There is an increasing interest in studying the concentration of the inhibitory neurotransmitter γ-Amino Butyric Acid (GABA), both in the healthy and diseased brain by using Magnetic Resonance Spectroscopy (MRS). Recent studies have shown correlations between an abnormal GABA concentration in certain regions of the brain and disorders as e.g. Parkinson’s disease and depressive disorders. There are presently many technical difficulties with the absolute quantification of GABA and the method MEGA-PRESS is currently the standard technique used in data acquisitions and processing of spectra. In this thesis, different techniques of GABA quantification have been evaluated and the most important aspect was to explore the precision of the method for further usage as a clinical tool. This project involved the exploration of data acquisitions by using a MEGA-PRESS sequence on a 3 T MR-system, processing of the resulting datasets using different methodologies, GABA quantification by using linear combination of model spectra (LCModel), and interpretation of the results by performing statistical analyses. The thesis resulted in a low resolution GABA-atlas of the brain which did not indicate any significant differences in the GABA concentration within the healthy subject group. However, a significant regional difference was observed in the brain. The main uncertainties arose mainly due to the relatively small subject groups and the large measurement error. Future measurements will require improvements both in the data acquisition and in analyzing these with an improved method of processing. The final conclusion was that the GABA quantification sequence MEGA-PRESS is useful both in diagnosis and as a research tool, although further improvements are required.

In rodents, stress and corticosteroids rapidly increase excitatory neurotransmission. During excitatory neurotransmission, glutamate concentrations are maintained by conversion of glutamine to glutamate. The hypothesis was that cortisol would alter human prefrontal glutamine or glutamate concentrations. Glutamine and glutamate were measured in prefrontal cortex (n = 12) using 3.0 Tesla proton magnetic resonance spectroscopy (1H-MRS) before and after intravenous cortisol (hydrocortisone 35mg), in a randomized, double blind, placebo-controlled, within-subjects design. Glutamine decreased following cortisol compared with placebo (session by time, F(2,22) = 5.51; p = 0.012), whereas glutamate did not change (F(4,44) = 0.71; p = 0.59). Glutamine may be utilized to maintain glutamate concentrations during increased excitatory neurotransmission following cortisol. A limitation is that 1H-MRS does not measure metabolic flux rates directly. The effects of cortisol on glutamine could be a useful measure of altered central glucocorticoid responses in psychiatric disorders.

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Question answering is a research field with the aim of providing answers to a user’s question, phrased in natural language. In this thesis I explore some techniques used in question answering, working towards the twin goals of using deep linguistic knowledge robustly as well as using language-independent methods wherever possible. While the ultimate aim is cross-language question answering, in this research experiments are conducted over Japanese data, concentrating on factoid questions. The two main focus areas, identified as the two tasks most likely to benefit from linguistic knowledge, are question classification and answer extraction. / In question classification, I investigate the issues involved in the two common methods used for this task—pattern matching and machine learning. I find that even with a small amount of training data (2000 questions), machine learning achieves better classification accuracy than pattern matching with much less effort. The other issue I explore in question classification is the classification accuracy possible with named entity taxonomies of different sizes and shapes. Results demonstrate that, although the accuracy decreases as the taxonomy size increases, the ability to use soft decision making techniques as well as high accuracies achieved in certain classes make larger, hierarchical taxonomies a viable option. / For answer extraction, I use Robust Minimal Recursion Semantics (RMRS) as a sentence representation to determine similarity between questions and answers, and then use this similarity score, along with other information discovered during comparison, to score and rank answer candidates. Results were slightly disappointing, but close examination showed that 40% of errors were due to answer candidate extraction, and the scoring algorithm worked very well. Interestingly, despite the lower accuracy achieved during question classification, the larger named entity taxonomies allowed much better accuracy in answer extraction than the smaller taxonomies.

Submitted by Heitor Rapela Medeiros (heitor.rapela@ufpe.br) on 2015-03-06T13:25:39Z No. of bitstreams: 2 Dissertação Marcelle Aquino Rabelo.pdf: 2399592 bytes, checksum: c68067abc87eeef6c24adc6f08c76a8f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) / Made available in DSpace on 2015-03-06T13:25:39Z (GMT). No. of bitstreams: 2 Dissertação Marcelle Aquino Rabelo.pdf: 2399592 bytes, checksum: c68067abc87eeef6c24adc6f08c76a8f (MD5) license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Previous issue date: 2012-03-05 / CNPq, Facepe / Desde o relato do primeiro caso de resistência à meticilina em Staphylococcus que esse micro-organismo vem sendo considerado como um dos agentes de maior impacto para as infecções associadas aos cuidados em saúde. A disseminação desses isolados bacterianos resistentes a múltiplas drogas em serviços hospitalares é muitas vezes atribuída a profissionais, sendo sugerida a importância do mesmo em surtos. O presente estudo teve como objetivo descrever a diversidade epidemiológica, genética e a susceptibilidade antimicrobiana de Staphylococcus spp. das amostras provenientes de secreção de nasal de profissionais de saúde e amostras clínicas de pacientes internados nas UTIs, hemodiálise/nefrologia e clínicas cirúrgicas do Hospital das Clínicas da Universidade Federal de Pernambuco, no período de abril a agosto do ano de 2011. Foram coletadas amostras de 91 pacientes internados nesses setores e 120 profissionais que trabalhavam nos mesmos, a fim de realizar isolamento e identificação de Staphylococcus spp. Estas amostras foram submetidas a testes de susceptibilidade antimicrobiana, detecção do gene mecA e avaliadas quanto a presença de clones por ribotipagem-PCR. Assim, MRS (Staphylococcus resistente à meticilina) foi prevalente entre os técnicos de enfermagem, 48,15% (13/27) dentre as amostras positivas, e 40,74% (11/27) dos isolados oriundos dos profissionais de saúde foram das clínicas cirúrgicas. Nos pacientes, a maior ocorrência de isolados mecA positivos esteve entre as amostras de ponta de cateter, representando 33,33% (3/9) dos isolados. Foram encontrados oito isolados resistentes à vancomicina dentre os MRS e com base nos padrões de amplificação, descreveu-se 23 ribotipos, sendo um deles descrito em uma amostra de um paciente e de um enfermeiro. O conhecimento do perfil fenotípico e molecular de amostras de Staphylococcus pode contribuir para orientar a conduta terapêutica no tratamento e controle das infecções hospitalares.

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(Thesis (Ph. D.)--University of Illinois, 1913.). / Reprinted from Deutsch-amerikanische Geschichtsblaetter, Jahrbuch der deutsch-amerikanischen historischen Gesellschaft von Illinois. Bibliography: p. 142-147.