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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Fonction cellulaire de la HNRNP A1B, une isoforme plus longue de HNRNPA1, qui est régulée à la hausse dans la SLA/DFT

Llasera Ballester García, Mariana 10 1900 (has links)
Les protéines de liaison à l'ARN (PLA) s'assemblent en complexes cytoplasmiques avec les ARNm pour contrôler la traduction locale des ARNm et le transport axonal. Ces processus sont essentiels au maintien de la survie des neurones et leur déficience est impliquée dans le développement de nombreuses maladies neurodégénératives, telles que la SLA. Il a été montré ultérieurement que la déplétion nucléaire de TDP-43, liée à la SLA, entraîne l'accumulation d'une variante épissée alternativement de la ribonucléoprotéine nucléaire hétérogène A1 (hnRNP A1). Cette isoforme, appelée hnRNP A1B, possède une région désordonnée (RID) et, dans le contexte neuronal, localise dans les neurites et dans le noyau, alors que la hnRNP A1 localise majoritairement dans le noyau. Ceci appui l'hypothèse que la hnRNP A1B peut avoir une fonction cytosolique dans les neurones qui n'est pas partagée avec la hnRNP A1. En outre, les hnRNP A1 et hnRNP A1B sont mutées dans de rares cas de SLA familiale, dont certaines mutations sont spécifiques à la hnRNP A1B. Jusqu'à présent, la littérature se concentre sur l'isoforme hnRNPA1 tandis que peu est répertorié sur la fonction de la hnRNP A1B. Ainsi, cette étude vise à déterminer et caractériser la fonction cytosolique de la hnRNP A1B dans les neurones. Puisque très peu est répertorié sur la hnRNP A1B, il a fallu tout d’abord déterminer des partenaires d’interaction. Ainsi, une immunoprécipitation utilisant un anticorps spécifique à la hnRNP A1B suivi d'une spectrométrie de masse (IP-MS) a été réalisée sur la moelle épinière de souris. Les résultats soulèvent que de nombreux interacteurs de la hnRNP A1B sont associés au trafic intracellulaire dépendant du cytosquelette. Les interactions avec KLC1/KIF5C/Myh9/DyncIHI ont été validées par des tests d'immunoprécipitation et de colocalisation. Aussi, l’impact de certains mutants hnRNP A1B associés à la SLA ont été étudiées au niveau des interactions avec les protéines motrices. Des expériences visant à évaluer comment la hnRNP A1B peut être transportée, ainsi que réguler le transport, sont en cours. Les résultats confirment que la hnRNP A1B peut avoir une fonction cytosolique dans les neurones pour le transport axonal/dendritique de l'ARNm. Des études futures exploreront cette nouvelle fonction dans le contexte de la SLA. / RNA-binding proteins (RBPs) assemble into cytoplasmic complexes with mRNAs to control mRNA local translation and axonal transport. These processes are essential for maintaining neuronal survival and their impairment is implicated in the development of many neurodegenerative diseases, such as ALS. We have discovered that TDP-43 depletion, linked to ALS, drives the accumulation of an alternatively spliced variant of heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1). This isoform, termed hnRNP A1B, has an elongated prion-like domain (PrLD) and is present in neuronal processes, while hnRNP A1 is not. This finding supports a hypothesis that hnRNP A1B may have a cytosolic function in neurons that is not shared with hnRNP A1. In addition, hnRNP A1 and hnRNP A1B are mutated in rare cases of familial ALS with some mutations specific to hnRNP A1B. To date, the literature has mostly focused on the hnRNPA1 isoform and little is known about hnRNP A1B function. Thus, this study aims to identify and characterize the cytosolic function of hnRNP A1B in neurons. Since very little is known about hnRNP A1B, it was first necessary to identify interaction partners of the protein. Thus, immunoprecipitation using an antibody specific to hnRNP A1B followed by mass spectrometry (IP-MS) was performed on mouse spinal cord. Our results show that many hnRNP A1B interactors are associated with cytoskeletal-dependent intracellular trafficking. We then proceed to validate the interactions with the motor proteins KLC1/KIF5C/Myh9, by immunoprecipitation and proximity ligation assays. In addition, some hnRNP A1B ALS mutants were studied in the context of these interactions. Experiments to evaluate how hnRNP A1B may be transported, as well as regulate transport are currently underway. Our findings support that hnRNP A1B may have a cytosolic function in neurons in mRNA axonal/dendritic transport. Future studies will explore this novel function in the ALS context.
52

