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1
Choi, Yunsoo. "Spring to summer transitions of ozone and its precursors over North America and photochemistry over Antarctica". Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-06262007-144619/.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2008.Cunnold, Derek, Committee Member ; Nenes, Athanasios, Committee Member ; Black, Robert, Committee Member ; Russell, Armistead (Ted), Committee Member ; Wang, Yuhang, Committee Chair.
2
Bertus, Thomas. "Devenir de l'azote lors de la combustion de biomasse dans le lit d'une chaudière à grille". Electronic Thesis or Diss., Ecole nationale des Mines d'Albi-Carmaux, 2024. http://www.theses.fr/2024EMAC0013.
Testo completoAbstract (sommario):
La combustion de biomasse dans des chaudières industrielles à grille produit plusieurs espèces polluantes dont les oxydes d'azote, aussi appelés NOx. Ces molécules sont nocives pour l'environnement (causes de pluies acides, gaz à effet de serre). Ces polluants sont majoritairement formés par l'oxydation de l'azote initialement contenu dans la biomasse. La limitation de leurs émissions est donc un enjeu important dans le domaine de la combustion de biomasse. Pour y parvenir, le recours à la modélisation est courant. La chimie de l'azote en phase gaz est bien connue ; la modélisation du devenir de l'azote dans la phase gaz au-dessus du lit ne pose donc pas de problème. En revanche, les phénomènes régissant la combustion hétérogène du lit de biomasse restent mal connus. Cela se traduit par une mauvaise prédiction de la forme de l'azote en sortie de lit. L'objectif de cette thèse est alors de proposer un modèle de lit permettant de fournir des données d'entrée fiables à un modèle numérique de chaudière ne simulant que la phase gaz. Pour ce faire, un modèle a été développé sur MATLAB à partir du code BASIC développé par l'Université de Aalborg. Ce modèle de lit est un modèle de type 1D Euler-Euler pouvant modéliser le lit d'une chaudière biomasse via l'approche de la colonne mobile. La chimie de l'azote a été ajoutée à ce modèle et un modèle à deux températures a également été implémenté. Pour confronter le modèle, des expériences en lit fixe traversé ont été réalisées. Pour cela, un dispositif expérimental existant a été adapté afin de pouvoir quantifier l'azote dans les différents produits de la combustion. Trois séries d'expériences ont été réalisées sur ce dispositif expérimental. La première consistait à comparer le devenir de l'azote de trois agrocombustibles lors de leur pyrolyse et de leur combustion. La deuxième série consistait en une étude paramétrique sur l'influence de la taille des particules et de la température de combustion sur les émissions de NOx lors de la combustion de panneaux de particules. La troisième série est une étude de l'influence du traitement chimique de panneaux de particules sur les émissions de NOx lors d'une pyrolyse ou d'une combustion. Les résultats des expériences en lit fixe traversé ont permis de caler certains paramètres cinétiques du modèle 1D. Le modèle développé constitue une première étape dans la modélisation des émissions d'espèces azotées lors de la combustion d'un lit de biomasseBiomass combustion in industrial-scale biomass grate-fired boilers produces several types of pollutants, including nitrogen oxides. These species, also known as NOx, are harmful to the environment because they cause acid rain and are greenhouse gases. These pollutants are mostly formed by the oxidation of the nitrogen that was initially present in the biomass. NOx emissions are a primary concern for biomass boiler manufacturers. Modeling is a great help in reducing NOx emissions. The gas phase chemistry of nitrogen is well known so gas phase reactions involving NOx species above the bed are not a problem. However, the chemistry governing the heterogeneous combustion of the fuel bed remains poorly understood. In particular, the nature of the nitrogen gases exiting the bed is not accurately predicted. The objective of this work is to provide a bed model capable of predicting the gas phase composition at the exit of the bed, with a particular focus on nitrogen species. To this end, a bed model was developed using MATLAB. This model is based on the BASIC model developed by the University of Aalborg. This is a 1D Euler-Euler bed that employs the walking column approach to simulate a biomass grate-fired boiler bed. Two significant modifications were made to the model: the incorporation of thermal non-equilibrium and the inclusion of nitrogen chemistry. To validate the model, experiments were conducted in a cross-fired fixed bed reactor. An existing experimental device was adapted to enable the quantification of nitrogen in all products. Three series of experiments were conducted. The first series compared the fate of nitrogen of three agrofuels during the pyrolysis and combustion. The second series investigated the influence of particle size and temperature on the fate of nitrogen during particleboard combustion and pyrolysis. The third series focused on the influence of chemical treatment on NOx emissions for three chemically treated particleboards. The results obtained with the experimental setup allowed us to fix some kinetic data for the model. This model represents a first step towards the prediction of nitrogen gas production in a biomass bed
3
Wei, Manqing. "Synthesis of Precursors to Non-isocyanate Polyurethanes". Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/29167.
Testo completoAbstract (sommario):
Biobased diamines are excellent precursors for the synthesis of non-isocyanate polyurethanes (NIPUs). We have prepared several biobased diamines using three different reactions for their synthesis. In the first method, we have carried out chain elongation of cellulose-derived 2,5-diformylfuran by the Henry reaction followed by reduction of the nitroalkene. Yields of the key step: Hantzsch Ester reduction, were 70-80%. Method two involves the Friedel-Crafts alkylation of furfurylamine with different ketones under acidic conditions. Yields of large-scale alkylation reaction were 60-77%. In method three, we combined the Henry reaction and Friedel-Crafts alkylation techniques to access diamines from hemicellulose-derived furfural. These diamines can be reacted with carbonates to access hydroxyalkylcarbamates in good yields, around 80%. We have also developed a novel method for accessing biscarbamates directly from dialdehydes in good yields, 70-94%. The hydroxyalkylcarbamates and biscarbamates are valuable precursors to obtain polyurethanes via the phosgene-free route.
4
Jiang, Yuan. "Precursor phases in non-classical crystallization". Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5246/.
Testo completoAbstract (sommario):
The main objective of this thesis is to understand molecular crystallization as a multistep process with or without polymeric additives, including transient liquid-liquid phase separation, nanocrystal nucleation within the dense phase, and subsequent nanocrystal self-assembly or self-organization in sequence.
The thesis starts with a quaternary model system, containing DL-Glutamic acid (Glu), polyethyleneimine (PEI), water, and EtOH, for the understanding of multistep precipitation of Glu with PEI as an additive. The experiments were performed by mixing Glu-PEI aqueous solution with a non-solvent EtOH. First, the phase diagram of the quaternary system is determined, obtaining precipitate, coacervates, or homogeneous mixtures by varying Glu/PEI w/w and water/EtOH v/v. Coacervation is observed to occur over a wide range of Glu/PEI with various volumes. The composition of coacervates is conveniently characterized by nuclear magnetic resonance spectroscopy. The observed coacervates are thermodynamically stable phases rich in solute, which is different from metastable polymer-induced liquid precursors. The combination of atomic force microscopy, small angle scattering, and ξ-potential measurements confirms the coexistence of monomers and Glu/PEI complexes and the aggregation of complexes in Glu-PEI-water systems. This suggests that there might be a direct structural transformation between the Glu-PEI complexes in aqueous solution and the metastable liquid precursors in a water-EtOH mixture.
The multistep mechanism of Glu precipitation with PEI as an additive is investigated thereafter. The combination of stopped flow and small angle scattering demonstrates that the initially formed liquid precursors pass through an alteration of growth and coalescence. Combined with results from optical microscopy and scanning electron microscopy, the nucleation of nanoplatelets happens within each liquid precursor droplet, and nanoplatelets reorient themselves and self-organize into a radial orientation in the crystalline microspheres.
The recipe was then extended to the precipitation of organics in other oppositely charged amino acid-polyelectrolyte systems.
After the success in preparing hierarchical microspheres in solution, the similar recipe can be extended to the preparation of patterned thin films on substrate. By dipping a quaternary DL-Lys·HCl (Lys)–polyacrylic acid (PAA)–water–EtOH dispersion on a hydrophilic slide, the fast evaporation process of the volatile solvent EtOH is responsible for the homogeneous nucleation of NPs. Then, the following complete evaporation causes the mesocrystallization of a continuous spherulitic thin film along the receding line of the liquid, which again transforms into a mesocrystalline thin film. Furthermore, annealing is used to optimize the property of mesocrystalline thin films. As evaporation is a non-equilibrium process, it can be used to tune the kinetics of crystallization. Therefore, hierarchical or periodical thin films are obtainable by starting the evaporation from microspheres recrystallization, obtaining mesocrystalline thin films with 4 hierarchy levels. The results reveal that evaporation provides an easy but effective way for the formation of patterned structures via the positioning of NPs after their fast nucleation, resulting in different kinds of patterns by controlling the concentration of NPs, solvent evaporation rate, and other physical forces.
Non-classical crystallization is not limited to crystallizations with polymeric additives. We also observed the nucleation and growth of a new molecular layer on the growing DL-Glu·H2O crystals from a supersaturated mother liquor by using an in-situ atomic force microscopy (AFM), where the nucleation and growth of a molecular layer proceed via amorphous nanoparticle (NP) attachment and relaxation process before the observation of the growth of a newly formed molecular layer. NP attachment to the crystal surface is too fast to observe by using in-situ AFM. The height shrinkage of NPs, combined to the structural transformation from 3D amorphous NPs to 2D crystalline layer, is observed during the relaxation process. The nucleation and growth of a newly formed molecular layer from NP relaxation is contradictory to the classical nucleation theory, which hypothesizes that nuclei show the same crystallographic properties as a bulk crystal. The formation of a molecular layer by NP attachment and relaxation rather than attachment of single molecules provides a different picture from the currently held classical nucleation and growth theory regarding the growth of single crystals from solution.Das Hauptziel dieser Arbeit ist das Verständnis der molekularen Kristallisation, sowohl mit als auch ohne polymere Additive, als einen mehrstufigen Prozess. Dieser beinhaltet eine transiente flüssig-flüssig Phasentrennung, die Nukleation von Nanokristallen in der dichten flüssigen Precursor-Phase so wie eine anschließende nanokristalline Selbstorganisation. Die Arbeit beginnt mit Untersuchungen an einem quaternären Modelsystem bestehend aus DL-Glutamat (Glu), Polyethylenimin (PEI), Wasser und Ethanol. Das Phasendiagramm dieses quaternären Systems wird durch Variation der Glu/PEI w/w und Wasser/EtOH v/v Verhältnisse bestimmt, wobei Präzpitat aus polymerinduzierten flüssigen Precursor, Koazervate oder homogene Mischungen erhalten werden Das thermodynamisch stabile Koazervat kann als Referenz für das Verständnis von flüssigen Precursorn angesehen werden, welche in der Natur metastabil und transient sind. Der mehrstufige Mechanismus der Glu-Präzipitation mit PEI als Additiv wird dann mittels Neutronen Kleinwinkelstreuung untersucht. Dies zeigt, dass die ursprünglich gebildeten flüssigen Precursor noch vor der Nukleation von Nanokristallen einen Wechsel von Wachstum und Koaleszenz durchlaufen. Die Ergebnisse aus optischer- und Eletronenmikroskopie zeigen, dass sowohl die flüssigen Precursor Superstrukturen ausbilden als auch, dass die Nukleation von Nanoplättchen in jedem einzelnen Precursor Tropfen von statten geht. Dies geschieht noch bevor sich die Nanoplättchen selbst in einer radialen Orientierung ausrichten. Diese Studie liefert die Kinetik der Präzipitation von organischen Stoffen in Gegenwart von polymeren Additiven. Eine ähnliche Vorgehensweise wie für die Herstellung von Mikrokügelchen kann für die Darstellung von gemusterten Filmen angewandt werden. Die homogene Nukleation von Nanopartikeln (NPs) findet während der Verdampfung einer quarternären DL-Lys·HCl-Polyacrylsäure-Wasser-Ethanol Dispersion auf einer hydrophilen Oberfläche statt. Die darauffolgende vollständige Verdampfung löst die Mesokristallisation eines kontinuierlichen sphärolithischen dünnen Films aus, welcher sich wiederum in einen mesokristallinen dünnen Film umwandelt. Mesokristalline Filme mit 4 Hierarchiestufen bzw. auch periodische Filme werden durch die Verdampfung der Mikrokügelchen-Dispersion erhalten. Die Ergebnisse zeigen, dass die Verdampfung eine einfache aber effektive Methode zur Herstellung von verschieden gemusterten hierarchischen Filmen darstellt. Nicht-klassische Kristallisation wird auch in der Abwesenheit von polymeren Additiven beobachtet. Wir verfolgen mittels Rasterkraftmikroskop (AFM) die Nukleation und das Wachstum einer neuen molekularen Schicht auf wachsenden DL-Glu·H2O Kristallen aus übersättigter Mutterlauge. Die Bildung einer neuen molekularen Schicht verläuft durch die Anlagerung von amorphen Nanopartikeln. Das Schrumpfen der NPs zusammen mit der strukturellen Änderung von dreidimensionalen NPs zu 2D Schichten wird während dieses Relaxationsprozesses beobachtet. Schließlich kommt es zu der Ausbildung einer neuen molekularen Schicht. Die Bildung einer molekularen Schicht durch die Anlagerung von Nanopartikeln aus der Lösung und die darauffolgende Relaxation liefert ein abweichendes Bild zu der bisher gängigen klassischen Theorie des Kristallwachstums.
