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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.
51

Atribuição automática de autoria de obras da literatura brasileira / Atribuição automática de autoria de obras da literatura brasileira

Nobre Neto, Francisco Dantas 19 January 2010 (has links)
Made available in DSpace on 2015-05-14T12:36:48Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 1280792 bytes, checksum: d335d67b212e054f48f0e8bca0798fe5 (MD5) Previous issue date: 2010-01-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Authorship attribution consists in categorizing an unknown document among some classes of authors previously selected. Knowledge about authorship of a text can be useful when it is required to detect plagiarism in any literary document or to properly give the credits to the author of a book. The most intuitive form of human analysis of a text is by selecting some characteristics that it has. The study of selecting attributes in any written document, such as average word length and vocabulary richness, is known as stylometry. For human analysis of an unknown text, the authorship discovery can take months, also becoming tiring activity. Some computational tools have the functionality of extracting such characteristics from the text, leaving the subjective analysis to the researcher. However, there are computational methods that, in addition to extract attributes, make the authorship attribution, based in the characteristics gathered in the text. Techniques such as neural network, decision tree and classification methods have been applied to this context and presented results that make them relevant to this question. This work presents a data compression method, Prediction by Partial Matching (PPM), as a solution of the authorship attribution problem of Brazilian literary works. The writers and works selected to compose the authors database were, mainly, by their representative in national literature. Besides, the availability of the books has also been considered. The PPM performs the authorship identification without any subjective interference in the text analysis. This method, also, does not make use of attributes presents in the text, differently of others methods. The correct classification rate obtained with PPM, in this work, was approximately 93%, while related works exposes a correct rate between 72% and 89%. In this work, was done, also, authorship attribution with SVM approach. For that, were selected attributes in the text divided in two groups, one word based and other in function-words frequency, obtaining a correct rate of 36,6% and 88,4%, respectively. / Atribuição de autoria consiste em categorizar um documento desconhecido dentre algumas classes de autores previamente selecionadas. Saber a autoria de um texto pode ser útil quando é necessário detectar plágio em alguma obra literária ou dar os devidos créditos ao autor de um livro. A forma mais intuitiva ao ser humano para se analisar um texto é selecionando algumas características que ele possui. O estudo de selecionar atributos em um documento escrito, como tamanho médio das palavras e riqueza vocabular, é conhecido como estilometria. Para análise humana de um texto desconhecido, descobrir a autoria pode demandar meses, além de se tornar uma tarefa cansativa. Algumas ferramentas computacionais têm a funcionalidade de extrair tais características do texto, deixando a análise subjetiva para o pesquisador. No entanto, existem métodos computacionais que, além de extrair atributos, atribuem a autoria baseado nas características colhidas ao longo do texto. Técnicas como redes neurais, árvores de decisão e métodos de classificação já foram aplicados neste contexto e apresentaram resultados que os tornam relevantes para tal questão. Este trabalho apresenta um método de compressão de dados, o Prediction by Partial Matching (PPM), para solução do problema de atribuição de autoria de obras da literatura brasileira. Os escritores e obras selecionados para compor o banco de autores se deram, principalmente, pela representatividade que possuem na literatura nacional. Além disso, a disponibilidade dos livros em formato eletrônico também foi considerada. O PPM realiza a identificação de autoria sem ter qualquer interferência subjetiva na análise do texto. Este método, também, não faz uso de atributos presentes ao longo do texto, diferentemente de outros métodos. A taxa de classificação correta alcançada com o PPM, neste trabalho, foi de aproximadamente 93%, enquanto que trabalhos relacionados mostram uma taxa de acerto entre 72% e 89%. Neste trabalho, também foi realizado atribuição de autoria com a abordagem SVM. Para isso, foram selecionados atributos no texto dividido em dois tipos, sendo um baseado em palavras e o outro na contagem de palavrasfunção, obtendo uma taxa de acerto de 36,6% e 88,4%, respectivamente.
52

Sistema Embarcado para um Monitor Holter que Utiliza o Modelo PPM na Compressão de Sinais ECG

