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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Valorisation de résidus d'exploitation d'argiles dans des applications industrielles et environnementales / Valuation of residues from the exploitation of clay for industrial and environmental applications

Armond Muzzi, Lydia 30 March 2007 (has links)
Les exploitations d’argiles kaoliniques réfractaire d’Água Limpa/Brésil et de kaolins de couchage de Rio Capim/Brésil laissent des résidus d’exploitation en très grands tonnages. Dans la perspective d’une valorisation plus complète assurant un développement durable de l’industrie extractive, on a envisagé d’utiliser ces argiles résiduelles dans la fabrication de zéolites. On a obtenue dès une durée de synthèse de 24h, une zéolite 4A très proche de sa définition théorique. Le rendement de synthèse est meilleur avec les produits de Rio Capim. Le volume nanoporeux de la zéolite 4A est inaccessible à l’azote mais accessible à la molécule d’eau. Les zéolites synthétisées ont été testées comme adsorbants cationiques pour le cuivre, le plomb, le cadmium, le zinc, le magnésium, potassium et mercure. La rétention a voisine 60% du remplissage théorique pour toutes les espèces testées, sauf pour le cuivre où elle dépasse la capacité théorique et pour le mercure où elle est très faible. / Working Kaolinic refractory clays from Água Limpa (Minas Gerais) and paper coating kaolins from Rio Capim (Pará) - Brazil throw over very large amounts of mining residues. With the outlook of a more complete beneficiation, aiming at a sustainable development of mineral industry, the use of these residual clays has been considered for manufacturing zeolites. For a synthesis time of only 24h, a zeolite 4A very close to its theoretical definition is obtained.The nano-porous volume of the zeolite 4A is inaccessible to nitrogen molecules, but accessible to water molecules. Synthesised zeolites have been tested as cationic adsorbents of Cu, Pb, Cd, Zn, Mg, K and Hg. The retention is better for materials derived from Rio Capim Kaolins. The retention is close to 60% of the theoretical completion of the exchange capacity in all cases, except for copper for which the retention exceeds the capacity, and mercury for which the retention is very low.
232

Nouvelles architectures de polymères à base de poly(2-méthyl-2-oxazoline) pour l'élaboration de nanoparticules destinées à la vectorisation / New architectures of polymers based on Poly(2-methyl-2-oxazoline) for the development of nanoparticles suitable for drug delivery

