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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.
81

Příjmy studentů a jejich zdanění

Vrtalová, Jana January 2008 (has links)
No description available.
82

Obtenção e propriedades de nanocompósitos borracha/argila a partir de látices de borrachas comerciais e borrachas epoxidadas

Azeredo, Luciane Klafke de January 2009 (has links)
Atualmente, nanocompósitos têm sido alvo de grande interesse científico e tecnológico. Além do negro-de-fumo e da sílica, materiais já consagrados como nanopartículas de reforço para uma grande variedade de borrachas, outras nanopartículas funcionalizadas têm sido o centro das atenções. Especialmente, nanopartículas bidimensionais (lâminas) e unidimensionais (tubos ou fibras, com destaque aos nanotubos de carbono) têm surgido como excelentes candidatos a partículas de reforço e apresentando efeito superior, já a frações volumétricas muito pequenas, bem inferiores às aplicadas tradicionalmente. Este trabalho tinha como objetivo investigar a epoxidação de polibutadieno e explorar a potencialidade de sílicas lamelares, especialmente filossilicatos 2:1, como agentes efetivos de reforço e barreira. Para alcançar este objetivo uma nova tecnologia de mistura e dispersão para a argila montmorilonita (MMT) foi desenvolvida. Baseia-se na Coagulação Dinâmica Contínua de Látex (“Continuous Dynamic Latex Coumpounding - CDLC"), na qual MMT é misturada ao látex de borracha e dispersa, adequadamente, em um regime especial de fluxo. O método vale-se do potencial que a água possui de enfraquecer os contatos interlamelares da MMT. Látices de NR, SBR, NBR e XNBR foram investigados. As condições de processo afetam a morfologia dos nanocompósitos, determinada por MET e DRX. A polaridade das borrachas influencia a dispersão da MMT e, consequentemente, as propriedades finais dos nanocompósitos. Comparando-se estes nanocompósitos com compósitos obtidos com negro-de-fumo, sílica precipitada ou mesmo com argila obtidos pelo processo da incorporação no estado fundido, os de CDLC exibem desempenho de reforço e uma resistência à permeação superiores, mesmo aplicando-se frações volumétricas de carga bem inferiores. Paralelamente, mostrou-se que é possível epoxidar polibutadieno comercial, a partir do meio reacional de polimerização, em ciclohexano, limitando-se em 30% em mol, face ao limite de solubilidade da borracha epoxidada no solvente. Nanocompósitos de polibutadieno epoxidado com argila foram preparados obtendose também propriedades melhores do que a borracha epoxidada pura. Com estes resultados, o presente trabalho mostra novas oportunidades para a obtenção de nanocompósitos elastoméricos. / Nowadays, polymer nanocomposites received an increasing scientific and technological interest. Besides carbon black and silica which have been proven reinforcing nanofillers for a large variety of rubber, other types of functional nanoparticles are coming in the center of this attention. Especially two-dimensional nanoparticles (platelets) and one-dimensional tubes or fibers (i.e. carbon nanotubes) are serious candidates to determine large reinforcing effects as for less volume fraction than traditional fillers. This work had as objective to investigate the epoxidation of polybutadiene and to explore the potential of layered silicas, especially 2:1 phylosilicates, as reinforcing agents and effective permeation barriers. In order to achieve this objective a new mixing and dispersion technology for montmorillonite (MMT) was developed in this work. This technology is based on “Continuous Dynamic Latex Compounding” (CDLC), in which MMT is mixed with a rubber latex and well dispersed in particular flow regime. Due to the coagulation of the latex, it was possible to prepare superior types of rubber nanocomposites. One important fact is that the interlayer contacts in the MMT tactoids are weakened by swelling in water. Latices of NR, SBR, NBR and XNBR have been used. It is shown that the process conditions affect the phase morphology of nanocomposites characterized by transmission electron microscopy and x-ray diffraction. The polarity of rubbers influence the dispersion of MMT as well as the properties of the resulting nanocomposites. Compared to nanocomposites filled with carbon black, precipitated silica, or those obtained by melt mixing, nanocomposites by CDLC demonstrate a better reinforcement and permeation resistance at far less volume fractions. The epoxidation of commercial polybutadiene with high cis content, from its commercial solution (cyclohexan), was possible, but due to the solubility of epoxidized polymer, the system coagulated and gelated when a epoxidation degree of 30 mol% was reached, independent of the initial concentrations of reagents. Nanocomposites from polybutadiene, 14 and 19 mol% epoxidation degree, and organoclay were prepared. The mechanical and barrier properties had been superior to those compositions of epoxidized polybutadiene without clay. By this achievements, the present work demonstrate new opportunities for polymeric nanocomposites.
83