Farias, Thyago Maia Tavares de 04 March 2010 (has links)
Made available in DSpace on 2015-05-14T12:36:54Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2004014 bytes, checksum: 3d8ca87826ca89996bb9c71a82501746 (MD5) Previous issue date: 2010-03-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work, we present the development of an embedded system prototyping with soft-core Nios II and FPGA for a holter monitor that implements data compression, using the PPM Algorithm, and simulate ECG signals through the implementation of the Fourier series. Through a holter monitor, cardiologists can obtain ECG signals, serving as the basis for the perception of symptoms and activities of patients. These signals are captured and recorded by monitors in periods greater than or equal to 24 hours, requiring large storage size to store them, therefore increasing cost of the monitor. Using the PPM algorithm, a monitor holter can considerably reduce the size of the signals stored, thus reducing storage space and cost of device, addition to allow rapid transmission of the data. Integrating the ECG signal simulator to the device, is possible to generate samples of ECG via the embedded system, saving time and eliminating difficulties in obtaining signals, compared with the capture of real ECG signals by invasive and noninvasive methods. It enables the analysis and study of normal and abnormal ECGs. An embedded system on programmable chip (SOPC) was prototyped with a development kit containing peripherals and FPGA chip compatible with the Nios II. Architecture soft-core was set to compact operating system and software modules have been successfully developed, ported and validated on this platform. / Neste trabalho, é apresentado o desenvolvimento de um sistema embarcado com prototipagem em FPGA contendo instanciação do processador soft-core Nios II (SOPC System on a Programmable Chip), para um monitor holter que implementa compressão de dados, utilizando o algoritmo PPM, e simula sinais ECG através da implementação das Séries de Fourier. Através de um monitor holter, cardiologistas podem obter sinais ECG, que servem de base para a percepção de sintomas e atividades em pacientes, captados e armazenados pelos monitores em períodos maiores ou iguais a 24 horas, requisitando grandes espaços de armazenamento, aumentando, assim, o custo deste monitor. Utilizando o PPM, o dispositivo desenvolvido poderá reduzir consideravelmente a quantidade de dados armazenados, reduzindo, portanto, o espaço de armazenamento e o custo do dispositivo, permitindo ainda a rápida transmissão dos dados. Integrando o simulador de sinais ECG ao dispositivo, possibilita-se a geração de amostras de sinais eletrocardiográficos através do sistema embarcado, economizando tempo e eliminando dificuldades na obtenção de sinais, em comparação com a captação real de sinais ECG através de métodos invasivos e nãoinvasivos. O mesmo permite a análise e o estudo de sinais ECG normais e anormais. Um sistema embarcado em chip programável (SOPC) foi prototipado com uma placa contendo periféricos e uma pastilha FPGA dotada de compatibilidade com o Nios II; a arquitetura do soft-core foi configurada em sistema operacional compacto e módulos de software foram exitosamente desenvolvidos, portados e validados sobre essa plataforma.
53

Reconhecimento de formas utilizando modelos de compressão de dados e espaços de escalas de curvatura