5
Redshaw, Carl. "Oxo and organoimido precursors for non-aqueous polytungstate synthesis". Thesis, University of Newcastle Upon Tyne, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328135.
Testo completo
6
Specchia, Michael. "Precursori non statistici di previsione dei terremoti". Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Cerca il testo completoAbstract (sommario):
I terremoti sono considerati una delle peggiori calamità naturali a causa del loro enorme impatto sulle vite e proprietà. La loro bassa prevedibilità è dovuta alla complessità del fenomeno e dall’impossibilità di accesso all’osservazione diretta della sorgente e dal parametro dello stress che non può essere misurato direttamente. Inoltre, la causalità, l’origine in faglie sconosciute e l’insorgere non sempre costante di eventuali precursori rendono il lavoro ancora più difficile. Di conseguenza, l’elevata incertezza associata alle loro previsioni, nonostante la grande quantità di dati sperimentali, il grandissimo impegno di scienziati e ricercatori e la formulazione di diverse teorie, ancora oggi non si riesce a comprendere a pieno il fenomeno. La prevedibilità si basa sullo studio e sul monitoraggio di precursori sismici, ovvero cambiamenti insoliti nell’intero regime ambientale fisico e chimico su scala regionale antecedenti a un terremoto. Gli studi si concentrano su anomalie di tipo sismico, geodetico, elettromagnetico, idrologico e chimico.
Recenti progressi sono dovuti in gran parte allo sviluppo e al miglioramento di strumenti di rilevazione e monitoraggio che hanno portato ad una maggiore quantità e precisione delle misurazioni.
Al momento la mitigazione dei danni è possibile grazie alla realizzazione di carte di probabilità e l’adozione di misure preventive e di emergenza.
La ricerca sulla previsione dei terremoti non sta procedendo in maniera significativa, e tutto il lavoro fatto risulta essere ancora a uno stadio primitivo e in feroce controversie scientifiche. Tuttavia il campo di ricerca è promettente, anche se difficile, inoltre i benefici di una soluzione anche parziale al problema della previsione sono così enormi da non poterne fare a meno.
Si è infatti arrivati alla conclusione che alcuni precursori possono dare un importante contributo, se opportunamente correlati tra loro, nella comprensione del fenomeno sismico e del suo accadimento.
7
Wolf, Stefan Leo Philipp [Verfasser]. "Liquid Precursors in Non-Classical Crystallization / Stefan Leo Philipp Wolf". Konstanz : KOPS Universität Konstanz, 2017. http://d-nb.info/1188564587/34.
Testo completo
8
Junior, Mario Godinho. "Síntese e caracterização do BIMEVOX pelo método dos precursores poliméricos". Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-20082015-165222/.
Testo completoAbstract (sommario):
As cerâmicas do tipo BIMEVOX, onde ME= metal dopante com estequiometria Bi4Me2xV2(1-x)Ox(11-3x), são conhecidas como eletrólitos sólidos e a utilização destes materiais está voltada principalmente para dispositivos como: sensores de oxigênio, células de combustíveis, conversão de energia, baterias e dispositivos associados à condução iônica. Dada a dificuldade de obter-se materiais policristalinos de alta densidade, buscou-se o método dos precursores poliméricos para obter-se um pó com maior área superficial específica e, consequentemente aumentar a densificação, para melhorar assim a condutividade iônica do oxigênio. As cerâmicas BIMEVOX dopadas com 20% de Titânio em relação ao Vanádio (BITIVOX.20) foram as que apresentaram a maior condutividade, sendo de 5,39 x10-4 (Ω.cm)-1 à temperatura de 200 °C com uma a densidade relativa de 98% Esses resultados são uns dos melhores até o momento reportado na literaturaThe BIMEVOX type ceramics present the general formula Bi4Me2xV2(1-x)Ox(11-3x), in which Me stands for the doping metal. They are known as soiid electrolytes and the utilization of these materiais is mairly directed towards devices such as: oxygen sensors, fuel cells, energy conversion, batteries and devices associated to the ionic conduction. Due to the difficulty of obtaining high density polycrystalline materiais, it was used the polymeric precursor method to produced a powder with higher specific surface area and therefore increase the densification, in order to improve the ionic conductivity of oxygen. BIMEVOX ceramics with titanium presenting a doping levei of 20 mol%, in relation to vanadium, (BITIVOX.20) where the ones that presented the highest conductivity, reaching the value of 5,39 x10-4 (Ω.cm)-1 at the temperature of 200 °C with a relative density of 98%. These figures represent one of the best results reported up to now in the literature
9
Boniol, Paul. "Detection of anomalies and identification of their precursors in large data series collections". Electronic Thesis or Diss., Université Paris Cité, 2021. http://www.theses.fr/2021UNIP5206.
Testo completoAbstract (sommario):
Les larges collections de séries temporelles deviennent une réalité dans un grand nombre de domaines scientifiques et sociaux, comme la finance, les sciences de l’environnement, l’astrophysique, les neurosciences, l’ingénierie ou les métiers du numérique. Il y a donc un intérêt et un besoin de plus en plus importants de développer des techniques efficaces pour analyser et traiter ce type de données. De manière informelle, une série temporelle est une séquence ordonnée de points ou de valeurs. Une fois les séries collectées et disponibles, les utilisateurs ont souvent besoin de les étudier pour en extraire de la valeur et de la connaissance. Ces analyses peuvent être simples, comme sélectionner des fenêtres temporelles, mais aussi complexes, comme rechercher des similarités entre des séries ou détecter des anomalies, souvent synonymes d’évolutions soudaines et inhabituelles possiblement non souhaitées, voire de dysfonctionnements du système étudié. Ce dernier type d’analyse représente un enjeu crucial pour des applications dans un large éventail de domaines partageant tous le même objectif : détecter les anomalies le plus rapidement possible pour éviter la survenue de tout événement critique, comme par exemple de prévenir les dégradations et donc d’allonger la durée de vie des systèmes. Par conséquent, dans ce travail de thèse, nous traitons les trois objectifs suivants : (i) l’exploration non-supervisée de séries temporelles pour la détection rétrospective d’anomalies à partir d’une collection de séries temporelles. (ii) la détection non-supervisée d’anomalies en temps réel dans les séries temporelles. (iii) l’explication de la classification d’anomalies connues dans les séries temporelles, afin d’identifier de possibles précurseurs. Dans ce manuscrit, nous introduisons d’abord le contexte industriel qui a motivé la thèse, des définitions fondamentales, une taxonomie des séries temporelles et un état de l’art des méthodes de détection d’anomalies. Nous présentons ensuite nos contributions scientifiques en suivant les trois axes mentionnés précédemment. Ainsi, nous décrivons premièrement deux solutions originales, NormA (basée sur une méthode de clustering de sous-séquences de la série temporelle à analyser) et Series2Graph (qui s’appuie sur une transformation de la séries temporelle en un réseau orienté), pour la tâche de détection non supervisée de sous-séquences anormales dans les séries temporelles statiques (i.e., n’évoluant pas dans le temps). Nous présentons dans un deuxième temps la méthode SAND (inspiré du fonctionnement de NormA) développée pour répondre à la tâche de détection non-supervisée de sous-séquences anormales dans les séries temporelles évoluant de manière continue dans le temps. Dans une troisième phase, nous abordons le problème lié à l’identification supervisée des précurseurs. Nous subdivisons cette tâche en deux problèmes génériques : la classification supervisée de séries temporelles d’une part, l’explication des résultats de cette classification par l’identification de sous-séquences discriminantes d’autre part. Enfin, nous illustrons l’applicabilité et l’intérêt de nos développements au travers d’une application portant sur l’identification de précurseurs de vibrations indésirables survenant sur des pompes d’alimentation en eau dans les centrales nucléaires françaises d’EDFExtensive collections of data series are becoming a reality in a large number of scientific and social domains. There is, therefore, a growing interest and need to elaborate efficient techniques to analyze and process these data, such as in finance, environmental sciences, astrophysics, neurosciences, engineering. Informally, a data series is an ordered sequence of points or values. Once these series are collected and available, users often need to query them. These queries can be simple, such as the selection of time interval, but also complex, such as the similarities search or the detection of anomalies, often synonymous with malfunctioning of the system under study, or sudden and unusual evolution likely undesired. This last type of analysis represents a crucial problem for applications in a wide range of domains, all sharing the same objective: to detect anomalies as soon as possible to avoid critical events. Therefore, in this thesis, we address the following three objectives: (i) retrospective unsupervised subsequence anomaly detection in data series. (ii) unsupervised detection of anomalies in data streams. (iii) classification explanation of known anomalies in data series in order to identify possible precursors. This manuscript first presents the industrial context that motivated this thesis, fundamental definitions, a taxonomy of data series, and state-of-the-art anomaly detection methods. We then present our contributions along the three axes mentioned above. First, we describe two original solutions, NormA (that aims to build a weighted set of subsequences that represent the different behaviors of the data series) and Series2Graph (that transform the data series in a directed graph), for the task of unsupervised detection of anomalous subsequences in static data series. Secondly, we present the SAND (inspired from NormA) method for unsupervised detection of anomalous subsequences in data streams. Thirdly, we address the problem of the supervised identification of precursors. We subdivide this task into two generic problems: the supervised classification of time series and the explanation of this classification’s results by identifying discriminative subsequences. Finally, we illustrate the applicability and interest of our developments through an application concerning the identification of undesirable vibration precursors occurring in water supply pumps in the French nuclear power plants of EDF
10
Tse, Erin. "The role of amyloid precursor protein in neuronal and non-neuronal cell lines". Thesis, Aston University, 2015. http://publications.aston.ac.uk/27532/.
Testo completoAbstract (sommario):
Models of Alzheimer’s disease (AD) have provided useful insights into the pathogenesis and mechanistic pathways that lead to its development. One emerging idea about AD is that it may be described as a hypometabolic disorder due to the reduction of glucose uptake in AD brains. Inappropriate processing of Amyloid Precursor Protein (APP) is considered central to the initiation and progression of the disease. Although the exact role of APP misprocessing is unclear, it may play a role in neuronal metabolism before the onset of neurodegeneration. To investigate the potential role of APP in neuronal metabolism, the SHSY5Y neuroblastoma cell line was used to generate cell lines that stably overexpress wild type APP695 or express Swedish mutated-APP observed in familial AD (FAD), both under the control of the neuronal promoter, Synapsin I. The effects of APP on glucose uptake, cellular stress and energy homeostasis were studied extensively. It was found that APP-overexpressing cells exhibited decreased glucose uptake with changes in basal oxygen consumption in comparison to control cell lines. Similar studies were also performed in fibroblasts taken from FAD patients compared with control fibroblasts. Previous studies found FAD-derived fibroblasts displayed altered metabolic profiles, calcium homeostasis and oxidative stress when compared to controls. As such, in this study fibroblasts were studied in terms of their ability to metabolise glucose and their mitochondrial function. Results show that FAD-derived fibroblasts demonstrate no differences in mitochondrial function, or response to oxidative stress compared to control fibroblasts. However, control fibroblasts treated with Aβ1-42 demonstrated changes in glucose uptake. This study highlights the importance of APP expression within non-neuronal cell lines, suggesting that whilst AD is considered a brain-associated disorder, peripheral effects in non-neuronal cell types should also be considered when studying the effects of Aβ on metabolism.
