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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.
101

Síntese, caracterização e estudo do processo de adsorção de filmes de nanocompósitos de PVDF/argila / Synthesis, characterization and study of the process of adsorption of movies of nanocomposites PVDF/clay

Faria, Luiz Affonso Souza [UNESP] 18 December 2015 (has links)
Submitted by Luiz Affonso Souza Faria (souzaffonso@gmail.com) on 2016-06-17T21:01:59Z No. of bitstreams: 1 Defesa_biblioteca_Luiz_Affonso.pdf: 3123195 bytes, checksum: 16931777d473b94f7e8908c291644f6a (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-21T16:45:54Z (GMT) No. of bitstreams: 1 faria_las_me_ilha.pdf: 3123195 bytes, checksum: 16931777d473b94f7e8908c291644f6a (MD5) / Made available in DSpace on 2016-06-21T16:45:54Z (GMT). No. of bitstreams: 1 faria_las_me_ilha.pdf: 3123195 bytes, checksum: 16931777d473b94f7e8908c291644f6a (MD5) Previous issue date: 2015-12-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho consiste na preparação de filmes por meio de soluções contendo poli(fluoreto de vinilideno) – PVDF dissolvido em N, N Dimetilformamida (DMF) e material cerâmico como argila montmorilonita (K10), pelo método de Fiação por Sopro em Solução (FSS). As partículas de argila foram introduzidas como um aditivo para filmes de PVDF. Os filmes obtidos foram caracterizados por Microscopia Eletrônica de Varredura (MEV), que mostrou que a introdução da argila ao PDVF não afetou a sua morfologia, as mesmas se apresentaram aleatoriamente dispersas, homogêneas, e sem uma direção preferencial. Os resultados obtidos por Difratometria de Raio – X (DRX) mostrou pico mais intenso em 2θ = 20,8o característico da fase β polar e um ombro em 2θ = 18,8o característico da fase cristalina α do PVDF, porém para argila K10 apresenta um pico em 2θ = 8,9o correspondendo a um espaçamento basal de 9,9 Ǻ e outros picos correspondentes ao mineral muscovita e também referente ao quartzo. Análises termogravimétricas (TGA) revelaram que o PVDF possui um comportamento estável até próximo de 420°C, para argila a perda ocorre abaixo de 120°C devido às moléculas de água e também a desidroxilação argilomineral. A determinação do pHPCZ é o ponto onde a curva experimental de pHfinal x pHinicial encontra a reta correspondente ao pHfinal = pHinicial, assim o ponto obtido foi de 6,57, pois neste ponto a carga da superfície do material é zero. A Espectrometria de Absorção Atômica de Alta Resolução com fonte contínua (HR – CS AAS - do inglês: High - resolution Continuum Source Atomic Absorption Spectrometry) foi utilizada para determinar a concentração dos íons metálicos de Pb e Cu nos estudos de adsorção. As concentrações das soluções em contato com o material PVDF/Argila k10 foram medidas para a determinação da capacidade de adsorção através de isotermas com diferentes concentrações molares dos íons metálicos. No estudo de adsorção de Pb e Cu, ambos apresentaram capacidade máxima de adsorção pelo adsorvente (Nfmáx) foram satisfatórios, no qual os valores Nfmáx (teórico) estiveram próximos do Nf (experimental) de 0,1804 x 10-5 para o Cu e de 0,2416 x 10-5 para o Pb e que o tempo necessário para que o equilíbrio fosse atingido é de 10h. O estudo cinético revelou que os dados experimentais no meio aquoso e seus respectivos íons metálicos podem ser descrito pelo modelo pseudo - segunda - ordem com um coeficiente de determinação (R²) de 0,9992 para o Pb e 0,9994 para o Cu. / This work is the preparation of films by means of solutions containing poly (vinylidene fluoride) - PVDF dissolved in N, N-dimethyl formamide (DMF) and ceramic material such as montmorillonite clay (K10), the wiring method Blow solution (FSS). The clay particles were introduced as an additive to PVDF films. The films were characterized by scanning electron microscopy (MEV), which showed that the introduction of the clay PDVF did not affect their morphology, they performed randomly dispersed, homogeneous, and without a preferred direction. The results obtained by diffraction of ray - X (XRD) showed the most intense peak at 2θ = 20,8o characteristic of β-polar phase and one shoulder at 2θ = 18,8o characteristic of the α crystal phase of PVDF, but to present a K10 clay peak at 2θ = 8,9o corresponding to a basal spacing of 9.9 Ǻ and other peaks corresponding to the mineral muscovite and also related to quartz. Thermogravimetric Analysis (TGA) revealed that the PVDF has a stable performance up to near 420°C to clay loss occurs below 120°C due to water molecules and also clay mineral dehydroxylation. The determination of pHPCZ is the point where the experimental curve pHend x pHearly finds the line corresponding to the pHend = pHearly therefore the point obtained was 6.57 because at this point the material surface charge is zero. The High - resolution Continuum Source Atomic Absorption Spectrometry (HR - CS ASS) it was used to determine the concentration of metallic Pb and Cu ion in the adsorption studies. The concentrations of the solutions in contact with the PVDF/K10 clay material were measured to determine the adsorption capacity through isotherms with different molar concentrations of metal ions. In the study of Pb and Cu adsorption, both showed adsorption capacity of the adsorbent (Nf máx) were satisfactory in which values Nf máx (theoretical) were close to Nf (experimental) from 0.1804 x 10-5 to Cu and from 0.2416 x 10-5 to Pb and the time required for equilibrium to be reached is 10h. The kinetic study showed that the experimental data in the aqueous medium and the respective metal ions can be described by the model pseudo - second - order with a coefficient of determination (R²) from 0.9992 for Pb and 0.9994 for Cu.
102

