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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.
61

Využití chromatografie na tenké vrstvě k frakcionaci a charakterizaci organické hmoty izolované z alginitu / Use of thin layer chromatography for fractionation and characterization of organic matter isolated from alginite

Solanský, Pavel January 2021 (has links)
This diploma thesis is focused on the study of structure and physicochemical properties of organic fractions of humic substances, which were obtained by the method of thin-layer chromatography. Humic substances, which were used in this study, were isolated from a sample of Slovak alginite based on the procedure of the International Humic Substances Society (IHSS). The following analytical techniques were selected for the characterization of isolated humic substances: thermogravimetric and elemental analysis, molecular absorption spectroscopy (UV/Vis), Fourier transform infrared spectroscopy (FTIR) and steady-state fluorescence spectroscopy. Each organic fraction of humic substances were characterized by molecular absorption spectroscopy (UV/Vis) and steady-state fluorescence spectroscopy. Using steady-state fluorescence spectroscopy, humic substances were found to be composed of fluorophores of humic and non-humic (protein) character. Organic fractions corresponding to the humic fluorophores were characterized by a higher content of oxygen substituents on the aromatic nukleus, a higher degree of aromaticity and also a higher molecular weight. The aim of this diploma thesis was to design and optimize the process of organic matter fractionation for the purpose of detailed understanding of the structure and properties of humic substances, which were isolated from the sedimentary rock alginite. Based on this, the practical applicability of the thin layer chromatography method to significantly reduce the molecular heterogenity of the studied humic substances was evaluated.
62