Lordão, Fernando Augusto Ferreira 27 August 2009 (has links)
Made available in DSpace on 2015-05-14T12:36:54Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2499209 bytes, checksum: 80d399f8f00f3e82d2a3b34e52fd6b05 (MD5) Previous issue date: 2009-08-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / As the processing power of computers increases, the quantity and complexity of stored data have growing in the same way, requiring more sophisticated mechanisms to accomplish retrieval with efficacy and efficiency over these information. In image processing, it has become common the retrieval based on its own content, namely Content-Based Image Retrieval (CBIR), which eliminates the need to place additional annotations as textual descriptions and keywords registered by an observer. The purpose of this work is the development of an image retrieval mechanism based on shape recognition. The mechanism consists in (1) compute the Full Curvature Scale Space (FullCSS) image descriptors; and (2) apply over them a lossless compression method objecting to (3) classify these descriptors and retrieve the corresponding images. The FullCSS descriptors register the curvature variations on the image contour indicating the degree and the signal of these variations, which allow identifying where the curvature is concave or convex. The adopted compression method uses the Prediction by Partial Matching (PPM) compression model, which has been successfully used in other works to classify texture images. The results obtained show that this novel approach is able to reach competitive levels of efficacy and efficiency when compared to other works recently developed in this same area. / Com o aumento do poder de processamento dos computadores, cresceu também a quantidade e complexidade dos dados armazenados, exigindo mecanismos cada vez mais sofisticados para se conseguir uma recuperação eficaz e eficiente destas informações. No caso do processamento de imagens, tem se tornado comum a recuperação baseada em seu próprio conteúdo, ou seja, Recuperação de Imagem Baseada em Conteúdo (Content-Based Image Retrieval CBIR), eliminando a necessidade de anotações adicionais como descrições textuais e palavras-chave registradas por um observador. A proposta deste trabalho é o desenvolvimento de um mecanismo de recuperação de imagens através do reconhecimento de sua forma. O mecanismo consiste em (1) calcular os descritores Full Curvature Scale Space (FullCSS) das imagens; e (2) aplicar sobre eles um método de compressão sem perdas com a finalidade de (3) classificar esses descritores e recuperar as imagens correspondentes. Os descritores FullCSS registram as variações na curvatura do contorno da imagem indicando o grau e o sinal dessas variações, permitindo identificar onde a curvatura é côncava ou convexa. O método de compressão adotado utiliza o modelo de compressão Prediction by Partial Matching (PPM), utilizado com sucesso em outros trabalhos para classificar imagens de texturas. Os resultados obtidos indicam que esta abordagem inovadora é capaz de atingir níveis competitivos de eficácia e eficiência quando comparada a outros trabalhos atualmente desenvolvidos nesta mesma área.
54

Inneklimat i kontorsmiljö : Utvärdering av inneklimat i en kontorsmiljö med fokus på ventilationen / Indoor climate in office environment : Assessment of indoor climate in an office environment with focus on ventilation

