The complexity of general-valued CSPs seen from the other side

The constraint satisfaction problem (CSP) is concerned with homomorphisms between two structures. For CSPs with restricted left-hand side structures, the results of Dalmau, Kolaitis, and Vardi [CP'02], Grohe [FOCS'03/JACM'07], and Atserias, Bulatov, and Dalmau [ICALP'07] establish the precise borderline of polynomial-time solvability (subject to complexity-theoretic assumptions) and of solvability by bounded-consistency algorithms (unconditionally) as bounded treewidth modulo homomorphic equivalence. The general-valued constraint satisfaction problem (VCSP) is a generalisation of the CSP concerned with homomorphisms between two valued structures. For VCSPs with restricted left-hand side valued structures, we establish the precise borderline of polynomial-time solvability (subject to complexity-theoretic assumptions) and of solvability by the $k$-th level of the Sherali-Adams LP hierarchy (unconditionally). We also obtain results on related problems concerned with finding a solution and recognising the tractable cases; the latter has an application in database theory.Comment: v2: Full version of a FOCS'18 paper; improved presentation and small correction

From perception to function, characterization of karrikin-like signaling in Lotus japonicus

Phytohormones are small molecules and key regulators for plant development. They translate and integrate perceived environmental cues into physiological responses. Recently, karrikins (KAR), smoke-derived compounds, were shown to trigger plant developmental responses by mimicking an unknown phytohormone called karrikin-like (KL). KAR and KL are perceived by the -hydrolase KAI2 which interacts with the F-box protein MAX2. Upon KL perception, a protein complex is formed with the repressor SMAX1, which is marked by ubiquitination for proteasomal degradation. At the beginning of this thesis, knowledge of KL function in plants was limited. Few reports in Arabidopsis showed its importance in seed germination and hypocotyl development. In rice, the discovery that the KL receptor complex is required for arbuscular mycorrhiza symbiosis (AMS) led to the question: Is KL signaling function in AMS conserved among other plant species, and particularly dicotyledons? Arabidopsis being unable to establish AMS, a new model plant was required. Thus, the goal of this thesis was to establish Lotus japonicus as a new model plant to study the role of KL signaling in plant development and AMS. To this end, L. japonicus homozygous mutant of each known KL signaling components, KAI2, MAX2, and SMAX1, were generated. In contrast to single-copy genes MAX2 and SMAX1, the KL receptor is duplicated in legumes. These two copies are functional as both rescued the elongated hypocotyl phenotype of the Arabidopsis thaliana kai2-2 mutant. However, genetic analysis of the KL perception mutants revealed that KL signaling is not required for inhibition of hypocotyl elongation in L. japonicus. However, transcriptional and developmental hypocotyl responses to the presence of KAR were dependent on only one LjKAI2 copy. Functional analysis in complemented A. thaliana kai2-2 and in-vitro binding assay demonstrated that the two LjKAI2 versions showed different affinities to ligands. Three amino-acids located in the ligand-binding cavities were shown to be determinant for ligand binding specificity. In conclusion, these results potentially indicate the presence of several KL molecules in planta to control different physiological responses through the divergent receptors. I also investigated the role of KL signaling in AMS using the L. japonicus KL receptor mutants. The level of colonization in the L. japonicus KL perception mutants was reduced to 50% compared to the wild-type level, where the two KL receptors have a redundant function. In rice, kai2 and max2 do not support colonization, whereas, in Pea, max2 mutant was less colonized than the wild-type. Recently in petunia, a kai2 mutant was shown to be impaired in AMS. Thus, the relative importance of KL signaling during AMS emerges as specific to phylogenetic-groups. Plant hormones can act in a local as well as in a systemic manner. Complementation by hairy-root transformation of max2 expressing the wild-type MAX2 showed that root colonization was only rescued only in transformed roots indicating that KL signaling is required locally for the optimum colonization. Due to the importance of KL signaling in roots for AMS, additional functions in L. japonicus root development were explored. Roots specifically responded, transcriptionally and developmentally, to KAR1 treatment in a KL perception component dependent manner. The root growth regulatory potential of KL signaling was confirmed by aberrant root phenotypes of two independent smax1 mutants. An RNAseq experiment of smax1 mutant roots revealed an increased transcript accumulation of ethylene biosynthesis genes. This increased ethylene production was shown to be causative for the root phenotypes in smax1 mutants. However, several differentially-expressed-genes were shown to be ethylene-signaling-independently-regulated and appeared as likely directly regulated by KL signaling. Thus, a member of the Ethylene Response Factor family was discovered as an early marker gene of KL signaling. Encoding a transcription factor, ERF could potentially act as a regulator for secondary KAR/KL responses. Altogether, our results illustrated that KL signaling influences root architecture development through SMAX1 removal, which acts as an inhibitor of ethylene biosynthesis. Collectively, results of this thesis open new frontiers of research on KL receptor evolution and the presence of multiple KL ligands, but also on the interaction of KL and ethylene signaling and the transcriptional cascade responding to KL/KAR. This work provides genetic tools and research axis for exciting future research using L. japonicus as a model plant to study KL signaling

