Control of a line robot system with Embedded Linux

Many, if not all, aspects of our everyday lives are related to computers and control. Microprocessors and wireless communications are involved in our lives. Embedded systems are an attracting field because they combine three key factors, small size, low power consumption and high computing capabilities. The aim of this thesis is to study how Linux communicates with the hardware, to answer the question if it is possible to use an operating system like Debian for embedded systems and finally, to build a Mechatronic real time application. In the thesis a presentation of Linux and the Xenomai real time patch is given, the bootloader and communication with the hardware is analyzed. BeagleBone the evaluation board is presented along with the application project consisted of a robot cart with a driver circuit, a line sensor reading a black line and two Xbee antennas. It makes use of Xenomai threads, the real time kernel. According to the obtained results, Linux is able to operate as a real time operating system. The issue of future research is the area of embedded Linux is also discussed.

Eletrical conductivity and deterioration of soybean seeds exposed to different storage conditions

Research with soybean seeds has revealed that the results of the electrical conductivity test may be influenced by storage temperature, particularly low temperature, such as 10ºC, suggesting that seed deterioration at low storage temperatures does not seem to be directly related to the loss of the cell membrane integrity. This study was conducted with seeds of two soybean cultivars with the objective of: a) studying the effect of different storage temperatures (10ºC; 20ºC; 25ºC; 20/10ºC and 25/10ºC) on the results of the electrical conductivity test; b) observing the behavior of fatty acids and carbohydrates during storage and studying its relation with the electrical conductivity results. Every three months, from a total of 18 months of storage, the physiological quality of seeds was evaluated using the germination, accelerated aging and electrical conductivity tests. Based on the obtained results, it can be concluded that the electrical conductivity test was not shown to be a good indicative of the deterioration process of seeds stored at low temperatures, and no direct relationship between changes in the fatty acids and carbohydrates and the behavior of the mentioned test for seeds stored at 10ºC was found.

Public-private partnership investments in dry ports – Russian logistics markets and risks