Le fer, Gaëlle 03 December 2015 (has links)
Ce sujet s'inscrit dans le domaine de la vectorisation de médicaments et de la nanomédecine, un domaine en pleine expansion. Les nanovecteurs destinés à la santé doivent être stables, non-toxiques et furtifs vis-à-vis du système immunitaire pour pouvoir circuler librement dans le sang. C'est pourquoi il est nécessaire d'élaborer des polymères pouvant former des nanoparticules possédant un caractère furtif. Le poly(acide lactique) (PLA) est un polyester hydrophobe et biodégradable couramment utilisé pour former des nanoparticules (NPs) capables d'encapsuler des composés apolaires. Le poly(2-méthyl-2-oxazoline) (PMeOx) est un polymère hydrophile, biocompatible et non toxique. Il peut être synthétisé par polymérisation cationique par ouverture de cycle (CROP), ce qui permet la préparation de polymères avec un bon contrôle de la masse molaire et une faible polymolécularité. Différentes architectures de copolymères PMeOx-co-PLA (di-,triblocs ou greffés) ont été développées en couplant la CROP et la chimie « clic ». Des NPs sont obtenues par nanoprécipitation de ces copolymères et caractérisées par un large éventail de techniques expérimentales dont, notamment, la diffusion dynamique de la lumière, la cryo-microscopie électronique à transmission, et la diffusion de neutrons aux petits angles. Ces techniques complémentaires ont permis de mettre en évidence l'obtention de NPs possédant des structures internes variées, telles que des polymersomes, des nanoparticules cœur-couronne ou multicouches. L'évaluation de la furtivité a été menée par l'étude de l'adsorption d'une protéine modèle, l'albumine de sérum bovin (BSA), sur la surface des nanoparticules. Enfin l'encapsulation de l'α-tocophérol et de quantum dots a démontré les nombreuses possibilités d'application de ces nouvelles NPs / This subject falls within the fields of drug delivery and nanomedecine, a topic of growing interest over the last years. Nanosystems dedicated to health must be stable, non-toxic and stealthy in the immune system in order to move freely in the blood. For this purpose, the design of elaborate polymers that can form stealthy nanoparticles is required. Poly(lactic acid) (PLA) is a hydrophobic and biodegradable polyester usually used to form nanoparticles able to encapsulate apolar compounds. Poly(2-methyl-2-oxazoline) (PMeOx) is a hydrophilic, biocompatible and non toxic polymer. PMeOx can be synthesized via cationic ring opening polymerization (CROP), which allows the design of polymers with a good control of the molecular weights and a low dispersity. Thus, in this context, we have developed several strategies to design different architectures of amphiphilic PMeOx-co-PLA copolymers such as di-, triblock or graft copolymers. Such strategies relied on the combined use of CROP and « click »chemistry ». Nanoparticles were obtained by nanoprecipitation, and characterized by a wide range of experimental techniques including dynamic light scattering, cryogenic transmission electron microscopy and small angle neutron scattering. These complementary approaches evidenced that nanoparticles could be obtained with a large variety of internal structure, such as polymersomes, core-shell or multilayer nanoparticles. The evaluation of the stealthiness was performed by considering the adsorption behavior of a model protein, bovin serum albumine (BSA), on the surface of the nanoparticles. The encapsulation of α-tocopherol and quantum dots demonstrated the numerous applicative possibilities offered by these new NPs
233

Le rôle des matériaux hybrides à base d'argiles dans la protection des œuvres d'art / The role of clay-based hybrid materials in the protection of works of art

Guillermin, David 08 October 2018 (has links)
Le travail de cette thèse s’intéresse à la stabilisation de plusieurs pigments hybrides.Une première partie traite de pigment obtenu à l’aide de l’acide carminique et de la montmorillonite, une argile commune. Un procédé d’inversion de la charge de surface de l’argile avec un polymère cationique, ou l’utilisation d’argiles modifiées par des polycations de Titane et d’Aluminium, permettent l’élaboration du pigment. La résistance des pigments à la photodégradation est alors testée. Les techniques couplées de RMN, DRX, FTIR et d’EPR permettent d’éclairer l’agencement des molécules organiques sur la surface minérale, et également de suivre le processus de dégradation du colorant.La description de pigments hybrides obtenus à l’aide d’un spiropyrane vient compléter l’étude. Le composé, qui joue le rôle de colorant organique, est ajouté à différentes matrices minérales : l’argile, modifiée ou non, ainsi que la co-précipitation avec des organo-silanes. Ces synthèses permettent d’observer la variété de couleur obtenus en mélangeant un même colorant avec plusieurs matrices de nature différente. / The work of this thesis focuses on the stabilization of several hybrid pigments.The first part deals with pigment obtained with carminic acid and montmorillonite, a common clay. A method of reversing the surface charge of the clay with a cationic polymer, or the use of clays modified with titanium and aluminum polycations, allows the elaboration of the pigment. The resistance of the pigments to photodegradation is then tested. Coupled NMR, DRX, FTIR and EPR techniques help to illuminate the arrangement of organic molecules on the mineral surface, and also to follow the dye degradation process.The description of hybrid pigments obtained using a spiropyran completes the study. The compound, which plays the role of organic dye, is added to different mineral matrices: clay, modified or not, and co-precipitation with organosilanes. These syntheses make it possible to observe the variety of color obtained by mixing the same dye with several matrices of different nature.
234

A Multifunctional Gelatin-Quaternary Ammonium Copolymer Exhibiting Superior Anionic Dye Adsorption for Efficient Emission Reduction in Leather Tanning Process