Dimensions fractales de l'occurrence de pluie en climat soudano-sahélien

L'occurrence de pluie relative à une station, définie comme l'ensemble des périodes pluvieuses observées en cette station, est considérée comme un objet fractal inclus dans l'espace unidimensionnel du temps. La dimension de cet objet, comprise entre 0 et 1, est estimée par la méthode du comptage de boîtes. Deux séries issues de deux stations en climat soudano-sahélien, l'une journalière d'une durée de 45 ans, l'autre horaire d'une durée de 6 mois, ont été analysées selon ce protocole. On constate une opposition très marquée entre l'échelle de temps allant de quelques heures à quelques jours et l'échelle de temps allant de quelques jours à quelques mois dont la dimension est proche de 0,8. (Résumé d'auteur

Iron Age to Medieval entomogamous vegetation and Rhinolophus hipposideros roost in south-eastern Wales (UK)

Karst cave systems are well developed in Wales (UK) and, in some instances, constitute important bat roosts. Ogof Draenen, near Blaenavon in south-east Wales, is the most recent major cave discovery (1994) with already > 70 km of passages explored spanning a vertical range of 148 m. With the exception of one small chamber (Siambre Ddu) located directly above the main Ogof Draenen system, very few bats have been noticed inside. Extensive accumulations of guano, attributable to Rhinolophus hipposideros, are however found in parts of the Ogof Draenen system. In places covering many square meters and sometimes building heaps > 0.5 m thick, these represent volumes not yet found in any other cave system in the British Isles. Although the date of the abandonment of the main Ogof Draenen system as a bat roost remains unknown, six radiocarbon dates on guano from Ogof Draenen place the occupation in the Iron Age to Medieval period at least. Palynological analysis was undertaken on ten samples distributed through the cave. Comparisons were made with a moss polster and a lake mud sample from the area to provide a first approximation of the regional modern pollen rain and with two modern guano samples, one from Siambre Ddu and one from Agen Allwedd cave (5 km to the north-west) to provide a temporal comparison with the fossil guano. Agen Allwedd cave currently is one of the largest active roosts for Lesser Horseshoe bats in Britain and lies close to the present northern limit of this endangered species in Europe. The main results are that the cave appears to have been used both as a summer and a winter roost; most of the Ogof Draenen guano is formed within c.1600 14C years and, if the largest heap is continuous, it has accumulated within 750 14C years, i. e. 0.16 mm.year-1; the fossil guano samples reflect a relatively closed oak forest with more abundant ivy (Hedera) and holly (Ilex) than at present; insect-pollinated plants such as Ilex, Acer, Hedera and Impatiens glandulifera are over–represented in the guano samples; in addition to the usual causes of bat roost decline (pesticides, pollution), in the case of Ogof Draenen, we may add entrance blocked by rock collapse and decline of the local forest cover as well as change in its composition

Le devenir à l'adolescence d'enfants atteints de troubles envahissants du développement : l'exemple de l'hôpital de jour d'Aix-en-Provence.

