile onset phenotype, Parkinson-like phenotype). Results: Here, we report on a subject who presented with early developmental delay, motor weakness and intellectual disability and who was considered during several years as having a non-progressive encephalopathy. At the age of six years, she had an epileptic seizure which was treated with sodium valproate. In the months after treatment was started, she developed acute liver failure and severe progressive encephalopathy. Although valproate was discontinued, she died six months later. Spectrophotometric analysis of the oxidative phosphorylation complexes in liver revealed a deficient activity of complex III and low normal activities of the complexes I and IV. Activity staining in the BN-PAGE gel confirmed the low activities of complex I, III and IV and, in addition, showed the presence of a subcomplex of complex V. Histochemically, a mosaic pattern was seen in hepatocytes after cytochrome c oxidase staining. Using Whole Exome Sequencing two known pathogenic variants were detected in WARS2 (c. 797delC, p. Pro266ArgfsTer10/c. 938 A > T, p. Lys313Met). Conclusion: This is the first report of severe hepatopathy in a subject with WARS2 deficiency. The hepatopathy occurred soon after start of sodium valproate treatment. In the literature, valproate-induced hepatotoxicity was reported in the subjects with pathogenic mutations in POLG and TWNK. This case report illustrates that the course of the disease in the subjects with a mitochondrial defect can be non-progressive during several years. The subject reported here was first diagnosed as having cerebral palsy. Only after a mitochondriotoxic medication was started, the disease became progressive, and the diagnosis of a mitochondrial defect was made

Filtrage conditionnel pour la trajectographie dans des sequences d'images - Application au suivi de points

National audienceIn this paper, we propose a new conditional formulation of classical filtering methods dedicated to image sequence based tracking. These conditional filters allow to consider a state model and a measure model which both depend on the image sequence data. On this basis, we derive two filters for the point tracking problem, which authorize to cope with trajectories exhibiting abrupt changes and occlusions. They combine a dynamic relying on the optical flow constraint and measures provided by a matching technique. The first tracker is linear, well-suited to image sequences exhibiting global dominant motion. This filter is deduced through the use of a new estimator called the conditional linear minimum variance estimator. The second one is a nonlinear tracker, implemented from a particle filter. This latter allows to track points whose motion may only be locally described.Dans cet article, nous proposons une nouvelle formulation conditionnelle des méthodes classiques de filtrage, dédiée à la trajectographie dans des séquences d'images. Ces filtres conditionnels permettent de considérer un modèle d'état et un modèle de mesure qui dépendent de la séquence. Dans ce cadre, deux filtres ont été construits pour la trajectographie de points. Ces méthodes permettent de suivre des trajectoires qui subissent des changements abrupts et des occlusions. Elles combinent une dynamique construite sur la contrainte de flot optique, et des mesures fournies par une méthode de corrélation. Le premier filtre est linéaire, particulièrement bien adapté aux séquences présentant un mouvement dominant. Il est dérivé de l'utilisation d'un nouvel estimateur appelé estimateur linéaire conditionnel de variance minimale. Le second filtre est non linéaire, construit à partir d'un filtre particulaire. Ce dernier permet de suivre des points dont le mouvement ne peut être décrit que localement

Tracking Articulated Bodies using Generalized Expectation Maximization

A generalized expectation maximization (GEM) algorithm is used to retrieve the pose of a person from a monocular video sequence shot with a moving camera. After embedding the set of possible poses in a low dimensional space using principal component analysis, the configuration that gives the best match to the input image is held as estimate for the current frame. This match is computed iterating GEM to assign edge pixels to the correct body part and to find the body pose that maximizes the likelihood of the assignments