Síntese, caracterização e estudo do processo de adsorção de filmes de nanocompósitos de PVDF/argila /

Faria, Luiz Affonso Souza January 2015 (has links)
Orientador: Mirian Cristina dos Santos / Resumo: Este trabalho consiste na preparação de filmes por meio de soluções contendo poli(fluoreto de vinilideno) – PVDF dissolvido em N, N Dimetilformamida (DMF) e material cerâmico como argila montmorilonita (K10), pelo método de Fiação por Sopro em Solução (FSS). As partículas de argila foram introduzidas como um aditivo para filmes de PVDF. Os filmes obtidos foram caracterizados por Microscopia Eletrônica de Varredura (MEV), que mostrou que a introdução da argila ao PDVF não afetou a sua morfologia, as mesmas se apresentaram aleatoriamente dispersas, homogêneas, e sem uma direção preferencial. Os resultados obtidos por Difratometria de Raio – X (DRX) mostrou pico mais intenso em 2θ = 20,8o característico da fase β polar e um ombro em 2θ = 18,8o característico da fase cristalina α do PVDF, porém para argila K10 apresenta um pico em 2θ = 8,9o correspondendo a um espaçamento basal de 9,9 Ǻ e outros picos correspondentes ao mineral muscovita e também referente ao quartzo. Análises termogravimétricas (TGA) revelaram que o PVDF possui um comportamento estável até próximo de 420°C, para argila a perda ocorre abaixo de 120°C devido às moléculas de água e também a desidroxilação argilomineral. A determinação do pHPCZ é o ponto onde a curva experimental de pHfinal x pHinicial encontra a reta correspondente ao pHfinal = pHinicial, assim o ponto obtido foi de 6,57, pois neste ponto a carga da superfície do material é zero. A Espectrometria de Absorção Atômica de Alta Resolução com fonte con... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This work is the preparation of films by means of solutions containing poly (vinylidene fluoride) - PVDF dissolved in N, N-dimethyl formamide (DMF) and ceramic material such as montmorillonite clay (K10), the wiring method Blow solution (FSS). The clay particles were introduced as an additive to PVDF films. The films were characterized by scanning electron microscopy (MEV), which showed that the introduction of the clay PDVF did not affect their morphology, they performed randomly dispersed, homogeneous, and without a preferred direction. The results obtained by diffraction of ray - X (XRD) showed the most intense peak at 2θ = 20,8o characteristic of β-polar phase and one shoulder at 2θ = 18,8o characteristic of the α crystal phase of PVDF, but to present a K10 clay peak at 2θ = 8,9o corresponding to a basal spacing of 9.9 Ǻ and other peaks corresponding to the mineral muscovite and also related to quartz. Thermogravimetric Analysis (TGA) revealed that the PVDF has a stable performance up to near 420°C to clay loss occurs below 120°C due to water molecules and also clay mineral dehydroxylation. The determination of pHPCZ is the point where the experimental curve pHend x pHearly finds the line corresponding to the pHend = pHearly therefore the point obtained was 6.57 because at this point the material surface charge is zero. The High - resolution Continuum Source Atomic Absorption Spectrometry (HR - CS ASS) it was used to determine the concentration of metallic Pb and Cu ion i... (Complete abstract click electronic access below) / Mestre
103

