Multiferroics are currently intensely investigated because the coexistence and coupling of ferroic arrangements brings about new physical effects and, for the few room-temperature examples, interesting prospects for applications in various fields. This interest is illustrated by the recent publication of several articles on multiferroics in high impact reviews over the last five years. The main goal of the thesis was to look for new multiferroics by exploiting overlooked and original polar and magnetic arrangements. We more precisely investigated compounds based on lead iron tungsten PbFe2/3W1/3O3 (PFW) and lead zirconate PbZrO3 (PZO) oxides. PFW displays long- and short-range both polar and magnetic orders (ferroelectric-relaxor and antiferromagnetic-spin-glass) while PZO is antiferroelectric with antiferrodistorsivity (oxygen tilts) and existence of ferroelectric instabilities. Combining various techniques from synthesis to electric, magnetic and structural characterizations, we demonstrated that it is possible to get a multiferroic compound (50%PFW-50%PZO) with coexistence of multiple ferroic and structural arrangements with room temperature properties of practical interest. This work opens new prospects in this rich field of multiferroics in peculiar by using antiferroelectrics.

Genomic sequence databases, like GenBank, EMBL, are widely used by molecular biologists for homology searching. Because of the long length of each genomic sequence and the increase of the size of genomic sequence databases, the importance of efficient searching methods for fast queries grows. The DNA sequences are composed of four kinds of nucleotides, and these genomic sequences can be regarded as the text strings. However, there is no concept of words in a genomic sequence, which makes the search of the genomic sequence in the genomic database much difficult. Approximate String Matching (ASM) with k errors is considered for genomic sequences, where k errors would be caused by insertion, deletion, and replacement operations. Filtration of the DNA sequence is a widely adopted technique to reduce the number of the text areas (i.e., candidates) for further verification. In most of the filter methods, they first split the database sequence into q-grams. A sequence of grams (subpatterns) which match some part of the text will be passed as a candidate. The match problem of grams with the part of the text could be speed up by using the index structure for the exact match. Candidates will then be examined by dynamic programming to get the final result. However, in the previous methods for ASM, most of them considered the local order within each gram. Only the (k + s) h-samples filter considers the global order of the sequence of matched grams. Although the (k + s) h-samples filter keeps the global order of the sequence of the grams, it still has some disadvantages. First, to be a candidate in the (k + s) h-samples filter, the number of the ordered matched grams, s, is always fixed to 2 which results in low precision. Second, the (k + s) h-samples filter uses the query time to build the index for query patterns. In this thesis, we propose a new approximate string matching method, the hash trie filter, for efficiently searching in genomic databases. We build a hash trie in the pre-computing time for the genomic sequence stored in database. Although the size q of each split grams is also decided by the same formula used in the (k + s) h-samples filter, we have proposed a different way to find the ordered subpatterns in text T. Moreover, we reduce the number of candidates by pruning some unreasonable matched positions. Furthermore, unlike the (k + s) h-samples filter which always uses s = 2 to decide whether s matched subpatterns could be a candidate or not, our method will dynamically decide s, resulting in the increase of precision. The simulation results show that our hash trie filter outperforms the (k +s) h-samples filter in terms of the response time, the number of verified candidates, and the precision under different length of the query patterns and different error levels.

