Electromyographic (EMG) signal decomposition is the process of resolving an EMG signal into its component motor unit potential trains (MUPTs). The extracted MUPTs can aid in the diagnosis of neuromuscular disorders and the study of the neural control of movement, but only if they are valid trains. Before using decomposition results and the motor unit potential (MUP) shape and motor unit (MU) firing pattern information related to each active MU for either clinical or research purposes the fact that the extracted MUPTs are valid needs to be confirmed. The existing MUPT validation methods are either time consuming or related to operator experience and skill. More importantly, they cannot be executed during automatic decomposition of EMG signals to assist with improving decomposition results. To overcome these issues, in this thesis the possibility of developing automatic MUPT validation algorithms has been explored. Several methods based on a combination of feature extraction techniques, cluster validation methods, supervised classification algorithms, and multiple classifier fusion techniques were developed. The developed methods, in general, use either the MU firing pattern or MUP-shape consistency of a MUPT, or both, to estimate its overall validity. The performance of the developed systems was evaluated using a variety of MUPTs obtained from the decomposition of several simulated and real intramuscular EMG signals. Based on the results achieved, the methods that use only shape or only firing pattern information had higher generalization error than the systems that use both types of information. For the classifiers that use MU firing pattern information of a MUPT to determine its validity, the accuracy for invalid trains decreases as the number of missed-classification errors in trains increases. Likewise, for the methods that use MUP-shape information of a MUPT to determine its validity, the classification accuracy for invalid trains decreases as the within-train similarity of the invalid trains increase. Of the systems that use both shape and firing pattern information, those that separately estimate MU firing pattern validity and MUP-shape validity and then estimate the overall validity of a train by fusing these two indices using trainable fusion methods performed better than the single classifier scheme that estimates MUPT validity using a single classifier, especially for the real data used. Overall, the multi-classifier constructed using trainable logistic regression to aggregate base classifier outputs had the best performance with overall accuracy of 99.4% and 98.8% for simulated and real data, respectively. The possibility of formulating an algorithm for automated editing MUPTs contaminated with a high number of false-classification errors (FCEs) during decomposition was also investigated. Ultimately, a robust method was developed for this purpose. Using a supervised classifier and MU firing pattern information provided by each MUPT, the developed algorithm first determines whether a given train is contaminated by a high number of FCEs and needs to be edited. For contaminated MUPTs, the method uses both MU firing pattern and MUP shape information to detect MUPs that were erroneously assigned to the train. Evaluation based on simulated and real MU firing patterns, shows that contaminated MUPTs could be detected with 84% and 81% accuracy for simulated and real data, respectively. For a given contaminated MUPT, the algorithm on average correctly classified around 92.1% of the MUPs of the MUPT. The effectiveness of using the developed MUPT validation systems and the MUPT editing methods during EMG signal decomposition was investigated by integrating these algorithms into a certainty-based EMG signal decomposition algorithm. Overall, the decomposition accuracy for 32 simulated and 30 real EMG signals was improved by 7.5% (from 86.7% to 94.2%) and 3.4% (from 95.7% to 99.1%), respectively. A significant improvement was also achieved in correctly estimating the number of MUPTs represented in a set of detected MUPs. The simulated and real EMG signals used were comprised of 3–11 and 3–15 MUPTs, respectively.

Continuous change and competition in the working environment necessitate increased efficiency and productivity which require different and enhanced skills and abilities. It is therefore important that the right people with the right skills are selected and employees are developed to enable them to meet the organisational and national demands of the future. This dissertation investigates the relationship between learning potential, English language proficiency and work-related training test results to establish why some production employees perform better on work-related training test results than others. The results indicate that there is no significant relationship between the work-related training test results and either learning potential or English language proficiency. There is, however, a significant correlation between learning potential and English language proficiency. It might be worthwhile exploring the availability and adequacy of assessors as well as the motivational level of the production employees as factors that influence the progress made with work-related training test results. / Industrial and Organisational Psychology / MCOM (Industrial Psychology)