Hochverzweigte Polymere als chromatographische Selektoren

Tripp, Sandra 25 November 2014 (has links)
Moderne analytische Verfahren ermöglichen eine höchst effiziente Auftrennung und eine selektive Detektion von Zielanalyten. Dies ist vor allem in der Medizin von Bedeutung, da eine frühzeitige Diagnose von Krankheiten in den meisten Fällen zu einer wesentlich erfolgreicheren Behandlung beiträgt. In unserer heutigen Industriegesellschaft werden daher hochsensitive und effiziente Analysemethoden stärker benötigt als je zuvor. Diverse Umweltgifte oder gesundheitliche Schadstoffe gelangen vermehrt in Grundwasser und Umwelt. Eine Analyse ist aufgrund der oft nur geringen Konzentrationen und der Komplexität diverser Proben häufig mit großen Schwierigkeiten verbunden. Obwohl die Sensitivität und Effizienz zur Bestimmung von Krankheitsmarkern (Biomarker) und Schadstoffen immer weiter zunimmt, stoßen selbst höchstsensitive Analysemethoden an ihre Grenzen. Gerade bei kleinsten Konzentrationen an Zielanalyten oder bei komplexen Gemischen ist eine direkte Detektion ohne weitere Vorbehandlung, wie Aufkonzentrierungen oder Markierungen, äußerst schwierig oder nicht möglich. Eine Optimierung dieser Methoden, deren Automatisierung sowie sensitivere Detektorsysteme werden benötigt. Darüber hinaus ist die Entwicklung von neuartigen, selektiveren mobilen und stationären Phasen ein hochinteressantes und umfangreich untersuchtes Forschungsgebiet. Die Verwendung von hochselektiven Additiven, wie Cyclodextrinen, Kronenethern, Mizellen und andere chirale Selektoren in der Hochleistungsflüssigkeitschromatographie (HPLC), Kapillarelektrophorese (CE)[1,2] oder in der Dünnschicht-Chromatographie (TLC)[3] wurde bereits umfangreich untersucht und etabliert. Hochfunktionalisierte Polymere als äußerst spezifische Selektoren mit hoher Selektivität stellen vielversprechende Materialien dar, die ebenfalls eine Optimierung in der HPLC und CE erzielen.[4-9] Der Einsatz von Polymeren in molekular geprägten Matrizen (molecular imprinted polymers, MIP) oder in monolithischen Trennsäulen wird bereits äußerst erfolgreich in der TLC, HPLC und CE genutzt.[7-11] Eine solch hochselektive Säulenmodifizierung bietet eine sehr gute Performance und hervorragende Trennleistungen. Ein Nachteil dieser hochselektiven Modifizierung ist jedoch die Spezialisierung nur auf das jeweilige Problem. Eine universelle Verwendung für komplexe Gemische und eine Fülle von Analyten ist limitiert. Ein sehr vielversprechender Aspekt ist der Einsatz von Polymeren als chirale Selektoren in der stationären wie auch in der mobilen Phase. Die große Anzahl an kommerziell erhältlichen Trennsäulen mit einer Polymermodifizierung und das ständig umfangreichere Angebot solcher Säulen[12] verdeutlichen diesen Trend und zeigen, dass die Nutzung von polymeren Architekturen für eine weitere Optimierung diverse Möglichkeiten bietet. Hochverzweigte Polymere stellen unter den Polymeren vielversprechende Materialien dar, die aufgrund ihrer Vorteile zu einer effektiven Optimierung beitragen können.[12] Die hohe Anzahl an terminalen Gruppen ermöglichen es, gut zugängliche anwendungsorientierte Modifizierungen durchzuführen, um gewünschte Eigenschaften zu generieren. Durch die hohe Variabilität der Polymere selbst und der diversen Modifizierungsmöglichkeiten zeigen maßgeschneiderte Polymere ein enormes Potential und die Möglichkeit hochselektive Wechselwirkungen mit Zielanalyten zu etablieren. Die Modifizierung mit einer Schale um den polymeren Kern ermöglicht weitere Optimierungen für den Einsatz von Kern-Schale-Architekturen. Beispiele hierfür sind unter anderem die Vermittlung höherer Löslichkeit durch eine Modifizierung des hydrophilen/hydrophoben polymeren Kerns zur Etablierung einer äußeren Schale. Ebenso können durch die Modifizierung gezielte Eigenschaften generiert werden, die eine spezifische Interaktion mit Oberflächen oder Wirkstoffen ermöglichen. Die Zielsetzung dieser Arbeit ist die Synthese und die Untersuchung von Kern-Schale-Architekturen als chromatographische Selektoren. Als polymerer Kern wird hochverzweigtes Poly(ethylenimin) (PEI) verwendet, das mit einer Oligosaccharidschale modifiziert wird. Das PEI wird mit den Kerngrößen 5 und 25 kDa verwendet, wodurch eine Untersuchung des Kerneinflusses möglich ist. Weiterhin wird die Dichte der Oligosaccharidschale eingestellt. Dafür wird eine dichte, moderate bis offene und eine sehr offene Oligosaccharidschale um den polymeren Kern generiert. Infolge dessen kann der Einfluss der Schalendichte auf die Interaktion mit Beispielanalyten evaluiert werden. Für die Oligosaccharidschale (OS) werden darüber hinaus drei verschiedene Oligosaccharide (Maltose, Lactose und Maltotriose) verwendet, um den Einfluss der Art der Schale zu prüfen. Durch diese Variationen können 15 unterschiedliche PEI-OS Kern-Schale-Architekturen synthetisiert und untersucht werden. Weiterhin soll der hydrophobe Anteil der Kern-Schale-Architekturen durch die Anbindung von unpolaren Seitenketten an einen PEI-Kern erhöht werden. Auf diese Art und Weise können nicht-kovalente Wechselwirkungen mit lipophilen Systemen untersucht werden. Um polymere Kern-Schale-Architekturen möglichst effizient in der TLC, HPLC und CE einsetzen zu können, ist es essentiell, ihre Eigenschaften und die Art und Weise der Wechselwirkungen zu kennen, die sie mit möglichen Gastmolekülen eingehen. Durch die Untersuchung dieser Wechselwirkungen können Informationen über deren Interaktionen und eine mögliche Manipulation bzw. Optimierung dieser erhalten werden. Ein zielgerichteter und effektiver Einsatz mit diesen Kern-Schale Architekturen kann so vorbereitet werden. [1] T. J. Ward, K. D. Ward, Anal. Chem. 2012, 84, 626-35. [2] W. J. Cheong, S. H. Yang, F. Ali, J. Sep. Sci. 2013, 36, 609-28. [3] M. D. Bubba, L. Checchini, L. Lepri, Anal. Bioanal. Chem. 2013, 405, 533-554. [4] M. Hanson, K. K. Unger, Trends Anal. Chem. 1992, 11, 368-373. [5] J. Kirkland, J. Chromatogr. A 2004, 1060, 9-21. [6] F. Gasparrini, D. Misiti, R. Rompietti, C. Villani, J. Chromatogr. A 2005, 1064, 25-38. [7] A. Martin-Esteban, Trends Anal. Chem. 2013, 45, 169-181. [8] I. Nischang, J. Chromatogr. A 2013, 1287, 39-58. [9] R. D. Arrua, M. Talebi, T. J. Causon, E. F. Hilder, Anal. Chim. Acta 2012, 738, 1-12. [10] P. Jandera, J. Chromatogr. A 2013, 1313, 37-53. [11] F. Svec, J. Sep. Sci. 2004, 27, 1419-1430. [12] M. Tang, J. Zhang, S. Zhuang, W. Liu, Trends Anal. Chem. 2012, 39, 180-194.
63