Essays on fiscal policy and political economy

Achury-Forero, Carolina January 2013 (has links)
This thesis consists of three essays concerned with endogenous fiscal policy and its interaction with political economy constraints. The first essay presented in Chapter 2 examines the cyclical behavior of endogenous government consumption over the business cycle absent a commitment mechanism in a neoclassical economy with Total Factor Productivity (TFP) shocks and investment shocks. Tax rates that finance public consumption are chosen in a time consistent way in a dynamic game between the government and a representative agent that values public goods in his utility. It is found that government consumption set without commitment behaves procyclical in response to the mentioned shocks. The government-consumption-output ratio is mildly procyclical or countercyclical depending on the selected calibration. Particularly, the elasticity of substitution between private and public goods plays an important role. The second essay showed in Chapter 3 extends the model studied in Chapter 2 adding agent heterogeneity in wealth and labor productivity. The aim of this study is to identify how policy outcomes are affected by inequality of households, particularly the median voter's choice of tax rates that finance public goods. For a standard RBC calibration to the U.S. economy the result is a strong procyclical comovement of public consumption with output, and a relatively weak procyclical comovement of the output share of public consumption with output, that becomes stronger with rising inequality. The politico-economic channel induces causality from output to lagged tax rates, therefore after a Hicks neutral productivity shock the median voter tries to delay the increase in the tax rate, such that the increment will take place just after the accumulation of more capital. In the case of equal agents the response is to decrease the tax rate in the first year after the shock. Additionally, the model predicts that the size of government consumption decreases with inequality. The last essay in Chapter 4 presents a stylized model of external sovereign debt that incorporates corruption in the form of rent-seeking groups by which the choice to cooperate or non-cooperate in providing public goods, in extracting rents and in issuing debt, is endogenized. More than one rent-seeking group originates a "tragedy of the commons" over fiscal resources that make the borrower economy to show collective fiscal impatience. External creditors envision that impatience and require higher interest rates for buying bonds, exacerbating the problem of high debt. The high level of interest rates decreases the wealth of the country and endangers its ability to repay the debt. We show that bailout plans, defined as temporary loans with lower than market level interest rates, are not effective in such economies.
53

An Automatic Code Generation Tool For Partitioned Software in Distributed Computing

Singh, Neeta S 30 March 2005 (has links)
In a large class of distributed embedded systems, most of the code generation models in use today target at object-oriented applications. Distributed computing using procedural language applications is challenging because there are no compatible code generators to test the partitioned programs mapped on to the multi-processor system. In this thesis, we design a code generator to produce procedural language code for a distributed embedded system. Unpartitioned programs along with the partition primitives are converted into independently executable concrete implementations. The process consists of two steps, first translating the primitives of the unpartitioned program into equivalent code clusters, and then scheduling the implementations of these code clusters according to the data dependency inherent in the unpartitioned program. Communication and scheduling of the partitioned programs require the original source code to be reverse engineered. A reverse engineering tool is used for the creation of a metadata table describing the program elements and dependency trees. This data gathered, is used by Parallel Virtual Machine message passing system for communication between the partitioned programs in the distributed environment. The proposed Code Generation Model has been implemented using C and the experimental results are presented for various test cases. Further, metrics are developed for testing the quality of the results taking into consideration the correctness and the execution of time.
54

Agent-Based Architecture for Multirobot Cooperative Tasks: Design and Applications

Nebot Roglá, Patricio 11 January 2008 (has links)
This thesis focuses on the development of a system in which a team of heterogeneous mobile robots can cooperate to perform a wide range of tasks. In order that a group of heterogeneous robots can cooperate among them, one of the most important parts to develop is the creation of an architecture which gives support for the cooperation. This architecture is developed by means of embedding agents and interfacing agent code with native low-level code. It also addresses the implementation of resource sharing among the whole group of robots, that is, the robots can borrow capabilities from each-other.In order to validate this architecture, some cooperative applications have been implemented. The first one is an application where a group of robots must cooperate in order to safely navigate through an unknown environment. One robot with camera calculates the optical flow values from the images, and from these values calculates the "time to contact" values. This information is shared among the team so that any robot can navigate without colliding with the obstacles.The second cooperative application consists of enabling the team of heterogeneous robots to create a certain formation and navigate maintaining this formation. The application consists of two parts or stages. The first one is the creation of the formation, where a robot with the camera can detect where the rest of the robots are in the environment and indicates to them which is their initial position in the formation. In the second stage the robots must be able to navigate through an environment following the path that the robot with the laser indicates. Due to the odometry errors of the robots, the camera of one of the robots is used so that robots which lose their correct position in the formation can re-align themselves. Finally, in an attempt to facilitate access to the robots of the team and to the information that their accessories provide, a system for the teleoperation of the team has been implemented. This system can be used for teaching robotics or to facilitate the tasks of programming and debugging in the research tasks.
55