The investments have always been considered as an essential backbone and so-called ‘locomotive’ for the competitive economies. However, in various countries, the state has been put under tight budget constraints for the investments in capital intensive projects. In response to this situation, the cooperation between public and private sector has grown based on public-private mechanism. The promotion of favorable arrangement for collaboration between public and private sectors for the provision of policies, services, and infrastructure in Russia can help to address the problems of dry ports development that neither municipalities nor the private sector can solve alone. Especially, the stimulation of public-private collaboration is significant under the exposure to externalities that affect the magnitude of the risks during all phases of project realization. In these circumstances, the risk in the projects also is becoming increasingly a part of joint research and risk management practice, which is viewed as a key approach, aiming to take active actions on existing global and specific factors of uncertainties. Meanwhile, a relatively little progress has been made on the inclusion of the resilience aspects into the planning process of a dry ports construction that would instruct the capacity planner, on how to mitigate the occurrence of disruptions that may lead to million dollars of losses due to the deviation of the future cash flows from the expected financial flows on the project. The current experience shows that the existing methodological base is developed fragmentary within separate steps of supply chain risk management (SCRM) processes: risk identification, risk evaluation, risk mitigation, risk monitoring and control phases. The lack of the systematic approach hinders the solution of the problem of risk management processes of dry port implementation. Therefore, management of various risks during the investments phases of dry port projects still presents a considerable challenge from the practical and theoretical points of view. In this regard, the given research became a logical continuation of fundamental research, existing in the financial models and theories (e.g., capital asset pricing model and real option theory), as well as provided a complementation for the portfolio theory. The goal of the current study is in the design of methods and models for the facilitation of dry port implementation through the mechanism of public-private partnership on the national market that implies the necessity to mitigate, first and foremost, the shortage of the investments and consequences of risks. The problem of the research was formulated on the ground of the identified contradictions. They rose as a continuation of the trade-off between the opportunities that the investors can gain from the development of terminal business in Russia (i.e. dry port implementation) and risks. As a rule, the higher the investment risk, the greater should be their expected return. However, investors have a different tolerance for the risks. That is why it would be advisable to find an optimum investment. In the given study, the optimum relates to the search for the efficient portfolio, which can provide satisfaction to the investor, depending on its degree of risk aversion. There are many theories and methods in finance, concerning investment choices. Nevertheless, the appropriateness and effectiveness of particular methods should be considered with the allowance of the specifics of the investment projects. For example, the investments in dry ports imply not only the lump sum of financial inflows, but also the long-term payback periods. As a result, capital intensity and longevity of their construction determine the necessity from investors to ensure the return on investment (profitability), along with the rapid return on investment (liquidity), without precluding the fact that the stochastic nature of the project environment is hardly described by the formula-based approach. The current theoretical base for the economic appraisals of the dry port projects more often perceives net present value (NPV) as a technique superior to other decision-making criteria. For example, the portfolio theory, which considers different risk preference of an investor and structures of utility, defines net present value as a better criterion of project appraisal than discounted payback period (DPP). Meanwhile, in business practice, the DPP is more popular. Knowing that the NPV is based on the assumptions of certainty of project life, it cannot be an accurate appraisal approach alone to determine whether or not the project should be accepted for the approval in the environment that is not without of uncertainties. In order to reflect the period or the project’s useful life that is exposed to risks due to changes in political, operational, and financial factors, the second capital budgeting criterion – discounted payback period is profoundly important, particularly for the Russian environment. Those statements represent contradictions that exist in the theory and practice of the applied science. Therefore, it would be desirable to relax the assumptions of portfolio theory and regard DPP as not fewer relevant appraisal approach for the assessment of the investment and risk measure. At the same time, the rationality of the use of both project performance criteria depends on the methods and models, with the help of which these appraisal approaches are calculated in feasibility studies. The deterministic methods cannot ensure the required precision of the results, while the stochastic models guarantee the sufficient level of the accuracy and reliability of the obtained results, providing that the risks are properly identified, evaluated, and mitigated. Otherwise, the project performance indicators may not be confirmed during the phase of project realization. For instance, the economic and political instability can result in the undoing of hard-earned gains, leading to the need for the attraction of the additional finances for the project. The sources of the alternative investments, as well as supportive mitigation strategies, can be studied during the initial phases of project development. During this period, the effectiveness of the investments undertakings can also be improved by the inclusion of the various investors, e.g. Russian Railways’ enterprises and other private companies in the dry port projects. However, the evaluation of the effectiveness of the participation of different investors in the project lack the methods and models that would permit doing the particular feasibility study, foreseeing the quantitative characteristics of risks and their mitigation strategies, which can meet the tolerance of the investors to the risks. For this reason, the research proposes a combination of Monte Carlo method, discounted cash flow technique, the theory of real options, and portfolio theory via a system dynamics simulation approach. The use of this methodology allows for comprehensive risk management process of dry port development to cover all aspects of risk identification, risk evaluation, risk mitigation, risk monitoring, and control phases. A designed system dynamics model can be recommended for the decision-makers on the dry port projects that are financed via a public-private partnership. It permits investors to make a decision appraisal based on random variables of net present value and discounted payback period, depending on different risks factors, e.g. revenue risks, land acquisition risks, traffic volume risks, construction hazards, and political risks. In this case, the statistical mean is used for the explication of the expected value of the DPP and NPV; the standard deviation is proposed as a characteristic of risks, while the elasticity coefficient is applied for rating of risks. Additionally, the risk of failure of project investments and guaranteed recoupment of capital investment can be considered with the help of the model. On the whole, the application of these modern methods of simulation creates preconditions for the controlling of the process of dry port development, i.e. making managerial changes and identifying the most stable parameters that contribute to the optimal alternative scenarios of the project realization in the uncertain environment. System dynamics model allows analyzing the interactions in the most complex mechanism of risk management process of the dry ports development and making proposals for the improvement of the effectiveness of the investments via an estimation of different risk management strategies. For the comparison and ranking of these alternatives in their order of preference to the investor, the proposed indicators of the efficiency of the investments, concerning the NPV, DPP, and coefficient of variation, can be used. Thus, rational investors, who averse to taking increased risks unless they are compensated by the commensurate increase in the expected utility of a risky prospect of dry port development, can be guided by the deduced marginal utility of investments. It is computed on the ground of the results from the system dynamics model. In conclusion, the outlined theoretical and practical implications for the management of risks, which are the key characteristics of public-private partnerships, can help analysts and planning managers in budget decision-making, substantially alleviating the effect from various risks and avoiding unnecessary cost overruns in dry port projects.