Los principales factores que influyen en el uso del e-commerce en las Mypes del sector textil - confecciones en el emporio de Gamarra en el periodo del 2013 al 2018

Del Carpio Hurtado, Dayana Isabel, Gilvonio Herrera, Harold Irwing 18 February 2019 (has links)
Hoy en día, los desarrollos tecnológicos están vinculados a la vida diaria de cada persona, reducen las distancias entre la gente y contribuyen a que los procesos empresariales sean más efectivos. El rubro con mayor impacto ha sido el comercio, las transacciones electrónicas han tomado protagonismo en todo el mundo, convirtiéndose en una alternativa viable, con diversas herramientas, capaz de atender las necesidades de clientes. Por ello, muchas empresas han decidido incorporar al comercio electrónico en el desarrollo de sus actividades, pueden obtener beneficios tales como la reducción de costos fijos, competitividad, captación de clientes, entre otros. En el Perú el comercio electrónico se ha venido desarrollando lentamente y de manera focalizada en grandes empresas, creando la falsa idea que es necesario invertir mucho dinero para incorporarlo en las actividades comerciales, lo que ha generado desconfianza y rechazo a los usuarios por temor a ser estafados. El objetivo principal de la tesis es determinar los principales factores del uso del E-commerce en las Mypes del sector textil - confecciones en el Emporio de Gamarra. Nos enfocamos en Gamarra por ser principal punto de actividad económica en el Perú. Actualmente, muchas entidades como la Cámara de Comercio de Gamarra contribuyen con la promoción y competitividad de Gamarra, mediante el soporte de un equipo de profesionales innovadores, cuyo principal aporte es la explotación de tecnologías de la información y comunicación, con el objetivo de promover a las empresas y/o usuarios a utilizar herramientas como el E-commerce, para poder expandir o incrementar ventas. / Nowadays, technological developments are linked to the daily life of each person, reduce the distances between people and contribute to making business processes more effective. The area with the greatest impact has been commerce, electronic transactions have taken center stage throughout the world, becoming a viable alternative, with various tools, capable of meeting the needs of customers. Therefore, many companies have decided to incorporate electronic commerce in the development of their activities, can obtain benefits such as the reduction of fixed costs, competitiveness, customer acquisition, among others. In Peru, electronic commerce has been developing slowly and focused on large companies, creating the false idea that it is necessary to invest a lot of money to incorporate it into commercial activities, which has generated distrust and rejection of users for fear of being scammed. The main objective of the thesis is to determine the main factors of the use of E-commerce in the Mypes of the textile sector - confections in the Emporium of Gamarra. We focus on Gamarra as the main point of economic activity in Peru. Currently, many entities such as the Chamber of Commerce of Gamarra contribute to the promotion and competitiveness of Gamarra, through the support of a team of innovative professionals, whose main contribution is the exploitation of information and communication technologies, with the aim of promoting Companies and / or users to use tools such as E-commerce, to expand or increase sales. / Tesis
64

Relaciones comerciales con la Unión Europea en el Spaghetti-bowl de la Comunidad Andina de Naciones / Relaciones comerciales con la Unión Europea en el Spaghetti-bowl de la Comunidad Andina de Naciones

Fairlie Reinoso, Alan 10 April 2018 (has links)
The article reflects on the roll that has the European Union like cohesion factor, considering that the relations are not limited the commercial plane in a context in which the Andean Community of Nations has had difficulties not only in its process of internal consolidation, but also to forge a common foreign policy. One discusses some differences with the FTA with the U.S.A., and the relations in these South-North agreements with regional integration.Of another side, one becomes a balance of the commerce flows, investment and cooperation between the EU and the Andean Community, being in evidence the fundamental importance that they have these bonds, beyond conjunctural losses of relative weight in the commercial aspect. There are limitations, but beyond the European restrictions or external these are fundamentally of internal character: insufficient exportable supply, competitiveness, infrastructure, etc. / El artículo reflexiona sobre el rol que tiene la Unión Europea como factor de cohesión, teniendo en cuenta que las relaciones no se limitan al plano comercial, especialmente en un contexto en el cual la Comunidad Andina de Naciones ha tenido dificultades no solo en su proceso de consolidación interna sino también en aquel que tiene como fin forjar una política exterior común. Se discute también algunas diferencias con el TLC con los Estados Unidos y las relaciones de estos acuerdos norte-sur con laintegración regional.De otro lado, se hace un balance de los flujos de comercio, inversión y cooperación entre la UE y la CAN, lo que evidencia la importancia fundamental que tienen estos vínculos, más allá de pérdidas  coyunturales de peso relativo, en el aspecto  comercial.Si bien existen limitaciones, más allá de las  restricciones europeas o externas, estas son fundamentalmente de carácter interno: oferta exportable insuficiente, competitividad, infraestructura, etcétera.
65