Xu, S. L., Xu, J., Lu, J. M., Li, T. D. 05 July 2019 (has links)
Leather wastewater is one of the most polluting industrial emissions. An in-situ, green, and innovative strategy that limits dye emissions is required to replace subsequent waste management. A novel cationic protein with a high quaternary ammonium degree was designed and synthesized. The results show that at concentrations ranging from 3 to 15 wt%, this cationic protein rapidly and completely adsorbs Direct Purple N and Acid Black 24 within 5 min. A remarkable efficiency in removing Acid Red 73, Acid Golden G, Acid Lake Blue A, Acid Green, and Acid Orange II, with >96% removal rates, was achieved. The cationic protein was most accurately represented by the pseudo-second-order kinetic model. Acid Orange II (2000 mg L-1) and 15 wt% cationic protein were used in an actual tanning process. The residual concentration of Acid Orange II in the wastewater was 23.1 mg L-1. These results reflect that the emission reduction targets have been effectively achieved.
235

Comparative Studies on Effect of Cationic and Anionic Finishing Agents on Surface Property of Finished Leather

Wajino, Mishamo, Dhathathreyan, A. D., Kanth, S. V. K. V. 05 July 2019 (has links)
Content: The present work attempts to analyze the surface and physical properties of leathers finished with cationic and anionic finishing chemicals. The contact angles of liquid drops resting on the leather surface have been used to evaluate surface energy, acidity, basicity components of the surface energy, polarity and work of adhesion. Contact angle values have been measured for chrome tanned and conventionally retanned crust and finished leather made by varying pigment and binder combinations. The wettability of finished leather has been correlated with the contact angle values: the higher the contact angle value the lesser is the wetting observed. Complete wetting can be obtained when the contact angle value is zero i.e. the drop of liquid spreads spontaneously on the surface and partial wetting is obtained when the contact angle value is in between 0and 900. Acrylic binders with different film forming properties, protein, polyurethane and butadiene binders have been combined to prepare different finish formulations.The results have been correlated with wet and dry rub fastness, finish adhesion, vamp flexing value, water vapour permeability and water proofness. It has been observed that when the surface of leather is coated with acrylic binder the contact angle value due to polar solvents(water) , non polar solvents(hexadecane) and moderately polar (DMSO) and methyl iodide show that as the thickness of coating increases, the contact angle value decreases for the base coat and sharply increases when top coat is applied. Top coats have the ability to increase the contact angle and they improve the performance properties of leather such as water resistance, fastness, finish adhesion etc. Cationic and anionic finishing formulations have been compared to study their effect in modifying the surface of finished leather based on contact angle values, wet and dry fastness to circular rubbing and water resistance. It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique. Take-Away: The effect of number of top coats on water contact angle value were determined ,and the experiment showed that the value were decreased gradually at the beginning of the coat because the top coats are water based so during the coating process the hydrophobic nature of the surface of chrome tanned leather have decreased. The experimental result from contact angle value showed that coating with pigments and binders have increased the contact angle value compared to the control crust. It has been observed that leathers finished using anionic finishing technique shows better wet rub fastness and water resistance effect compared to cationic finishing technique.
236

Synthèse et caractérisation de nouvellespolycétones aliphatiques à partir des cétènes / Synthesis and characterization of new aliphatic polyketones from ketenes