Multiplicidade de soluções para problemas elípticos singulares envolvendo crescimento crítico

Xavier de Souza, Manassés 31 January 2010 (has links)
Made available in DSpace on 2014-06-12T18:28:40Z (GMT). No. of bitstreams: 2 arquivo637_1.pdf: 901737 bytes, checksum: 0ab7823a865239707eb0c5143fe95131 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Usando métodos variacionais e o método de sub e super soluções, neste trabalho estudamos existência e multiplicidade de soluções para algumas classes de problemas elípticos singulares envolvendo crescimento crítico do tipo Trudinger-Moser. Tratamos também de uma generalização para desigualdade de Trudinger-Moser e a existência de uma função extremal. A prova deste resultado é baseada na análise de blow-up
104

Cauchy problem for the incompressible Navier-Stokes equation with an external force and Gevrey smoothing effect for the Prandtl equation / Problème de Cauchy pour les équations de Navier-Stokes en présence d'une force extérieure et l'effet régularisant Gevrey de l'équation de Prandtl

Wu, Di 06 November 2017 (has links)
Dans cette thèse on étudie des équations de la mécanique des fluides. On considère deux modèles : les équations de Navier-Stokes équation dans R3 en présence d'une force extérieure, et l'équation de Prandtl dans le demi plan. Pour le système de Navier-Stokes, on s'intéresse à l'existence locale en temps, l'unicité, le comportement global en temps et des critères d'explosion. Pour l'équation de Prandtl dans le demi plan, on s'intéresse à la régularité Gevrey. Le manuscrit est constitué de quatre chapitres. Dans le premier chapitre, on introduit quelques concepts de base sur les équations de la mécanique des fluides et on rappelle le sens physique des deux modèles précédents ainsi que quelques résultats mathématiques. Ensuite on énonce brièvement nos principaux résultats et les motivations. Enfin on mentionne quelques problèmes ouverts. Le second chapitre est consacré au problème de Cauchy pour les équations de Navier-Stokes dans R3 en présence d'une petite force extérieure, peu régulière. On démontre l'existence locale en temps pour ce système pour toute donnée initiale appartenant à un espace de Besov critique avec régularité négative. On obtient de plus trois résultats d'unicité pour ces solutions. Enfin on étudie le comportement en temps grand et la stabilité de solutions a priori globales. Le troisième chapitre traite d'un critère d'explosion pour les équations de Navier-Stokes avec une force extérieure indépendante du temps. On met en place une décomposition en profils pour les équations de Navier-Stokes forcées. Cette décomposition permet de faire un lien entre les équations forcées et non forcées, ce qui permet de traduire une information d'explosion de la solution non forcée vers la solution forcée. Dans le Chapitre 4 on étudie l'effet régularisant Gevrey de la solution locale en temps de l'équation de Prandtl dans le demi plan. Il est bien connu que l'équation de couche limite de Prandtl est instable pour des données initiales générales, et bien posée dans des espaces de Sobolev pour des données initiales monotones. Sous une hypothèse de monotonie de la vitesse tangentielle du flot, on démontre la régularité Gevrey pour la solution de l'équation de Prandtl dans le demi plan pour des données initiales dans un espace de Sobolev. / This thesis deals with equations of fluid dynamics. We consider the following two models: one is the Navier-Stokes equation in R3 with an external force, the other one is the Prandtl equation on the half plane. For the Navier-Stokes system, we focus on the local in time existence, uniqueness, long-time behavior and blowup criterion. For the Prandtl equation on the half-plane, we consider the Gevrey regularity. This thesis consists in four chapters. In the first chapter, we introduce some background on equations of fluid dynamics and recall the physical meaning of the above two models as well as some well-known mathematical results. Next, we state our main results and motivations briefly. At last we mention some open problems. The second chapter is devoted to the Cauchy problem for the Navier-Stokes equation equipped with a small rough external force in R3. We show the local in time existence for this system for any initial data belonging to a critical Besov space with negative regularity. Moreover we obtain three kinds of uniqueness results for the above solutions. Finally, we study the long-time behavior and stability of priori global solutions.The third chapter deals with a blow-up criterion for the Navier-Stokes equation with a time independent external force. We develop a profile decomposition for the forced Navier-Stokes equation. The decomposition enables us to connect the forced and the unforced equations, which provides the blow-up information from the unforced solution to the forced solution. In Chapter 4, we study the Gevrey smoothing effect of the local in time solution to the Prandtl equation in the half plane. It is well-known that the Prandtl boundary layer equation is unstable for general initial data, and is well-posed in Sobolev spaces for monotonic initial data. Under a monotonicity assumption on the tangential velocity of the outflow, we prove Gevrey regularity for the solution to Prandtl equation in the half plane with initial data belonging to some Sobolev space.
105