Factores determinantes de la evolución de la exportación de pota congelada en el periodo 2009 – 2017 en el marco de TLC Perú y la República Popular China

Bendezú Chávez, Kevin Andy, Ccama Leiva, Alejandra Pamela 16 April 2019 (has links)
La siguiente investigación consistió en realizar un análisis cualitativo a fin de detectar los factores determinantes en la evolución de la exportación de Pota congelada, con partida arancelaria 0307490000, en el marco del Tratado de Libre Comercio (TLC) Perú - China en el periodo 2009 – 2017, tiempo en el cual la partida mencionada ha tenido una desgravación gradual, llegando a 0% al inicio del 2019. La exportación de pota congelada ha tenido un crecimiento significativo en el periodo 2017, respecto al 2016 al incrementarse en 24.2%, pasando de US $ 315.2 a 391.5 millones durante el 2017, consolidándose como el producto pesquero más importante con un 42.2% de participación. Se realizó un análisis de campo utilizando fuentes primarias como entrevistas a empresas y entidades del estado, principales actores influyentes en la exportación de Pota congelada, además de expertos académicos. Se condujo una investigación de tipo descriptiva debido a que asocia conceptos o variables, teniendo como finalidad conocer la relación de los factores y sus categorías determinantes en la exportación de la partida arancelaria antes mencionada, hacia el mercado de la República popular de China, en el marco del Tratado de Libre Comercio. Se concluyó que el factor más importante de la exportación de Pota congelada en el marco antes descrito, es el mercado y la demanda China, la cual determina el crecimiento o caída en las variaciones porcentuales de los índices de exportación; teniendo como segundo factor externo a la flota internacional y la competitividad como factor interno más relevante. / Tesis
66

BFL - Ett framgångsrikt skolutvecklingsprojekt? : En studie av effekterna av ett uppifrån kommande utvecklingsinitiativ. / Formative Assessment - A successful school improvement project? : A study of the effects of a top-down improvement initiative.