11
Ward, S. J. "A new synthetic route to the explosive TATB (1,3,5-triamino-2,4,6-trinitrobenzene) using non-halogenated precursors". Thesis, Cranfield University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422710.
Testo completo
12
Ill-Raga, Gerard. "Study of the pathophysiological role of nitric oxide and nitrative stress in brain: translational effects on the cleavage of the amyloid precursor protein in Alzheimer's disease and post-translational effects on fibrinogen in brain ischemia". Doctoral thesis, Universitat Pompeu Fabra, 2010. http://hdl.handle.net/10803/31907.
Testo completoAbstract (sommario):
Nitric oxide (NO) is a neurotransmitter involved in memory processes. Currently, the
only recognized physiological signalling pathway controlled by NO is the activation of
guanylyl cyclase. In this thesis, we propose an alternative NO-signalling pathway that
involves the Heme-regulated eukaryotic initiation factor-2a kinase (HRI) and eIF2a
phosphorylation. We have found that the enzyme BACE1, a key protein in Alzheimer’s
disease (AD), is controlled by this novel pathway. This pathway would be involved in
the physiology of memory formation and learning processes. We have also studied how
an external stress factor, the Herpes Simplex Virus 1, can disrupt this cascade leading to
a pathological increase in BACE1 and amyloid ß-peptide (Aß) production. Aß
aggregates forming fibrils that generate free radicals. These react with NO producing
peroxynitrite, which contribute to AD progression. Since NO turns toxic when produced
in a pro-oxidant environment we have also studied the effect of peroxynitrite in Stroke.L’òxid nítric (NO) és un neurotransmissor involucrat en processos de memòria. Actualment, l’única cascada de senyalització fisiològica controlada per NO consisteix en l’activació de la guanilat ciclasa. En aquesta tesi, en proposem una d’alternativa que inclou la fosforilació de eIF2a per la Heme-regulated eukaryotic initiation factor-2a kinase (HRI). Hem mostrat com l’enzim BACE1, una proteïna clau en la malaltia d’Alzheimer (AD), és controlat per aquesta nova cascada de senyalització, que podria estar involucrada en la fisiologia de l’aprenentatge i la memòria. També hem estudiat com un factor d’estrès extern, l’ Herpes Simplex Virus 1, pot pertorbar aquesta cascada donant lloc a increments patològics en BACE1 i pèptid ß-amiloide (Aß). L’Aß agrega formant fibril·les que generen radicals lliures. Aquests reaccionen químicament amb NO produint peroxinitrit, que contribueix a la progressió de l’AD. Pel fet que l’NO esdevé tòxic quan és produït en un entorn pro-oxidant, hem estudiat també l’impacte que el peroxinitrit té en l’ictus.
13
Patta, Yoda Rante. "Non-fluorine precursor solutions for high critical current density REBa₂Cu₃O₇₋x̳ films". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44207.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
In title on t.p., double underscored "x" appears as subscript.
Includes bibliographical references (p. 68-71).
The past two decades have seen advancements in high temperature superconducting cables for use in applications such as electrical transmission lines, propulsion systems, and mobile power generation systems. This work describes the development of a non-fluorine precursor solution for YBCO films with high critical current densities (Jc). An aqueous nitrate precursor solution system was selected from three possible precursor solution systems. It was further developed to produce YBCO films with Jc > 1 MA/cm2. Films up to ~800 nm thickness were made, and Jc > 1 MA/cm2 was obtained for films of over ~400 nm thickness. The developed aqueous solution contained a rheology modifier (hydroxyethyl cellulose / HEC), nitrates of Y, Ba, and Cu, and chelating agents (polyethylene glycol / PEG and sucrose). The total organic content was ~12 wt% of the entire solution, and the total cation concentration was ~0.7 M. The rheology modifying polymer determined the thickness of the deposited films. This allowed for the deposition of films with higher thickness than would be dictated by the total dissolved cations alone. A low temperature decomposition process was developed based on analyses of the chemical reactions that take place in the precursor films as they were heated. This process produced smooth and defect-free intermediate films that were stable under ambient conditions. These films were then heat treated to convert them into YBCO films. Recommendations for future work include further improvements to the precursor solution, including more effective chelating agents and possible alternative solvent systems. Intermediate films thicker than 2.5 [mu]m still tended to have surface defects.
(cont.) Additional in-depth thermal analysis would further show how these defects develop, and adjustments to the decomposition process could be made accordingly. High resolution plan-view and cross-sectional microstructures of the films between the precursor state and their converted forms is recommended. These future studies will be valuable in further improving the performance and thickness of films derived from the non-fluorine precursor solution developed in this thesis.
Yoda Rante Patta.
S.M.
14
Kuhlmann, Rolf von. "Tropospheric photochemistry of ozone, its precursors and the hydroxyl radical a 3d-modeling study considering non-methane hydrocarbons /". [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0141/diss.pdf.
Testo completo
15
Huang, Jin. "An evaluation of NOM precursors and bromide ion in the formation of haloacetic acids (HAAs) in water treatment". Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/5601.
Testo completoAbstract (sommario):
Haloacetic acids (HAAs) are a group of disinfection by-products (DBPs) found in drinking water which are regulated in the USA but not yet in the EU. Epidemiology tests have shown that they may have carcinogenic and mutagenic effects on human beings. HAAs are produced during the disinfection process from the use of chlorination and they may persist during water distribution and finally reach the customers’ tap at concentrations of concern. The formation of HAAs arises from the reaction between precursor material – principally natural organic matter (NOM) – and chlorine, and the species and amount of HAAs produced depends on the nature of the NOM and the reaction conditions, such as the temperature, chlorine dose, pH, and the presence of bromide. NOM is a heterogeneous mixture of numerous organic molecules originating from aquagenic and pedogenic sources, and its content changes significantly with water source, and temporarily for a given water source. Due to the complex properties of NOM, no conclusive connections have been established between the properties of precursor materials and HAA formation (compound yield or individual species distribution). The thesis provides details of a new-developed fractionation method that has been used to characterise NOM obtained from natural waters. This method can effectively reveal the effect of seasonal variation and traditional treatment on NOM properties. The reactivity of each organic fraction in terms of HAA formation, seasonal variation and treatment efficiency has also been studied and is discussed in the thesis. Algae represent an important component of NOM, and as such algae species can also be responsible for the formation of HAAs. The thesis describes an extensive study of two prominent algae species in terms of their role in producing trihalomethane (THM) and HAA compounds, and their productivity in comparison with other organic precursors. Finally, the presence of bromide ion in source water leads to formation of brominated HAA species during chlorination which are believed to be of greater toxicological significance than non-brominated species. This thesis summarises an experimental investigation of the fundamental role of bromide in HAA formation and the relationship with initial NOM concentration and chlorine dose.
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Silva, Jerônimo Júnior Araújo. "Cinética pontual com realimentação de temperatura considerando um grupo de precursores de nêutrons atrasados". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/37386.
Testo completoAbstract (sommario):
Recentemente, surgiu na literatura uma solução analítica das equações de cinética pontual que considera a reatividade como função do tempo, utilizando o método da decomposição. O presente trabalho dá um passo a frente, considerando as equações de cinética pontual em conjunto com efeitos de realimentação de temperatura. Mas, primeiro, uma breve introdução do modelo de cinética pontual e dos aspectos relevantes desta abordagem são apresentados. O trabalho prossegue acrescentando a realimentação de temperatura como uma perturbação de primeira ordem na equação reatividade, e através de manipulações algébricas, o conjunto de equações de cinética pontual passa a ser expresso como uma equação diferencial não linear de segunda ordem. Esta equação é, então, resolvida pelo método de decomposição, ou seja, expandindo as variáveis dependentes como séries infinitas, construindo-se então um sistema recursivo que permite calcular cada um dos termo destas séries. A não linearidade é tratada utilizando os polinômios Adomian. Os resultados aqui obtidos são comparados com a literatura, apresentando variações percentuais máximas da ordem de [0,1%]. Faz-se uma breve análise da convergência e da estabilidade da solução, usando um método baseado no critério de Lyapunov.An analytical solution of the point kinetics equations to calculate reactivity as a function of time by the decomposition method has recently appeared in the literature. The present work goes one step forward, by considering the neutron point kinetics equations together with temperature feedback effects. But first, a brief introduction of the point kinetics model and the relevant aspects of this approach are presented. The work proceeds adding the temperature feedback as a first order perturbation in the reactivity equation, and using algebraic manipulation, the set of point kinetics equations becomes expressed as a non linear second order differential equation. This equation is then solved by the decomposition method, that is, expanding the dependent variables as infinite series, building a recursive system that allows the evaluation of each term of these series. The non linearity is treated using the Adomian polynomials. The results obtained are compared with literature, with maximum percentage changes of about [0,1%]. A brief analysis of the convergence and stability of the solution is made, using a method based on the Lyapunov criterion.
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CARREAUX, FRANCOIS, e Jean-Claude Depezay. "Aziridines fonctionnalisees chirales precurseurs de composes amines d'interet biologique; syntheses d'alpha-aminoacides non proteiniques". Paris 6, 1992. http://www.theses.fr/1992PA066076.
Testo completoAbstract (sommario):
Nous decrivons une methode generale de syntheses d'alcools, d'aldehydes, et d'acides alpha-amines enantiomeriquement purs a partir d'aziridines fonctionnalisees derivant de sucres ou analogues. L'etape cle de cette methode est le rearrangement de pummerer applique sur des thioesthers beta-amines. Cette approche a ete utilisee pour realiser une synthese de l'acide polyoximique, principal constituant des polyoxines (antibiotiques antifongiques), a partir du l-arabinose, ainsi que du 3-amino-3-desoxy-d-2-erythrose, precurseur chiral de l'acide mugineique (phytosiderophore), de la l-erythro sphingosine, a partir du diethyl-l-tartrate. Enfin, nous montrons que les 1,3-amino alcools sont des precurseurs precieux pour la synthese d'azetidines fonctionnalisees, et en particulier, nous decrivons la synthese d'une azetidine 3-one, precurseur potentiel de l'acide polyoximique
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SRINIVASAN, GANESH. "STUDY OF OZONE NON-ATTAINMENT COUNTIES IN OHIO USING COMPREHENSIVE AIR QUALITY MODEL WITH EXTENSIONS/ANTHROPOGENIC PRECURSOR CULPABILITY ASSESSMENT". University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1116260215.
Testo completo
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Murat-Onana, Marie Laure. "N-hydroxylamines pyrroliques : precurseurs de bis(pyrrolyl)alcanes non symetriques et de α-n-hydroxyamino esters". Grenoble, 2010. http://www.theses.fr/2010GRENV060.