Achieving controllable continuous variable damping within a semi-active hydro-pneumatic suspension system

De Wet, Benjamin January 2020 (has links)
The compromise between ride comfort and handling for a passive suspension system is a well-known and often researched problem. Semi-active suspension systems offer significant improvements to this compromise. One example of a semi-active system, that can change both spring and damper characteristics between two discrete values is the 4-state semi-active hydro-pneumatic suspension system. This system can switch between a ”ride comfort mode” (soft spring and low damping) and a ”handling mode” (stiff spring and high damping) within 100ms, improving both ride comfort and handling. The discrete 4S4 could be improved upon further by adding continuous variable damping. Work on this topic showed great promise but also posed its challenges in achieving this in a safe and controllable manner. In order to make continuous variable damping a reality a new configuration for the 4S4 is proposed. This new configuration incorporates a blow-off damper in parallel with a proportional flow control valve. The system ensures that, in the highly non-linear closing region of the proportional flow control valve, adequate damping for handling is maintained and uncontrollable peak pressure differences are avoided. Experimental work conducted showed that the system was capable of achieving the required spring and variable damping characteristics in a safe and controllable manner. The experimental data was used for parametrizing and validating a physics based mathematical model of the suspension system. The mathematical model incorporates the: pressure drop vs: flow characteristics for both the blow-off and proportional valves, response time for the on-off valves as well as the gas pressure vs: flow characteristic incorporating the compressibility of the oil and thermal properties of the gas. This model can be used to make informed decisions on further prototype development or in full vehicle simulations. The system makes continuous variable damping possible ranging from the optimal damping characteristic for handling to the low damping characteristic required for ride comfort. The system also shows a significant reduction in friction. / Dissertation (MEng)--University of Pretoria, 2020. / VDG / University of Pretoria / Mechanical and Aeronautical Engineering / MEng / Unrestricted
106

Characterization and Processing Evaluation of Starch/High-Density Polyethylene Materials in Extrusion Blow Molding

Bacigalupi, Bradley Dale 01 December 2013 (has links) (PDF)
The growing negative impacts of non-biodegradable plastics derived from non-renewable materials have created increasing interest throughout the world for new materials that are both biodegradable and renewable, that can be combined with or replace traditional plastics. Plant-based thermoplastic starch (TPS), a promising alternative material to traditional petroleum based resin, is both biodegradable and renewable and has great potential for use in plastic manufacturing processes. Two major obstacles that prevent more widespread use of TPS include; TPS base material, which is typically manufactured in a flake or powder, is incompatible with standard plastics production equipment that require pelletized resin, the second reason is that TPS is difficult to mix with standard plastic materials such as High Density Polyethylene (HDPE). BiologiQ of Blackfoot Idaho through a unique manufacturing process has created a new type of TPS called EcoStarch™ Resin (ESR) that overcomes these two obstacles the material can be both pelletized and combined with various standard base plastics such as HDPE. This study evaluated and characterized the processability materials properties of ESR and HDPE blends in the Extrusion Blow Molding (EBM) by measuring wall thickness, tensile strength, tensile elongation, modulus of elongation and formability compared to 100% HDPE bottles. As the ESR content increased the uniformity of the wall thickness increased. The tensile strength increased from ESR content of 30% to 50% while the elongation decreased. Bottles were successfully extrusion blow molded with ESR content of 50%.
107

Desarrollo de micro y nanofibras antifúngicas para el control de antracnosis en aguacate "Hass" (Persea americana Mill. cv. Hass) obtenidas por procesado electrohidrodinámico y aerohidrodinámico