Alhakim, Ali, Hakim, Roz January 2018 (has links)
I dagens samhälle tillbringar människan ca 90 procent av sin tid inomhus, vilket innebär att människan befinner sig i konstgjort inomhusklimat. Då människan tenderar att befinna sig inomhus är det stor vikt att ventilationen ska fungera så bra som möjligt och att inomhusklimatet är tillfredsställande för vårt välmående och välbefinnande på arbetsplatsen. Tidigare studier visar att nästan hälften av svenskar är missnöjda med ventilationen i deras arbetsmiljö (kontor). Ett bra inomhusklimat i kontorsmiljöer ökar tillfredställandet hos personalen, ökar produktiviteten samt minskar sjukfrånvaron. Detta leder till att organisationen/företaget besparar pengar i slutändan, då personalen arbetar mer effektivt och har mindre sjukfrånvaro. Syftet med denna studie är att undersöka klimatet i kontorsmiljön med fokus på termisk komfort samt se hur ventilation systemen påverkar inomhusklimatet. Vidare kommer sambanden mellan dessa att analyseras. Målet är undersöka hur komforten på kontoret påverkar människors hälsa, produktivitet och välmående. Målet är även att identifiera om det råder bristfällig ventilation samt att presentera eventuella förbättringar. I studien genomförs en undersökning av sex kontor på Brinellvägen 23. I undersökningen tillämpas en enkätstudie och ett antal olika mätningar, flödesmätningar, koldioxidsmätningar, temperaturmätningar och den relativa fuktigheten. I flödesmätningarna mäts till – och frånluften på samtliga kontor. Medan koldioxidmätningarna mäter även temperaturen och relativa fuktigheten. Koldioxidsmätningarna pågick i två timmar i 4 kontor, medan i de två resterande kontoren fortsatte mätningarna under en hel arbetsdag. Enkätstudien tilldelades ut till personalen i kontoren i syfte att ta del av subjektiva åsikter kring miljön i kontoren. Resultaten från mätningarna och enkätundersökningen visar att klimatet i kontoren i överlag inte var tillfredställande och obehag upplevdes utav personerna som arbetar där. Endast ett kontor uppfyllde det projekterade tilluftsflödet, medan de resterande kontoren varken uppfyllde projekterade flödena eller BBR:s krav för mängden flöde i kontorsmiljöer. Koldioxidhalten i kontoren med en person klarade av gränsen under 1000 ppm. Dock är kontoren projekterade för två personer och när två personer arbetade i kontoren översteg koldioxidhalten till ca 1200 ppm. Då koldioxidhalten överstiger 1000 ppm bör ventilationen kontrolleras, vilket behövs i detta fall. / In today's society, humans spend about 90 percent of their time indoors, in an artificial indoor climate. As people tend to be indoors more and more, it is important that the ventilation work as well and efficiently as possible, and that the indoor climate is pleasing for our well-being at the workplace. Previous studies show that almost half of Swedes are dissatisfied with the ventilation in their work environment (offices). A good indoor climate in offices increases employee satisfaction, increases productivity, and reduces absenteeism. This causes the organization / company to save money in the end, as staff work more efficiently and have less sick leave. The purpose of this study is to investigate the climate in office environment, focusing on thermal comfort and to see how ventilation systems affect the indoor climate. Furthermore, the relationships between these will be analyzed. The aim is to investigate how the comfort in the office affects human health, productivity and well-being. The goal is also to identify if there is insufficient ventilation to the offices that will be investigated and to eventually present possible improvements. In this report a study of six offices on Brinellvägen 23 was carried out. In the study, a number of flow measurements are carried out for each office's supply and exhaust air, carbon dioxide measurements, temperature and the relative humidity for four hours in four of the offices, with open and closed doors. While in two of the offices, the measurements continued for a whole working day, 6-8h. In addition to these measurements, surveys were distributed to the staff in the offices in order to share subjective opinions about the environment in the offices. The results from the measurements and the survey showed that the overall climate was not satisfactory, and discomfort was experienced by the people working there. Only one office met the projected supply airflow, while the remaining offices neither met the projected flows nor BBR requirements for the amount of flow in office environments. The carbon dioxide levels in the offices with one person was acceptable, they did not pass the limit of 1000 ppm. However, the offices were projected for two persons and when two persons worked in the offices, the carbon dioxide levels exceeded about 1200 ppm. When the carbon dioxide level exceeds 1000 ppm, it is recommended that the ventilation be checked, as needed in this case.
55

Communication and Error Correction via Polarisation of Single Photons and Time Ordering / Kommunikation och felkorrigering via polarisering av enstaka fotoner och tidsordning

Leung, Shek Lun January 2023 (has links)
This research study aims to investigate the capacity of single photons to carry information through polarization and time ordering and proposes a protocol called Beyond Pulse Position Modulation (BPPM) to improve photon-based communication reliability over longer distances with limited power. Such a protocol may be used in any communication scenario where energy efficiency is important, e.g., in satellite communication or where pulse position modulation (PPM) typically is used. The study compares various metrics such as information bits per symbol, photon, and time bin to evaluate the system’s efficiency and conducts a comparative analysis of BPPM, Pulse Position Modulation (PPM), On-Off Keying (OOK), andGeneral protocol’s effectiveness. (The simulations were conducted using the Python programming language with Visual Studio Code IDE.) / Denna forskningsstudie syftar till att undersöka informationskapaciteten hos enstaka fotoner då dessa kodats med avseende på polarisering och tidsordning. Ett nytt protokoll som kallas Beyond Pulse Position Modulation (BPPM) använder felkorrigering för att förbättra kommunikationstillförlitligheten över längre avstånd med begränsad effekt. Ett sådant protokoll kan användas i vilket kommunikationsscenario som helst där energieffektivitet är viktigt, t.ex. vid satellitkommunikation eller där pulspositionsmodulering (PPM) vanligtvis används. Studien jämför olika mätvärden som informationsbitar per symbol, per foton och per tidslucka för att utvärdera systemets effektivitet och genomför en jämförande analys av BPPM, Pulse Position Modulation (PPM), On-Off Keying (OOK) och ett protokoll med fixt antal fotoner per block avseende protokollens effektivitet. (Simuleringarna utfördes med Python-programmeringsspråket med Visual Studio Code IDE.)
56