Aνάπτυξη κρυπτογραφικών αλγορίθμων για ετερογενή ασύρματα δίκτυα αισθητήρων

Πυργελής, Απόστολος 15 May 2012 (has links)
Ένα ασύρματο δίκτυο αισθητήρων αποτελείται από χωρικά κατανεμημένες αυτόνομες συσκευές, οι οποίες χρησιμοποιούν αισθητήρες για την συνεργατική παρακολούθηση φυσικών και περιβαλλοντικών συνθηκών. Ένας κόμβος ενός δικτύου αισθητήρων συνήθως αποτελείται από ένα μικροελεγκτή, ένα ραδιο-πομποδέκτη, μια πηγή ενέργειας, η οποία συχνά είναι μια μπαταρία και διαφόρων ειδών αισθητήρες (π.χ. θερμοκρασίας, υγρασίας, φωτεινότητας). Τα ασύρματα δίκτυα αισθητήρων προσφέρουν οικονομικά βιώσιμες λύσεις σε ποικίλες εφαρμογές. Δίκτυα τέτοιου τύπου δραστηριοποιούνται σε βιοιατρικές, στρατιωτικές, βιομηχανικές εφαρμογές καθώς και εφαρμογές παρακολούθησης του φυσικού περιβάλλοντος. Επιπλέον, τα δίκτυα αισθητήρων είναι κλειδί για τη δημιουργία έξυπνων χώρων που ενθέτουν τεχνολογία πληροφορίας στα καθημερινά περιβάλλοντα εργασίας και κατοικίας. Λόγω της χρήσης τέτοιων δικτύων σε περιβάλλοντα που ανταλλάσσονται ευαίσθητες πληροφορίες, δημιουργούνται θέματα ασφάλειας και μυστικότητας. Χαρακτηριστικά των διαφόρων εφαρμογών όπως η λειτουργία σε αντίξοα περιβάλλοντα, η ελλιπής γνώση της τοπολογίας του δικτύου, οι δυνατότητες αυτο-οργάνωσης και αυτόματης διόρθωσης λειτουργιών και η λειτουργία χωρίς ανθρώπινη επιτήρηση καθιστούν τη διατήρηση της ασφάλειας μια μεγάλη πρόκληση. Ένας κλάδος που παρέχει λύσεις σε προβλήματα ασφαλείας είναι αυτός της κρυπτογραφίας. Η κρυπτογραφία είναι μια καλά εδραιωμένη επιστημονική περιοχή, με πρωτόκολλα και πρότυπα τα οποία τυγχάνουν ευρείας αναγνώρισης. Παρόλα αυτά, η χρήση τους σε περιβάλλοντα περιορισμένων πόρων όπως αυτά των ασυρμάτων δικτύων αισθητήρων, απαιτεί προσαρμογές. Η απαίτηση αυτή προκύπτει λόγω των ιδιαίτερων χαρακτηριστικών των δικτύων αυτών και των κόμβων που τα απαρτίζουν όπως η χαμηλή υπολογιστική ισχύς, οι περιορισμένες δυνατότητες αποθήκευσης και η περιορισμένη διαθέσιμη ενέργεια καθώς και η επικοινωνία ασύρματης φύσης που υιοθετείται. Ένα επιπλέον πρόβλημα που παρουσιάζεται στα ασύρματα δίκτυα αισθητήρων, είναι η ετερογένεια. Οι συσκευές αισθητήρων που παράγονται από τη βιομηχανία σήμερα, έχουν διαφορετικές υπολογιστικές δυνατότητες και εκτελούν διαφορετικά λειτουργικά συστήματα. Κάποιες αποτελούνται από μικροεπεξεργαστές 8-bit και έχουν ελάχιστη ποσότητα μνήμης RAM, ενώ άλλες έχουν πολύ μεγάλη υπολογιστική δύναμη και μπορούν να εκτελέσουν desktop λειτουργικά συστήματα όπως Linux. Έτσι, ενώ είναι σχετικά εύκολο να αναπτύξει κανείς μια εφαρμογή για μια συγκεκριμένη πλατφόρμα, είναι πολύ δύσκολο να γράψει γενικό κώδικα ανεξάρτητο της πλατφόρμας μεταγλώτισσης. Έτσι, υπάρχοντες υλοποιημένοι αλγόριθμοι και εφαρμογές πρέπει να τροποποιούνται κατάλληλα για να μπορούν να προσαρμοστούν σε διαφορετικά περιβάλλοντα ανάπτυξης. Μια απάντηση στο παραπάνω πρόβλημα δίνει η βιβλιοθήκη Wiselib η οποία προσφέρει ένα προγραμματιστικό περιβάλλον για την ανάπτυξη γενικών αλγορίθμων που έχουν ως στόχο την εκτέλεσή τους σε ετερογενή δίκτυα αισθητήρων. Σκοπός της παρούσας διπλωματικής εργασίας είναι να προσφέρει λύσεις στα δύο προαναφερθέντα προβλήματα, ανάπτυσσοντας κρυπτογραφικούς αλγόριθμους για ετερογενή ασύρματα δίκτυα αισθητήρων. Για την επίτευξη του σκοπού αυτού, αναπτύσουμε μια κρυπτογραφική βιβλιοθήκη στο προγραμματιστικό περιβάλλον της Wiselib, μιας γενικής βιβλιοθήκης αλγορίθμων για ετερογενή δίκτυα αισθητήρων. Η Wiselib είναι υλοποιημένη σε C++ και με χρήση τεχνικών όπως τα πρότυπα και οι inline συναρτήσεις, επιτρέπει τη