Tengelin, Hannah January 2019 (has links)
Studien syftar till att belysa huruvida bedömning för lärande (BFL) har institutionaliserats bland lärarna på Lindängsgymnasiet efter ett genomfört skolutvecklingsprojekt. Den har också som mål att, med utgångspunkt i en teori om framgångsrik skolutveckling som utvecklats av Ulf Blossing, ta reda på vilka faktorer under initierings- och implementeringsfasen som kan ha varit avgörande för huruvida projektet nådde institutionaliseringsfasen eller inte. Studien syftar vidare till att klargöra om det finns skillnader mellan lärare som undervisar på yrkesförberedande program och lärare som undervisar på högskoleförberedande program samt mellan lärare som undervisar i karaktärsämnen och lärare som undervisar i allmänna ämnen när det gäller institutionaliseringen av BFL i undervisningen. Studiens ansats är kritiskt realistisk och består dels av en kvantitativ enkät, som besvarats av 58 lärare på Lindängsgymnasiet, och dels av en kvalitativ intervju med den förstelärare som fungerade som projektledare under skolutvecklingsprojektet. Enkätresultatet visar att BFL inte har institutionaliserats bland lärarna på Lindängsgymnasiet och analys av både enkätresultat och intervju gör gällande att förklaringarna står att finna i såväl initierings- som implementeringsfasen. För att ta reda på om det finns skillnader mellan lärare som undervisar på yrkesförberedande program och lärare som undervisar på studieförberedande program samt mellan lärare som undervisar i karaktärsämnen och allmänna ämnen användes Chi2-test, t-test och Mann-Whitney U-test. Resultaten av testen tyder inte på några skillnader mellan lärare som undervisar på yrkesförberedande och högskoleförberedande program när det gäller institutionaliseringen av BFL. Resultaten tyder dock på att lärare som undervisar på yrkesförberedande program i något större utsträckning upplever att de har förändrat sin undervisning beroende på BFL-projektets genomförande än lärare som undervisar på högskoleförberedande program. Testen visar inte på några skillnader mellan lärare som undervisar i karaktärs- respektive allmänna ämnen. Studien kan vara användbar för till exempel skolledare vid planering av utvecklingsarbete och kollegialt lärande, då studien bland annat pekar på vikten av en genomtänkt initieringsfas samt kontinuerlig medverkan av skolledare under ett skolutvecklingsprojekt. / This study aims to highlight whether assessment for learning (AFL) has become institutionalized among the teachers at Lindängsgymnasiet after a school improvement project. It also aims to investigate, based on a theory on successful school improvement developed by Ulf Blossing, what factors during the initiation and the implementation phase that may have been crucial for whether the project reached the institutionalization phase or not. The study further aims to clarify if there are differences between teachers who teach on vocational programs and teachers who teach on preparatory programs and between teachers who teach characteristic subjects and teachers who teach general subjects regarding the institutionalization of AFL in the classroom. The approach of the study is critical realistic and it consists of a quantitative survey, that was answered by 58 teachers at Lindängsgymnasiet. It also consists of a qualitative interview with the head teacher that had the role of project manager during the school improvement project. The results of the survey show that AFL has not been institutionalized among the teachers at Lindängsgymnasiet and analysis of both survey results and the interview claims that the explanations can be found in the initiation and implementation phase. In order to find out if there are differences between teachers who teach on vocational and teachers who teach on preparatory programs, and between teachers who teach characteristics and teachers who teach general subjects, Chi2 test, t-test and Mann-Whitney U test were used. The results of these tests do not indicate any differences between teachers who teach on vocational and on preparatory programs in the institutionalization of AFL. The results indicate that teachers who teach on vocational programs to a greater extent experience that they have changed their education due to the implementation of the AFL-project than teachers who teach on preparatory programs. The tests do not indicate any differences between teachers who teach characteristics and teachers who teach general subjects. The study can be useful for school leaders in planning of school improvement work and collaborative learning, as the study focuses on the importance of a well-considered initiation phase and continuous participation by school leaders during a school development project.
67

Avaliação do potencial metabólico de linhagens de fungos isolados de uma espécie de alga marinha do gênero Sargassum / Evaluation of the metabolic potential of fungal lineages isolated from a species of marine algae of the Sargassum genus

Romminger, Stelamar 20 November 2008 (has links)
Os fungos são microrganismos amplamente dispersos, podendo ser encontrados em vegetais, animais, solo e ambientes aquáticos, participando do ciclo de elementos na natureza. Embora muitos papéis ecológicos tenham sido estudados e descritos para os fungos terrestres, a ecologia de fungos marinhos ainda é pouco conhecida. Assim, os oceanos, que representam aproximadamente metade da biodiversidade global, são uma fonte enorme e virtualmente inexplorada de microrganismos produtores de novos produtos naturais. O objetivo deste trabalho foi isolar linhagens de fungos derivados de uma espécie de alga marinha do gênero Sargassum, visando à avaliação do seu potencial para a produção de metabólitos secundários bioativos. Ao todo foram isoladas 58 linhagens, das quais 52 foram crescidas em meio de cultura líquido e, após a extração com solventes orgânicos, deram origem a 99 extratos. Tais extratos foram avaliados por ensaios de atividade biológica, cromatografia em camada delgada (CCD), ressonância magnética nuclear (RMN) e cromatografia líquida acoplada a detectores de arranjo de diodos, espalhamento de luz evaporativo e espectrômetro de massas (LC - PDA - ELSD - MS). A avaliação pelo ensaio antibiótico foi o que resultou no maior número de extratos ativos (n = 13), seguido dos ensaios enzimático (n = 8), citotóxico (n = 3) e anti-tuberculose (n = 1). O extrato AS Fub 39, que apresentou atividade antibiótica, foi selecionado para estudos adicionais. Este extrato foi purificado por HPLC, e o seu composto majoritário identificado como sendo o 8-metóxi-3,5-dimetilisocroman-6-ol. Posteriormente, a linhagem AS Fub 39 foi taxonomicamente identificada como pertencendo à espécie Penicillium steckii. / Fungi are widely disperse microorganisms, typically associated with plants, animals, soil and aquatic environments (fresh and sea water), participating in the elements cycling. Although many ecological roles have been described for terrestrial fungi, ecological studies of marine derived fungi are still scarce. Therefore, oceans, which represent approximately half of the global biodiversity, are a huge and virtually unexplored source of microorganisms producers of interesting metabolites. The aim of this study was to isolate fungal strains derived from a marine algae of the Sargassum genus, and the evaluation of their metabolical potential for the production of secondary metabolites. Overall, 58 strains were isolated, of which 52 were grown in liquid culture media and extracted with organic solvents, originating 99 crude extracts. These extracts were analyzed by bioassays, thin layer chromatography (TLC), nuclear magnetic resonance (NMR) and liquid chromatography coupled with a photo diode array, an evaporative light scattering, and a mass spectrometry detectors (LC - PDA - ELSD - MS). The evaluation with the antibiotic assay resulted in the largest number of active extracts (n = 13), followed by the enzymatic (n = 8), the cytotoxic (n = 3) and the antituberculosis (n = 1) assays. The crude extract AS Fub 39, which presented antibiotic activity, was selected for additional studies. This extract was purified by HPLC, and its major compound identified as the 8-methoxy-3,5-dimethylisocroman-6-ol. Later, the AS Fub 39 strain was taxonomically identified as Penicillium steckii.
68