Vázquez González, Yuliana 05 December 2024 (has links)
Tesis por compendio / [ES] La pérdida y el desperdicio de alimentos supone un problema global de gran magnitud con implicaciones significativas en los ámbitos ambiental, económico y social. Una fracción importante de dichas pérdidas está producida por las enfermedades postcosecha causadas por fitopatógenos. Meyerozyma caribbica encapsulada en recubrimientos comestibles ha demostrado ser efectiva como control biológico en frutos. Sin embargo, las técnicas convencionales de producción de recubrimientos no garantizan la homogeneidad del tratamiento sobre el alimento, pudiendo afectar a su efectividad. En este sentido, las nanofibras hiladas mediante procesos electro y aerohidrodinámicos pueden actuar como una matriz biopolimérica para atrapar dichos microorganismos, y pueden ser depositadas homogéneamente en la superficie de los alimentos, y esto, junto a que son estructuras con una gran superficie-volumen, las hace más activas y eficientes. La etapa 1, consistió en la optimización y la caracterización fisicoquímica de las disoluciones poliméricas (goma de anacardo, CG; FucoPol, FP; poli óxido de etileno, PEO; pululano, Pul). La etapa 2, consistió en la obtención de estructuras mediante electrospray y electrospinning, éstas se caracterizaron mediante SEM, ATR-FTIR, WAXS, TGA y DSC. La etapa 3 consistió en la encapsulación de M. caribbica en nanofibras de pululano, CG:PEO y FP:PEO mediante electrospinning. Las nanofibras se caracterizaron mediante SEM, ATR-FTIR y TGA. Se determinó la viabilidad de M. caribbica y se evaluó la actividad antifúngica de las nanofibras frente a 6 hongos de interés comercial. La etapa 4, consistió en el análisis in vivo de frutos cubiertos con nanofibras adicionadas con M. caribbica aplicadas por Solution Blow Spinning (SBS) para ello se determinó la viabilidad de M. caribbica en las nanofibras y se evaluó la actividad antifúngica in vitro e in vivo como tratamientos preventivos y curativos frente a C. gloeosporioides. Finalmente, se evaluó el efecto de las nanofibras sobre los parámetros de calidad de los aguacates. Las microestructuras obtenidas con CG, mostraron cápsulas esféricas sin depresiones irregulares que encapsularon al compuesto modelo (ß-caroteno). Las cápsulas de CG brindaron protección térmica y fotoestabilidad al ß-caroteno. Por otro lado, FP, FP:Pul y FP:PEO mostraron fibras helicoidales cilíndricas, lisas y gruesas. Mediante WAXS, en las nanofibras de FP:Pul y FP:PEO se detectaron nuevos picos a ángulos por debajo de los 10º, lo que sugiere que FucoPol podría afectar la estructura polimérica de otros materiales con una estructura secundaria helicoidal. Las nanofibras de pululano, CG:PEO y FP:PEO con M. caribbica mostraron nanofibras cilíndricas, lisas y homogéneas. Los polímeros utilizados brindaron protección térmica a la levadura. Las nanofibras de pululano mostraron la viabilidad más alta de M. caribbica y el mayor porcentaje de inhibición del crecimiento de los 6 hongos evaluados. Mediante SBS se obtuvieron fibras homogéneas, continuas y rizadas. SBS garantizó una alta viabilidad de M. caribbica en las nanofibras aplicadas en la superficie de los aguacates bajo diferentes condiciones evaluadas. Las nanofibras de pululano con M. caribbica como tratamiento preventivo inhibieron por completo el crecimiento de C. gloeosporioides. Además, la aplicación de las nanofibras sobre los aguacates no afectó los parámetros de calidad. El pululano, la CG y el FP en combinación con PEO y pululano se han estudiado por primera vez para formar estructuras mediante procesos electrohidrodinámicos y aerohidrodinámicos. Estos resultados obtenidos, sugieren un alto potencial de las nanofibras para su uso en la industria alimentaria y representan una alternativa interesante para el tratamiento post-cosecha de frutos en el control de enfermedades fúngicas, contribuyendo de esta manera a reducir la pérdida en la producción de alimentos. / [CA] La pèrdua i el malbaratament d'aliments representen un gran problema mundial amb implicacions significatives en els àmbits ambiental, econòmic i social. Una part considerable d'estes pèrdues es deu a malalties post collita causades per fitopatògens. Meyerozyma caribbica, encapsulada en recobriments comestibles, ha demostrat ser efectiva com a control biològic en fruites. No obstant això, els mètodes tradicionals de producció de recobriments sovint no asseguren un tractament uniforme a la superfície dels aliments, cosa que pot comprometre l'eficàcia. En este context, les nanofibres filades mitjançant processos electro- i aerohidrodinàmics poden servir com a matriu bio polimèrica per atrapar estos microorganismes, garantint la deposició homogènia sobre les superfícies dels aliments. El seu gran ràtio superfície-volum enfortix l'activitat i l'eficiència. L'etapa 1 va implicar l'optimització i la caracterització fisicoquímica de les solucions de polímers (goma d'anacard, CG; FucoPol, FP; i poli òxid d'etilè, PEO); pululan, Pul). L'etapa 2 es va centrar en la fabricació d'estructures mitjançant electrospray i electrospinning, caracteritzades per SEM, ATR-FTIR, WAXS, TGA i DSC. L'etapa 3 va incloure l'encapsulació de M. caribbica en nanofibres de pullulan, CG:PEO i FP:PEO per electrofilat. Les nanofibres van ser caracteritzades per SEM, ATR-FTIR i TGA. La viabilitat de M. caribbica es va determinar i l'activitat antifúngica de les nanofibres es va avaluar contra 6 fongs d'interés comercial. L'etapa 4 va consistir en l'anàlisi in vivo de fruites recobertes amb nanofibres afegides amb M. caribbica aplicades per mitjà de Solution Blow Spinning (SBS); per això, es