Testo completoAbstract (sommario):
Le pyrrole est un hétérocycle souvent présent dans les produits naturels et les composés biologiquement actifs. Son étude intensive en synthèse organique est donc d'un grand intérêt. Ainsi, la première réaction acido-catalysée de pyrroles sur des nitrones, reportée par notre équipe, a conduit selon les conditions expérimentales employées, soit aux 2,2-bis(pyrrolyl)alcanes symétriques, soit aux N-benzylhydroxylamines pyrroliques de façon sélective. Les N-hydroxylamines pyrroliques sont des composés intéressants et ont été le point de départ des deux études méthodologiques développées dans ce manuscrit. Les bis(pyrrolyl)alcanes non symétriques ont pu être synthétisés efficacement et avec une bonne diversité, en une étape, par réaction entre des N-hydroxylamines pyrroliques et des pyrroles. La méthode a aussi permis la préparation de ter(pyrrolyl)alcanes symétriques et non symétriques. Une application de cette méthodologie a été la préparation de marqueurs de fluorescence F-Bodipy® non symétriques. Ces derniers ont été obtenus pour la première fois et avec de bons rendements, directement à partir de 2,2'-bis(pyrrolyl)alcanes non symétriques. De plus, un F-Bodipy® présentant une chiralité axiale a pu être synthétisé. Nous avons également étudié l'accès aux acides a-N-hydroxyaminés, analogues N-hydroxylés des acides a-aminés. Une réaction hautement diastéréosélective entre le pyrrole et une nitrone cyclique chirale a donné accès à une hydroxylamine pyrrolique. Une séquence en trois étapes a permis d'obtenir un a-N-hydroxyamino ester avec un bon rendement et un bon excès énantiomère de 80%. La méthode a ensuite été appliquée à d'autres hétéroaromatiques pyrroliques, indoliques et furaniques. Aucun acide a-N-hydroxaminé comportant l'un de ces hétérocycles n'était décrit précédemment dans la littérature. Les rendements globaux obtenus sont bons (36-62%) et les excès énantiomères peuvent atteindre des valeurs ≥ 98%The pyrrole ring is present in many natural and biologically active compounds. Therefore, its intensive study in organic synthesis is of a great interest. Thus, the first acid-catalyzed reaction of pyrroles onto nitrones was reported by our team. According to the experimental procedure, either pyrrolic Nbenzylhydroxylamines or 2,2'-bis(pyrrolyl)alkanes were selectively produced. Pyrrolic Nhydroxylamines are important compounds and have been used as starting building blocks for the two methodologies described in this manuscript. Unsymmetrical bis(pyrrolyl)alkanes were obtained efficiently in one step, with high molecular diversity, by the reaction of pyrrolic N-hydroxylamines and various pyrroles. This method also allowed the preparation of symmetrical and unsymmetrical tripyrromethanes. Our results were applied to the preparation of unsymmetrical F-Bodipy® probes. They were obtained, in high yields and for the first time, directly from unsymmetrical 2,2'-bis(pyrrolyl)alkanes. Moreover, an axially chiral F-Bodipy® has been prepared. A-N-Hydroxyamino acids which are N-hydroxylated analogues of a-amino acids have been synthesized. A highly diastereoselective reaction between pyrrole and a suitable cyclic chiral nitrone yielded a pyrrolic N-hydroxylamine. A three-step sequence afforded the expected a-N-hydroxyamino ester in a good yield and a good enantiomeric excess (80%). This method has been applied to other pyrrolic, indolic and furanic heteroaromatics. No a-N-hydroxyamino acids holding these heterocycles in their structures were described. Good overall yields (36-62%) were obtained and good enantiomeric excesses, up to 98%
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Ribeiro, Elisangela. "A influencia da amifostina sobre a expressão dos antigenos de superficie FAS e FASL nos precursores hematopoeticos na mielodisplasia". [s.n.], 2002. http://repositorio.unicamp.br/jspui/handle/REPOSIP/309701.
Testo completoAbstract (sommario):
Orientadores : Irene Lorand-Metze, Carmen Silvia Passos LimaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas
Made available in DSpace on 2018-08-02T16:54:51Z (GMT). No. of bitstreams: 1 Ribeiro_Elisangela_M.pdf: 23459196 bytes, checksum: e3c3f69e1b6470bb9cfa7570a9a84ff0 (MD5) Previous issue date: 2002
Resumo: Síndromes mielodisplásicas (SMD) são um grupo heterogêneo de doenças clonais caracterizadas por citopenias periféricas persistentes de uma ou mais linhagens e com possibilidade para transformação leucêmica. Níveis aumentados de apoptose nas células precursoras hematopoéticas (células CD34l foram observados em pacientes com SMD de baixo risco (AR e ARSA), sugerindo esse mecanismo como o responsável pela hematopoes e ineficaz nessa doença. A Amifostina (AMF) é considerada um agente citoprotetor, com ação antioxidante, potente estimulador da hematopoese normal e supressor apoptótico nos precursores mielodisplásicos. Analisamos a expressão dos marcadores da apoptose, (Fas e FasL) nas células CD34+ em pacientes com SMD de baixo risco, submetidos ao tratamento com a AMF. Foram estudados 17 pacientes, sendo 11AR e 6 ARSA. A resposta terapêutica em relação ao nível da hemoglobina, ao número de neutrófilos e às plaquetas, aos critérios de inclusão e às respostas foi definida pelo protocolo de tratamento da AMF. Dos 17 pacientes tratados, 10 apresentaram critérios de resposta em pelo menos uma série do hemograma após 2 ciclos de AMF, os quais receberam mais 4 ciclos adicionais. Quatro pacientes (3 não respondedores e um respondedor) apresentaram evolução da SMD (aumento de blastos medulares) durante ou após o tratamento. As atipias celulares na medula óssea (MO) e o número de células CD34+ diminuíram nos pacientes respondedores após o ciclo 2. No grupo dos não respondedores não houve alterações significativas em nenhum desses parâmetros. Os pacientes que responderam à amifostina tinham, antes do tratamento, uma percentagem menor de expressão de Fas e FasL nas células CD34+ e de linfócitos na medula óssea em relação aos que não responderam. A percentagem de linfócitos aumentou ainda mais após o tratamento neste último grupo. Esse resultado sugere que, no grupo que não respondeu à amifostina o sistema imune pode estar impedindo a resposta ao tratamento. Esses resultados favorecem a hipótese de que a resposta à AMF é influenciada pela expressão dos marcadores apoptóticos e/ou pela percentagem de linfócitos na MO. A resposta à AMF não depende apenas da supressão apoptótica. Um seguimento maior de pacientes é necessário para observar a durabilidadede resposta
Abstract: Not informed.
Mestrado
Ciencias Basicas
Mestre em Clinica Medica
21
Srinivasan, Ganesh. "Study of ozone non-attainment counties in Ohio using comprehensive air quality model with extensions anthropogenic precursor culpability assessment /". Cincinnati, Ohio : University of Cincinnati, 2005. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1116260215.
Testo completo
22
Rivera, Jorgelina. "Duas poéticas da leitura : radição e invenção de precursores nos projetos literários de Jorge Luis Borges e Haroldo de Campos /". São José do Rio Preto, 2015. http://hdl.handle.net/11449/127718.
Testo completoAbstract (sommario):
Orientador: Diana Junkes Bueno MarthaBanca: Maria Celeste Tommasello Ramos
Banca: Antonio Roberto Esteves
Resumo: Neste trabalho de pesquisa, o objetivo é analisar e comparar aspectos dos projetos literários de Jorge Luis Borges e Haroldo de Campos, dando ênfase ao modo pelo qual os dois escritores se relacionam com a tradição literária para construir em suas obras uma releitura do cânone a partir de um movimento que Borges enunciou no conhecido texto "Kafka y sus precursores" e Haroldo de Campos denominou Poética Sincrônica. Assim, o trabalho atrelará, centralmente, o desenvolvimento do projeto literário de ambos em relação ao seu paideuma, procurando apontar como cada um percebe a importância da tradição estabelecendo relações entre o aspecto local das culturas nas quais estão inseridos e o universal. Para realizar este estudo, utilizaremos, como base, alguns caminhos teóricos, colocando-os em diálogo: em primeiro lugar, um estudo de cunho histórico-crítico para contextualizar as obras do escritor argentino e brasileiro, apontando, a partir desse estudo histórico, as relações entre literatura, cultura e sociedade que suas obras deixam entrever. Em seguida, será feito um estudo de alguns textos críticos desses autores, para esclarecermos de que modo percebem a relação com a tradição. Para isso será necessário contar o suporte de referências da teoria da literatura, sobretudo aqueles voltados para a compreensão da relação do escritor moderno e contemporâneo com a tradição, tais como Harold Bloom (A angústia da influência); Leyla Perrone-Moisés (Altas Literaturas); Ezra Pound (ABC da Literatura); T.S. Eliot (Tradição e Talento Individual); Ítalo Calvino (Por que Ler os clássicos) e Octavio Paz (Os Filhos do Barro). Em um primeiro momento, descreveremos a poética de leitura borgiana e haroldiana. Depois, executaremos uma comparação entre ambas poéticas a partir da leitura que ambos os autores fazem do escritor Dante Alighieri e de sua obra A Divina Comédia, com o intuito de ilustrar, em linhas gerais...
Abstract: En este trabajo de investigación, el objetivo es analizar y comparar aspectos de los proyectos literarios de Jorge Luis Borges y Haroldo de Campos, dando énfasis al modo por el cual los dos escritores se relacionan con la tradición literaria para construir en sus obras una relectura del canon a partir de un movimiento que Borges enunció en el conocido texto "Kafka y sus precursores" y Haroldo de Campos denominó Poética Sincrónica. Así, el trabajo destacará, centralmente, el desarrollo del proyecto literario de ambos en relación a su paideuma, buscando apuntar cómo cada uno percibe la importancia de la tradición estableciendo relaciones entre el aspecto local de las culturas en las cuales están insertos y lo universal. Para realizar este estudio, utilizaremos, como base, algunos caminos teóricos, colocándolos en diálogo: en primer lugar, un estudio de cuño histórico-crítico para contextualizar las obras del escritor argentino y brasilero, apuntando, a partir de ese estudio histórico, las relaciones entre literatura, cultura y sociedad que sus obras dejan vislumbrar. En seguida, será hecho un estudio de algunos textos críticos de los autores, para que podamos esclarecer de qué modo perciben la relación con la tradición. Para eso será necesario contar con el soporte de referencias de la teoría de la literatura, principalmente aquellos dirigidos para la comprensión de la relación del escritor moderno y contemporáneo con la tradición, tales como Harold Bloom (La angustia de la influencia); Leyla Perrone-Moisés (Altas Literaturas); Ezra Pound (ABC de la Literatura) y Octavio Paz (Los hijos del limo). En un primer momento, describiremos la poética de lectura borgeana y haroldiana. Después, ejecutaremos una comparación entre ambas poéticas a partir de la lectura que ambos autores hacen del escritor Dante Alighieri y su obra La Divina Comedia, con el interés de ilustrar, en líneas generales, la discusión...
Mestre
23
Rivera, Jorgelina [UNESP]. "Duas poéticas da leitura: radição e invenção de precursores nos projetos literários de Jorge Luis Borges e Haroldo de Campos". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/127718.
Testo completoAbstract (sommario):
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000844057.pdf: 1205459 bytes, checksum: f2702ce00df26a58c624af49ccfc8d29 (MD5)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Neste trabalho de pesquisa, o objetivo é analisar e comparar aspectos dos projetos literários de Jorge Luis Borges e Haroldo de Campos, dando ênfase ao modo pelo qual os dois escritores se relacionam com a tradição literária para construir em suas obras uma releitura do cânone a partir de um movimento que Borges enunciou no conhecido texto Kafka y sus precursores e Haroldo de Campos denominou Poética Sincrônica. Assim, o trabalho atrelará, centralmente, o desenvolvimento do projeto literário de ambos em relação ao seu paideuma, procurando apontar como cada um percebe a importância da tradição estabelecendo relações entre o aspecto local das culturas nas quais estão inseridos e o universal. Para realizar este estudo, utilizaremos, como base, alguns caminhos teóricos, colocando-os em diálogo: em primeiro lugar, um estudo de cunho histórico-crítico para contextualizar as obras do escritor argentino e brasileiro, apontando, a partir desse estudo histórico, as relações entre literatura, cultura e sociedade que suas obras deixam entrever. Em seguida, será feito um estudo de alguns textos críticos desses autores, para esclarecermos de que modo percebem a relação com a tradição. Para isso será necessário contar o suporte de referências da teoria da literatura, sobretudo aqueles voltados para a compreensão da relação do escritor moderno e contemporâneo com a tradição, tais como Harold Bloom (A angústia da influência); Leyla Perrone-Moisés (Altas Literaturas); Ezra Pound (ABC da Literatura); T.S. Eliot (Tradição e Talento Individual); Ítalo Calvino (Por que Ler os clássicos) e Octavio Paz (Os Filhos do Barro). Em um primeiro momento, descreveremos a poética de leitura borgiana e haroldiana. Depois, executaremos uma comparação entre ambas poéticas a partir da leitura que ambos os autores fazem do escritor Dante Alighieri e de sua obra A Divina Comédia, com o intuito de ilustrar, em linhas gerais...