συγγραφή γενικού κώδικα ο οποίος αναλύεται και δεσμεύεται κατά τη διαδικασία μεταγλώττισσης χωρίς να δημιουργείται πλεονασμός μνήμης ή υπολογισμού. Λόγω των απαιτήσεων ασφαλείας που δημιουργούνται από τις εφαρμογές δικτύων αισθητήρων καθώς και των περιορισμένων υπολογιστικών πόρων, η κρυπτογραφική μας βιβλιοθήκη παρέχει αλγορίθμους τόσο συμμετρικής όσο και ασυμμετρικής κρυπτογραφίας. Οι αλγόριθμοι ασυμμετρικής κρυπτογραφίας βασίζονται στην κρυπτογραφία ελλειπτικών καμπυλών. Οι ελλειπτικές καμπύλες αποτελούν ένα ιδανικό σύστημα για ανάπτυξη κρυπτογραφίας δημοσίου κλειδιού σε ενσωματωμένα περιβάλλοντα τα οποία υστερούν σε επεξεργαστική ισχύ, μνήμη και ενέργεια. Αυτό ισχύει διότι τα συστήματα ελλειπτικών καμπυλών προσφέρουν το ίδιο επίπεδο ασφάλειας με άλλα κρυπτοσυστήματα (π.χ. RSA) με χρήση πολύ μικρότερου μεγέθους κλειδιών. Έτσι, συνολικά η βιβλιοθήκη μας παρέχει τους εξής αλγορίθμους: τον αλγόριθμο συμμετρικής κρυπτογράφησης AES, τον αλγόριθμο κατακερματισμού SHA-1, το σχήμα συμφωνίας κλειδιών Diffie Hellman (ECDH), τον αλγόριθμο ασυμμετρικής κρυπτογράφησης ECIES και το σχήμα ψηφιακής υπογραφής ECDSA. Για την ανάλυση της απόδοσης της κρυπτογραφικής μας βιβλιοθήκης γίνεται πειραματική αξιολόγηση (χρόνος εκτέλεσης, ενέργεια,μέγεθος μεταφρασμένου κώδικα) των παραπάνω αλγορίθμων σε δύο συσκευές ( iSense, TelosB) με διαφορετικές επεξεργαστικές δυνατότητες (16 MHz, 8 MHz) που τρέχουν διαφορετικά λειτουργικά συστήματα (iSense OS, Contiki Sky). Το γεγονός ότι αξιολογήσαμε τους κρυπτογραφικούς αλγορίθμους σε δύο συσκευές διαφορετικών δυνατοτήτων και περιβαλλόντων ανάπτυξης, αποδεικνύει τη γενικότητα της υλοποίησης μας.Τέλος, για να αποδείξουμε την ευκολία χρήσης των υλοποιημένων αλγορίθμων παρουσιάζουμε τρεις εφαρμογές δικτύων αισθητήρων που τους χρησιμοποιούνε. Πιο συγκεκριμένα, επιδεικνύουμε πως οι κρυπτογραφικοί αλγόριθμοι μπορούν να συνδυαστούν με αλγορίθμους δρομολόγησης και ομαδοποίησης που παρέχει η βιβλιοθήκη Wiselib, με αποτέλεσμα να δημιουργηθούν ασφαλείς εφαρμογές δικτύων αισθητήρων. / A wireless sensor network consists of spatially distributed autonomous devices, that use sensors in order to cooperatively monitor natural and environmental conditions. A wireless sensor network node typically consists of a micro-processor, a radio transceiver, an energy source (usually a battery) and various kinds of sensors that measure different environmental conditions (e.g. temperature, humidity, lightness). Wireless sensor networks are economically viable solutions to various applications. Networks of this type are used in biomedical, military, industrial as well as in applications that monitor the natural environment. Moreover, sensor networks are a key for the creation of smart spaces that introduce information technology in everyday environments like those of home and work. Because sensor networks are typically deployed in environments where sensitive information is communicated, security and privacy issues arise. Application characteristics like deployment in adverse environments, the incomplete knowledge of the network topology, the possibility of self-organization and the operation without human surveillance make the maintenance of security a big challenge. Cryptography is a science field that provides solutions to security problems. Cryptography is a well established science field that has provided protocols and standards of wide acceptance. However, the use of such protocols and standards in resource constrained environments, like those of sensor