Lignoselluloosapohjaisten väkevähappohydrolysaattien kromatografinen fraktiointi

Väkevän hapon katalysoiman hydrolyysin avulla lignoselluloosasta on mahdollista valmistaa arvokkaita sokereita. Katalyyttinä toimiva happo voidaan käyttää uudelleen hydrolyysissä, jos se saadaan erotettua sokereista ilman neutralointia. Tämän kandidaatintyön tavoitteena oli selvittää, soveltuuko happoretardaatiotekniikka väkevähappohydrolysaatin fraktiointiin. Työssä verrattiin happoretardaatiotekniikkaa elektrolyyttiekskluusiotekniikkaan. Työn kirjallisuusosassa käsiteltiin happoretardaation ja elektrolyyttiekskluusion teoriaa. Lisäksi esiteltiin elektrolyyttiekskluusioon ja happoretardaatioon liittyviä tutkimuksia. Työn kokeellisessa osassa suoritettiin panoskromatografiakokeita käyttäen syöttöliuoksena rikkihappoa, etikkahappoa, glukoosia ja ksyloosia sisältävää synteettistä liuosta. Erotusmateriaaleina käytettiin neljää eri anionin- ja yhtä kationinvaihtohartsia. Kokeiden perusteella tutkittiin anioninvaihtohartsin tyypin ja kolonnin latauksen vaikutusta happoretardaatiotekniikalla saavutettavaan erotustulokseen sekä verrattiin elektrolyyttiekskluusiota happoretardaatioon. Työn tulosten perusteella rikkihappo laimeni happoretardaatiotekniikalla jopa 20-kertaisesti kromatografiakolonniin syötettyyn liuokseen verrattuna, riippumatta kolonnin latauksesta ja anioninvaihtohartsista. Rikkihapon laimenemisen vuoksi happoretardaatio ei soveltunut lignoselluloosapohjaisten väkevähappohydrolysaattien fraktiointiin. Elektrolyyttiekskluusiotekniikalla rikkihapon laimeneminen oli merkittävästi vähäisempää, minkä vuoksi elektrolyyttiekskluusion todettiin soveltuvan happoretardaatiota paremmin lignoselluloosapohjaisten väkevähappohydrolysaattien fraktiointiin.

Coopetition as a lead generating mechanism: design, modelling and simulation

The aim of this research is to develop a tool that could allow to organize coopetitional relationships between organizations on the basis of two-sided Internet platform. The main result of current master thesis is a detailed description of the concept of the lead generating internet platform-based coopetition. With the tools of agent-based modelling and simulation, there were obtained results that could be used as a base for suggestion that the developed concept is able to cause a positive effect on some particular industries (e.g. web-design studios market) and potentially can bring some benefits and extra profitability for most companies that operate on this particular industry. Also on the basis of the results it can be assumed that the developed instrument is also able to increase the degree of transparency of the market to which it is applied.

Modelling ecological values in heterogeneous and dynamic landscapes with geospatial data

Our surrounding landscape is in a constantly dynamic state, but recently the rate of changes and their effects on the environment have considerably increased. In terms of the impact on nature, this development has not been entirely positive, but has rather caused a decline in valuable species, habitats, and general biodiversity. Regardless of recognizing the problem and its high importance, plans and actions of how to stop the detrimental development are largely lacking. This partly originates from a lack of genuine will, but is also due to difficulties in detecting many valuable landscape components and their consequent neglect. To support knowledge extraction, various digital environmental data sources may be of substantial help, but only if all the relevant background factors are known and the data is processed in a suitable way. This dissertation concentrates on detecting ecologically valuable landscape components by using geospatial data sources, and applies this knowledge to support spatial planning and management activities. In other words, the focus is on observing regionally valuable species, habitats, and biotopes with GIS and remote sensing data, using suitable methods for their analysis. Primary emphasis is given to the hemiboreal vegetation zone and the drastic decline in its semi-natural grasslands, which were created by a long trajectory of traditional grazing and management activities. However, the applied perspective is largely methodological, and allows for the application of the obtained results in various contexts. Models based on statistical dependencies and correlations of multiple variables, which are able to extract desired properties from a large mass of initial data, are emphasized in the dissertation. In addition, the papers included combine several data sets from different sources and dates together, with the aim of detecting a wider range of environmental characteristics, as well as pointing out their temporal dynamics. The results of the dissertation emphasise the multidimensionality and dynamics of landscapes, which need to be understood in order to be able to recognise their ecologically valuable components. This not only requires knowledge about the emergence of these components and an understanding of the used data, but also the need to focus the observations on minute details that are able to indicate the existence of fragmented and partly overlapping landscape targets. In addition, this pinpoints the fact that most of the existing classifications are too generalised as such to provide all the required details, but they can be utilized at various steps along a longer processing chain. The dissertation also emphases the importance of landscape history as an important factor, which both creates and preserves ecological values, and which sets an essential standpoint for understanding the present landscape characteristics. The obtained results are significant both in terms of preserving semi-natural grasslands, as well as general methodological development, giving support to science-based framework in order to evaluate ecological values and guide spatial planning.