National audienceWhat is the future for children affected by pervasive developmental disorders (PDD) ? In this paper, we wish to contribute answering this question by studying how children with PDD being treated into the child day care unit of Montperrin Hospital at Aix-en-Provence between 1988 and 2005 evolved when reaching adolescence and adulthood. Our study includes 32 subjects (29 boys and three girls) with PDD. In order to describetheir initial clinical status at the day care unit during childhood, we built individual assessment scales including the following items: i) diagnosis according to ICD-10 (WHO, 1994) and CFTMEA-R (2000); ii) verbal and intellectual levels; iii) level of social interaction, and iv) scholar status, and we fulfilled these scales according to information found in their files archived at Montperrin Hospital. To describe their current clinical status, we established individual questionnaires including the same items plus their current type of care, the various activities they practice, and their life project, and we sent the questionnaires to the psychiatrists of the medico-social structures and services where the subjects are currently treated.Results of our study overall show that the outcome of children with PDD is not that dark comparatively to what was first described in the literature. For instance, the number of mute subjects was divided by two. When reaching adolescence, subjects interact more with their peers (more than 80% of the children did not have any social interaction at the day care unit versus 50% now). Several symptoms significantly improved such as self-injury, hetero-aggressive behaviours and hyperactivity. On the other hand inadequate, stereotyped and odd behaviours and movements mostly persisted, which constitute limitations for their social and professional adaptation. As already underlined in previous studies, a low IQ and the absence of language after five years old are bad prognosis factors. The diagnosis category is also a prognosis factor, infantile autism having theworstprognosis. We also suggest that the change of nosographic references, which corresponds to changes of representations and of type of treatments and education, is able to explain the better prognosis of PDD. The main problem confirmed by our study is the lack of structures and services really adapted to their disorders.Quel est le devenir à l'adolescence des enfants atteints de troubles envahissants du développement ? Nous avons souhaité contribuer à répondre à cette question en étudiant le devenir des enfants pris en charge à l'hôpital de jour de l'hôpital Montperrin d'Aix-en-Provence entre 1988 et 2005. Notre étude porte sur 32 patients dont 29 garc¸ons. Pour décrire leur état clinique initial à l'hôpital de jour, nous avons réalisé des grilles d'évaluations comprenant la symptomatologie présentée lors de leur hospitalisation de jour, le diagnostic selon la CIM-10 et la CFTMEA-R, le niveau verbal, intellectuel, scolaire et d'interaction sociale. Puis nous avons rempli ces grilles grâce aux informations obtenues dans les dossiers archivés à l'hôpital Montperrin. Pour connaître leur état actuel, nous avons établi des questionnaires reprenant les mêmes items ainsi que le typede prise en charge, les activités pratiquées et les orientations envisagées et nous avons envoyé ces questionnaires aux responsables médicaux des structures où sont actuellement placés les patients. Les résultats de cette enquête montrent que globalement, le devenir à l'adolescence des enfants atteints de TED n'est pas aussi sombre que ce qui était décrit dans les premiers résultats de la littérature. Ainsi, le nombre de patients mutiques a été divisé par deux. Les adolescents interagissent plus avec leurs pairs (plus de 80% des enfants n'avaient pas de relation sociale à l'entrée de l'hôpitalde jour contre 50% actuellement). Certains symptômes se sont nettement atténués comme les troubles du comportement auto- et hétéro-agressifs, l'instabilité. En revanche, on observe souvent la persistance de comportements inadaptés, de mouvements stéréotypés et de bizarreries qui limitent leur capacité d'adaptation sociale et professionnelle. Comme cela a déjà été souligné dans d'autres études, nous retrouvons qu'un QI bas et uneabsence de langage après cinq ans semblent être des facteurs de mauvais pronostic. La catégorie diagnostique est aussi un facteur pronostique, l'autisme infantile étant la pathologie la plus grave. Nous pensons que le changement de repères nosographiques, via les représentations qu'ils sous-tendent et les changements de pratiques qu'ils suscitent, peuvent expliquer au moins en partie l'amélioration actuelle du pronostic des TED à l'adolescence. Le problème majeur que vient confirmer cette enquête est le manque de structures véritablement adaptées à leurs troubles

Statistical Language Models for On-line Handwritten Sentence Recognition

International audienceThis paper investigates the integration of a statistical language model into an on-line recognition system in order to improve word recognition in the context of handwritten sentences. Two kinds of models have been considered: n-gram and n-class models (with a statistical approach to create word classes). All these models are trained over the Susanne corpus and experiments are carried out on sentences from this corpus which were written by several writers. The use of a statistical language model is shown to improve the word recognition rate and the relative impact of the different language models is compared. Furthermore, we illustrate the interest to define an optimal cooperation between the language model and the recognition system to re-enforce the accuracy of the system

On the Computational Complexity of Non-dictatorial Aggregation

We investigate when non-dictatorial aggregation is possible from an algorithmic perspective, where non-dictatorial aggregation means that the votes cast by the members of a society can be aggregated in such a way that the collective outcome is not simply the choices made by a single member of the society. We consider the setting in which the members of a society take a position on a fixed collection of issues, where for each issue several different alternatives are possible, but the combination of choices must belong to a given set $X$ of allowable voting patterns. Such a set $X$ is called a possibility domain if there is an aggregator that is non-dictatorial, operates separately on each issue, and returns values among those cast by the society on each issue. We design a polynomial-time algorithm that decides, given a set $X$ of voting patterns, whether or not $X$ is a possibility domain. Furthermore, if $X$ is a possibility domain, then the algorithm constructs in polynomial time such a non-dictatorial aggregator for $X$. We then show that the question of whether a Boolean domain $X$ is a possibility domain is in NLOGSPACE. We also design a polynomial-time algorithm that decides whether $X$ is a uniform possibility domain, that is, whether $X$ admits an aggregator that is non-dictatorial even when restricted to any two positions for each issue. As in the case of possibility domains, the algorithm also constructs in polynomial time a uniform non-dictatorial aggregator, if one exists. Then, we turn our attention to the case where $X$ is given implicitly, either as the set of assignments satisfying a propositional formula, or as a set of consistent evaluations of an sequence of propositional formulas. In both cases, we provide bounds to the complexity of deciding if $X$ is a (uniform) possibility domain.Comment: 21 page

Colloque Nordeste-Sahel

L'étude de la pluviométrie de stations réparties dans les différentes zones écologiques du Burkina Faso montre que ce pays a subi depuis 1969 une période de sécheresse persistante, caractérisée par une forte diminution des pluies journalières supérieures à 40 mm. La persistance de la faiblesse de l'hydraulicité annuelle accompagne celle de la pluviosité. La majorité des périodes de déficit céréalier et de production de pâturages sahéliens se situe dans les années à pluviométrie défavorable. Pour le coton, les fluctuations de la production observées autour d'une courbe de production théorique correspondent aux différentes périodes climatiques définies sans qu'il y ait une relation univoque entre rendement et pluie annuels. (Résumé d'auteur