networks, requires changes and adaptations. This applies due to the special characteristics of such networks and the devices that consist them, e.g. the restricted processing power, the limited storage possibility and energy as well as the wireless nature of communication. A second problem that arises in wireless sensor networks is that of heterogeneity. The nodes produced by the industry today have different processing possibilities and execute various operating systems. Some nodes consist of 8-bit micro-processors that offer tiny amounts of RAM memory, whereas others are produced with 32-bit processors that can even execute desktop operating systems like Linux. Thus, while it is easy for a developer to implement a platform specific application, it is quite difficult to write some generic platform independent code. In order to re-use implemented applications and algorithms in different development environments a programmer has to make adaptations and changes according to the new platform specifications. A solution to this problem is provided by Wiselib. Wiselib offers an development environment suitable for the implementation of generic algorithms that can be compiled and executed on heterogenous wireless sensor networks. The objective of this work is to provide solutions to the aforementioned sensor network problems (security, heterogeneity). For this reason, we develop a cryptographic library on the generic program environment of Wiselib, a generic algorithm library for heterogenous sensor networks. Wiselib is implemented in C++ and employing advanced techniques, like templates and inline functions, it allows writing of generic code that can be allocated and resolved during compilation without producing computation or memory overhead. Due to the security requirements imposed by the sensor network applications and the resource restrictions by the sensor nodes, our cryptographic library provides symmetric as well as asymmetric cryptographic algorithms. The public key algorithms are based on elliptic curve cryptography. Elliptic curves consist an ideal system for the development of public key cryptography in resource constrained environments that offer restricted computation power, memory and energy. That is because elliptic curve cryptosystems offer the same level of security with other public key cryptosystems (e.g. RSA), using much smaller key sizes. Thus, in total our cryptographic library provides the following algorithms: the symmetric encryption algorithm AES, the hash algorithm SHA-1, the key agreement scheme Diffie Hellman (ECDH), the public key encryption algorithm ECIES and the signature scheme ECDSA. In order to evaluate the performance of our cryptographic library we experimentally test (in terms of execution time, compiled code size, energy consumption) its algorithms on two devices (iSense, TelosB) with different processing possibilities (16 MHz, 8 MHz) that execute different operating systems (iSense OS, Contiki Sky). The fact that we evaluated the cryptographic algorithms on two different devices with unlike capabilities and that execute different operating systems proves that our implementation is generic. Finally, in order to prove the ease of use of the implemented cryptographic algorithms we present three sensor network applications that employ them. More precisely, we show how our cryptographic algorithms can be combined with routing and clustering algorithms (provided by Wiselib), resulting in secure sensor network applications.
56

