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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.
201

Estudo de bandas oligoclonais restritas ao líquido cefalorraquidiano em pacientes com esclerose múltipla na cidade de São Paulo / Study of oligoclonal bands restricted to the cerebrospinal fluid in multiple sclerosis patients in the city of São Paulo

Gama, Paulo Diniz da 02 October 2009 (has links)
Introdução: O diagnóstico da esclerose múltipla (EM) embora seja clínico, se completa com os resultados de imagem de ressonância magnética, somados ainda com a análise do líquido cefalorraquidiano (LCR), que se constituem em ferramentas indispensáveis. A presença das bandas oligoclonais (BOC) no LCR faz parte do estudo da EM, assim como auxilio no diagnóstico. Existem grandes variações quanto à frequência de BOC em pacientes com EM nas diferentes populações, desde 90% em países nórdicos europeus, até 30 a 60% no Japão, China, Índia e Líbano. O presente estudo tem o objetivo de estabelecer o valor da análise do LCR para o diagnóstico da EM em nossa população, com ênfase na pesquisa de BOC. O estudo também objetiva correlacionar os resultados destas análises com as características clínicas e demográficas da amostra selecionada. Casuística e Métodos: Foram estudados 145 pacientes selecionados do Centro de Referência de Doenças Desmielinizantes do Hospital das Clínicas da Faculdade de Medicina de Universidade de São Paulo, no período de agosto de 2005 a janeiro de 2008. Foram registrados para o estudo os dados demográficos, clínicos e da evolução da doença. O diagnóstico da EM foi estabelecido segundo o painel internacional de McDonald, revisado em 2005. A técnica utilizada para a pesquisa de BOC foi a focalização isoelétrica, seguida do immunoblotting, simultaneamente no LCR e no soro sanguíneo. Os resultados desta análise não foram utilizados para estabelecer o diagnóstico, ou para incluir pacientes na casuística da pesquisa. O grupo controle foi selecionado entre aqueles que se submeteram à anestesia raquidiana para cirurgias de pequeno porte. Resultados: Apresentaram BOC: 54,4% dos 90 pacientes com EM; 31,2% dos 16 pacientes com síndrome clínica isolada; 17,9% dos 39 pacientes com doenças neurológicas inflamatórias. No grupo controle, os 19 pacientes não apresentaram BOC. A sensibilidade das BOC foi calculada em 54,4%. A especificidade foi de 100% quando comparado ao grupo controle. Quando comparado com o grupo de pacientes com doenças neurológicas inflamatórias, a especificidade foi de 82,1%. Nos pacientes que se autodeclaram de cor parda ou preta, a frequência de BOC foi maior, com significância na borda do nível de significância de 5% (p=0,0518). Quanto aos aspectos clínicos evolutivos foi constatada maior presença de BOC nas formas progressivas recorrentes (100%); seguida da forma primariamente progressiva (87,5%); secundariamente progressiva (54,5%) e forma remitente recorrente (44,3%). A homogeneidade das BOC segundo as formas clínicas foi significante (p=0,0103), ao nível de significância de 5%. Conclusões: Este trabalho demonstra que a frequência de BOC em pacientes com EM foi de 54,4%, sendo menor que em outras séries mundiais. Estes resultados também não confirmam aqueles obtidos em estudos brasileiros prévios. A etnia e as formas de evolução clínica da doença influenciaram com significância na frequência de aparecimento das BOC. A baixa frequência das BOC no LCR de pacientes com EM pode ser decorrente de fatores associados à baixa e média prevalência da doença nesta região. / Introduction: The diagnosis of multiple sclerosis (MS) although clinical, is rounded out with the results of magnetic resonance imaging, in addition to an analysis of the cerebrospinal fluid (CSF), which form a set of indispensible tools. The presence of oligoclonal bands (OCB) in the CSF is used in the study and for the diagnosis of MS. The frequency of OCB in MS patients varies widely in different populations, ranging from 90% in Nordic countries, to 30 to 60% in Japan, China, India and Lebanon. The objective of the present study is to establish a reference value for the analysis of CSF for the diagnosis of MS in our population, with an emphasis on the study of OCB. A further objective of the study is to correlate the results of these analyses with the clinical and demographic characteristics of the sample selected. Methods: The sample was composed of 145 patients selected from the Demyelinating Diseases Reference Center of the Clinical Hospital of the University of São Paulo, from August 2005 to January 2008. Records containing demographic, clinical and disease progression were used for the study. The diagnosis of MS was established according to 2005 Revisions of the McDonald Criteria. To detect OCB, isoelectric focusing was employed, followed by immunoblotting, simultaneously in both the CSF and blood serum. The results of this analysis were not used to establish the diagnosis or to include patients in the study sample. The control group was selected from those who were submitted to spinal tap for anesthesia in minor surgery. Results: OCB were found in 54.4% of the 90 patients with MS, 31.2% of the 16 patients with isolated clinical syndrome, and 17.9% of the 39 patients with inflammatory neurological diseases. In the control group, 19 patients did not present OCB. The sensitivity of OCB was calculated to be 54.4%. The specificity was 100% when compared to the control group. When compared with the group of patients with inflammatory neurological diseases, the specificity was 82.1%. For the patients who classified themselves as colored or black, the frequency of OCB was higher, with borderline significance using a significance level of 5% (p=0.0518). With regard to clinical evolution of MS, the highest presence of OCB was found in the relapsing progressive types (100%); followed by the primary progressive type (87.5%); secondary progressive type (54.5%); and relapsing remitting type (44.3%). The homogeneity of the OCB in relation to the clinical types was significant (p=0.0103), at a significance level of 5%. Conclusions: This study shows that the frequency of OCB in patients with MS was 54.4%, lower than the findings of other worldwide series. Moreover, these results do not confirm those obtained in other Brazilian studies. Race and clinical progression of the disease influenced, in a statistically significant manner, the frequency of the presence of OCB. The low frequency of OCB in the CSF of patients with MS may be the result of factors associated with the low and medium prevalence of this disease in this region.
202