L’étude des matériaux multiferroiques est sans doute un des domaines de recherche actuelle les plus actifs et prolifiques de la matière condensée. Dans ces matériaux, coexistent polarisation, aimantation et élasticité. On comprend bien que cette coexistence permet une multifonctionnalité très attrayante pour un grand nombre d’applications mais aussi fournit un vivier extraordinaire pour étudier les interactions entre ces grandeurs ainsi que les mécanismes microscopiques sous-jacents. Cet attrait s’en trouve d’autant plus renforcé du fait des phénomènes de couplage entre ces grandeurs physiques autorisant des fonctionnalités nouvelles comme par exemple le renversement d’une aimantation avec un champ électrique au lieu d’un champ magnétique classiquement. Cependant, ces matériaux multiferroiques sont d’une part en petit nombre et d’autre part, exploitent pour beaucoup d’entre eux, la polarisation d’un ferroélectrique et l’aimantation d’un antiferromagnétique. Ceci étant, il existe d’autres types d’arrangements polaires et magnétiques encore non-exploités, c’est dans ce cadre que s’inscrit ce travail de thèse. L’objectif de la thèse était de synthétiser de nouveaux multiferroiques présentant des arrangements polaires et magnétiques originaux et d’en caractériser les propriétés. Nous nous sommes tout particulièrement intéressés aux oxydes PbFe2/3W1/3O3 (PFW) et PbZrO3 (PZO). PFW présente des ordres polaires et magnétiques à longue et à courte portée : ferroélectrique-relaxeur et antiferromagnétique-verre de spin (ou ferromagnétisme faible). PZO est quant à lui antiferroélectrique avec antiferrodistorsivité (rotation des octaèdres d’oxygène) et présence d’instabilité ferroélectrique. Nous avons d’une part combiné ces deux matériaux pour former une solution solide et d’autre part réalisé un dopage de PZO avec des ions magnétiques. Après avoir synthétisé ces matériaux, nous les avons caractérisés électriquement (constante diélectrique, phénomène de relaxation, polarisation, température de Curie), magnétiquement (susceptibilité magnétique, aimantation) et structuralement (transition de phase). Ainsi, nous avons montré qu’il était possible d’obtenir un matériau multiferroique (50%PFW-50%PZO) présentant l’ensemble des instabilités ferroiques et structurales. Ces nouveaux matériaux ouvrent ainsi de nouvelles perspectives d’étude dans ce riche domaine en particulier en utilisant des antiferroélectriques. / Multiferroics are currently intensely investigated because the coexistence and coupling of ferroic arrangements brings about new physical effects and, for the few room-temperature examples, interesting prospects for applications in various fields. This interest is illustrated by the recent publication of several articles on multiferroics in high impact reviews over the last five years. The main goal of the thesis was to look for new multiferroics by exploiting overlooked and original polar and magnetic arrangements. We more precisely investigated compounds based on lead iron tungsten PbFe2/3W1/3O3 (PFW) and lead zirconate PbZrO3 (PZO) oxides. PFW displays long- and short-range both polar and magnetic orders (ferroelectric-relaxor and antiferromagnetic-spin-glass) while PZO is antiferroelectric with antiferrodistorsivity (oxygen tilts) and existence of ferroelectric instabilities. Combining various techniques from synthesis to electric, magnetic and structural characterizations, we demonstrated that it is possible to get a multiferroic compound (50%PFW-50%PZO) with coexistence of multiple ferroic and structural arrangements with room temperature properties of practical interest. This work opens new prospects in this rich field of multiferroics in peculiar by using antiferroelectrics.

Cette thèse a pour ambition de voir l'implication des acteurs locaux dans les projets touristiques qui se déroulent sur leur territoire. En utilisant le cadre théorique de la sociologie des organisations, notamment celui de Friedberg (1997) et l'outil de diagnostic territorial (Moine, 2007), une analyse de l'activité touristique sur le fleuve Tsiribihina a été menée. A partir de l'identification de problèmes communs que chaque acteur doit résoudre, nos résultats ont permis de voir que les solutions adoptées par ces derniers ont fait émerger des ordres locaux qui cristallisent les relations d'échanges. A travers ces résultats, nous pouvons comprendre comment s'organise l'activité touristique sur notre terrain d'étude, les rôles des acteurs locaux dans le système, ainsi que les retombées socio-économique de cette activité sur le territoire étudié. / This thesis aims to see local population involvement in tourism projects that take place on their territory. By using the theoretical frame of the sociology of organizations, in particular that of Friedberg (1997) and the diagnostic tool territorial (Moine, 2007), an analysis of tourism activity on the river Tsiribihina was led. From the identification of common problems that every player must solve, our results highlight that the solutions adopted lead to locals orders formation. Through these results, we can understand: how tourism activities are organized on the river Tsiribihina, the role of local actors in the system, and the socio- economic impacts of this activity particularly in local level.

Nous avons exploré les potentialités de la RMN 14N à l'état solide pour étudier l'ordre et le désordre local dans les zéolithes structurées à l'aide des cations de tétraalkylkammoniums. Cette étude est effectuée en combinant les approches expérimentales et théoriques. Les halogénures de tétraalkylkammonium CnH2n+1+X- (n : 1–4 ; X : Br, I) considérés comme des cristaux modèles, sont étudiés dans une première partie. Nous avons pu corréler des aspects structuraux spécifiques (distorsion des angles CNC, répartition spatiale des anions) aux paramètres spectroscopiques de l'interaction quadripolaire 14N.Dans une deuxième partie, nous décrivons l'ordre local dans la silicalite-1 (MFI), en nous basant notamment sur les paramètres de l'interaction quadripolaire 14N. Des variations chimiques au niveau des agents minéralisateurs ou structurants ont des effets mesurés sur ces paramètres qui peuvent être corrélés à l'ordre local au niveau de l'agent structurant et de la charpente minérale. Des modélisations théoriques effectuées à T = 0 et 300 K ont permis de mieux comprendre ces systèmes.Enfin, dans une troisième partie nous avons démontré la sensibilité des paramètres RMN de l'azote-14 à la distribution des sites actifs (Al, B) dans la zéolithe ZSM-5 en utilisant une large palette d'expériences RMN et de calculs théoriques.Ce travail a permis pour la première fois d'établir l'intérêt de la RMN 14N pour l'étude de l'ordre local dans les zéolithes et de montrer les principales informations qui peuvent en être tirées. / We explored the 14N solid state NMR potential to study the local order and disorder in zeolites structured using tetraalkylkammonium cations. This study is performed by combining experimental and theoretical approaches.Tetraalkylkammonium halides CnH2n+1+X- (n: 1-4, X: Br, I) considered as crystal models are studied in the first part. We were able to correlate specific structural aspects (CNC angles distortions, anions spatial distribution) to the 14N NMR parameters. In the second part, we describe the local order in the silicalite-1 (MFI), based in particular on the 14N quadrupolar parameters. Chemical variations in mineralizing or structure directing agents have effects on these measured parameters which can be correlated to the organic and inorganic local orders. Theoretical modeling carried out at T = 0 and 300 K led to a better understanding of these systems. Finally, in the third part we have demonstrated the sensitivity of 14N NMR parameters to the distribution of active sites (Al, B) in ZSM-5 zeolites using a wide range of NMR experiments and theoretical calculations.This work allowed to establish for the first time the interests of 14N NMR to study the local order in zeolites and display key information that can be extracted.