va determinar la viabilitat de M. caribbica a les nanofibres i es va avaluar l'activitat antifúngica in vitro i in vivo com a tractaments preventius i curatius enfront de C. gloeosporioides. Finalment, es va avaluar l'efecte de les nanofibres en els paràmetres de qualitat dels alvocats. Les microestructures obtingudes amb CG van mostrar càpsules esfèriques sense depressions irregulars que encapsulaven el compost model (ß-caroté). Les càpsules de CG van proporcionar protecció tèrmica i foto estabilitat al ß-caroté. D'altra banda, FP, FP:Pul i FP:PEO van mostrar fibres cilíndriques, suaus i gruixudes. Mitjançant WAXS es van detectar nous pics a angles per davall dels 10°, la qual cosa suggerix que FucoPol podria afectar l'estructura d'altres materials amb una estructura secundària helicoidal. Les nanofibres de pululan, CG:PEO i FP:PEO amb M. caribbica van mostrar nanofibres cilíndriques, suaus i homogènies. Els polímers utilitzats van proporcionar protecció tèrmica al llevat. Les nanofibres de pululan van mostrar la màxima viabilitat de M. caribbica i el màxim percentatge d'inhibició del creixement dels 6 fongs provats. Utilitzant SBS, es van obtindre fibres homogènies, contínues i arrissades. SBS va garantir una alta viabilitat de M. caribbica a les nanofibres aplicades a la superfície dels alvocats en diferents condicions avaluades. Les nanofibres de pululan amb M. caribbica com a tractament preventiu van inhibir completament el creixement de C. gloeosporioides. A més, l'aplicació de nanofibres en alvocats no va afectar els paràmetres de qualitat. El Pululan, la CG i l'FP en combinació amb PEO i pululan han estat estudiades per primera vegada per a formar estructures mitjançant processos electro hidrodinàmics i aero hidrodinàmics. Estos resultats obtinguts suggerixen un alt potencial de les nanofibres per a ser utilitzades en la indústria alimentària i representen una interessant alternativa per al tractament post collita de les fruites en el control de les malalties fúngiques, contribuint a reduir la pèrdua en la producció d'aliments. / [EN] Food loss and waste represent a significant global challenge with substantial implications across environmental, economic, and social domains. A considerable portion of these losses stems from postharvest diseases caused by phytopathogens. Meyerozyma caribbica, encapsulated in edible coatings, has demonstrated effectiveness as a biological control agent in fruits. However, conventional coating production methods often fail to ensure uniform treatment on food surfaces, potentially compromising efficacy. In this context, nanofibers spun through electro- and aerohydrodynamic processes can serve as a biopolymeric matrix to entrap such microorganisms, ensuring homogeneous deposition on food surfaces. Their large surface-area-to-volume ratio enhances activity and efficiency. Stage 1 involved optimizing and characterizing polymer solutions (cashew gum, CG; FucoPol, FP; polyethylene oxide, PEO; pullulan, Pul). Stage 2 focused on fabricating structures via electrospray and electrospinning, characterized by SEM, ATR-FTIR, WAXS, TGA, and DSC. Stage 3 entailed encapsulating M. caribbica in pullulan, CG:PEO, and FP:PEO nanofibers via electrospinning, fibers were characterized by SEM, ATR-FTIR, and TGA. M. caribbica viability and the nanofibers' antifungal activity were assessed against six commercially relevant fungi. Stage 4 comprised in vivo analysis of fruits coated with nanofibers containing M. caribbica applied via Solution Blow Spinning (SBS). Viability of M. caribbica in the nanofibers and their antifungal efficacy were determined in vitro and in vivo as preventive and curative treatments against C. gloeosporioides. The impact of nanofibers on avocado quality parameters was evaluated. The microstructures obtained with CG exhibited spherical capsules encapsulated the model compound (ß-carotene), providing thermal and photostability. FP, FP:Pul, and FP:PEO showed cylindrical, smooth, and thick helical fibers. Using WAXS, new peaks at angles below 10º were detected in FP:Pul and FP:PEO nanofibers, suggesting that FucoPol could affect the polymer structure of other materials with a secondary helical structure. Pullulan, CG:PEO, and FP:PEO nanofibers with M. caribbica were cylindrical, smooth, and homogeneous, offering thermal protection to the yeast. Pullulan nanofibers exhibited the highest M. caribbica viability and highest percentage of growth inhibition of the tested fungi. SBS showed homogeneous, continuous, and curly fibers, ensuring high M. caribbica viability on avocado surfaces under diferent conditions. Pullulan nanofibers with M. caribbica as preventive treatment completely inhibited C. gloeosporioides growth without affecting avocado quality parameters. This study represents the first investigation of pullulan, CG, and FP combined with PEO and pullulan for forming structures via electrohydrodynamic and aerohydrodynamic processes. The results underscore the high potential of nanofibers in the food industry, offering a promising alternative for postharvest fruit treatment against fungal diseases and contributing to reducing food loss in fruit production. / Agradezco al Consejo Nacional de Ciencia y Tecnología (CONACyT) por la beca número 754518 concedida para hacer posible el desarrollo de este proyecto de investigación. / Vázquez González, Y. (2024). Desarrollo de micro y nanofibras antifúngicas para el control de antracnosis en aguacate "Hass" (Persea americana Mill. cv. Hass) obtenidas por procesado electrohidrodinámico y aerohidrodinámico [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/206250 / Compendio
108