Equisetum giganteum l. : parâmentros de controle de qualidade, análise química e desenvolvimento de extrato seco por spray drying

Francescato, Leandro Nicolodi January 2012 (has links)
As partes aéreas de Equisetum giganteum L. (Equisetaceae), espécie nativa da América do Sul, denominada cavalinha e rabo-de-cavalo, são utilizadas popularmente sob a forma de infuso ou decocto no tratamento de afecções urinárias e hepáticas e principalmente como diurética, hemostática, adstringente, remineralizante e emagrecedora. Entretanto, poucos estudos científicos foram realizados envolvendo esta espécie. Quanto às propriedades biológicas de seus extratos, têm sido relatadas atividades diurética e antimicrobiana, e ausência de efeitos tóxicos agudos em camundongos, quando administrados por via oral. Considerando a ampla disponibilidade de E. giganteum no mercado brasileiro e o seu potencial terapêutico, torna-se necessária a definição de parâmetros de controle de qualidade para a matéria-prima vegetal, bem como o desenvolvimento de produtos padronizados. Assim, este trabalho objetivou avaliar parâmetros de controle de qualidade e estabelecer critérios químicos que permitam diferenciar E. giganteum de outras espécies do gênero e, a partir de uma solução extrativa aquosa, desenvolver extrato seco por spray drying e caracterizá-lo. Para isso, partes aéreas de E. giganteum e outras espécies disponíveis foram utilizadas. Análises comparativas destas amostras foram realizadas por CCD, CLAE e teor de flavonóides totais. Para E. giganteum, o teor de cinzas, os constituintes fenólicos e flavonóides totais foram determinados por método espectrofotométrico no UV/VIS. Análise por CCD foi realizada em placas de gel de sílica; fase móvel acetato de etila:ácido fórmico:ácido acético glacial:água (100:11:11:26); e detecção com reagente Natural / UV a 365 nm. Análises por CLAE dos extratos metanólicos foram realizadas empregando coluna de fase-reversa (C18) e detector de arranjo de diodos. O material vegetal foi também submetido à hidrólise ácida, a qual foi otimizada empregando Desenho Composto Central Rotacional e Análise de Superfície de Resposta para investigar os efeitos da concentração de HCl e do tempo de hidrólise. As agliconas correspondentes aos flavonóides heterosídicos foram extraídas e analisadas por método de CLAE previamente validado. O teor de flavonóides totais foi avaliado por ensaio colorimétrico com cloreto de alumínio a 425 nm. Análises por CLAE-DAD e CLAE-EM/EM também foram realizadas na intenção de caracterizar os compostos fenólicos presentes em E. giganteum. Uma solução extrativa aquosa foi obtida por decocção a partir da matéria-prima vegetal e posteriormente seca por spray drying empregando equipamento NIRO® atomizer semi-industrial. O extrato seco obtido foi então caracterizado. Os resultados demonstraram para E. giganteum um teor de cinzas totais e insolúveis em ácido (a 600ºC) respectivamente de 20,07 ± 0,21% e 13,75 ± 0,39%. O teor de fenólicos totais foi de 7,27 ± 0,05 mg equivalente a ácido gálico por grama, e de 0,420 ± 0,014 g% para os flavonóides totais. Na análise por CCD de E. giganteum foi verificada a presença de manchas características de polifenóis, sendo que, na análise por CLAE, alguns constituintes apresentaram espectro de UV característicos de derivados do ácido cinâmico e do canferol A diferenciação entre E. giganteum e E. arvense, e em menor extensão para E. hyemale e E. bogotense, foi possível através do perfil cromatográfico obtido nas análises por CCD e CLAE. A possível presença de tiamina foi caracterizada por CCD nestas amostras. Nas condições ótimas de hidrólise determinadas para E. giganteum, canferol e, em menor teor, quercetina foram encontradas. A análise comparativa das agliconas dos flavonóides por CLAE e dos flavonóides totais por espectrofotometria revelou similaridades químicas entre E. giganteum, E. hyemale e E. bogotense, mas não para E. arvense, o qual apresentou um perfil de agliconas distinto. A maior parte dos compostos fenólicos puderam ser caracterizados em E. giganteum por meio da análise por CLAE-EM/EM, sendo encontrado principalmente derivados heterosídicos do canferol, mas também outros compostos fenólicos raros. A obtenção de extrato seco por spray drying a partir de solução extrativa aquosa de E. giganteum mostrou-se viável, com alto rendimento do processo (85,6%). O produto foi caracterizado como um pó fino com baixa densidade, baixa fluidez e alta umidade residual, mas baixa atividade de água. Com relação a sua composição química, o extrato seco apresentou alto teor de minerais e açúcares redutores. A presença na droga vegetal e no extrato seco de E. giganteum de alto teor de minerais, corrobora seu uso como remineralizante. Os resultados obtidos neste trabalho representam as primeiras contribuições para o estabelecimento de parâmetros e métodos para a caracterização e o controle de qualidade da droga vegetal de E. giganteum. A viabilidade de produção e a caracterização do extrato seco obtido