En este trabajo de investigación, el objetivo es analizar y comparar aspectos de los proyectos literarios de Jorge Luis Borges y Haroldo de Campos, dando énfasis al modo por el cual los dos escritores se relacionan con la tradición literaria para construir en sus obras una relectura del canon a partir de un movimiento que Borges enunció en el conocido texto Kafka y sus precursores y Haroldo de Campos denominó Poética Sincrónica. Así, el trabajo destacará, centralmente, el desarrollo del proyecto literario de ambos en relación a su paideuma, buscando apuntar cómo cada uno percibe la importancia de la tradición estableciendo relaciones entre el aspecto local de las culturas en las cuales están insertos y lo universal. Para realizar este estudio, utilizaremos, como base, algunos caminos teóricos, colocándolos en diálogo: en primer lugar, un estudio de cuño histórico-crítico para contextualizar las obras del escritor argentino y brasilero, apuntando, a partir de ese estudio histórico, las relaciones entre literatura, cultura y sociedad que sus obras dejan vislumbrar. En seguida, será hecho un estudio de algunos textos críticos de los autores, para que podamos esclarecer de qué modo perciben la relación con la tradición. Para eso será necesario contar con el soporte de referencias de la teoría de la literatura, principalmente aquellos dirigidos para la comprensión de la relación del escritor moderno y contemporáneo con la tradición, tales como Harold Bloom (La angustia de la influencia); Leyla Perrone-Moisés (Altas Literaturas); Ezra Pound (ABC de la Literatura) y Octavio Paz (Los hijos del limo). En un primer momento, describiremos la poética de lectura borgeana y haroldiana. Después, ejecutaremos una comparación entre ambas poéticas a partir de la lectura que ambos autores hacen del escritor Dante Alighieri y su obra La Divina Comedia, con el interés de ilustrar, en líneas generales, la discusión...
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DURIEZ, CHRISTOPHE. "Synthese de precurseurs moleculaires de la ceramique nitrure de bore isotopiquements enrichis ou non en azote quinze". Rennes 1, 1999. http://www.theses.fr/1999REN10175.
Testo completoAbstract (sommario):
Ce travail se place a l'interface chimie-materiaux et a ete entrepris dans le but d'elucider les mecanismes regissant les reactions mises en jeu a tous les stades de l'elaboration d'un materiau, du monomere a la ceramique et d'avoir une meilleure connaissance de la structure des precurseurs polymeriques. Dans un premier temps, nous nous sommes interesses a l'etude mecanistique de la formation de la borazine b 3n 3h 6 par thermolyse du complexe nh 3. Bh 3. La thermolyse des complexes nd 3. Bh 3 et nh 3. Bd 3 a montre qu'un scrambling de deuterium dans les deux sens avait lieu. Grace a une etude sur des molecules modeles, nous avons propose un mecanisme de formation de la borazine. La seconde partie rapporte la synthese de produits enrichis de 10% en 1 5n tel que le complexe amine-borane et la borazine. Cet enrichissement permet d'acceder aux spectres rmn 1 5n solide et liquide dans de tres bonnes conditions. La troisieme partie rapporte les travaux concernant l'acces a des polymeres enrichis en 1 5n soit de type sneddon soit obtenus par ammonolyse, ainsi que de leurs caracterisations par rmn en phase liquide et solide. La rmn 1 5n permet de mettre en evidence la complexite de la structure de ces deux polymeres. Une structure elaboree sur la base des etudes par rmn 1 5n a ete proposee. Les mecanismes de formation de ces polymeres ont ete approfondis. La derniere partie est consacree a l'etude de la pyrolyse des polymeres de sneddon et de vaultier par rmn du solide (collaboration avec f. Babonneau, universite de paris 6). La synthese de nouveaux precurseurs de nitrure de bore par copolymerisation de la borazine b 3n 3h 6 et d'alkylaminoborazines a ete realisee. La pyrolyse de ces copolymeres conduit a du bn turbostratique dont le taux de carbone depend de la nature du copolymere utilise. Suivant leur origine, les ceramiques obtenues ont une morphologie differente. Dans certains cas, des mousses sont obtenues qui pourraient etre utilisees comme adsorbeurs de gaz.
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Machek, Edward Joseph Jr. "Iopamidol as a Precursor to Iodinated Disinfection Byproduct (DBP) Formation as a Function of NOM concentration, pH, and Chlorinated Oxidants". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1439045967.
Testo completo
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Woods, Keenan. "Amorphous Metal Oxide Thin Films from Aqueous Precursors: New Routes to High-κ Dielectrics, Impact of Annealing Atmosphere Humidity, and Elucidation of Non-uniform Composition Profiles". Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23173.
Testo completoAbstract (sommario):
Metal oxide thin films serve as critical components in many modern technologies, including microelectronic devices. Industrial state-of-the-art production utilizes vapor-phase techniques to make high-quality (dense, smooth, uniform) thin film materials. However, vapor-phase techniques require large energy inputs and expensive equipment and precursors. Solution-phase routes to metal oxides have attracted great interest as cost-effective alternatives to vapor-phase methods and also offer the potential of large-area coverage, facile control of metal composition, and low-temperature processing.
Solution deposition has previously been dominated by sol-gel routes, which utilize organic ligands, additives, and/or solvents. However, sol-gel films are often porous and contain residual carbon impurities, which can negatively impact device properties. All-inorganic aqueous routes produce dense, ultrasmooth films without carbon impurities, but the mechanisms involved in converting aqueous precursors to metal oxides are virtually unexplored. Understanding these mechanisms and the parameters that influence them is critical for widespread use of aqueous approaches to prepare microelectronic components. Additionally, understanding (and controlling) density and composition inhomogeneities is important for optimizing electronic properties. An overview of deposition approaches and the challenges facing aqueous routes are presented in Chapter I. A summary of thin film characterization techniques central to this work is given in Chapter II.
This dissertation contributes to the field of solution-phase deposition by focusing on three areas. First, an all-inorganic aqueous route to high-κ metal oxide dielectrics is developed for two ternary systems. Chapters III and IV detail the film formation chemistry and film properties of lanthanum zirconium oxide (LZO) and zirconium aluminum oxide (ZAO), respectively. The functionality of these dielectrics as device components is also demonstrated. Second, the impact of steam annealing on the evolution of aqueous-derived films is reported. Chapter V demonstrates that steam annealing lowers processing temperatures by effectively reducing residual counterion content, improving film stability with respect to water absorption, and enhancing dielectric properties of LZO films. Third, density and composition inhomogeneities in aqueous-derived films are investigated. Chapters VI and VII examine density inhomogeneities in single- and multi-metal component thin films, respectively, and show that these density inhomogeneities are related to inhomogeneous metal component distributions.
This dissertation includes previously published coauthored material.
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Thomas, Caroline. "Préservation de l'arôme dans un jambon cuit non nitrité". Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22522.
Testo completoAbstract (sommario):
Le nitrite est un ingrédient essentiel à la fabrication du jambon cuit, pourtant les risques sanitaires dont il est accusé remettent en question son utilisation. L’emploi de cet unique additif permet de remplir de nombreuses fonctions comme la protection antioxydante et antimicrobienne mais aussi le développement de la couleur et de l’arôme. C’est sur cette dernière fonction que ce travail de thèse s’est focalisé avec pour objectif la suppression du nitrite dans la fabrication du jambon cuit. La mise en œuvre de plusieurs techniques complémentaires de chromatographie en phase gazeuse couplées à l’olfactométrie a permis dans une première partie d’identifier le 2-methyl-3-furanthiol, 2-methyl-3-(methyldithio)furan, et le bis(2-methyl-3-furyl)disulfide comme les molécules soufrées responsables de l’arôme du jambon cuit. Il est apparu qu’en l’absence de nitrite et par conséquent en absence de protection antioxydante, les composés odorants issus de l’oxydation sont produits massivement et ont tendance à perturber l’arôme global du jambon cuit. Afin de restaurer l’arôme en l’absence de nitrite, l’étude a été organisée selon 2 axes : le premier visant à favoriser la production des molécules soufrées clés de l’arôme et le second visant à limiter la formation des composés d’oxydation perturbateurs de l’arôme grâce à l’utilisation d’antioxydants naturels. Les recherches ont été conduites sur des mini-jambons cuits modèles. La thiamine a été identifiée comme précurseur majoritaire du 2-methyl-3-furanthiol, du 2-methyl-3-(methyldithio)furan, et du bis(2-methyl-3-furyl)disulfide dans les conditions de fabrication du jambon cuit et des extraits d’acérola, de canneberge, d’oignon et de thé ont été sélectionnés pour leurs propriétés antioxydantes. L’évaluation en parallèle de l’oxydation et de l’arôme a montré que ces quatre extraits utilisés en mélange permettaient, non seulement d’égaler les performances antioxydantes du nitrite, mais aussi de rehausser la note aromatique « jambon cuit » par rapport à la formulation non nitritée de référence. L’association de la thiamine et des extraits végétaux a finalement permis de réaliser des jambons non nitrités qui, en termes d’arôme et d’oxydation, se rapprochent fortement d’un jambon nitrité. Les formulations réalisées constituent donc une première piste satisfaisante pour répondre à la problématique de la suppression du nitrite dans le jambon cuit. La protection antimicrobienne des nouvelles formulations doit être validée et la restauration de la couleur rose du jambon demeure une problématique organoleptiqueSodium nitrite is an essential ingredient in the cooked ham production process, yet its use is under challenge due to food safety concerns. Sodium nitrite is a multifunctional additive used for its ability to act on several fronts—from inhibiting oxidation and preventing microbial growth to giving desirable colour and aroma. This study focused on the aroma function under a wider objective to reduce nitrite use in cooked ham processing. Using several complementary methods with gas chromatography–olfactometry, we first identified 2- methyl-3-furanthiol, 2-methyl-3-(methyldithio)furan and bis(2-methyl-3-furyl)disulfide as the odour- active sulphur-compounds responsible for cooked ham flavour. It emerged that in the absence of nitrite—and therefore the absence of inhibited oxidation—the massive formation of an array of odour-active compounds produced by oxidative breakdown tended to disrupt the overall aroma of the final cooked ham. Next, in an effort to restore this aroma in the absence of nitrite, the study was organized into two strands, where the first strand aimed to promote the production of key aroma-active sulphur-compounds while the second strand aimed to minimize the formation of aroma-disruptive oxidation compounds by using natural antioxidants. This research was led on model cooked mini-hams. We identified thiamine as the major precursor of 2-methyl-3-furanthiol, 2-methyl-3-(methyldithio)furan and bis(2-methyl-3-furyl)disulfide under cooked ham production conditions, and we selected acerola, cranberry, onion and tea extracts as natural antioxidants. The coupled evaluations of oxidation and aroma showed that the formulated mixture of these four extracts not only equalled the antioxidant performances of added sodium nitrite but also lifted the “cooked ham” head note compared to the reference no-added-nitrite formulation. The association of thiamine and vegetal extracts ultimately made it possible to produce no-added-nitrite hams that, in terms of aroma and oxidation levels, proved almost identical to nitrite-added ham. The engineered formulations thus offer a good research track to suppress the sodium nitrite in cooked ham. The problem of how to restore the distinctive pink colour of cooked ham is an issue that remains to be resolved, and the ability of these new formulations to inhibit microbial growth needs to be validated
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Haug, Annegret Veronika [Verfasser], e H. [Akademischer Betreuer] Kalt. "Properties of the Back Contact Interface for Non-Vacuum Deposited Precursor-Based Cu(In,Ga)Se₂ Solar Cells / Annegret Veronika Haug ; Betreuer: H. Kalt". Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1155474317/34.
Testo completo
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Xavier, Júnior José Cândido Caldeira [UNESP]. "Risco estimado das lesões precursoras do colo do útero nos exames citológicos em função do tipo de lesão, intervalo entre os controles e da idade". Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/142980.
Testo completoAbstract (sommario):
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000865266.pdf: 2803905 bytes, checksum: 8b210e35895c7a340ae000f9b3b39336 (MD5)INTRODUÇAO: A utilização do exame de citologia cérvico-vaginal para rastreamento do carcinoma do colo do útero diminuiu a incidência e mortalidade desse carcinoma e não há dúvidas que a identificação de lesões precursoras é importante nos cuidados com a saúde da mulher. Há poucos estudos sobre a associação do resultado de citologia cérvico-vaginal alterado em mulheres gestantes e mulheres com sangramento genital brasileiras. Além disso, ainda permanece controverso se as gestantes deveriam ser submetidas ao exame de citologia cérvico-vaginal como rotina do pré-natal e se a citologia cérvico-vaignal pode ser utilizada como método único de exclusão de neoplasia do colo do útero para as mulheres com informação clínica de sangramento genital. OBJETIVOS: Estudar os fatores associados ao resultado do exame de citologia cérvico-vaginal alterado para mulheres gestantes e não-gestantes (idade, idade de início da atividade sexual, intervalo entre exames); e para mulheres com informação clínica de sangramento genital. MÉTODOS: Estudo observacional analítico que avaliou os resultados dos exames de citologia cérvico-vaginal encaminhados ao laboratório de Citopatologia Dr José Aristodemos Pinotti do Centro de Atenção Integrada à Saúde da Mulher da Universidade Estadual de Campinas durante o período de Janeiro de 2000 a Dezembro de 2009 (10 anos) oriundos de mais de 70 municípios da região de Campinas, São Paulo - Brasil. O resultado do exame de citologia cérvico-vaginal foi reportado de acordo com o Sistema Bethesda. A partir dos formulários próprios da Instituição foram extraídos dados clínicos, citopatológicos e sociodemográficos necessários para a realização do presente estudo. RESULTADOS: Controlada a idade, idade de início da atividade sexual e intervalo entre exames não há diferença quanto a prevalência de lesão intraepitelial escamosa de alto grau entre mulheres gestantes e...