Aktiv eller inte aktiv i PPM – Får du betalt för din risk? En teoriprövande analys genom Markowitz moderna portföljteori / Active or inactive in the Swedish Pension System A theory-testing analysis by Markowitz modern portfolio theory

Jansson, Nils-Henrik, Winberg, Madelene January 2016 (has links)
I och med pensionsreformen vid sekelskiftet lades ett större ansvar på den individuelle pensionsspararen då man nu själv ska besluta hur en del av den allmänna pensionen ska placeras. Syftet med denna uppsats är att analysera huruvida det hade varit möjligt för en pensionssparare att uppnå en högre riskjusterad avkastning för sin premiepension genom att göra ett aktivt val i form av en egen sammansatt portfölj, än att låta staten förvalta pensionen i förvalsalternativet AP7 Såfa. Analysen är baserad på Harry Markowitz etablerade moderna portföljteori där han uppmärksammade hur sparare genom diversifiering kan reducera risken i sin placering genom att välja tillgångar som inte fullt samvarierar. Genom användning av tillgänglig data för tidsperioden 2000 – 2014 över de fonder som finns valbara i PPM-systemet har vi beräknat de optimala portföljer med samma risknivå som förvalsalternativet. Därefter har dessa jämförts med försvarsalternativet med avseende på risk och avkastning. Dessutom har tre teoretiska portföljer satts samman över en period på tio år, som placerats som dessa optimala portföljer och omallokerats efter Markowitz rekommendation att se över sitt sparande en gång om året. Analysen visar att det har gått att uppnå en högre riskjusterad avkastning genom att själv göra ett aktivt val av portfölj i sitt sparande. Problemet ligger i att det är svårt att identifiera dessa portföljer i förtid. De tre teoretiska portföljerna har samtliga presterat väsentligt mycket sämre än vad förvalsalternativet har gjort under samma tidsperiod. Resultatet visar att förvalsalternativet inte är fullt riskjusterat, man har alltså inte fullt fått betalt för den risk man tagit i sitt sparande. Vi drar ändå slutsatsen att förvalsalternativet är ett fullgott alternativ. / The Swedish premium pension reform at the turn of the century resulted in a greater responsibility for the individual saver. The decision concerning how the premium pension should be invested now lies with the investor. The purpose of this thesis is to analyze whether it had been profitable for a saver to achieve a higher risk-adjusted return for its premium pension money contributions by making an active choice by a self-composed portfolio, rather than to allow the State to invest the capital in the Seventh AP Fund (AP7 Såfa) which is the default option. The analysis is based on Harry Markowitz’s established Modern Portfolio Theory by which he drew attention to how investors through diversification can reduce risk in its investment by choosing assets that are not fully correlated. By using the available data of the funds that were selectable in the Swedish Premium Pension system by the time period 2000 – 2014, we have calculated the optimized portfolios with the same risk level as the default option. Subsequently, a comparison of these optimized portfolios and the default option are made in terms of risk and return. Furthermore, three theoretical portfolios are put together over a period of ten years and are invested as these optimized portfolios and reallocated after Markowitz's recommendation to review their savings once a year. The analysis shows that it has been possible to achieve higher risk-adjusted returns by making an active choice of portfolio. The problem though is that it is difficult to identify these portfolios in advance. The three theoretical portfolios have all generated a lower return than the default option did during the same period. The result shows that the default option is not fully risk-adjusted. Nonetheless, we conclude that the default fund is a good alternative.
57

Text Augmentation: Inserting markup into natural language text with PPM Models

Yeates, Stuart Andrew January 2006 (has links)
This thesis describes a new optimisation and new heuristics for automatically marking up XML documents, and CEM, a Java implementation, using PPM models. CEM is significantly more general than previous systems, marking up large numbers of hierarchical tags, using n-gram models for large n and a variety of escape methods. Four corpora are discussed, including the bibliography corpus of 14682 bibliographies laid out in seven standard styles using the BibTeX system and marked up in XML with every field from the original BibTeX. Other corpora include the ROCLING Chinese text segmentation corpus, the Computists' Communique corpus and the Reuters' corpus. A detailed examination is presented of the methods of evaluating mark up algorithms, including computation complexity measures and correctness measures from the fields of information retrieval, string processing, machine learning and information theory. A new taxonomy of markup complexities is established and the properties of each taxon are examined in relation to the complexity of marked up documents. The performance of the new heuristics and optimisation are examined using the four corpora.
58