Análise de anticorpos antiparasitários dosados em soro sanguíneo e sua relação com a presença de bandas oligoclonais em pacientes com esclerose múltipla / Analysis of antiparasitic antibodies measured In Blood serum and their selationship with the presence of oligoclonal bands in patients with multiple Sclerosis

Papavero, Fabiana Cruz Gomes da Fonseca 17 June 2013 (has links)
Introdução: A frequência de detecção de bandas oligoclonais (BOC) em doentes com esclerose múltipla (EM) na cidade de São Paulo é significativamente mais baixa do que em outras cidades do Brasil e de outros países, principalmente da Europa e da América do Norte. Não se conhece o motivo pelo qual isso ocorre. Uma das hipóteses mais interessantes relacionada à imunopatogenia da EM é a chamada Hipótese Higiênica, que postula uma relação inversamente proporcional entre a prevalência de infecções por parasitas e a frequência da EM. Objetivo: verificar se há relação entre a ocorrência de anticorpos contra parasitas no soro sanguíneo e a detecção de BOC em pacientes diagnosticados com EM na cidade de São Paulo. Métodos: Foram estudados 164 pacientes do Ambulatório de Doenças Desmielinizantes da Divisão de Neurologia Clínica e da Divisão de Anestesia do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo dos quais foram obtidas as amostras de LCR e de soro em que foi realizado este estudo. Esses pacientes foram separados em 4 grupos (EM, CIS, Grupo Controle com Pacientes de DNI e Grupo Controle com Pacientes sem Queixas Neurológicas) nos quais foram identificadas as presenças de BOC e de anticorpos parasitários. Para a detecção de anticorpos parasitários, foi utilizada a técnica de eletroforese unidimensional de proteínas em gel de poliacrilamida em sistema descontínuo, com antígenos LV-Tcra (líquido vesicular de Taenia crassiceps) e ES-Tcra (líquido excreção/secreção de Taenia crassiceps). Resultados: Dos 164 pacientes estudados, separados em seus respectivos grupos, foram pesquisados anticorpos antiparasitários de baixo e de alto peso molecular. Esses anticorpos foram observados em 103 pacientes nos quais não havia 13 BOC. Destes, 2 apresentaram anticorpos de baixo peso molecular e 59 anticorpos de alto peso molecular. Dos 61 pacientes em que havia BOC, foram encontrados anticorpos de baixo peso molecular em um; 16 apresentaram anticorpos de alto peso molecular. Conclusão: Em doentes com EM clinicamente definida anticorpos anti-Taenia foram detectados com a mesma frequência em pacientes com BOC e em pacientes sem BOC / Introduction: The frequency of oligoclonal bands (OCB) detection in patients with multiple sclerosis (MS) in the city of São Paulo is significantly lower than in other cities of Brazil and other countries, mainly Europe and North America. To date, the reason for its occurrence is still unknown. One of the most interesting hypotheses related to the immunopathogenesis of MS is the so-called Hygiene Hypothesis, which postulates an inverse relationship between the prevalence of parasitic infections and the frequency of MS. Objective: This study examined whether there is a relationship between the occurrence of antibodies against parasites in blood serum and the detection of OCB in patients diagnosed with MS in the city of São Paulo. Methods: We have studied 164 patients from the Demyelinating Diseases Clinic of the Division of Clinical Neurology and Division of Anesthesia Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo from whom CSF and serum samples were obtained and which were used to conduct the present study. These patients were divided into 4 groups: MS, Clinically Isolated Syndrome (CIS), control group with patients with Inflammatory Neurologic Diseases (IND) and Control Group with patients without neurologic complaints, in whom the presence of OCB and anti- parasitic antibodies was identified. For the detection of parasitic antibodies, the unidimensional electrophoresis of proteins in polyacrylamide gel in a batch system with LV-Tcra antigens (Taenia crassiceps vesicular fluid) and ES-Tcra (net excretion / secretion of Taenia crassiceps) was used. Results: Of the 164 patients studied, separated into their respective groups, anti- parasite antibodies of low and high molecular weight were analyzed. A total of 103 patients presented no OCB, and of these, 2 had antibodies of low molecular weight and 59 presented antibodies of high molecular weight. Of the 61 patients with OCB positive, one showed antibodies of low molecular weight and 16 antibodies of high molecular weight. Conclusion: This study showed that in patients with clinically established MS. anti-Taenia antibodies occurred with the same frequency in patients with OCB and in patients without OCB
203