contribuem para o desenvolvimento de novos produtos farmacêuticos e a avaliação de outras atividades biológicas. / Aerial stems of Equisetum giganteum L. (Equisetaceae, traditional name: ‘‘horsetail’’), a native plant from South America, are used in folk medicine for treating kidney and hepatic illness, due to their diuretic, hemosthatic, adstringent, remineralizant and weight loss properties. However, few scientific studies have been performed regarding this species. Concerning the biological properties, diuretic and antimicrobial activities, as well as no oral acute toxicity in mice have been reported. Considering the large availability of the E. giganteum in the Brazilian market and its therapeutic potential, the definition of the quality control parameters for the raw material, as well as the development of standardized products with well-established biological activities becomes necessary. Thus, the aim of this work was to establish identification methods and to evaluate quality control parameters for the E. giganteum raw material in order to compare this species with others of the genus, as well as to develop and to characterize a spray-dried product from an aqueous E. giganteum extractive solution. Dried aerial stems of E. giganteum and other species available were employed in the comparative analysis by TLC, HPLC and UV/VIS total flavonoid content. The ash content was determined. Total phenolic and flavonoid contents were determined by UV/VIS spectrophotometric method. The TLC analysis was carried out on silica gel plates; mobile phase ethyl acetate:formic acid:glacial acetic acid:water (100:11:11:26); and detection with Natural Product reagent / UV at 365 nm. HPLC analysis of methanol extracts was performed with a C18 column and a diode-array detector. The plant raw material was also submitted to acid hydrolysis which was optimized using Central Composite Rotational Design and Response Surface Analysis for investigate the effects of HCl concentration and hydrolysis time. The corresponding flavonoid aglycones were extracted and analyzed by a previously validated HPLC method. Total flavonoid content was measured also by aluminium chloride colorimetric assay at 425 nm. In attempt to characterize phenolic compounds in E. giganteum, HPLC-DAD and HPLC-MS/MS analysis were performed. An aqueous extractive solution (AES) was prepared by decoction of E. giganteum grounded stems using water. The resulting AES was spray-dried using a Niro Production Minor equipped with rotary atomizer (GEA, Copenhagen, Denmark). The spray-dried extract was then characterized. The content of total ash and acidinsoluble ash (at 600 °C) in E. giganteum stems were 20.07 ± 0.21% and 13.75 ± 0.39% (mean ± S.D.), respectively. The total phenolic content was 7.27 ± 0.05 mg expressed as gallic acid equivalent per gram (GAE/g), and the total flavonoid content was 0.420 ± 0.014 g% (w/w). In the TLC of E. giganteum was verified the presence of spots characteristic of polyphenols. The HPLC fingerprint revealed the existence of some constituents with UV spectra characteristics of cinnamic acid and kaempferol derivatives. The differentiation between E. giganteum and E. arvense, and in a minor extension for E. hyemale and E. bogotense, was possible by the chromatographic profile in TLC and HPLC analysis. The possible presence of thiamine was characterized by TLC in these samples. In the optimum condition found for hydrolysis of E. giganteum raw material, quercetin and kaempferol aglicones were found. The comparative analysis of flavonoids aglycones using HPLC and total flavonoids spectrophotometric methods revealed similarities between E. giganteum, E. hyemale and E. bogotense, but not for E. arvense, which showed a distinct profile of aglycones. The HPLC-MS/MS analysis of E. giganteum hydroethanol extractive solution allowed to characterize some flavonoids heterosides, mainly quercetin and kaempferol derivatives, and other rare compounds. The spray-dried extract (SDE) of E. giganteum was obtained with a high process yield (85.6%) and characterized as a very fine powder with low density, poor flowability and high loss on drying, but low water activity. The high content of reducing sugars and minerals, represented by total ash, was also observed in the SDE and can explain some these characteristics. The high content of sugars and minerals in the SDE also corroborate the traditional use of the plant as remineralizant. The results obtained in this study represent one of the first contributions to the establishment of parameters and methods for the characterization and quality control of raw material of E. giganteum. The feasibility of production and subsequent characterization of dried extract obtained contributes to the development of new pharmaceuticals products and to the evaluation of new biological activities.
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Fluctuations de fonctionnelles spectrales de grandes matrices aléatoires et applications aux communications numériques