ProteÃnas isoladas do lÃtex de Himatanthus drasticus (MART.) Plumel apocynaceae reduzem a resposta inflamatÃria e nociceptiva na artrite induzida por zymosan em camundongos / Protein isolated from Himatanthus drasticus LATEX ( MART . ) Plumel apocynaceae reduce inflammatory response and nociceptive in arthritis induced by zymosan in mice

Luana David do Carmo 19 January 2015 (has links)
CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Himatanthus drasticus à uma planta laticÃfera pertencente à famÃlia Apocynaceae encontrada na AmÃrica do Sul e conhecida popularmente como janaguba. Seu lÃtex à conhecido como âleite de janagubaâ e apresenta vÃrias atividades farmacolÃgicas. O presente trabalho teve como objetivo estudar o efeito das proteÃnas isoladas do lÃtex de Himatanthus drasticus (HdLP) em modelo de artrite experimental induzida por zymosan (Zy). A artrite foi induzida em camundongos machos swiss (n=6) atravÃs da administraÃÃo de 0,1 mg Zy i.a. Os animais foram tratados com HdLP (5 e 50 mg/kg i.v.) ou Salina i.v. 1 hora apÃs o Zy e com HdLP (50 mg/kg v.o.) ou Dexametasona (2 mg/kg s.c.) 1 hora antes do Zy. Seis horas apÃs a induÃÃo os animais foram eutanasiados, foi realizada a lavagem da articulaÃÃo e o lavado articular coletado para avaliaÃÃo do efeito de HdLP sobre a migraÃÃo de leucÃcitos, atividade da mieloperoxidase (MPO) e liberaÃÃo de mediadores inflamatÃrios (NO, TNF-&#945;, IL-1&#946;, IL-6 e IL-10). O edema foi avaliado pela mediÃÃo do diÃmetro transversal da articulaÃÃo e pela avaliaÃÃo da permeabilidade vascular. AlÃm disso, foi avaliado o efeito de HdLP sobre processo inflamatÃrio na membrana sinovial e sobre a hipernocicepÃÃo mecÃnica utilizando uma versÃo eletrÃnica (VonFrey). Para as anÃlises estatÃsticas foi utilizado o teste ANOVA/Bonferroni ou Kruskal Wallis/Dunns; p <0,05 foi considerado significante. Este estudo foi aprovado pela ComissÃo de Ãtica em Pesquisas com Animais da UFC - CEPA (38/14). HdLP 50 mg/kg i.v. apresentou uma diminuiÃÃo significativa na contagem de leucÃcitos, nos nÃveis de MPO e na liberaÃÃo de medidores inflamatÃrios (NO, IL-1&#946;, e IL-6). TambÃm foi observado uma diminuiÃÃo do edema e no dano à membrana sinovial. Na hipernocicepÃÃo mecÃnica os grupos (HdLP 50 mg/kg i.v. e 50 mg/kg v.o.) apresentaram um aumento no limiar nociceptivo. HdLP apresenta atividade antinociceptiva e anti-inflamatÃria no modelo de artrite induzida por Zy. O efeito parece estar relacionado com a diminuiÃÃo da migraÃÃo de neutrÃfilos e da liberaÃÃo de mediadores inflamatÃrios, reduzindo o dano na membrana sinovial e a hipernocicepÃÃo. / Himatanthus drasticus is a laticiferous plant of the family Apocynaceae found in South America and popularly known as janaguba. Your latex is known as "janaguba milk" and has several pharmacological activities. This work aimed to study the effect of isolated proteins from Himatanthus drasticus latex (HdLP) zymosan (Zy) induced arthritis. Arthritis was induced in male Swiss mice (n = 6) by administering 0.1 mg Zy intra-articular. The animals were treated with HdLP (5 and 50 mg/kg i.v.) or Saline i.v. 1 hour after the Zy and HdLP (50 mg/kg v.o.) or Dexamethasone (2 mg/kg s.c.) 1 hour before Zy. After six hours of induction the animals were euthanized, the joint washing carried, and collected for leukocyte count, determination of the myeloperoxidase (MPO) activity and inflammatory mediators (NO, TNF-&#945;, IL-1&#946;, IL-6 and IL-10). The edema was evaluated by measuring the diameter articular and the vascular permeabilitym through extravasation. In addition, we evaluated the effect of HdLP on synovial inflammation as well the mechanical hypernociception. For statistical analysis we used the ANOVA/Bonferroni or Kruskal Wallis/Dunns; p <0.05 considered significant. This study was approved by the Ethics Committee on Animal Research of the UFC - CEPA (38/14). HdLP (50 mg/kg i.v.) a significant decrease on the leukocyte count in MPO activity and levels (NO, IL-1&#946;, and IL-6). It was also observed a decrease in swelling and damage to the synovial membrane. The nociceptive threshold was increased by HdLP 50 mg/kg i.v. and 50 mg/kg v.o. HdLP has antinociceptive and anti-inflammatory activity in the model of arthritis induced by Zy. The effect seems to be related to the decreased migration of neutrophils and the release of inflammatory mediators, reducing damage to the synovial membrane and hypernociception.
84