Efeitos de bandas de frequência espacial alta e baixa no reconhecimento de faces em campo visual lateralizado / Effects of high and low spatial frequency bands in face recognition in lateralized visual field.

Rodriguez, Lina Maria Perilla 04 March 2008 (has links)
O presente trabalho teve por objetivo pesquisar os efeitos que as bandas de freqüência espacial alta e baixa têm no reconhecimento de faces em campo visual lateralizado. Foram distribuídos aleatoriamente 40 participantes em dois grupos. Os voluntários observaram 14 fotos de faces sem filtragem até memorizá-las. A seguir foram apresentadas 56 fotos de faces com filtragens de freqüências espaciais, intercaladas aleatoriamente com apresentações de faces não mostradas anteriormente. Cada uma delas foi exibida na tela durante 300 ms mediante a metodologia de apresentação dicótica. O participante devia responder se a face mostrada pertencia ao grupo de fotos inicialmente observado. As freqüências de respostas permitiram calcular as curvas ROC (Receiver Operating Characteristic) e os parâmetros Az e da preconizado pela Teoria de Detecção de Sinal (MACMILLAN; CREELMAN, 2005) para as faces naturais, faces compostas de freqüências espaciais baixas e faces compostas de freqüências espaciais altas. Os resultados obtidos mostram que as faces Originais foram melhor reconhecidas do que as faces com Freqüências Espaciais Altas (FEA) ou Freqüências Espaciais Baixas (FEB). Ao contrário do achado na literatura, o Hemisfério Esquerdo (HE) teve uma tendência a reconhecer mais eficazmente as faces do que o Hemisfério Direito (HD), independente da condição de filtragem. O HD é igualmente competente do que o HE para processar FEB, mas pior do que o HE para processar FEA. Quanto à performance por gênero, tanto homens quanto mulheres tiveram um desempenho similar quando as faces foram processadas com o HD. O desempenho das mulheres ficou de acordo com a hipótese da FE, pois o reconhecimento que fizeram para as faces com FEA foi melhor do que para as que tinham predomínio de FEB. Os homens, mesmo com o HE, fizeram um reconhecimento melhor das faces com predomínio de FEB do que das faces com FEA. / This study was made with the objective of investigate the effects of high and low spatial frequency bands in face recognition in lateralized visual field. 40 participants were randomly distributed in two groups. The volunteers viewed fourteen non-filtered pictures of faces until they managed to memorize them. After that, fifty six spatial frequency filtered pictures of faces were presented randomly interspersed with pictures of faces previously showed. Each one of them was exhibited in the screen for three hundred milliseconds using the dichotic presentation procedure. The participant should answer whether the face presented belonged to the group of pictures initially viewed. The frequency of responses allowed to calculate the ROC (Receiver Operating Characteristic) Curves and the Az and da parameters praised by the Signal Detection Theory (Macmillan; Creelman, 2005) for natural faces, low spatial frequency composed faces and high spatial frequency composed faces. Results showed that original faces were better recognized than faces with high spatial frequencies (HSF) and low spatial frequencies (LSF). Differently from literature, the left hemisphere was more accurate than the right to recognize faces, regardless of the filter condition. The RH was equivalent to the LH to process LSF, but worse than the LH to process HSF. Concerning the performance of the genders, men and women judged faces in a very similar way when they used the RH. The performance of women agreed with the FE hypothesis, being faces with HSF recognized better than faces with LSF. Men, even using the LH, were more accurate to recognize faces with LSF than HSF.
204