Kharouf, Malika 19 June 2010 (has links) (PDF)
La théorie des matrices aléatoires présente un ensemble d'outils mathématiques efficaces pour l'étude de performances des systèmes de communications numériques. L'objectif de cette thèse est de développer des résultats analytique basés sur la théorie des matrices aléatoires pour étudier les fluctuations de quelques indices de performances pour les systèmes de communications sans fil. Nous étudions dans un premier temps, les fluctuations du rapport signal sur bruit (SINR), indice de performance mesuré à la sortie d'un récepteur linéaire de Wiener, récepteur minimisant l'erreur quadratique des symboles estimés (LMMSE) pour les transmissions par la technique CDMA. Basés sur la méthode REFORM, nous montrons le comportement gaussien asymptotique pour le SINR. L'étude du SINR permet la compréhension de comportements d'autres indices de performances comme l'erreur binaire et la probabilité de dépassement. Basés sur la nature gaussienne des entrées de la matrice canal, nous utilisons des outils mathématiques dédiés aux variables gaussiennes pour évaluer ces deux indices de performances. Des simulations montrent bien la pertinence de cette approche. Il est bien connu que l'information mutuelle entre le signal émis et le signal reçu augmente avec l'utilisation des techniques de transmission multi-antennes. Nous nous intéressons à l'étude des fluctuations de cette statistique pour un modèle séparable non centré, cas Rice. Nous développons des outils mathématiques basés sur la théorie des matrices aléatoires permettant de montrer la nature gaussienne des fluctuations de l'information mutuelle.
70

Lateral Position Detection Using a Vehicle-Mounted Camera

Ågren, Elisabeth January 2003 (has links)
<p>A complete prototype system for measuring vehicle lateral position has been set up during the course of this master’s thesis project. In the development of the software, images acquired from a back-ward looking video camera mounted on the roof of the vehicle were used. </p><p>The problem of using computer vision to measure lateral position can be divided into road marking detection and lateral position extraction. Since the strongest characteristic of a road marking image are the edges of the road markings, the road marking detection step is based on edge detection. For the detection of the straight edge lines a Hough based method was chosen. Due to peak spreading in Hough space, the difficulty of detecting the correct peak in Hough space was encountered. A flexible Hough peak detection algorithm was developed based on an adaptive window that takes peak spreading into account. The road marking candidate found by the system is verified before the lateral position data is generated. A good performance of the road marking tracking algorithm was obtained by exploiting temporal correlation to update a search region within the image. A camera calibration made the extraction of real-world lateral position information and yaw angle data possible. </p><p>This vision-based method proved to be very accurate. The standard deviation of the error in the position detection is 0.012 m within an operating range of ±2 m from the image centre. During continuous road markings the rate of valid data is on average 96 %, whereas it drops to around 56 % for sections with intermittent road markings. The system performs well during lane change manoeuvres, which is an indication that the system tracks the correct road marking. This prototype system is a robust and automatic measurement system, which will benefit VTI in its many driving behaviour research programs.</p>

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