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Xavier, Júnior José Cândido Caldeira. "Risco estimado das lesões precursoras do colo do útero nos exames citológicos em função do tipo de lesão, intervalo entre os controles e da idade /". Botucatu, 2015. http://hdl.handle.net/11449/142980.
Testo completoAbstract (sommario):
Orientador: Rozany Mucha DuflothCoorientador: Luiz Carlos Zeferino
Banca: Cesar Cabello dos Santos
Banca: Sophie Françoise Mauricette Derchain
Banca: Gilberto Uemura
Banca: Maria Luiza Cotrim Sartor de Oliveira
Resumo: INTRODUÇAO: A utilização do exame de citologia cérvico-vaginal para rastreamento do carcinoma do colo do útero diminuiu a incidência e mortalidade desse carcinoma e não há dúvidas que a identificação de lesões precursoras é importante nos cuidados com a saúde da mulher. Há poucos estudos sobre a associação do resultado de citologia cérvico-vaginal alterado em mulheres gestantes e mulheres com sangramento genital brasileiras. Além disso, ainda permanece controverso se as gestantes deveriam ser submetidas ao exame de citologia cérvico-vaginal como rotina do pré-natal e se a citologia cérvico-vaignal pode ser utilizada como método único de exclusão de neoplasia do colo do útero para as mulheres com informação clínica de sangramento genital. OBJETIVOS: Estudar os fatores associados ao resultado do exame de citologia cérvico-vaginal alterado para mulheres gestantes e não-gestantes (idade, idade de início da atividade sexual, intervalo entre exames); e para mulheres com informação clínica de sangramento genital. MÉTODOS: Estudo observacional analítico que avaliou os resultados dos exames de citologia cérvico-vaginal encaminhados ao laboratório de Citopatologia Dr José Aristodemos Pinotti do Centro de Atenção Integrada à Saúde da Mulher da Universidade Estadual de Campinas durante o período de Janeiro de 2000 a Dezembro de 2009 (10 anos) oriundos de mais de 70 municípios da região de Campinas, São Paulo - Brasil. O resultado do exame de citologia cérvico-vaginal foi reportado de acordo com o Sistema Bethesda. A partir dos formulários próprios da Instituição foram extraídos dados clínicos, citopatológicos e sociodemográficos necessários para a realização do presente estudo. RESULTADOS: Controlada a idade, idade de início da atividade sexual e intervalo entre exames não há diferença quanto a prevalência de lesão intraepitelial escamosa de alto grau entre mulheres gestantes e...
Abstract: Not available
Doutor
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Khalida, Nargis Verfasser], Beate [Gutachter] Brand-Saberi e Lars [Gutachter] [Steinsträßer. "Chemokine signalling and the migration of "non-resident limb-derived myogenic precursors" for pectoral girdle muscle formation / Nargis Khalida ; Gutachter: Beate Brand-Saberi, Lars Steinsträßer ; Fakultät für Biologie und Biotechnologie". Bochum : Ruhr-Universität Bochum, 2011. http://d-nb.info/1227707347/34.
Testo completo
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Maldonado, Rojas Paloma P. "Communication synaptique et non-synaptique entre neurones et cellules précurseurs d’oligodendrocytes dans le cortex somatosensoriel". Thesis, Paris 5, 2013. http://www.theses.fr/2013PA05T064/document.
Testo completoAbstract (sommario):
Les cellules précurseur d'oligodendrocytes (CPOs) représentent la majeure source d'oligodendrocytesmyélinisants durant le développement post-natal. Ces progéniteurs, identifiés par l'expression du protéoglycane NG2, sont non seulement extrêmement abondants avant la myélinisation, mais ils persistent aussi dans le cerveau mature. À l'instar d'autres cellules non-neuronales, elles expriment un large panel de canaux ioniques et de récepteurs pour des neurotransmetteurs. Cependant, ils sont uniques de part leur capacité à recevoir de véritables contacts synaptiques neuronaux glutamatergiqueset GABAergiques. Durant cette thèse, nous avons caractérisé les propriétés électrophysiologiques des CPOs durant le développement post-natal du cortex en champ de tonneaux de la souris (premier mois post-natal). En effectuant des enregistrements de patch-clamp, des analyses par RT-PCR sur cellule unique et des analyses pharmacologiques, nous avons observé que la courbe I-V à rectification sortante devient linéaire durant le développement, résultant d'une régulation positive de l'expression des canaux potassiques de type Kir4.1. Dotés de ces canaux, les CPOs adultes sont capables de détecter les augmentations locales de potassium extracellulaire générées par l'activité neuronale. Cette régulation positive développementale des canaux Kir4.1 dans les CPOs révèle que ces cellules ont un gain de fonction durant le développement, leur conférant la capacité de communiquer avec les neurones via un mécanisme non-synaptique lié au potassium. Ce changement développemental soutient aussi l'idée que les CPOs sont probablement plus que des progéniteurs. Dans la deuxième partie de cette thèse, nous nous sommes intéressés à l'étude des patrons de connectivité du réseau GABAergique interneurones-CPOs dans le cortex en champ de tonneaux jeune (deuxième semaine post-natale). Dans un premier temps, nous avons tiré avantage de la haute précision latérale et axiale de la photolyse holographique en mono-photon pour stimuler les interneurones GABAergiques avec une résolution à l'échelle de la cellule, de manière à évoquer un potentiel d'action. Nous avons ensuite utilisé cette technique pour cartographier la connectivité entre interneurones et CPOs. Nous avons trouvé que la probabilité de connexion des CPOs est près de moitié moins que celle des cellules pyramidales, et implique plutôt une microcircuitrie locale. De plus, en effectuant des enregistrements pairés, nous avons observé que les CPOs sont contactés transitoirement par des interneurones à décharge rapide et à décharge régulière. Ces connections se caractérisents pour la présence d'un ou deux sites de libération uniquement. Étonnamment, les sites post-synaptiques contenant des récepteurs GABAA avec la sous-unité γ2 sont principalement connectés par les interneurones à décharge rapide, indiquant que ces cellules constituent une afférence spécifique auprès des CPOs. Ici nous décrivons pour la première fois l'émergence de réseaux corticaux spécifiques entre neurones et cellules non-neuronalesOligodendrocyte precursor cells (OPCs) are the main source of myelinating oligodendrocytes during postnatal development. These progenitors, identified by the expression of the proteoglycan NG2, are extremely abundant before myelination, but also persist in the mature brain. Similarly to other non-neuronal cells they express a wide range of ionic and ligand-gated ion channels. However, they are unique by their ability to receive truly glutamatergic and GABAergic synaptic contacts from neurons. During this thesis, we characterized the electrophysiological properties of OPCs during the postnatal development of the mouse somatosensory cortex (post postnatal month). By performing patch-clamp recordings, single-cell RT-PCR analyses and pharmacological approaches, we found that outwardly rectifying I-V curves become linear during development, as the result of an upregulation of Kir4.1 potassium channels. Endowed with these channels, adult OPCs are able to sense local extracellular potassium increases generated by neuronal activity. This developmental upregulation of Kir4.1 channels in OPCs revealed that these cells gain physiological properties during development, conferring them the capacity to communicate with neurons, via a non-synaptic potassium-mediated mechanism. This developmental change also supports the view that OPCs are probably more than simple progenitors. In the second part of this thesis, we were interested in study the connectivity patterns underlying the GABAergic interneuron-OPC network in the young somatosensory cortex (second postnatal week). First, we took advantage of the high lateral and axial precision of one-photon holographic photolysis to stimulate GABAergic interneurons at a single cell resolution in order to evoke an action potential. We then used this technique to map the connectivity between interneurons and OPCs. We found that the connectivity probability of OPCs was around half less than that of pyramidal cells and involved more local microcircuits. In addition, by performing paired-recordings, OPCs showed to be transiently contacted by fast-spiking (FSI) and non-fast-spiking (NFSI) interneurons, through single or double release sites. Interestingly, postsynaptic sites containing GABAA receptors with the γ2 subunit were predominantly connected by FSI, indicating that these cells provide a specific input to OPCs. Here we described for the first time the emergence of specific cortical network between neurons and non-neuronal cells. In conclusion, this thesis contributed to get a better understanding of the different modes of communication between neurons and OPCs and the establishment of new signaling mechanisms used by neurons to control the activity of these precursors
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GUERREIRO, BARBOSA KARINE. "Nouveaux complexes mononucleaires precurseurs de complexes dinucleaires du fer(iii) : modeles de sites actifs de proteines a fer non heme. etude de leur reactivite vis-a-vis des derives de reduction de l'oxygene". Paris 11, 1998. http://www.theses.fr/1998PA112396.
Testo completoAbstract (sommario):
Le travail de these presente dans ce memoire se situe dans le cadre de la chimie biomimetique. La proteine que nous prenons pour cible est l'enzyme superoxyde dismutase a fer. Les nouvelles molecules que nous avons synthetisees et caracterisees sont construites a partir d'un ligand tripode tetradente, le n, n, n-tris(1-methylimidazol-2-yl) methyl) amine (tmima) et de ligands labiles cl# et n#3#. Dans le premier chapitre, nous avons presente quelques proteines mononucleaires et dinucleaires a fer non heme et plus particulierement les superoxyde dismutases a fer. Dans le deuxieme chapitre, une etude bibliographique des modeles et des ligands biomimetiques utilisant des ligands tetradentes tripodes a centre azote a ete presentee. Le troisieme chapitre est consacre a la synthese et a la caracterisation des nouveaux complexes du fer(iii) : fe#2(tmima)cl#2#+, (clo#4)#, fe#2(tmima)#2(n#3)#2o#2#+, 2(clo#4)#, fe#2(tmima)#2cl#2o#+, 2(clo#4)#et fe#2(tmima)#2(n#3)#2o#2#+, 2(clo#4#. Enfin, dans le quatrieme chapitre, nous etudions la reactivite des complexes vis-a-vis du superoxyde. Nous avons demontrer que les complexes monomeriques fe(tmima)cl#2#+, (clo#4)# et fe(tmima)(n#3)#2#+, (clo#4)#, conduisent invariablement aux complexes dimeriques fe#2(tmima)#2cl#2o#+, 2(clo#4)#, et fe#2(tmima)#2(n#3)#2o#2#+, 2(clo#4)#, respectivement, en presence de superoxyde, les composes dimeriques reagissant eux aussi avec le superoxyde, conduisant a la formation d'une nouvelle espece en solution que l'on peut ecrire feo#2#n#.
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Cochet, Maud. "Implication du complexe récepteur 5-HT4/APP/ADAM10 dans la voie non-amyloïdogénique de la maladie d’Alzheimer". Thesis, Montpellier 1, 2011. http://www.theses.fr/2011MON1T005.