Linhas de Frente das Bandas Marciais de São Paulo: memórias, tensões e negociações (1957-2000)

Corrêa, Elizeu de Miranda 26 February 2016 (has links)
Made available in DSpace on 2016-04-27T19:31:17Z (GMT). No. of bitstreams: 1 Elizeu de Miranda Correa.pdf: 9916752 bytes, checksum: e10d8c79486f784821162bdecf51f893 (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This thesis aims to analyze the disputes, transformations, innovations, permanencies and ruptures, the resistances and negotiations, outlining the approach of this study to front lines (LF) that permeated the Martial Band of Grand São Paulo in the twentieth century, between years 1957 and 2000. However, reflecting on the events and the impacts occurred in the structure and choreographic conceptions of front lines. Their forms of representations, their meanings and discourses produced on these sets over the years chosen for this study. In the moment it was noticed the front lines Martial bands were protagonists of a series of clashes and tensions to stay ahead of the Musical Group and that this cultural practice is not limited only to its subject, it is necessary to think and understand this cultural practice in the academic scenario , justifying thus historicizing it. It is assumed that one of the inherent LF features along this historic route, it is your limitation and insecurity when facing obstacles, and the indulgence of the instructors "choreographers" in not promote the boldness, even if this costs you loss of titles in competitions. Thus, it is quite possible that it has a huge difficulty to reinvent itself, making it stable and exhausting in its materiality. It was used as a methodological theoretical resource use of the Press (Newspapers and Magazines), Images (Pictures and Movies), Regulations and fanfare and bands, laws and Decrees, and the use of oral history techniques (interviews). Overall, it was realized that the LF constitute a cultural practice and aesthetics defined by specific rules (dance, body movement, gestures and expression) certainly include or socially excluded individuals who aim to integrate it. On the other hand, they are for excellence the space of leisure and sociability, the space of dialogue between the body, movement and music. It is assumed, therefore, that it holds meanings and multiple versions: influence, love, reinvents itself and discipline its members, that according to its proponents. In short, it is to know, and maybe so cannot be defined / Essa tese tem como objetivo analisar as disputas, as transformações, as inovações, as permanências e rupturas, as resistências e as negociações, delimitando o recorte deste estudos às Linhas de Frente (LF) que permearam as Bandas Marciais da Grande São Paulo no limiar do século XX, entre os anos de 1957 e 2000. Não obstante, refletir sobre as vicissitudes e os impactos ocorridos na estrutura e nas concepções coreográficas das Linhas de Frente. Bem como perceber as suas formas de representações, os seus significados e os discursos produzidos acerca desses conjuntos ao longo dos anos eleitos para esse estudo. No instante em que se verificou as Linhas de Frente das Bandas Marciais foram protagonistas de uma série de embates e de tensões para permanecerem à frente do Corpo Musical e que essa prática cultural, não se esgota apenas aos seus sujeitos, faz necessário pensar e compreender essa prática cultural no universo acadêmico, justificando, portanto, historicizá-la. Pressupõe-se que, uma das características inerentes das LF ao longo desse percurso histórico, é a sua limitação e insegurança ao enfrentar obstáculos, bem como o comodismo dos instrutores coreógrafos , em não promover a ousadia, ainda que para isso lhe custe a perda de títulos em concursos. Deste modo, é bem possível que, há nela uma dificuldade imensa em se reinventar, tornando-a estável e esgotando-se em sua materialidade. Foi utilizada como recurso teórico metodológico a Imprensa (Jornais e Revistas), Imagens (Fotografias e Filmes), Regulamentos e Planilhas de Notas de Concursos de Fanfarras e Bandas, Leis e Decretos, além do uso das técnicas de História Oral (entrevistas). De modo geral, percebeu-se que as LF constituem uma prática cultural e estética, definida por regras específicas (dança, movimento do corpo, gestos e expressão) certamente incluem ou excluem socialmente os indivíduos que almejam integrá-la. Por outro lado, elas são por excelência o espaço do lazer e da sociabilidade, o espaço do diálogo entre o corpo, o movimento e a música. Pressupõe-se, assim, que ela é detentora de significados e de versões múltiplas que: influência, apaixona, se reinventa e disciplina os seus integrantes, isso de acordo com seus intérpretes. Em síntese, ela é saber, e, talvez por isso não possa ser definida
205