Using genetic algorithms for the single allocation hub location problem

Hub location problem is an NP-hard problem that frequently arises in the design of transportation and distribution systems, postal delivery networks, and airline passenger flow. This work focuses on the Single Allocation Hub Location Problem (SAHLP). Genetic Algorithms (GAs) for the capacitated and uncapacitated variants of the SAHLP based on new chromosome representations and crossover operators are explored. The GAs is tested on two well-known sets of real-world problems with up to 200 nodes. The obtained results are very promising. For most of the test problems the GA obtains improved or best-known solutions and the computational time remains low. The proposed GAs can easily be extended to other variants of location problems arising in network design planning in transportation systems.

New Contig Creation Algorithm for the de novo DNA Assembly Problem

DNA assembly is among the most fundamental and difficult problems in bioinformatics. Near optimal assembly solutions are available for bacterial and small genomes, however assembling large and complex genomes especially the human genome using Next-Generation-Sequencing (NGS) technologies is shown to be very difficult because of the highly repetitive and complex nature of the human genome, short read lengths, uneven data coverage and tools that are not specifically built for human genomes. Moreover, many algorithms are not even scalable to human genome datasets containing hundreds of millions of short reads. The DNA assembly problem is usually divided into several subproblems including DNA data error detection and correction, contig creation, scaffolding and contigs orientation; each can be seen as a distinct research area. This thesis specifically focuses on creating contigs from the short reads and combining them with outputs from other tools in order to obtain better results. Three different assemblers including SOAPdenovo [Li09], Velvet [ZB08] and Meraculous [CHS+11] are selected for comparative purposes in this thesis. Obtained results show that this thesis’ work produces comparable results to other assemblers and combining our contigs to outputs from other tools, produces the best results outperforming all other investigated assemblers.

Polynuclear Ni(II) Complexes with Schiff Bases as Bridging Ligands: A Molecular Approach to Nanoscience

The initial employment of N-salicylidene-2-amino-5-chlorobenzoic acid (sacbH2) as bridging/chelating ligand in metal cluster chemistry has provided access to five new polynuclear NiII complexes with large nuclearities, unprecedented metal core topologies, and interesting magnetic properties. The obtained results are presented in two projects. The first project includes the investigation of the general Ni2+/RCO2-/sacbH2 reaction system (where R- = CH3-, But-, ButCH2-) in which the nature of the carboxylic acid was found to be of crucial importance, affecting enormously the nuclearity of the resulting complexes. The second project deals with the study of the general Ni2+/X-/sacbH2 reaction system (where X- = inorganic anions) under basic conditions, yielding new cluster compounds with molecular chain-like structures and ferromagnetic exchange interactions between the metal centers.