Motivated by a zero-intelligence approach, the aim of this thesis is to unify the microscopic (discrete price and volume), mesoscopic (discrete price and continuous volume) and macroscopic (continuous price and volume) frameworks of limit order books, with a view to providing a novel yet analytically tractable description of their behaviour in a high to ultra high-frequency setting. Starting with the canonical microscopic framework, the first part of the thesis examines the limiting behaviour of the order book process when order arrival and cancellation rates are sent to infinity and when volumes are considered to be of infinitesimal size. Mathematically speaking, this amounts to establishing the weak convergence of a discrete-space process to a mesoscopic diffusion limit. This step is initially carried out in a reduced-form context, in other words, by simply looking at the best bid and ask queues, before the procedure is extended to the whole book. This subsequently leads us to the second part of the thesis, which is devoted to the transition between mesoscopic and macroscopic models of limit order books, where the general idea is to send the tick size to zero, or equivalently, to consider infinitely many price levels. The macroscopic limit is then described in terms of reflected SPDEs which typically arise in stochastic interface models. Numerical applications are finally presented, notably via the simulation of the mesocopic and macroscopic limits, which can be used as market simulators for short-term price prediction or optimal execution strategies.

Our society changed, but the urban water and sanitation system of today is roughly the same as it was 100 years ago. The system is designed for, developed from and sustained by human activities, and has since its introduction affected household patterns of routine activities. The urban water and sanitation system is now being criticised for not being sustainable due to excessive material, energy and chemical use, and failure to recycle and reuse resources. Altering household practices is perceived as one important step towards improved sustainability. In this study, two changes in water and sanitation arrangements at the household level are analysed: individual meters for volumetric billing of hot and cold water, and dry toilets with separate collection of urine and faeces. These arrangements increase system transparency, and their proponents believe that the arrangements enhance resource recycling and/or rsource savings. However, success in this regard can only be achieved if accompanied by appropriate household routines. The extent to which such appropriate routines come about and why (not) is the focus of attention in this study; the aim is to describe and analyse the interaction between householder routines and changes in water and sanitation arrangements. This study takes as its starting point household everyday life. A methodological combination of time-diaries, interviews, physical measurements and simple observations is developed and implemented in two cases; the housing area Ringdansen with flats (volumetric billing) and the collective Gebers based on an ecological way of life (dry toilets). The theoretical approach is developed from time-geography and culture analysis. The methodological and theoretical approaches have proven useful and can be developed further. Household responded differently to the volumetric billing in Ringdansen, but in general, no sweeping routine changes took place in the households. A comparison of average total water usage per household (at an aggregated level) between the two cases, showed no significant difference. Water-use routines are also similar in the two areas, even though variations appear between households. There seems to be a socio-culturally defined lower limit for water use, regarded as necessary for maintaining sufficient standards of cleanliness and comfort, irrespective of the influence of ecological or economic incentives. Differences in household composition, built-in technical arrangements and existence of a garden (Gebers) explain the differences in hot and cold water usage between the two areas. The dry toilet was shown to have a decisive impact on toilet disposal routines; only biodegradable waste products are thrown into it and the cleaning agents are environmentally friendly toilet disposal routines that reach beyond the 'good' routines evolving from environmental concern. The relationship between changes in water and sanitation arrangements and householder routines may be expressed as follows: an extensive change in arrangements, either technical/physical, organisational and/or economical, results in more radical routine changes, and more so if combined. However, the improvement as regard ecological sustainability is conditional on what is socio-culturally accepted - social sustainability.