Wang, Hanbin 28 November 2013 (has links)
L’objectif de cette étude est de synthétiser de nouvelles architectures de polycétones aliphatiques à base de cétènes, possédant une température de fusion plus basse que le polydiméthylcétène, tout en conservant une température de dégradation élevée, afin d’élargir sa fenêtre de mise en œuvre.La synthèse du diméthylcétène et / ou de l’éthylcétène a été réalisée par pyrolyse de l’anhydride isobutyrique et/ou butyrique à 625°C sous 40 mbar. Un copolymère statistique a été d’abord synthétisé par copolymérisation entre le diméthylcétène et l’éthylcétène, par voie cationique à -78°C ; ensuite en utilisant un amorceur de Friedel-Craft, un polydiméthylcétène possédant une architecture étoilée a été obtenu. Ces deux polymères ont permis d’atteindre l’objectif initialement fixé : ils présentent un endotherme de fusion à environ 180°C, une bonne stabilité thermique similaire à celle du polydiméthylcétène (Tdégradation = 300°C), et en particulier, de très bonnes propriétés barrières à l’oxygène en milieu humide (jusqu’à 95% HR). / The objective of this study is to synthesize new architectures of ketene-based aliphaticpolyketones, having a lower melting temperature than polydimethylketene, while maintaining a high degradation temperature, in order to widen the processing window. The synthesis of dimethylketene and / or ethylketene was succeeded by the pyrolysis of isobutyric and / or butyric anhydride at 625°C under 40 mbar. A random copolymer was first synthesized by the cationic copolymerization between dimethylketene and ethylketene, at -78 ° C; then using a Friedel-Craft initiator, a star-shaped polydimethylketene was obtained. These two polymers have reached the initial goal of this study: they possess a melting endotherm at about 180°C, a good thermal stability similar to polydimethylketene (Tdegradation = 300°C), and in particular, excellent oxygen barrier properties in wet atmosphere (up to 95% RH).
237

Homo- and co-polymerization of disubstituted ketenes / Homo- et co-polymérisation de cétènes disubstitués

Jiang, Bo 29 March 2019 (has links)
Ce travail vise à synthétiser avec un rendement satisfaisant de nouvelles architectures de polymères à hautes performances, possédant une structure définie et une bonne fenêtre de transformation, sur la base de cétènes aliphatiques ou aromatiques disubstitués. Les synthèses de diméthylcétène (DMK), méthyléthylcétène (MEK), diéthylcétène (DEK), éthylphénylcétène (EPK) et diphénylcétène (DPK) ont été étudiées. Puis l’homo- et la copolymérisation de ces monomères avec différents amorceurs ont été étudiées. L’influence de l’encombrement stérique présent sur les cétènes influence grandement leur réactivité. Ainsi, des mélanges DMK / DEK et DMK / DPK ont été copolymérisés avec succès pour donner des polycétones dont les propriétés thermiques présentent une plage de transformation satisfaisante (Tf ~ 160°C et Td₅% ~ 260°C). Le DMK est le seul monomère conduisant à un homopolymère par voie cationique classique. Les tentatives de photopolymérisation cationique n’ont pas conduit à la polycétone attendue. L’utilisation de métallocènes conduit à la structure polyester. Des structures semi cristallines de très haute masse molaire et faible polydispersité ont été ainsi obtenues (Mn ~ 300000 g·mol−1, Ɖ < 2, Tg ~ 70°C, Tf ~ 200°C,Td₅% ~ 330°C). / This study is aimed at synthesizing with a satisfying yield new architectures of high performance polymers, possessing a neat structure and good processing window, on the basis of disubstituted aliphatic or aromatic ketenes. The synthesis of dimethylketene (DMK), methylethylketene (MEK), diethylketene (DEK), ethylphenylketene (EPK) and diphenylketene (DPK) were approached. Then homo and copolymerization of these monomers with different initiators were studied. The influence in steric hindrance of the monomers affected their reactivity. Thus copolymers based on DMK/ DEK and DMK / DPK were successfully obtained and afforded polyketones having good thermal properties and processing window (Tm ~ 160°C and Td₅% ~ 260°C). Only DMK homopolymerized by classic cationic initiation. Photopolymerization did not lead to any polymer formation. Initiation with metallocenes polymerized DMK to a crystallized polyester in an insertion chain growth mechanism. Excellent properties (Mn ~300 000 g·mol−1, Tg ~ 70°C, Tm ~ 200°C, Td₅% ~ 330°C) were obtained.
238