Disease-Gene Association Using Genetic Programming

As a result of mutation in genes, which is a simple change in our DNA, we will have undesirable phenotypes which are known as genetic diseases or disorders. These small changes, which happen frequently, can have extreme results. Understanding and identifying these changes and associating these mutated genes with genetic diseases can play an important role in our health, by making us able to find better diagnosis and therapeutic strategies for these genetic diseases. As a result of years of experiments, there is a vast amount of data regarding human genome and different genetic diseases that they still need to be processed properly to extract useful information. This work is an effort to analyze some useful datasets and to apply different techniques to associate genes with genetic diseases. Two genetic diseases were studied here: Parkinson’s disease and breast cancer. Using genetic programming, we analyzed the complex network around known disease genes of the aforementioned diseases, and based on that we generated a ranking for genes, based on their relevance to these diseases. In order to generate these rankings, centrality measures of all nodes in the complex network surrounding the known disease genes of the given genetic disease were calculated. Using genetic programming, all the nodes were assigned scores based on the similarity of their centrality measures to those of the known disease genes. Obtained results showed that this method is successful at finding these patterns in centrality measures and the highly ranked genes are worthy as good candidate disease genes for being studied. Using standard benchmark tests, we tested our approach against ENDEAVOUR and CIPHER - two well known disease gene ranking frameworks - and we obtained comparable results.

Caractérisation de l’apoptose observée dans le système limbique après une ischémie myocardique transitoire chez le rat

Au niveau clinique, il a été observé que de 15 à 30 % des patients qui ont subi un infarctus du myocarde développent une dépression majeure. De plus, la population atteinte de dépression post-infarctus présente un risque de mortalité de trois à quatre fois plus élevé, et ce, en comparaison avec la population non dépressive post-infarctus. Dans un modèle de rat développé pour étudier la dépression post-infarctus, des cellules apoptotiques ont été retrouvées au niveau du système limbique. Il apparaît que les cytokines seraient en partie responsables de cette mort cellulaire qui relie le cœur en ischémie et le système nerveux central. Donc, les objectifs de cette thèse sont : 1) de caractériser spatialement et temporellement la survenue de la mort cellulaire par apoptose dans les structures du système limbique du rat, à la suite d’un infarctus du myocarde ; 2) de déterminer l’effet de l’anti-inflammatoire celecoxib sur cette apoptose observée au niveau de l’amygdale et de déterminer l’implication de l’enzyme COX-2 ; 3) de déterminer l’implication de la cytokine pro-inflammatoire TNF-α dans l’apoptose observée au niveau des structures du système limbique du rat, à la suite d’un infarctus du myocarde. Afin d’atteindre ces objectifs, les rats ont subi une ischémie de 40 minutes, suivi d’une période de reperfusion qui varie d’un protocole à l’autre (15 minutes, 24, 48, 72 heures ou 7 jours). De plus, en fonction du protocole, ces rats ont été traités avec soit du célécoxib (inhibiteur sélectif de la COX-2), soit avec du PEG sTNF-R1 (inhibiteur du TNF-α). À la suite de ces protocoles, les rats ont été sacrifiés, la taille de l’infarctus a été déterminée et les différentes structures cérébrales du système limbique prélevées. Des tests biochimiques propres à chaque protocole ont été réalisés afin de documenter l'apoptose. Il a alors été observé qu’aucun des deux traitements ne présentait d’effet sur la taille de l’infarctus. L’étude de l’apoptose dans le système limbique a révélé que : 1) le processus apoptotique se mettait en place dans l’hippocampe dès les 15 premières minutes de reperfusion suivant l’infarctus du myocarde et que ce processus était spatialement dynamique dans le système limbique jusqu’au septième jour postreperfusion ; 2) il est apparu que la COX-2 était impliquée dans l'apoptose du système limbique ; 3) il a été observé que le TNF-α périphérique était impliqué dans ce processus apoptotique après 72 heures de reperfusion en activant la voie extrinsèque de l'apoptose. Ces résultats ont permis de caractériser la survenue de l’apoptose au niveau du système limbique chez le rat à la suite d’un infarctus du myocarde et de documenter l'implication de la COX-2 et du TNF-α dans ce processus. Bien que ces résultats n’apportent pas de schémas thérapeutiques clairs ou de mécanismes physiopathologiques globaux ces derniers permettent une meilleure compréhension de la relation existante entre le cœur et le système nerveux central dans le cadre de l’infarctus du myocarde. De manière moins spécifique ils précisent la relation entre le système inflammatoire et le système nerveux central.