Late glacial (Younger Dryas) glaciers and ice-sheet deglaciation in the Cairngorm Mountains, Scotland : glacier reconstructions and their palaeoclimatic implications

Standell, Matthew R. January 2014 (has links)
The Cairngorm Mountains contain an outstanding assemblage of glacial landforms from both the deglaciation of the last British Irish Ice Sheet and the Younger Dryas readvance. Glaciers are recognised as sensitive indicators of past and present climate change and, thus, these landforms provide information about past climate and glacier-climate interaction that can be used to contextualise the present climate change. Previous interpretations have left doubt over the extent and style of the Younger Dryas readvance. In addition, the pattern and timing of deglaciation in the southern Cairngorms and, particularly, how local and external ice masses interacted is unclear. New geomorphological mapping from aerial images and fieldwork has been compiled in a GIS for a 600km2 area of the Cairngorm Mountains. This has allowed a complex pattern of ice-dammed lakes and local and regionally sourced ice margins to be reconstructed during the retreat of the last British Irish Ice Sheet. The mapping has been combined with new cosmogenic surface exposure ages taken from areas of hummocky moraine previously subject to differing age interpretations. The effect of moraine denudation on apparent 10Be ages has been checked by inverse modelling of the 10Be concentration vs. boulder height. The results indicate more extensive Younger Dryas glaciation, with glacier reconstructions and equilibrium-line altitudes (ELAs) comparable with the surrounding areas. Reconstruction of both valley and plateau-fed glaciers are presented, with modelling of local topoclimatic factors, such as radiation, avalanche and snow drifting, combined with precipitation gradients, explaining most of the variation within the glacier ELAs. The geomorphological evidence and palaeoclimatic inferences are important, alongside a growing number of palaeoglaciological studies, in acting as evaluation areas for current numerical models of ice-sheet growth and decay.
109