Kationické povrchově aktivní látky a hodnocení jejich vlastností / Cationic surface active compounds and evaluation of its properties

Pekařová, Kateřina January 2018 (has links)
Charles University Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Consultant: PharmDr. Jan Marek, Ph.D. Supervisor: doc. PharmDr. Veronika Nováková, Ph.D. Student: Kateřina Pekařová Title of Thesis: Cationic surface active compounds and evaluation of its properties Quaternary ammonium salts are used as surfactants in many branches of the food, pharmaceutical and chemical industries. The basic properties of these substances were studied in the thesis. The critical micellar concentration of the homologous series of five substances was determined using the conductometric method. The theory of declining critical micellar concentration with the increasing length of the side alkyl chain has been verified. The hydrolytic activity of two commonly used cationic surfactants benzalconium chloride and benzoxonium chloride for the decomposition of the organophosphorus pesticide fenitrothion was tested. For these two substances, the effect of pH and temperature changes was evaluated. The influence of tenside concentration was also monitored. Benzoxonium chloride at 50 řC and pH 11was found as the most effective hydrolytic catalyst for the decomposition of the organophosphorus pesticide fenitrothione.
239

Cationização de amidos de tuberosas tropicais para fabricação de papéis /

Horimoto, Lídia Kazumi, 1977- January 2006 (has links)
Orientador: Claudio Cabello / Banca: Claudio Angeli Sansígolo / Banca: José Luis Agapito Fernandes / Resumo: Apesar dos amidos serem quimicamente iguais, a organização e funcionalidade desses polímeros dependem das propriedades físico-químicas de cada fonte botânica. Esses amidos podem sofrer diferentes modificações com a finalidade de aperfeiçoar certas características para aplicações industriais específicas. Dentre os amidos modificados, os catiônicos são largamente utilizados na fabricação de papel/papelão a fim de aumentar sua resistência física e mecânica. Neste trabalho, amidos de mandioca, batata doce e mandioquinha salsa foram cationizados com o reagente 3-cloro-2-hidroxipropil-trimetilamônio que em meio alcalino reage com o amido tornando-o carregado positivamente.As amostras foram submetidas a diferentes tempos de reação (0,5 a 24 horas) e relação molar de hidróxido de sódio/monômero. Os melhores parâmetros encontrados para as amostras foram de 6 horas de reação e relação molar de 2,0 NaOH/monômero, que resultaram em maiores DS (grau de substituição) e rendimento percentual, determinados a partir do teor de nitrogênio presente em cada amostra. Em seguida os amidos catiônicos com os melhores parâmetros foram submetidos a diferentes tratamentos após a derivatização: etanol a 25%, etanol a 50% e água a temperatura de 35°C, para avaliar a interferência dos sais residuários no grau de substituição das amostras derivatizadas. A seguir essas amostras de amidos catiônicos de mandioca, batata doce e mandioquinha salsa foram aplicadas em folhas de papel, onde testes físicos-mecânicos como resistências ao rasgo, arrebentamento, tração, permeância ao ar entre outros foram realizados com a finalidade de verificar a influência da adição de diferentes tipos de amido. / Abstract: In spite of starches are chemically the same, the organization of biopolymers and the functionality of the starches depend on physical and chemical properties of each botanical source, which can undergo modifications with the purpose of improving certain characteristics for specific industrial applications. Among the modified starches, the cationic are widely used in the papermaking process in order to increase their physical and mechanical resistances. In this study, cassava, sweet potato and Peruvian carrot starches were cationized with 3-chloro-2-hydroxypropyltrimethylammonium choride reagent, that in a high pH reacts with starch become it positively loaded. The samples were submitted to different reaction time (0.5 to 24 hours) and the NaOH/monomer mole ratio. The best parameters found for the samples were of 6 hours of reaction time and 2.0 NaOH/monomer mole ratio, which resulted in larger degree of substitution (DS) and reaction efficiency (RE), determined by the 3 content of nitrogen present in each sample. Then the cationic starches with the best parameters were submitted to different treatments after derivatization: ethanol at 25%, ethanol at 50% and water at the temperature of 35°C, in order to evaluate the interference of the residual salts in the degree of substitution of the derivatized samples. In the sequence, these samples of cationic cassava, sweet potato and Peruvian carrot starches were applied in sheets of paper, where physical and mechanical tests such as air resistance, bursting strength, tensile strength, internal tearing resistance, among others, were performed with the purpose of verifying the influence of the addition of different types of starch. / Mestre
240