Testo completoAbstract (sommario):
En plus d'être clivée par les β- et les γ-sécrétases lors du processus amyloïdogénique de la maladie d'Alzheimer, l'APP (Amyloid Precursor Protein) peut également subir un clivage grâce à l'α-sécrétase qui conduit à la libération des fragments d'APP soluble α (sAPPα)(voie non-amyloïdogénique) prévenant ainsi l'accumulation des peptides β-amyloïdes pathogènes. Les études sur le clivage de l'APP par l'α-sécrétase ont montré que l'activité de cette enzyme était constitutive mais aussi régulée. Lors de mon travail de thèse, nous avons montré que l'expression du récepteur de la sérotonine de type 4 (R 5-HT4) favorise la coupure constitutive de l'APP par l'α sécrétase ADAM10 et la libération des fragments non-amyloïdogéniques, sAPPα, aussi bien dans les cellules HEK-293 que dans les neurones corticaux en culture primaire. Ce mécanisme est totalement indépendant de la production d'AMPc, mais reste dépendant d'une interaction entre le R 5-HT4, l'APP et la forme mature de l'ADAM10. Le R 5-HT4, contrairement à d'autres récepteurs couplés aux protéines G (RCPG) décrits pour promouvoir la libération de sAPPα, est en effet capable d'interagir physiquement avec l'α-sécrétase ADAM10 et son substrat, l'APP. Cette interaction, directe ou indirecte, favorise l'adressage de l'ADAM10 et de l'APP à la membrane plasmique, là où la coupure en α est majoritaire. Toute rétention du R 5-HT4 à l'intérieur de la cellule retient également l'APP et l'ADAM10 sous sa forme inactive et annule la production de sAPPα. La régulation de l'α-sécrétase est toujours dépendante de l'activation du R 5-HT4 par un agoniste. Cet effet étant cette fois dépendant de la voie de signalisation de l'AMPc et de la protéine Epac comme cela avait déjà été démontré. Ces résultats décrivent pour la première fois un mécanisme par lequel un RCPG stimule le clivage constitutif de l'APP par l'α sécrétase et fournit de nouvelles perspectives pour la régulation de l'APP et le contrôle de l'adressage de l'α-sécrétase ADAM10In addition to the amyloidogenic pathway of Alzheimer's disease whereby Amyloid Precursor Protein (APP) is cleaved by β- et γ-secretases, the substrate can also be cleaved by α secretases, producing soluble APP alpha (sAPPα)(non-amyloidogenic pathway) and thus preventing the generation of pathogenic Amyloid-beta peptides. Despite, intensive research, the mechanisms regulating APP cleavage by α-secretases remain poorly understood. In this study, we tried to elucidate how 5-HT4Rs stimulate the release of sAPPα. We show that expression of serotonin type 4 receptors (5-HT4Rs) constitutively induces APP cleavage by the α-secretase ADAM10 and release of non-amyloidogenic fragments, sAPPα, in HEK-293 cells and cortical neurons. This effect is fully independent of cAMP production and relies on the transport of the 5-HT4R/APP/mature ADAM10 complex to the plasma membrane. Indeed, 5-HT4Rs but not other G protein-coupled receptors (GPCRs) known to activate sAPPα release, physically interact, directly or indirectly, with ADAM10 and APP to promote their targeting to the plasma membrane. Stimulation of 5 HT4Rs by an agonist further increases sAPPα fragments release and this effect is mediated through cAMP/Epac signalling. These findings describe a new mechanism whereby a GPCR stimulates the cleavage of APP by α-secretases and provide novel insights into the regulation of APP and α-secretase sorting
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Kothe, Blanka. "Nachweis von TEL-Genrekombinationen mittels Southern Blot bei Kindern mit akuter lymphoblastischer Leukämie". Doctoral thesis, Humboldt-Universität zu Berlin, Medizinische Fakultät - Universitätsklinikum Charité, 2003. http://dx.doi.org/10.18452/14891.
Testo completoAbstract (sommario):
Das in der vorliegenden Arbeit vorgestellte Verfahren der nicht-radioaktiven Southern Blot Hybridisierung unter Verwendung einer Digoxigenin Markierung hat sich für die Darstellung von Rekombinationen im TEL-Genlokus genomischer DNA als sensitive Vergleichsmethode bewiesen. Es wurden insgesamt 122 Kinder mit dieser Methode auf das Vorliegen der Translokation t(12;21) untersucht. Bei einer nur relevante Faktoren berücksichtigenden Beschränkung des PatientInnenkollektivs auf protokollgerecht nach ALL-REZ BFM behandelte B-Vorläufer-Zell-ALL und Erstrezidive konnte eine Rekombination von TEL in 5 von 65 PatientInnen (7,7%) nachgewiesen werden. Lässt man die Einschlusskriterien der ALL-REZ BFM Studie unberücksichtigt, handelt es sich sogar um 7 von 71 (9,9%) PatientInnen. Damit bestätigen die hier vorliegenden Ergebnisse den Trend der aktuellen Diskussion über die Häufigkeit des Vorliegens des Fusionsgenes TEL-AML1 bei Erstrezidiven, die eine kumulative Inzidenz bei einem 10-jährigen Untersuchungszeitraum von 9 ± 5% angeben. Weiterhin konnte mit ereignisfreien Beobachtungszeiträumen nach dem 1. Rezidiv im Median von 8,6 Jahren ein Trend zu späten Rezidiven und somit eine mittelfristig günstige Prognose für die TEL-Rearrangement positiven Rezidivfälle konstatiert werden. Zusammenfassend kann gesagt werden, dass TEL-AML1 positive PatientInnen eine Subgruppe darstellen, die lange erkrankungsfreie Intervalle mit zur Zeit üblichen Therapieprotokollen erreichen, nach Therapie der Ersterkrankung aber auch nach dem ersten Rezidiv. Auf Grund der sich aus dem retrospektiven PatientInnekollektiv ergebenen Selektion war es nicht möglich, statistisch signifikante Aussagen zur unabhängigen prognostischen Bedeutung für die langfristige Prognose von ALL im Kindesalter mit TEL-Rekombinationen zu treffen.The presence of TEL/AML1 fusion gene in childhood acute lymphoblastic leukaemia (ALL) defines a subgroup of patients with better than average outcome. Around 20% of the patient at point of initial ALL diagnosis are characterised by this fusion transcript from translocation t(12;21)(p12;q22). However, the prognostic significance of this aberration has recently been disputed by the Berlin-Frankfurt-Munster (BFM) study group due to its relatively high incidence found in relapsed patients (19.6% and 21.9%, in two cohorts). Here we wanted to get more data in a long term follow up retrospect investigation by analysing DNA from frozen conserved bone marrow samples of 65 children. In the study presented here only five out of 65 (7.7%) patients selected as childhood B cell precursor acute lymphoblastic leukaemia only treated according to Berlin-Frankfurt-Munster (BFM) ALL relapse trial protocols (ALL-REZ BFM 82-96) (excluding T-lineage and Philadelphia chromosome (Ph)-positive leukaemia) carry this fusion. The detection was done due to a new developed non-radioactive Southern blotting with a Digoxigenin marked template. We could confirm the still good middle term prognosis in the relapsed TEL-AML1 positive subgroup. The TEL-AML1-positive and negative patients differed with respect to duration of last remission and age at initial diagnosis. At a median follow-up time of 8.6 years, children positive for TEL-AML1 had a higher probability of disease-free survival. Because of the small number of patients in this study it was not possible to get statistical significant facts about the independent prognostic impact for the long term prognosis of ALL in childhood with TEL rearrangement.
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Ahmed, Abdullah. "Dévelopement d'une méthode bio-informatique pour la prédiction des régions amyloidogéniques dans les protéines". Phd thesis, Université Montpellier II - Sciences et Techniques du Languedoc, 2013. http://tel.archives-ouvertes.fr/tel-00998437.
Testo completoAbstract (sommario):
La formation d'agrégats protéiques insolubles et fibreux, appelés fibrilles amyloïdes, est impliquée dans une large variété de maladies humaines. Parmi elles, figurent entre autres, le diabète de type II, l'arthrite rhumatoïde et, notamment, les atteintes neurodégénératives débilitantes, telles que les maladies d'Alzheimer, de Parkinson ou encore de Huntington. Actuellement, il n'existe ni traitement, ni diagnostic précoce pour aucune de ces maladies.De nombreuses études ont montré que la capacité à former des fibrilles amyloïdes est une propriété inhérente à la chaîne polypeptidique. Ce constat a conduit au développement d'un certain nombre d'approches computationnelles permettant de prédire les propriétés amyloïdogéniques à partir de séquences d'amino-acides. Si ces méthodes s'avèrent très performantes vis à vis de courts peptides (~ 6 résidus), leur application à des séquences plus longues correspondant aux peptides et protéines en lien avec les maladies, engendre un nombre trop élevé de faux positifs. Le principal objectif de cette thèse consiste à développer une meilleure approche bioinformatique, capable de prédire les régions amyloïdogéniques à partir d'une séquence protéique. Récemment, l'utilisation de nouvelles techniques expérimentales a permis de mieux appréhender la structure des amyloïdes. Il est ainsi apparu que l'élément caractéristique de la majorité des fibrilles amyloïdes impliquées dans les maladies, était constitué d'une structure étagée (β-arcade), résultant de l'empilement de motifs " feuillet β - coude - feuillet b " appelés " β-arches ". Nous avons mis à profit cette particularité structurale pour créer une approche bioinformatique permettant de prédire les régions amyloïdogéniques d'une protéine à partir de l'information contenue dans sa séquence. Les résultats provenant de l'analyse des structures de type β-arcade, connues et modélisées, ont été compilés et traités à l'aide d'un algorithme écrit en langage Java, afin de créer le programme ArchCandy.L'application de ce programme à une sélection de séquences protéiques et peptidiques, connues pour leur lien avec les maladies, a permis de démontrer qu'il était en mesure de prédire correctement la majorité de ces séquences, de même que les séquences mutées impliquées dans les maladies familiales. Outre la prédiction de régions à haut potentiel amyloïde, ce programme suggère la conformation structurale adoptée par les fibrilles amyloïdes. Le séquençage de génomes entiers devenant toujours plus abordable, notre méthode offre une perspective de détermination individuelle des profils à risque, vis à vis de maladies neurodégénératives, liées à l'âge ou autres. Elle s'inscrit ainsi pleinement dans l'ère de la médecine personnalisée.
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Ma, Xing Hua. "Chemoenzymatic syntheses of rare carbohydrates from non-carbohydrate precursors". Phd thesis, 2003. http://hdl.handle.net/1885/148547.
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Liu, Wen-Da, e 劉文達. "The Syntheses and Reactions of non-Kekule' Biradical Precursors(I)". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/26309560896203891450.
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Jiang, Yuan [Verfasser]. "Precursor phases in non-classical crystallization / von Yuan Jiang". 2010. http://d-nb.info/101425289X/34.
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Richardson, William. "Vascular Smooth Muscle Precursor Cell Behavior in Non-Uniform Stretch Environments". Thesis, 2012. http://hdl.handle.net/1969.1/148094.
Testo completoAbstract (sommario):
Cells in the body respond to mechanical loads in ways that are crucial to normal and disease physiology. Understanding these processes is difficult due to the complex mechanical environment in vivo. In this research, we have developed several cell-stretching devices capable of subjecting cell cultures to non-uniform stretch distributions in order to investigate pathological responses of vascular smooth muscle cells to physiologic stretches. 10T1/2 cells were cyclically stretched with these devices for 24 hours upon silicone membranes, PDMS tubes, and within 3D PEGDA hydrogels. After stretching, altered cell behaviors were measured, including orientation, proliferation (quantified by BrdU incorporation), and gene expression (quantified by real-time, RT-PCR).
Cells demonstrated marked changes in orientation, proliferation, and mRNA expression, which all varied with cellular location in the non-uniform environment. More specifically, increased orientation, increased proliferation, and more dramatically altered mRNA expression were found in regions of high, uniaxial stretch, relative to regions of low, near-equibiaxial stretch. These findings demonstrate the capabilities of graded stretch distributions to produce graded cell responses, indicating potentially localized smooth muscle cell behavior in a diseased artery. The novel devices employed herein will hopefully improve our understanding of these complicated cellular pathways, ultimately allowing for improved treatment or prevention of vascular disease.
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Brederlau, Anke Odin Per. "Bone morphogenetic proteins but not growth differentiation factors induce dopaminergic differentiation in mesencephalic precursors /". 2003. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=012987749&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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42
Scharner, Dörte [Verfasser]. "The non-apoptotic function of Caspase-8 in enothelial precursor cells / Dörte Scharner". 2009. http://d-nb.info/997805242/34.
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Pai, Yi-Fang, e 白易芳. "The Synthesis of Precursors for Thieno-o-Quinodimethanes and non-Kekulé Tetraradicals and Their Thermal and Photochemical". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/05283739662425603588.