Etude asymptotique et multiplicité pour l'équation de Sobolev Poincaré

Dellinger, Marie 30 March 2007 (has links) (PDF)
Sur une variété riemanienne compacte de dimension supérieure à 3,<br />on considère une edp elliptique non linéaire à exposant critique particulière : l'équation de Sobolev Poincaré. D'une part, nous décrivons le comportement asymptotique d'une suite de solutions de cette équation grâce à une analyse fine de phénomènes de concentration. D'autre part, en imposant des invariances par des groupes d'isométries, nous montrons des résultats de multiplicité de solutions pour cette équation. Notre méthode permet aussi d'obtenir des multiplicités de solutions pour des équations plus classiques provenant du problème deYamabe et de Nirenberg, ainsi que <br /> pour des équations à exposants sur critiques. Notre travail est intimement lié à la description des meilleures constantes dans des inégalités fonctionnelles de Sobolev associées aux équations.
110

Characterization of the unfolding of a weak focus and modulus of analytic classification

Arriagada Silva, Waldo G. 06 1900 (has links)
La thèse présente une description géométrique d’un germe de famille générique déployant un champ de vecteurs réel analytique avec un foyer faible à l’origine et son complexifié : le feuilletage holomorphe singulier associé. On montre que deux germes de telles familles sont orbitalement analytiquement équivalents si et seulement si les germes de familles de difféomorphismes déployant la complexification de leurs fonctions de retour de Poincaré sont conjuguées par une conjugaison analytique réelle. Le “caractère réel” de la famille correspond à sa Z2-équivariance dans R^4, et cela s’exprime comme l’invariance du plan réel sous le flot du système laquelle, à son tour, entraîne que l’expansion asymptotique de la fonction de Poincaré est réelle quand le paramètre est réel. Le pullback du plan réel après éclatement par la projection monoidal standard intersecte le feuilletage en une bande de Möbius réelle. La technique d’éclatement des singularités permet aussi de donner une réponse à la question de la “réalisation” d’un germe de famille déployant un germe de difféomorphisme avec un point fixe de multiplicateur égal à −1 et de codimension un comme application de semi-monodromie d’une famille générique déployant un foyer faible d’ordre un. Afin d’étudier l’espace des orbites de l’application de Poincaré, nous utilisons le point de vue de Glutsyuk, puisque la dynamique est linéarisable auprès des points singuliers : pour les valeurs réels du paramètre, notre démarche, classique, utilise une méthode géométrique, soit un changement de coordonée (coordonée “déroulante”) dans lequel la dynamique devient beaucoup plus simple. Mais le prix à payer est que la géométrie locale du plan complexe ambiante devient une surface de Riemann, sur laquelle deux notions de translation sont définies. Après avoir pris le quotient par le relèvement de la dynamique nous obtenons l’espace des orbites, ce qui s’avère être l’union de trois tores complexes plus les points singuliers (l’espace résultant est non-Hausdorff). Les translations, le caractère réel de l’application de Poincaré et le fait que cette application est un carré relient les différentes composantes du “module de Glutsyuk”. Cette propriété implique donc le fait qu’une seule composante de l’invariant Glutsyuk est indépendante. / The thesis gives a geometric description for the germ of the singular holomorphic foliation associated with the complexification of a germ of generic analytic family unfolding a real analytic vector field with a weak focus at the origin. We show that two such germs of families are orbitally analytically equivalent if and only if the germs of families of diffeomorphisms unfolding the complexified Poincaré map of the singularities are conjugate by a real analytic conjugacy. The Z2-equivariance of the family of real vector fields in R^4 is called the “real character” of the system. It is expressed by the invariance of the real plane under the flow of the system which, in turn, carries the real asymptotic expansion of the Poincaré map when the parameter is real. After blowing up the singularity, the pullback of the real plane by the standard monoidal map intersects the foliation in a real Möbius strip. The blow up technique allows to “realize” a germ of generic family unfolding a germ of diffeomorphism of codimension one and multiplier −1 at the origin as the semi-monodromy of a generic family unfolding an order one weak focus. In order to study the orbit space of the Poincaré map, we perform a trade-off between geometry and dynamics under the Glutsyuk point of view (where the dynamics is linearizable near the singular points): in the resulting “unwrapping coordinate” the dynamics becomes much simpler, but the price we pay is that the local geometry of the ambient complex plane turns into a much more involved Riemann surface. Over the latter, two notions of translations are defined. After taking the quotient by the lifted dynamics we get the orbit space, which turns out to be the union of three complex tori and the singular points (this space is non- Hausdorff). The Glutsyuk invariant is then defined over annular-like regions on the tori. The translations, the real character and the fact that the Poincaré map is the square of the semi-monodromy map, relate the different components of the Glutsyuk modulus. That property yields only one independent component of the Glutsyuk invariant.

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