Construction et Analyse de Nouveaux Codes Spatio-Temporels pour les Systèmes Ultra Large Bande par Impulsions

Abou Rjeily, Chadi 05 October 2006 (has links) (PDF)
Ce rapport de thèse présente des nouvelles méthodes d'émission et de réception basées sur les transmissions ULB pour les canaux à antennes multiples. Pour les systèmes ULB il devient excessivement difficile de récupérer l'information de phase et les codes espace-temps existants ne peuvent pas être appliqués. Pour résoudre ce problème, nous proposons la construction de nouvelles familles de codes espace-temps pour les systèmes ULB impulsionnels. Dans un premier temps, les outils mathématiques basés sur les algèbres cycliques de division ont été adaptés pour la construction d'un schéma de codage totalement réel. Dans un deuxième temps, nous avons proposé une autre famille de codes basée sur l'introduction du codage conjoint symbole-impulsion. Finalement, nous proposons des nouvelles constructions spécifiques aux modulations de positions ou aux modulations conjointes de position et d'amplitude. Ces constructions permettent d'obtenir une famille de code présentant les meilleures performances parmi tous les schémas de codage espace-temps ULB existant dans la littérature. Dans certains cas, cette famille de codes totalement réels satisfait toutes les contraintes de construction des codes parfaits. Enfin, nous nous sommes intéressés à des constructions de codes distribués pour les systèmes ULB coopératifs. Nous présentons des nouvelles techniques de coopération pour les stratégies type "amplify-and-forward" et "decode-and-forward". Nous présentons une analyse analytique, semi-analytique et numérique des solutions proposées sur des canaux ULB sélectifs en fréquence. Nous présentons aussi des schémas pratiques de transmission, réception et décodage des systèmes multi-antennes ULB.
59

Evaluation of endothelial cell response to drug for intraocular lens delivery

Doody, Laura January 2011 (has links)
Cataract is one of the leading causes of vision loss worldwide. The rate of cataract surgery has been steadily increasing. Toxic Anterior Segment Syndrome (TASS) is a sterile inflammatory response in the anterior segment of the eye that may occur following cataract surgery. When left untreated, it can lead to permanent vision loss. Corneal endothelial cells are the cells most affected by TASS. These cells are unable to reproduce in vivo and consequently once the density of these cells drops below a certain level, vision is reduced and cannot be reversed. The damage is thought to be mediated by cytokines and endotoxins, primarily through the NF-κΒ pathway. It is hypothesized that anti-inflammatory drug delivery intraocular lenses may help reduce the occurrence of TASS and consequent vision loss. In this research thesis project, an in vitro model was developed as a tool to select drug and delivery material to be used in an anti-TASS ophthalmic biomaterial. In an attempt to find a novel and more effective approach to TASS prevention, dexamethasone, a potent anti-inflammatory steroid drug, was compared to triptolide, a cytokine inhibitor; aprotinin, a general protease inhibitor; and PPM-18, a NF-κΒ inhibitor. To assess the efficacy of these drugs, an in vitro assay using human umbilical vein endothelial cells (HUVEC) and lipopolysaccharide as a stimulant was developed. Cell response to dexamethasone (10 nM), triptolide (3 nM), aprotinin (20 μM) and PPM-18 (10 μM) with or without LPS was characterized by cell viability and flow cytometry analysis of cell activation. Activation was characterized using markers for cell adhesion and activation ICAM-1, PECAM-1, VCAM-1, β1-integrin, CD44 and E-selectin. Following preliminarily testing, the efficacy of dexamethasone (10 nM) and PPM-18 (10 μM) loaded polymer (PDMS) and copolymer (PDMS/pNIPAAm) interpenetrating polymer networks were evaluated over a 4 day release period. The results from soluble drug and LPS (100 ng/mL) testing indicated no decrease in cell viability after 24 h. Dexamethasone, triptolide, aprotinin, and PPM-18 did not reduce the significant ICAM-1 upregulation seen in HUVECs after exposure to LPS for 4 days. PPM-18 in combination with LPS significantly upregulated E-selectin iv and CD44 from unstimulated HUVEC cells. The polymer materials without drug loading did not influence the cell phenotype. However, PPM-18 delivering polymer and copolymer materials significantly upregulated VCAM-1, CD44 when compared to all other treatments. Propidium iodide uptake in HUVEC exposed to PPM-18 drug delivering polymer and copolymer treatments indicated that these treatments caused cell necrosis. None of the drugs, or the drug delivering materials were shown to counteract the upregulation seen from LPS stimulation of HUVEC cells. Future work should focus on validating the in vitro model to more closely replicate the in vivo environment of the anterior segment with the use of primary bovine corneal endothelial cells.
60