The organization, administration, and function of bands in selected New England colleges

Siragusa, Peter C. January 1965 (has links)
Thesis (M.M.E.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / 2031-01-01
206

Temperature Driven Topological Switch in 1T’-MoTe2 and Strain Induced Nematicity in NaFeAs

Berger, Ayelet January 2018 (has links)
Quasiparticle interference (QPI) is a powerful technique within Scanning Tunneling Microscopy (STM) that is used to probe the electronic bandstructure of materials. This thesis presents two examples using QPI to measure the bandstructure in materials with exotic electronic states that can be tuned via outside parameters (temperature and strain). In Part I of the thesis, we discuss the temperature dependence of Fermi Arcs in 1T’-MoTe2, and then in Part II, the strain dependent nematic state in NaFeAs. The recent discovery of Weyl semimetals has introduced a new family of materials with topologically protected electronic properties and potential applications due to their anomalous transport effects. Even more useful is a Weyl semimetal that can be turned “on” and “off,” switching between a topological and trivial state. One possible material is MoTe2, which undergoes a phase transition at 240K. This thesis consists of experiments using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS) at different temperatures to visualize changes in the electronic bandstructure of MoTe2 across the topological phase transition. We show that a signature of topologically protected Fermi Arcs is present at low temperatures but disappears at room temperature, in the trivial phase. We include an in-depth discussion of how to account for thermal effects when comparing these two types of measurements. In Part II, we discuss strain induced nematicity in NaFeAs, an iron pnictide. Nematic fluctuations and spin correlations play an important role in the phase diagram of the iron pnictides, a family of unconventional superconductors. Illuminating the mechanism behind this symmetry breaking is key to understanding the superconducting state. Previous work has shown that nematicity in the iron pnictides responds strongly to applied strain [1, 2]. In this thesis, I present results from a new experimental technique, elasto-scanning tunneling microscopy (E-STM), which combines in situ strain and atomic resolution STM/STS. For the first time, we are able to observe the effects of strain on nematicity at the local level. We perform E-STM measurements in both the spin density wave phase and the tetragonal phase of NaFeAs and measure a distinct response in each. We successfully use strain to manipulate domain boundaries in the spin density wave state and we find the intensity of nematic fluctuations is coupled to strain in NaFeAs in the tetragonal phase.
207

Spectroscopie des transitions électroniques des cations hydrocarbures aromatiques polycycliques et de leurs agrégats / Electronic Spectroscopy of Polycyclic Aromatic Hydrocarbon Cations and their Clusters

Friha, Hela 18 December 2012 (has links)
Ce travail est une étude expérimentale de la spectroscopie électronique des cations hydrocarbures aromatiques polycycliques (PAH) et de leurs agrégats dans des conditions simulant celles régnant dans le milieu interstellaire, froids et totalement isolés. L’objectif principal est d’obtenir des spectres au laboratoire qui puissent être comparés aux spetres des Bandes Diffuses Interstellaires et d’explorer les propriétés des agrégats de PAH. / This work is mainly an experimental study of the electronic spectroscopy of the polycyclic aromatic hydrocarbon cations and their clusters in conditions close to those of the interstellar medium. The aim of this study is to obtain data that can be compared with the spectrum of the diffuse interstellar bands and to explore the properties of PAH clusters.
208

Effect Sizes, Significance Tests, and Confidence Intervals: Assessing the Influence and Impact of Research Reporting Protocol and Practice