Estabilização de latex polimericos por sorção de solventes organicos

Cardoso, Atilio de Oliveira 23 July 2018 (has links)
Orientador: Fernando Galembeck / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-07-23T16:56:55Z (GMT). No. of bitstreams: 1 Cardoso_AtiliodeOliveira_M.pdf: 3590694 bytes, checksum: 019518a9cec37131bcf337e2ada11d63 (MD5) Previous issue date: 1998 / Mestrado
85

Ontogenese dos laticiferos continuos

Milanez, Fernando Romano 14 July 2018 (has links)
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-07-14T16:16:45Z (GMT). No. of bitstreams: 1 Milanez_FernandoRomano_D.pdf: 10497219 bytes, checksum: ae02cbd588e415dcdc0c8615d7ed4e3c (MD5) Previous issue date: 1974 / Resumo: Não informado / Abstract: Not informed / Doutorado / Doutor em Ciências
86

Extração, purificação, imobilização, estudo cinetico e calorimetrico das enzimas proteoliticas presentes no latex do mamoeiro

Basilio, Carmelita Aparecida 20 July 2018 (has links)
Orientador: Pedro L. O. Volpe / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-07-20T13:03:55Z (GMT). No. of bitstreams: 1 Basilio_CarmelitaAparecida_D.pdf: 8571891 bytes, checksum: 0a50639f606b123c07a704e885789a2f (MD5) Previous issue date: 1994 / Doutorado
87

Caracterização de latex poliestirenicos por centrifugação em gradiente de densidade

Moita Neto, Jose Machado 19 July 2018 (has links)
Orientador : Fernando Galembeck / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-07-19T10:21:19Z (GMT). No. of bitstreams: 1 MoitaNeto_JoseMachado_D.pdf: 6382667 bytes, checksum: 7007522baf1d0e7bbf6a17729b7fb734 (MD5) Previous issue date: 1994 / Doutorado
88

Film formation from latexes.