SnO2 suportado em argila para síntese de Biodiesel / SnO2 Supported on Clay for Synthesis of Biodiesel

Sales, Herbet Bezerra 30 November 2009 (has links)
Made available in DSpace on 2015-05-14T13:21:33Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1872624 bytes, checksum: 82d5c5729cedad38a0a2aa4e489a50cd (MD5) Previous issue date: 2009-11-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Biodiesel production is based on the is transesterification of vegetable oils or animal fat, using homogeneous or heterogeneous catalysts. Wheres, the heterogeneous-based processing presents slower conversions compared to homogenous ones, such processes lead to noncorrosive manufacturing and avoids the occurrence of saponification reactions. Thus, this work aims at evaluating the catalytic activity of the SnO2 supported on vermiculite clay [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] for the transesterification of soybean oil. The several catalysts were obtained by impregnation of vermiculite with tin resin, previously synthesized by the polymeric precursor method. All samples were characterized thermal analysis (TG/DTA), X-ray diffraction (XRD), grazing angle XRD, X-ray fluorescence (XRF), scanning electron microscopy (SEM), infrared (IR) and confocal Raman spectroscopy is Biodiesels were synthesized using a molar ratio of 1:10 (soybean oil: ethanol), 5,0 % (wt / wt) catalys treational temperature q 65 °C, besing characterized by dynamic and kinematic viscosities. In this work the vermiculite was treated with nitric acid (HNO3). The leaching process did not modifi, the thermal stability of inorganic solids. XRF date indicates satisfactory impregnation of the catalyst supports by the precursor resins. The XRD patterns identified the presence of cassiterite phase as well as the presence of characteristic phases of clay minerals which was confirmed by grazing incidence XRD. The spectroscopic data indicated the presence of peaks characteristic of the catalytic support as well as the active phase of catalyst (SnO2). The formation of active species (alkoxide) at low temperature, on the surface of catalysts, favored the soybean oil transesterification process. Rheological studies gave preliminary evidence that the catalytic reaction occurred with reduction of 40 % in the viscosity. / A produção de biodiesel é baseada na transesterificação de óleos vegetais ou gorduras animais, utilizando catalisadores homogêneos ou heterogêneos. O processo de transesterificação heterogênea apresenta conversões mais baixas em comparação com o homogêneo, porém, não apresenta problemas de corrosão e reduz à ocorrência de reações paralelas como saponificação. Neste sentido, este trabalho visa avaliar a atividade catalítica do SnO2 suportado em vermiculita [(Mg, Fe, Al)3(Al, Si)4O10(OH)2.4H2O] para a transesterificação do óleo de soja. Os diversos catalisadores foram obtidos pela impregnação da vermiculita com resina de estanho previamente sintetizada pelo método dos precursores poliméricos. Todas as amostras foram caracterizadas por análise térmica (TG/DTA), difração de raios-X (DRX), DRX de ângulo rasante, fluorescência de raios-X (FRX), microscopia eletrônica de varredura (MEV), espectroscopia vibracional na região do infravermelho (IV), espectroscopia Raman confocal. Os biodieseis foram sintetizados utilizando uma razão molar de 1:10 (óleo de soja: etanol) e 5,0 % (wt/catalisador) em peso, a 65 °C, e cujas caracterizações foram feitas por intermédio de medidas de viscosidade dinâmica e cinemática. Neste trabalho a vermiculita foi submetida a tratamento ácido utilizando ácido nítrico. O processo de lixiviação não causou mudanças na estabilidade térmica do sólido inorgânico. Dados da FRX apresentaram resultados satisfatórios de impregnação dos suportes catalíticos pelas resinas precursoras. Os DRX tanto identificaram a presença da fase cassiterita como também a presença das fases características dos argilominerais, confirmada pelas análises do DRX de ângulo rasante. Os dados espectroscópicos indicaram a presença dos picos típicos do suporte catalítico como também da fase ativa do catalisador (SnO2). A formação da espécie ativa (alcóxido) a baixa temperatura sobre a superfície dos catalisadores favoreceu o processo de transesterificação do óleo de soja comercial. Os estudos reológicos deram uma confirmação preliminar de que ocorreu o fenômeno da catálise, com redução de até 40 % da viscosidade.
57

Heterogeno integrisani pasivni induktivni senzori / Heterogenous integrated passive inductive sensors