Testo completoAbstract (sommario):
碩士國立交通大學
應用化學系
90
The objectives of our research are to synthesize stable precursors for non-Kekulé tetraradicals, and to study the electronic states of their ground states. After successfully synthesized meta-disultine 32, and para-disultine 36, we have explored their potential application in Diels-Alder reaction and studied their photochemistry and EPR spectroscopy. From these studies, sultines were found to be good precursors for non-Kekulé tetraradicals. When compounds 32 and 36 were reacted with dienophiles in a sealed tube at high temperature, one obtained not only the rearranged disulfolenes 57 and 58 but also fused adducts of Type A and Type B. The reaction patterns of these disultines are very similar to those of corresponding tetraradical molecule 16a. When sultines 42a and 42b were reacted with C60, the mono-adducts of the 3,4-bismethylene thiophenes with C60 were obtained in good yields. Variable temperature 1H-NMR experiments show that the coalescence temperature (Tc) and activation free energy (ΔGc≠) for the boat-to-boat inversion of C60 mono-adducts 82a and 82b are 14.3 and 13.5 kcal/mol, respectively. These ΔGc≠ are similar to those reported for carbocyclic derivatives in the literatures. Compare the mono adducts of C60, 82a-d, we found that compound 82a is the only product that is unstable in air (with room light). This dimethylthienoadduct of C60 is a very good singlet oxygen sensitizer which is very similar to those by Komatsu (J. Org. Chem., 2001, 66, 8187.) The products from photochemical reactions of these disultines 36 (irradiated with 300 nm UV-light) are similar to those from thermochemical reactions. Furthermore, it was interesting to find that one of these disultine isomers is selectively photolyzed by 300 nm light. ESR on these sultine molecules give spectra consistent with triplet biradical intermediates, which is different from the result of singlet biradical intermediates 5 reported by Berson in diazene photolysis. A possible reason for this observation is the cleavage of carbon-oxygen bond of a triplet excited sultine. The extremely low quantum yield (Φ) for the photolysis of sultine explains why we did not observe a quintet in low temperature EPR spectroscopy.
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(11146737), Swapnil Dattatray Deshmukh. "UNVEILING THE AMINE-THIOL MOLECULAR PRECURSOR CHEMISTRY FOR FABRICATION OF SEMICONDUCTING MATERIALS". Thesis, 2021.
Cerca il testo completoAbstract (sommario):
Inorganic metal chalcogenide materials are of great importance in the semiconducting field for various electronic applications such as photovoltaics, thermoelectrics, sensors, and many others. Compared to traditional vacuum processing routes, solution processing provides an alternate cost-effective route to synthesize these inorganic materials through its ease of synthesis and device fabrication, higher material utilization, mild processing conditions, and opportunity for roll-to-roll manufacturing. One such versatile solution chemistry involving a mixture of amine and thiol species has evolved in the past few years as a common solvent for various precursor dissolutions including metal salts, metal oxides, elemental metals, and chalcogens.
The amine-thiol solvent system has been used by various researchers for the fabrication of inorganic materials, but without the complete understanding of the chemistry involved in this system, utilizing its full potential, and overcoming any inherent limitations will be difficult. So, to identify the organometallic complexes and their reaction pathways, the precursor dissolutions in amine-thiol solutions, specifically for elemental metals like Cu, In and chalcogens like Se, Te were studied using X-ray absorption, nuclear magnetic resonance, infrared, and Raman spectroscopy along with electrospray ionization mass spectrometry techniques. These analyses suggested the formation of metal thiolate complexes in the solution with the release of hydrogen gas in the case of metal dissolutions confirming irreversibility of the dissolution. Insights gained for chalcogen dissolutions confirmed the formation of different species like monoatomic or polyatomic clusters when different amine-thiol pair is used for dissolution. Results from these analyses also identified the role of each component in the dissolution which allowed for tuning of the solutions by isolating the complexes to reduce their reactivity and corrosivity for commercial applications.
After identifying complexes in metal dissolution for Cu and In metals, the decomposition pathway for these complexes was studied using X-ray diffraction and gas chromatography mass spectrometry techniques which confirmed the formation of phase pure metal chalcogenide material with a release of volatile byproducts like hydrogen sulfide and thiirane. This allowed for the fabrication of impurity-free thin-film Cu(In,Ga)S2 material for use in photovoltaic applications. The film fabrication with reduced carbon impurity achieved using this solvent system yielded a preliminary promising efficiency beyond 12% for heavy alkali-free, low bandgap CuInSe2 material. Along with promising devices, by utilizing the understanding of the chalcogen complexation, a new method for CuInSe2 film fabrication was developed with the addition of selenide precursors and elemental selenium which enabled first-ever fabrication of a solution-processed CuInSe2 thin film with thickness above 2 μm and absence of any secondary fine-grain layer.
Along with thin-film fabrication, a room temperature synthesis route for lead chalcogenide materials (PbS, PbSe, PbTe) with controlled size, shape, crystallinity, and composition of nanoparticle self-assemblies was demonstrated. Micro-assemblies formed via this route, especially the ones with hollow-core morphology were subjected to a solution-based anion and cation exchange to introduced desired foreign elements suitable for improving the thermoelectric properties of the material. Adopting from traditional hot injection and heat up synthesis routes, a versatile synthesis procedure for various binary, ternary, and quaternary metal chalcogenide (sulfide and sulfoselenide) nanoparticles from elemental metals like Cu, Zn, Sn, In, Ga, and Se was developed. This new synthesis avoids the incorporation of impurities like O, Cl, I, Br arising from a traditional metal oxide, halide, acetate, or other similar metal salt precursors giving an opportunity for truly impurity-free colloidal metal chalcogenide nanoparticle synthesis.
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Ren-JheWang e 王仁哲. "A study on NOM and disinfection by-products precursor removal by PAC adsorption-coagulation process". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/2s9nwf.
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Samajdar, Aniruddha. "Molecular pathways governing maturation and decay of precursor piRNAs in Caenorhabditis elegans". Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6155.
Testo completoAbstract (sommario):
Piwi-interacting RNAs (piRNAs) are an animal-specific class of germline-enriched small non-coding RNAs that play a crucial role in germline development and fertility in diverse organisms. In Caenorhabditis elegans (C. elegans), mature piRNAs are uniformly 21 nucleotides (nt) long, and begin with monophosphorylated uridine (therefore, also known as 21U-RNA). They are processed from 25-30 nt long capped RNA precursors, which are transcribed by RNA polymerase II and initiate precisely 2 nt upstream of the 5’-end of mature 21U-RNAs. Therefore, to generate 21 nt long mature piRNAs, the 5’ cap and first two nucleotides from the 5’-end must be removed, and extra nucleotides must be trimmed from the 3’-end. It has previously been shown that PARN-1, a conserved 3’-5’ exoribonuclease, contributes to the 3’-end processing of the precursors. However, the enzyme(s) responsible for processing the 5’-end of precursor piRNAs is still unknown.
Objective 1: Identification and characterization of factor(s) involved in the processing of precursor piRNAs in C. elegans.
Here, we report that the endoribonuclease activity of XRN-2 is involved in the 5’-end processing of a small set of piRNAs in C. elegans. Our findings also demonstrate that XRN-2 is capable of degrading precursor piRNAs that are not bound and protected by PRG-1, revealing a potential surveillance mechanism for ensuring quality control during precursor piRNA processing. Our research suggests that piRNAs originating from longer precursor molecules (≥ 60 nt) undergo an initial ribonucleolytic processing of their 3’-ends, which is mediated by ENDU-1, either directly or indirectly. Finally, we show that XRN-2 is not only important for the generation of mature piRNAs and piRNA-dependent 22G-RNAs, but through yet unknown pathways, it also affects piRNA-independent 22G-RNAs that shape transcriptome, as well as contribute to genomic integrity via regulation of transposable elements.
Objective 2: Elucidating a tailing-mediated surveillance pathway for the degradation of unprocessed intermediate precursor 21UR-1 in C. elegans.
Here, we report on a surveillance pathway mediated by 3’-tailing that targets unprocessed intermediate precursor 21UR-1 in the adult germline of C. elegans. The absence of proper 5’- and 3’-end processing events leads to the tailing of intermediate precursor 21UR-1, which acts as a signal for their degradation. CID-1 is identified as the mediator of 3’-tailing of precursor 21UR-1. Additionally, it has been shown that tailing affects the stability of PRG-1. Abrogation of the tailing event leads to a significant accumulation of unprocessed intermediate precursor 21UR-1 in C. elegans embryo, which would otherwise be degraded during the maternal to zygotic transition.
Overall, our study provides insight into precursor piRNA processing and quality control mechanisms in C. elegans.Council of Scientific and Industrial Research (CSIR)
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Hao, Haijun [Verfasser]. "Non-Cp metal complexes supported by nitrogen donor ligands : precursors for the synthesis of new metal fluorides / vorgelegt von Haijun Hao". 2001. http://d-nb.info/964920867/34.
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Kuhlmann, Rolf von [Verfasser]. "Tropospheric photochemistry of ozone, its precursors and the hydroxyl radical : a 3d-modeling study considering non-methane hydrocarbons / Rolf von Kuhlmann". 2001. http://d-nb.info/963248766/34.
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Tsogo, Onana (murat) Marie Laure. "N-HYDROXYLAMINES PYRROLIQUES : PRECURSEURS DE BIS(PYRROLYL)ALCANES NON SYMETRIQUES ET DE a-N-HYDROXYAMINO ESTERS". Phd thesis, 2010. http://tel.archives-ouvertes.fr/tel-00551023.
Testo completoAbstract (sommario):
Le pyrrole est un hétérocycle souvent présent dans les produits naturels et les composés biologiquement actifs. Son étude intensive en synthèse organique est donc d'un grand intérêt. Ainsi, la première réaction acido-catalysée de pyrroles sur des nitrones, reportée par notre équipe, a conduit selon les conditions expérimentales employées, soit aux 2,2-bis(pyrrolyl)alcanes symétriques, soit aux N-benzylhydroxylamines pyrroliques de façon sélective. Les N-hydroxylamines pyrroliques sont des composés intéressants et ont été le point de départ des deux études méthodologiques développées dans ce manuscrit. Les bis(pyrrolyl)alcanes non symétriques ont pu être synthétisés efficacement et avec une bonne diversité, en une étape, par réaction entre des N-hydroxylamines pyrroliques et des pyrroles. La méthode a aussi permis la préparation de ter(pyrrolyl)alcanes symétriques et non symétriques. Une application de cette méthodologie a été la préparation de marqueurs de fluorescence F-Bodipy® non symétriques. Ces derniers ont été obtenus pour la première fois et avec de bons rendements, directement à partir de 2,2'-bis(pyrrolyl)alcanes non symétriques. De plus, un F-Bodipy® présentant une chiralité axiale a pu être synthétisé. Nous avons également étudié l'accès aux acides a-N-hydroxyaminés, analogues N-hydroxylés des acides a-aminés. Une réaction hautement diastéréosélective entre le pyrrole et une nitrone cyclique chirale a donné accès à une hydroxylamine pyrrolique. Une séquence en trois étapes a permis d'obtenir un a-N-hydroxyamino ester avec un bon rendement et un bon excès énantiomère de 80%. La méthode a ensuite été appliquée à d'autres hétéroaromatiques pyrroliques, indoliques et furaniques. Aucun acide a-N-hydroxaminé comportant l'un de ces hétérocycles n'était décrit précédemment dans la littérature. Les rendements globaux obtenus sont bons (36-62%) et les excès énantiomères peuvent atteindre des valeurs ≥ 98%.
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Huang, Chun-Ying, e 黃春櫻. "A Non-phosgene Route to Polyurea Using Diphenyl 4,4''-Methylene Diphenylcarbamate (DP-MDC) as The Key Precursor". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/49298631981329611377.
Testo completoAbstract (sommario):
碩士國立中興大學
化學工程學系所
98
In this research, an improved non-phosgene process of making polyurea has been developed based on a method found previously in our laboratory. In the new process, diphenyl 4,4''-methylene diphenylcarbamate (DP-MDC), long-chained polyether diamines (eg., Jeffamines) and several different diamine extenders were carried out in the tetramethylene sulfone (TMS; bp 285 ℃) in replacing dimethyl solfoxide (DMSO) as the solvent in the polymerization. In our most desirable polymerization condition, the initial mixing temperature of 90 ℃ for 1 hours was initiated to start out the amination reaction, and that was followed by a subsequent step of vacuum distillation at about 140 ℃(under about 7×10-3mm of pressure) to drive off Phenol from the reaction mixture, in shifting the reaction equilibrium toward polyurea formation that lasted for 1-2 hours. After the distillation, the resulting polyurea was isolated by precipitation in water. TMS being a high boiling solvent could be separated from Phenol and water to recover > 90% after each runs. Through this rapid and efficient process, high yields and high molecular weights of polyurea were prepared with the recovery of the by-product and the solvent.