El-Aasser, Mohamed S. January 1971 (has links)
No description available.
89

Studies on porphyrin-based nanorods for artificial light harvesting applications

Mongwaketsi, Nametso Precious 04 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The work presented in this thesis throws light on the supramolecular approach in exploration of bi-porphyrin nanorods system wherein self-assembly plays an important role. Porphyrin based nanorods were synthesized via self-assembly of meso-tetrakis (4-phenylsulfonicacid) porphyrin dihydrochloride and Sn (IV) tetrakis (4-pyridyl) porphyrin. Understanding the sizes and growth mechanism of the porphyrin nanorods by self-assembly and molecular recognition is essential for their successful implementation in nanodevices. Spectroscopic and microscopic studies were carried out to investigate the effect that time, concentration and solvents have on the fabrication of the porphyrin nanorods by ionic self- assembly. This study demonstrated that aggregates of the di- acid form of meso-tetrakis (4-phenylsulfonic acid) porphyrin dihydrochloride and Sn (IV) tetrakis (4-pyridyl) porphyrin resulted in porphyrin nanorods with diameters between 20 nm and 60 nm, and μm in lengths. Enhanced optical properties illustrated the potential for slightly modifying the method of synthesis to influence the physical and optical properties of porphyrin nanorods. The porphyrin nanorods reflectance data demonstrated that these structures are good absorbers of light and therefore could potentially be used to harvest light. The nonlinear optical (NLO) properties of the porphyrin nanorods were investigated for the first time in this study by second and third harmonic generation techniques. Such study was influenced by the fact that porphyrins have great thermal stability and extended -conjugated macro cyclic ring which give them large nonlinear optical effects. The NLO results showed that the porphyrin nanorods may have many potential uses in photonic applications due to larger third order nonlinear susceptibility. Single molecule spectroscopy was also used to investigate the dynamics of intermolecular and intramolecular processes. Porphyrin nanorods were incorporated into polymer matrices to achieve an arrangement where they can be directly used as a device. The assembly of porphyrin nanorods on track-etched membranes was achieved through altering the surface charge of the respective membranes. Porphyrin nanorods-polymer composites were produced using latex technology and electrospinning techniques. The fibres were characterized with respect to morphology and optical properties. / AFRIKAANSE OPSOMMING: Die werk wat in hierdie tesis beskryf word werp lig op die supramolekulêre benadering in die ondersoek van bi-porfirien nano-silinders waarin self-versameling ‘n belangrike rol speel. Porifirien nano-silinders was voorberei via self-versameling van meso-tetrakis(4-feniel sulfoonsuur) porfirien dihidrochloried en Sn (IV) terakis (4-piridiel) porfirien. Dit is belangrik om die meganismes wat verband hou met die groei en grootte van die nano-silinder struktuur te ondersoek. Dit het ‘n invloed op die self-versameling asook die uiteindelike toepassing. Spectroskopiese en mikroskopiese studies was uitgevoer om die effek van tyd, konsentrasie en oplosmiddel op die selfversamelling te bestudeer. Die studie dui daarop dat bondels van die disuur vorm van meso-tetrakis(4-feniel sulfoonsuur) porfirien dihidrochloried en Sn (IV) terakis (4-piridiel) porfirien het gelei tot porfirien nano-silinders met lengtes tussen 20 nm en 60 nm asook in die mikro meter skaal. Verhoogde optiese eienskappe het die potensiaal om effense veranderinge in die metode om die nano-silinders voor te berei om sodoende ‘n groter invloed op die fisiese en optiese einskappe te hê. Die reflektansie data wys dat hierdie strukture goeie absorbsies van lig toon en daarom geskik sal wees om lig te stoor. Die nie-liniêre optisie (NLO) eienskappe van die profirien nano-silinders was vir die eerste keer ondersoek deur middel van tweed en derde hormoniese generasie tegnieke. Hierdie studie was beïnvloed deur die feit dat porfiriene goeie stabiliteit by hoë temperatuur en ‘n verlengde -gekonjugeerde makro-sikliese ring bevat wat dan groot nie-liniêre optiese effekte gee. Die NLO resultate wys dat die profirien nano-silinders groot potensiaal het in die gebruik van fotoniese toepassings as gevolg van derde orde nie-liniêre vatbaarheid. Enkel molekuul spektroskopie was ook gebruik om die dinamika van intermolekulêre en intramolekulêre prosesse te ondersoek. Porfirien nano-silinders was geïnkorporeer in polimeer matrikse om ‘n eweredige verspreiding te verkry en om direk as ‘n toestel te gebruik. Die versameling van porfirien nano-silinders op baan-ingeëtse membrane was bereik deur die verandering in oppervlak lading van die membrane. Porfirien nano-silinder / polimeer samestellings was verkry deur lateks tegnologie en elektrospin tegnieke. Die vesels was gekarakteriseer in terme van morfologie en optiese eienskappe.
90

Synthesis, characterization and evaluation of macromonomers used to prepare rheology modifiers for possible improvement of the pigmentation of decorative coatings