Kisić Milica 29 December 2016 (has links)
<p>U disertaciji je prikazano teorijsko i praktično istraživanje koje se odnosi na projektovanje, fabrikaciju i karakterizaciju heterogeno integrisanih induktivnih senzora za mjerenje sile, pritiska i pomjeraja. Cilj istraživanja doktorske disertacije je kombinovanje različitih tehnologija izrade i materijala, kako bi se projektovali senzori koji će biti konkurentni aktuelnim rešenjima, i koji bi se mogli koristiti za konkretne primjene. U okviru istraživanja, heterogenom integracijom su kombinovane prednosti tehnologije štampanih ploča (Printed Circuit Board - PCB), fleksibilne tehnologije i tehnologije niskotemperaturne zajedno-pečene keramike (Low Temperature Co-fired Ceramics &ndash; LTCC). Razvijena su tri prototipa senzora za mjerenje sile, pritiska i pomjeraja korišćenjem struktura sa induktorom i feritom u njegovoj blizini. Mjerenje realizovanih prototipova senzora vrši se bežično pomoću spregnutog antenskog namotaja. Na osnovu početnih rezultata ispitivanja, senzori su modifikovani u cilju poboljšanja i optimizovanja performansi. Projektovani senzori omogućavaju bežično mjerenje, jeftini su, kompaktni i jednostavni. Na osnovu teorijske analize, simulacija, eksperimetnalnih mjerenja, ustanovljena je ispravnost rada i primjenljivost realizovanih senzora.</p> / <p>In doctoral thesis theoretical and practical investigation on design, fabrication and characterisation of heterogenous integrated inductive sensors for measuring force, pressure and displacement are shown. The aim of the thesis is to investige the usage of different technologies and materials in order to design sensors which will be competitive to actual solutions and usable for specific aplications. Using heterogenous integraton, advantages of Printed Circuit Board technology (PCB), flexible and Low Temperature Co-fired Ceramics (LTCC) technologies are used. Three sensor prototypes for measuring force, pressure and displacement are developed using inductor and ferrite in its near proximity. Measurements of the realised sensor prototypes are wirelessly done using an external surrounding coil as an antenna. Based on the initial measuring results, sensors are redesigned in order to improve and optimize their performance. Projected sensors are low-cost, compact, simple, and enable wireless measurement. The proper operation and applicability of realized sensors are confirmed using theoretical analysis, simulation and experimental testing with presented results.</p>
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De nouveaux biocatalyseurs hétérogènes pour des réactions d'oxydation : des cristaux de métalloenzymes artificielles / New heterogeneous biocatalysts for oxidation reactions : crystals of artificial metalloenzymes

Lopez, Sarah 12 October 2018 (has links)
Depuis la révolution industrielle, la chimie ne cesse de prospérer en développant des procédés de plus en plus performants souvent aux dépens de l’environnement. Dans le cadre du développement d’une chimie durable, des procédés catalytiques dans le domaine de la chimie d’oxydation sont mis en place en utilisant des métaux physiologiques et des oxydants doux. En combinant les avantages de la catalyse homogène et de la biocatalyse, de nouveaux catalyseurs bio-inspirés ont émergé, les métalloenzymes artificielles. Elles sont constituées d’un complexe inorganique, choisi en fonction de la réaction visée, qui est ancré au sein d’une protéine, qui apporte la sélectivité de la réaction. Au cours des travaux de cette thèse, de nouvelles métalloenzymes artificielles ont été créées par ancrage de divers complexes de Fe ou de Ru au sein de la protéine NikA. Dans un premier temps, l’hybride NikA/Ru-bpza a été synthétisé pour réaliser l’hydroxychloration d’alcènes en présence d’un iode hypervalent. Bien que d’excellentes propriétés catalytiques aient été obtenues, l’amélioration de la stabilité de ce type de catalyseurs, en particulier pour des réactions d’oxydation, reste un challenge important à relever pour leur utilisation au niveau industriel. Une des solutions originale est basée sur le développement de la catalyse hétérogène, en utilisant de cristaux de métalloenzymes artificielles grâce à la technologie CLEC (Cross-Linked Enzyme Crystals). Cette technologie permet, d’une part, d’améliorer la stabilité et la recyclabilité des catalyseurs, et d’autre part, d’élargir les conditions réactionnelles utilisées (solvants, pH, températures). Trois réactivités ont été développées à base de CLEC NikA/FeL : (i) la sulfoxydation de thioéthers, (ii) l’hydroxychloration d’alcènes en présence d’Oxone® et de chlore et (iii) la coupure oxydante d’alcènes par activation d’O2. Ces résultats ont permis d’explorer de nouvelles réactivités en chimie cascade soit en combinant les CLEC mis au point, soit en combinant différents catalyseurs homogènes. / Since the industrial revolution, chemistry has continually thriven by developing new efficient processes at the expense of the environment. As an example, oxidation reactions are performed under harsh conditions with the use of toxic oxidants. With the emergence of green chemistry, catalytic processes using physiological metals and soft oxidants are privileged. Combining the advantages of biocatalysis and homogeneous catalysis, the design of novel bioinspired catalysts, consisting on the synthesis of artificial enzymes has recently emerged. These hybrids are composed of an inorganic complex, driving the reactivity of the enzyme, inserted into a protein, which drives the reaction selectivity. The thesis described new developments in original artificial metalloenzymes, based on the use of the NikA protein and Fe or Ru catalysts. First, a new hybrid has been developed by anchoring the Ru-bpza complex to NikA to catalyze alkene hydroxychloration with hypervalent iodine. Although excellent catalytic efficiencies were obtained, the stability improvement remains a major challenge for the industrial use of these catalytic processes, especially when oxidation chemistry is concerned. One possible strategy is based on the development of heterogeneous catalysis, by using a crystal/solution version of the artificial metalloenzymes thank to the cross-linked enzyme crystals (CLEC) technology. On the one hand, this technology allows to increase the stability and the recyclability of the catalysts. On the other hand, catalysis can be performed under a various reactions conditions (organic solvent, temperature, pH). Three reactivities have been developed with NikA/FeL-CLEC catalysts: (i) thioether sulfoxidation with NaOCl, (ii) alkene hydroxychloration with Oxone® and chloride source and (iii) oxidative cleavage of alkenes by O2 activation. To go further, new reactivities in cascade reactions have been explored combining either NikA-based CLEC developed, or different homogenous catalysts.
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Agents hétérogènes et formation des prix sur les marchés financiers / Heterogeneous agents and price formation on financial markets