Étude des aimants quantiques et supraconducteurs non conventionnels

Une première partie de ce mémoire portera sur l’analyse des états fondamentaux ma- gnétiques de deux composés isolants et magnétiquement frustrés SrDy2O4 et SrHo2O4. Une étude de la chaleur spécifique à basse température sous l’effet de champs magné- tiques de ces échantillons a été menée afin de détecter la présence de transitions de phases. L’utilisation d’un composé isotructurel non magnétique, le SrLu2O4, a permis l’isolement de la composante magnétique à la chaleur spécifique. Les comportements observés sont non conformes avec les transitions magnétiques conventionnelles. De plus, le calcul de l’entropie magnétique ne montre qu’un recouvrement partiel de l’entropie associée à un système d’ions magnétiques. En second lieu, une analyse des oscillations quantiques de Haas-van Alphen a été effectuée dans le LuCoIn5, composé apparenté au supraconducteur à fermions lourds CeCoIn5. Les résultats obtenus montrent une topologie de la surface de Fermi très différente comparativement aux CeCoIn5 et LaCoIn5, ayant un comportement beaucoup plus tridimensionnel sans les cylindres caractéristiques présents chez les autres membres de cette famille. Finalement, le montage d’un système de détection PIXE a permis l’analyse nucléaire d’échantillons afin de déterminer la concentration de chacun des éléments les constituant. L’analyse a été effectuée sur une série d’échantillons YbxCe1−xCoIn5 dont le changement de concentration a des effets importants sur les propriétés du système.

Mealtime experiences of hospitalized older patients requiring a puree consistency diet

Le concept d’Hôpital Promoteur de Santé (HPS) a pris beaucoup d’importance depuis son élaboration vers la fin des années quatre-vingt. Dans le contexte de la dernière réforme, le réseau montréalais des HPS et CSSS a été créé. Le Centre Universitaire de Santé McGill (CUSM) fait partie de ce réseau depuis 2007. Cette étude vise la création d’un milieu hospitalier promoteur de la santé pour les patients et s’adresse à l’expérience d’un repas pour les personnes âgées nécessitant une diète purée. Une étude de cas qualitative a été utilisée pour explorer la perception de patients vis-à-vis les aspects relatifs à leur cabaret, l’assistance qu’ils recevaient et le contexte social de leur repas. Les impressions des professionnels de la santé quant à l’expérience des patients ont aussi été obtenues. Les résultats indiquent que l’identification difficile des aliments en purée, la saveur, l’apparence et la variété sont tous des éléments qui affectent négativement leur expérience repas. Des sentiments d’impuissance ont aussi été rapportés par les patients et les professionnels de la santé. Le contexte social du repas a été souligné comme étant un aspect à cibler pour améliorer l’expérience des patients. Un programme utilisant des purées formées pourrait contrecarrer les effets négatifs de la prescription d’une diète purée. Des changements dans les pratiques infirmières, à savoir la création d’une ambiance sociale agréable au moment des repas, semble être une option peu couteuse qui pourrait améliorer l’expérience repas des patients et diminuer les sentiments d’impuissance relevés par les professionnels de la santé à l’égard de cet aspect de soin.

Évaluation des effets de l’expansion palatine rapide assistée chirurgicalement (EPRAC) sur les voies aériennes supérieures à l’aide de la tomodensitométrie à faisceau conique