Evaluation of endothelial cell response to drug for intraocular lens delivery

Doody, Laura January 2011 (has links)
Cataract is one of the leading causes of vision loss worldwide. The rate of cataract surgery has been steadily increasing. Toxic Anterior Segment Syndrome (TASS) is a sterile inflammatory response in the anterior segment of the eye that may occur following cataract surgery. When left untreated, it can lead to permanent vision loss. Corneal endothelial cells are the cells most affected by TASS. These cells are unable to reproduce in vivo and consequently once the density of these cells drops below a certain level, vision is reduced and cannot be reversed. The damage is thought to be mediated by cytokines and endotoxins, primarily through the NF-κΒ pathway. It is hypothesized that anti-inflammatory drug delivery intraocular lenses may help reduce the occurrence of TASS and consequent vision loss. In this research thesis project, an in vitro model was developed as a tool to select drug and delivery material to be used in an anti-TASS ophthalmic biomaterial. In an attempt to find a novel and more effective approach to TASS prevention, dexamethasone, a potent anti-inflammatory steroid drug, was compared to triptolide, a cytokine inhibitor; aprotinin, a general protease inhibitor; and PPM-18, a NF-κΒ inhibitor. To assess the efficacy of these drugs, an in vitro assay using human umbilical vein endothelial cells (HUVEC) and lipopolysaccharide as a stimulant was developed. Cell response to dexamethasone (10 nM), triptolide (3 nM), aprotinin (20 μM) and PPM-18 (10 μM) with or without LPS was characterized by cell viability and flow cytometry analysis of cell activation. Activation was characterized using markers for cell adhesion and activation ICAM-1, PECAM-1, VCAM-1, β1-integrin, CD44 and E-selectin. Following preliminarily testing, the efficacy of dexamethasone (10 nM) and PPM-18 (10 μM) loaded polymer (PDMS) and copolymer (PDMS/pNIPAAm) interpenetrating polymer networks were evaluated over a 4 day release period. The results from soluble drug and LPS (100 ng/mL) testing indicated no decrease in cell viability after 24 h. Dexamethasone, triptolide, aprotinin, and PPM-18 did not reduce the significant ICAM-1 upregulation seen in HUVECs after exposure to LPS for 4 days. PPM-18 in combination with LPS significantly upregulated E-selectin iv and CD44 from unstimulated HUVEC cells. The polymer materials without drug loading did not influence the cell phenotype. However, PPM-18 delivering polymer and copolymer materials significantly upregulated VCAM-1, CD44 when compared to all other treatments. Propidium iodide uptake in HUVEC exposed to PPM-18 drug delivering polymer and copolymer treatments indicated that these treatments caused cell necrosis. None of the drugs, or the drug delivering materials were shown to counteract the upregulation seen from LPS stimulation of HUVEC cells. Future work should focus on validating the in vitro model to more closely replicate the in vivo environment of the anterior segment with the use of primary bovine corneal endothelial cells.

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