Donier, Jonathan 10 October 2016 (has links)
Cette thèse est consacrée à l'étude de la formation des prix sur les marchés financiers, en particulier lorsque ceux-ci se composent d'un grand nombre d'agents. On commence par l'étude empirique d'un marché émergent -- le bitcoin -- de manière à mieux comprendre comment les actions individuelles affectent les prix -- ce que l'on appelle « l'impact de marché ». On développe ensuite un modèle théorique d'impact basé sur le concept d'agent hétérogène, qui parvient à reproduire les observations empiriques d'un impact concave dans un marché non manipulable. Le cadre de l'agent hétérogène nous permet de revisiter les concepts d'offre et de demande dans un cadre dynamique, de mieux comprendre l'impact du mécanisme de marché sur la liquidité, ou encore de poser les bases d'un simulateur de marché réaliste. On montre enfin, à travers l'étude empirique de plusieurs bulles et crashs sur le marché du bitcoin, le rôle crucial de la micro-structure dans la compréhension des phénomènes extrêmes. / This thesis is devoted to the study of price formation on financial markets, in particular when these are composed of a large number of agents. We start by the empirical study of an emergent market -- the bitcoin -- in order to better understand how individual actions impact prices -- a phenomenon known as « market impact ». We then develop a theoretical model based on the concept of heterogeneous agents, that allows to reproduce the empirical observations of a concave impact in a market that remains non-manipulable. The heterogeneous agents framework allows us to revisit the concepts of supply and demand in a dynamic context, to better understand how the choice of a particular market mechanism can impact liquidity, and to lay some grounds for a realistic market simulator. By studying several bubbles and crashes that happened on the bitcoin market, we finally show how relevant microstructure effects can be, in particular for understanding the occurrence of extreme phenomena.
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Studium tepelných vlastností materiálů / Study of Thermal Properties of Materials

Štefková, Pavla January 2012 (has links)
The doctoral thesis deals with study of thermal properties of materials. Behavior of homogeneous matters at different temperatures is well described in theory and experimentally verified. Overall effect of all components of mixture and other influences related with material creation affect behaviour and properties of heterogeneous matters. For study of thermal properties can be used transient method of measurement which provide a picture about overall influence of all components of mixture on studied heterogeneous material and among others enable determination of thermophysical properties of whole macroscopic system in observed temperature range. Properties of solid matters, thin foil and liquids can be measured by means of pulse and step-wise transient method which is used for experimental activity in the thesis. It is contact measurement method and its principle is based on small quantity of heat generating inside the specimen and temperature response measuring. Theoretical part of thesis is focused on creation of method for determination of thermophysical parameters. The base is differential equation of the heat conduction. Its solution is temperature function. Three methods of evaluation are described mathematically. They start from general relations designed for study of fractal structure physical properties (maximum of function method, differential method and multi-parametric non-linear regression method).

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