Hess, Melinda Rae 30 October 2003 (has links)
This study addresses research reporting practices and protocols by bridging the gap from the theoretical and conceptual debates typically found in the literature with more realistic applications using data from published research. Specifically, the practice of using findings of statistical analysis as the primary, and often only, basis for results and conclusions of research is investigated through computing effect size and confidence intervals and considering how their use might impact the strength of inferences and conclusions reported. Using a sample of published manuscripts from three peer-rviewed journals, central quantitative findings were expressed as dichotomous hypothesis test results, point estimates of effect sizes and confidence intervals. Studies using three different types of statistical analyses were considered for inclusion: t-tests, regression, and Analysis of Variance (ANOVA). The differences in the substantive interpretations of results from these accomplished and published studies were then examined as a function of these different analytical approaches. Both quantitative and qualitative techniques were used to examine the findings. General descriptive statistical techniques were employed to capture the magnitude of studies and analyses that might have different interpretations if althernative methods of reporting findings were used in addition to traditional tests of statistical signficance. Qualitative methods were then used to gain a sense of the impact on the wording used in the research conclusions of these other forms of reporting findings. It was discovered that tests of non-signficant results were more prone to need evidence of effect size than those of significant results. Regardless of tests of significance, the addition of information from confidence intervals tended to heavily impact the findings resulting from signficance tests. The results were interpreted in terms of improving the reporting practices in applied research. Issues that were noted in this study relevant to the primary focus are discussed in general with implicaitons for future research. Recommendations are made regarding editorial and publishing practices, both for primary researchers and editors.
209

Mechanical response of glassy materials : theory and simulation

Tsamados, Michel 14 December 2009 (has links) (PDF)
Il est bien établi que les propriétés mécaniques et rhéologiques d'une large classe de matériaux vitreux amorphes met en jeu - contrairement aux dislocations dans les cristaux - des rearrangements structuraux localisés formant par un processus de cascade des bandes de cisaillements. Cette localisation de la déformation est observée dans divers systèmes vitreux ainsi que dans des simulations numériques. Cette réponse mécanique complexe reste mal comprise à une échelle microscopique et il n'est pas clair si l'écoulement plastique peut être associé à une origine structurale locale ou à des processus purement dynamiques.Dans cette thèse nous envisageons ces problématiques à l'aide de simulations atomiques athermales sur un système Lennard-Jones modèle. Nous calculons le tenseur élastique moyenné localement sur une échelle nanométrique. A cette échelle, le verre est assimilable à un matériau composite comprenant un échafaudage rigide et des zones fragiles. L'étude détaillée de la déformation plastique à différents taux de cisaillement met en évidence divers régimes d'écoulement. En dessous d'un taux de cisaillement critique dépendant de la taille du système, la réponse mécanique atteind une limite quasistatique (effets de taille fini, cascades d'événements plastiques, contrainte seuil) alors que pour des taux de cisaillement plus importants les propriétés rhéologiques sont fixées par le taux de cisaillement imposé. Dans ce régime nous mettons en évidence la croissance d'une longueur de coopérativité dynamique et discutons de sa dépendance avec le taux de cisaillements.
210

High-Speed Downlink Shared Channel in Unlicensed Frequency Bands / HS-DSCH i olicensierade frekvensband

Zetterberg, Kristina January 2004 (has links)
<p>In the standardized air interface for third generation mobile communication systems, WCDMA release 5, a concept called High Speed Downlink Packet Access (HSDPA) is introduced. HSDPA enables faster transmissions from base stations to mobile users by using a shared, high-capacity channel called the High-Speed Downlink Shared Channel (HS-DSCH) that is designed for best effort services. The HS-DSCH is developed for usage in the frequency band licensed for third generation communication systems. As the use of licensed frequency bands is costly it may be interesting to make use of the unlicensed frequency bands at 2.4 GHz and 5 GHz with higher interference and stricter regulations. Using HS- DSCH in unlicensed frequency bands would lead to smaller costs and a new kind of usage of the HS-DSCH. </p><p>In order to transmit in unlicensed frequency bands, some requirements set up by the public authorities must be followed. This means that the maximum transmit power used by the HS-DSCH must be decreased and, on the 5 GHz frequency band, that features to avoid disturbing radar systems have to be implemented. The HS- DSCH has a bandwidth of 5 MHz. To use the available frequency spectra more efficiently, multiple carriers could be used. </p><p>Wireless Local Area Networks (WLANs) are the most common way to transfer data in unlicensed frequency bands today. Assessments and simulations of WLAN and the HS-DSCH in unlicensed frequency bands show that WLAN can provide higher bitrates than the HS-DSCH for low loads. HS-DSCH can however provide a larger coverage per base station, and is more bandwidth effective than WLAN. Using a larger bandwidth is necessary for HS-DSCH to compete with WLAN, which uses a bandwidth approximately four times as large as the HS-DSCH bandwidth. The usage of the HS-DSCH in unlicensed frequency bands also has the advantage that the services provided by the third generation communication systems can be accessed easily.</p>

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