Introduction : L’expansion palatine rapide assistée chirurgicalement (EPRAC) est une option de traitement privilégiée chez les patients ayant atteint la maturité squelettique et présentant une déficience transverse du maxillaire. L’effet bénéfique de l’EPRAC sur la fonction respiratoire est régulièrement mentionné, toutefois, encore peu d’études ont évalué son impact sur les voies aériennes supérieures. L’objectif de cette étude clinique prospective comparative consistait à évaluer les effets tridimensionnels de l’EPRAC sur la cavité nasale, le nasopharynx et l’oropharynx à l’aide de la tomodensitométrie. Méthodologie : L’échantillon était constitué de 14 patients (5 hommes, 9 femmes) dont l’âge moyen était de 23,0 ± 1,9 ans (16 ans 4 mois à 39 ans 7 mois). Tous ont été traités avec un appareil d’expansion de type Hyrax collé et l’expansion moyenne a été de 9,82 mm (7,5 - 12,0 mm). Tous ont eu une période de contention d’une année avant le début de tout autre traitement orthodontique. Une évaluation par tomodensitométrie volumique à faisceau conique a été réalisée aux temps T0 (initial), T1 (6 mois post-expansion) et T2 (1an post-expansion) et le volume des fosses nasales, du nasopharynx et de l’oropharynx ainsi que les dimensions de la zone de constriction maximale de l’oropharynx ont été mesurés sur les volumes tridimensionnels obtenus. Résultats : Les résultats radiologiques ont démontré une augmentation significative du volume des fosses nasales et du nasopharynx ainsi qu’une augmentation de la zone de constriction maximale de l’oropharynx à 6 mois post-expansion. Par la suite, une portion du gain enregistré pour ces trois paramètres était perdue à un an post-EPRAC sans toutefois retourner aux valeurs initiales. Aucun effet significatif sur le volume de l’oropharynx n’a été observé. De plus, aucune corrélation significative entre la quantité d’expansion réalisée et l’ensemble des données radiologiques n’a été observée. L’analyse de la corrélation intra-classe a démontré une excellente fiabilité intra-examinateur. Conclusions : L’EPRAC entraîne un changement significatif du volume de la cavité nasale et du nasopharynx. L’EPRAC ne modifie pas le volume de l’oropharynx, par contre, un effet significatif sur la zone de constriction maximale de l’oropharynx est noté. Les effets observés n’ont pas de corrélation avec le montant d’activation de la vis d’expansion.

Étude du rôle de Pax6 dans la gliogenèse

Les astrocytes sont des cellules gliales présentes dans le système nerveux central, qui exercent de nombreuses fonctions physiologiques essentielles et sont impliquées dans la réponse aux lésions et dans plusieurs pathologies du cerveau. Les astrocytes sont générés par les cellules de la glie radiale, les précurseurs communs de la plupart des cellules neuronales et gliales du cerveau, après le début de la production des neurones. Le passage de la neurogenèse à la gliogenèse est le résultat de mécanismes moléculaires complexes induits par des signaux intrinsèques et extrinsèques responsables du changement de propriété des précurseurs et de leur spécification. Le gène Pax6 code pour un facteur de transcription hautement conservé, impliqué dans plusieurs aspects du développement du système nerveux central, tels que la régionalisation et la neurogenèse. Il est exprimé à partir des stades les plus précoces dans les cellules neuroépithéliales (les cellules souches neurales) et dans la glie radiale, dérivant de la différenciation de ces cellules. L’objectif de cette étude est d’analyser le rôle de Pax6 dans la différenciation et dans le développement des astrocytes. À travers l’utilisation d’un modèle murin mutant nul pour Pax6, nous avons obtenu des résultats suggérant que la suppression de ce gène cause l'augmentation de la prolifération et de la capacité d'auto-renouvellement des cellules souches neurales embryonnaires. In vitro, les cellules mutantes prolifèrent de façon aberrante et sous-expriment les gènes p57Kip2, p16Ink4a, p19Arf et p21Cip1, qui inhibent la progression du le cycle cellulaire. De plus, Pax6 promeut la différenciation astrocytaire des cellules souches neurales embryonnaires et est requis pour la différenciation des astrocytes dans la moëlle épinière. Les mutants nuls pour Pax6 meurent après la naissance à cause de graves défauts développementaux dus aux fonctions essentielles de ce gène dans le développement embryonnaire de plusieurs organes. En utilisant un modèle murin conditionnel basé sur le système CRE/ loxP (hGFAP-CRE/ Pax6flox/flox) qui présente l’inactivation de Pax6 dans les cellules de la glie radiale, viable après la naissance, nous avons montré que Pax6 est impliqué dans la maturation et dans le développement post-natal des astrocytes. Le cortex cérébral des souris mutantes conditionnelles ne présente pas d’astrocytes matures à l’âge de 16 jours et une très faible quantité d’astrocytes immatures à l’âge de trois mois, suggérant que Pax6 promeut la différenciation et la maturation des astrocytes. De plus, Pax6 semble jouer un rôle même dans le processus de différenciation et de maturation de cellules gliales rétiniennes. L’étude des gènes et des mécanismes moléculaires impliqués dans la génération des astrocytes est crucial pour mieux comprendre le rôle physiologique et les altérations pathologiques des ces cellules.