Combating Multidrug Resistant Reservoirs in HIV and Bacterial Pathogens

Moises Morales Padiilla (8766684) 21 June 2022 (has links)
<p>Multidrug resistance is a major issue in treatment and eradication of diseases. There are many mechanisms by which pathogens develop multi drug resistance. Here we focus on the ability of pathogens to evade drug treatment by establishing multi drug resistant reservoirs. In the case of HIV, the virus is able to evade drug treatment and forms both latent and active replicating reservoirs throughout the body. In the case of many bacterial pathogens, multidrug resistance reservoirs are established within mammalian cells, such as macrophages. Many classes of antibiotics are unable to penetrate mammalian cells, making intracellular bacteria difficult to clear</p><p>Previously our research group has developed a Trojan horse strategy to deliver antivirals to HIV cellular reservoirs. Ester based prodrug dimers of abacavir, a reverse transcriptase inhibitor, acted to both inhibit efflux transporters at the BBB and revert to the monomeric therapy in the reducing environments of the cell. Herein we present a new group of sterically hindered carbonate based disulfide linkers that shows improved payload delivery of abacavir and maintain the stability of prodrug molecules towards hydrolysis. We employed these linker molecules to synthesize prodrug dimers of the HIV latency reversal agent prostratin with the hope of targeting latent HIV reservoirs. Payload release studies as well as latency reversal experiments with a latently infected T-helper cell model confirmed that the prostratin carbonate homodimers (<b>ProS<sub>2</sub>Me<sub>2</sub></b> and <b>ProS<sub>2</sub>Me<sub>4</sub></b>) were able to revert to monomeric prostratin and reverse HIV latency. We next sought to synthesize a prostrain-protease inhibitor heterodimer. While our initial study of a prostratin-lopinavir heterodimer employing this linker strategy (<b>ProLpvS<sub>2</sub>Me<sub>2</sub></b>) did not show significant HIV latency reversal activity, we hope to expand our heterodimer studies to achieve dual therapeutic molecules that can both reverse HIV latency and deliver antivirals to HIV reservoirs.</p><p>In order to combat intracellular bacteria our group has focused on development of a novel class of cell penetrating peptides with intrinsic broad spectrum antimicrobial activity that are based on a repeating amino acid triad which forms a cationic amphiphilic polyproline helix (CAPH) scaffold. <sup> </sup>The first member of this class, <b>P14LRR</b>, exhibited clearance of intracellular bacteria and concentration dependent co-localization within mammalian cells. In efforts to optimize antimicrobial activity we have expanded the CAPHs library by adjusting the chain length between the proline backbone and the guanadinium groups of the cationic amino acids. The first peptide from this expanded library, <b>P14GAP</b> showed much greater cell penetration and antimicrobial activity against a wide range of pathogenic bacteria. However, <b>P14GAP</b> also showed greater toxicity towards mammalian cells, increased hemolysis, and greater membrane binding with mammalian cells as compared to <b>P14LRR</b>. Here we describe the design and synthesis of <b>P14GAP-C1</b>, which contains a methylene between the proline backbone and the guanadinium group. This new analogue decreased the hemolysis activity as compared to <b>P14GAP</b>, although similar membrane binding with mammalian cells was observed. This improvement in hemolysis activity and a slight improvement in cell viability may allow us to use higher concentrations of peptide to treat multidrug resistant bacterial infections.</p><p> </p>

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