Sprong, Ewan 03 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: There is a decrease in viscosity when universal colorants are added to the latex coating system. Two different routes were taken to investigate this problem. The first was to investigate the thickening mechanism of the coating system. For this purpose six different hydrophobically modified alkali-soluble (HASE) thickeners were synthesized. The second was to compile new color concentrate formulations. The HASE thickeners consist of acrylic acid and a second associative monomer. The associative monomer (macromonomer) contained a long chain hydrophilic segment, terminated with a hydrophobic group. The hydrophilic segment consists of polyethoxylation, situated between the ethylenic unsaturation at one end of the molecule and the terminal hydrophobe at the other end. Three different macromonomers were prepared by coupling the hydroxyl end groups of three commercially available nonionic surfactants with either acrylic acid or acryloyl chloride. A much higher yield of macromonomer was obtained when the nonionic surfactants were reacted with the acryloyl chloride. Six HASE thickeners were synthesized by means of free radical addition polymerization. The first three HASE thickeners had the same backbone length and each thickener containing one type of hydrophobic macromonmer. The hydrophobic macromonomers differed in the length of their repeating oxyethylene units. They contained either 20, 50 or 100 oxyethylene units. The next three HASE thickeners were very similar to the first three except that 5% of the acrylic acid in the backbone was substituted with a second, phosphated, macromonomer, meaning that these thickeners each contained two types of macromonomers. These thickeners were then introduced into a standard latex coating formulation. By comparing the rheology profiles of the different coatings it was possible to determine the thickening efficiencies of the different thickeners. These coatings were also evaluated for their viscosity stability when tinted with a universal colorant. The HASE thickeners containing the second phosphated macromonomer showed superior thickening efficiency. All six coatings showed excellent stability on tinting with a universal colorant. Following the second route of investigation, eight universal colorant formulations consisting of only one polymeric dispersant in each of the formulations as sole wetting and dispersing additive were made up. A commercially available universal colorant was used as standard against which the new formulations were tested. The colorants were tested for color strength, their compatibility with the different coating groups, and the rheology profiles of the tinted vs. untinted coating systems. The two colorant formulations that contained EFKA 4550 as the polymeric dispersant performed very well in all the coating groups. / AFRIKAANSE OPSOMMING: Daar is 'n afname in viskositeit wanneer universele kleurstowwe by die lateks-bedekkingsisteem gevoeg word. Twee verskillende roetes is gevolg om die probleem te ondersoek. Die eerste was om die verdikkingsmeganisme van die bedekkingsisteem te ondersoek. Vir die doel is ses verskillende hidrofobies gemodifiseerde alkali-oplosbare (HASE)-verdikkers gesintetiseer. Die tweede was om nuwe kleurkonsentraatformulerings saam te stel. Die HASE-verdikkers bestaan uit akrielsuur en 'n tweede assosiatiewe monomeer. Die assosiatiewe monomeer (makromonomeer) bevat 'n langketting-hidrofiliese segment, met 'n hidrofobiese endgroep. Die hidrofiliese segment bestaan uit herhalende oksi-etileen eenhede, tussen die etileniese onversadigdheid aan die een punt van die molekuul en die hidrofobiese endgroep aan die ander punt. Drie verskillende makromonomere is voorberei deur die koppeling van die hidroksiel-endgroepe van drie kommersieel beskikbare anioniese sepe met akrielsuur of akriloielchloried. 'n Baie hoër opbrengs van makromonomere is verkry toe die anioniese sepe met die akriloielchloried gereageer is. Ses HASE-verdikkers is gesintetiseer deur middel van vrye radikaal addisie polimerisasie. Die eerste drie HASE-verdikkers het dieselfde ruggraatlengte en elke verdikker bevat een tipe hidrofobiese makromonomeer. Die hidrofobiese makromonomere verskil in die lengte van hul herhalende oksi-etileen eenhede. Die hidrofobiese makromonomere bevat of 20, 50 of 100 oksietileen eenhede. Die volgende drie HASE-verdikkers stem baie ooreen met die eerste drie behalwe dat 5% van die akrielsuur in die ruggraat vervang is deur 'n tweede, fosfaatbevattende makromonomeer, wat beteken dat hierdie verdikkers elk twee tipes makromonomere bevat. Hierdie verdikkers is in 'n standaard lateks bedekking formulering gevoeg. Deur die vergelyking van die reologie profiele van die verskillende bedekkings was dit moontlik om die verdikkings effektiwitiet van die verskillende verdikkers te bepaal. Hierdie bedekkings is ook geevalueer vir hulle viskositeits stabiliteit as dit met 'n universele kleurstof gekleur word. Die HASE-verdikkers wat die tweede fosfaatbevattende makromonomeer bevat, het uitstekende verdikkings effektiwiteit getoon. Al ses bedekkings het uitstekende stabiliteit getoon tydens kleuring met 'n universele kleurstof. Deur die tweede roete van ondersoek te volg, is agt universele kleurstof formulerings wat bestaan uit slegs een polimeriese dispergeermiddel opgemaak. 'n Kommersieel beskikbare universele kleurstof is gebruik as standaard waarteenoor die nuwe formulerings getoets is. Die kleurstowwe is getoets vir kleursterkte, hul verenigbaarheid met die verskillende bedekkingsgroepe, en die reologie profiele van die gekleurde teenoor die ongekleurde bedekkingsisteme. Die twee kleurstof formulerings wat EFKA 4550 as die polimeriese dispergeer middel bevat, het baie goed gevaar in al die bedekkingsgroepe.

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