Cette thèse a pour objectif de contribuer à la modélisation, à la simulation et à l’analyse des signaux contenant des potentiels d’action extracellulaires (EAPs), tels que mesurés in-vivo par des microélectrodes implantées dans le cerveau. Les modèles actuels pour la simulation des EAPs consistent soit en des modèles compartimentaux très détaillés et lourds en calcul, soit en des modèles dipolaires jugés trop simplistes. Dans un premier temps, une approche de simulation des EAPs se situant entre ces deux extrêmes est proposée, où la somme des contributions des compartiments du neurone est traitée comme une convolution, appliquée aux courants membranaires d’un seul compartiment actif. L'analyse des EAPs passe par une étape de classification des potentiels d'action détectés dans le signal enregistré, qui consiste à discriminer les formes de potentiels d’action et ainsi à identifier l'activité de neurones uniques. Dans cette thèse, une nouvelle approche basée sur l’inférence bayésienne est développée permettant l'extraction et la classification simultanées des EAPs. La méthode est appliquée à des signaux générés à l'aide de l'approche de simulation proposée plus haut, confirmant la qualité de la méthode de classification introduite et illustrant la capacité de la méthode de simulation à générer des EAPs réalistes de formes diverses et discriminables. Nous avons enrichi une modélisation de l’activité hippocampique réalisée dans l’équipe permettant de reproduire des oscillations dans ces bandes fréquentielles spécifiques en introduisant les EAPs, ceci afin d’évaluer les contributions de l'activité synaptique et celle des potentiels d’action à certaines bandes de fréquence des signaux enregistrés. Finalement, une étude sur signaux réels enregistrés dans le cadre de l'étude de la perception des visages chez l'homme a été menée, illustrant les performances de la méthode de spike sorting proposée dans un cadre réel et ouvrant la discussion sur les perspectives qu'offrent ces travaux de thèse pour l'étude de questions neuroscientifiques basées sur l'analyse de signaux multi-échelle. / The objective of this thesis is to contribute to the modelling, simulation and analysis of signals containing extracellular action potentials (EAPs), as measured in vivo by microelectrodes implanted in the brain. Current models for the EAPs simulation consist either of very detailed and computationally heavy compartmental models or dipole models considered too simplistic. An EAP simulation approach between these two extremes is proposed, where the sum of the contributions of the neuron compartments is treated as a convolution, applied to the membrane currents of a single active compartment. The analysis of EAPs involves a step of classifying the action potentials detected in the recorded signal, which consists in discriminating the forms of action potentials and thus identifying the activity of single neurons In this thesis, a new approach based on Bayesian inference is developed allowing the simultaneous extraction and classification of EAPs. The method is applied to signals generated using the simulation approach proposed above, confirming the quality of the sorting method introduced and illustrating the ability of the simulation method to generate realistic EAPs of various and discriminatory forms. We modified a model of hippocampal activity previously proposed in our team, able to reproduce oscillations in specific frequency bands, by including the EAPs model, which allowed to evaluate the contributions of synaptic activity and that of action potentials the recorded signals. Finally, a study on real signals recorded as part of the study of face perception in humans is conducted, illustrating the performance of the proposed spike sorting method in a real setting and opening the discussion on the perspectives offered by this thesis work for the study of neuroscientific questions based on multiscale signal analysis.

Le rythme lent lié à la respiration est une caractéristique proéminente de l’activité du bulbe olfactif de rat. Il se définit par des oscillations de grande amplitude du potentiel de champ local, une activité de décharge des cellules mitrales/ à panache (M/P) synchronisée à la respiration et des oscillations lentes de leur potentiel de membrane (OPLM). Des relations spécifiques entre ces activités détermineraient la participation d’une cellule M/P au traitement de l’information olfactive. Jusqu’à présent, il n'existait que très peu de données sur ces relations. L’objectif de cette thèse a été de caractériser les OLPM des cellules M/P et d’étudier les relations qu’elles entretiennent avec l’activité de décharge et l’activité du réseau bulbaire. Pour répondre à cet objectif, nous avons mis au point une technique d’enregistrements simultanés de l’activité intracellulaire des cellules M/P et du potentiel de champ local du bulbe olfactif chez l’animal anesthésié et libre de respirer. Nous montrons que plusieurs types d’OLPM existent. Des relations spécifiques s’établissent entre ces OLPM et la synchronisation de l’activité de décharge à la respiration. Nous observons également l’existence de relations complexes entre les OLPM et les oscillations du réseau bulbaire. L’ensemble de ces résultats nous permet d’intégrer la dynamique lente, et plus particulièrement celle du potentiel de membrane, à un schéma général du traitement de l’information olfactive et de proposer son implication dans la formation d’assemblée de neurones. / The respiration-related slow rhythm strongly shapes the activity of the olfactory bulb. This rhythm is characterized by high amplitude oscillations in the local field potential, respiration synchronization of mitral/tufted (M/T) cell discharge and slow oscillation of M/T cell membrane potential (OLPM). Specific relationships between these activities could determine the M/T cell participation to olfactory processing. However, little is known on these relationships. The aim of my thesis has been to characterize M/T cell OLPM and to study the relationships between OLPM and both discharge and bulbar network activities. In this way, we recorded simultaneously intracellular activity of M/T cell and local field potential of olfactory bulb in anesthetized freely breathing rat. We showed that several types of OLPM can be distinguished and exhibited specific relationship with the respirations ynchronization of M/T cell discharge activity. We observed also specific and complex relationships between OLPM and local field potential oscillation. Taken together, our results allowed us to integrate slow rhythm, and more particularly OLPM, in the more general scheme of olfactory processing.

Na primeira parte do trabalho estudamos a equação de Schrödinger logarítmica com um delta potencial; $V(x)=-\\gamma \\,\\delta(x)$, onde $\\delta$ é a distribuição de Dirac na origem e o parâmetro real $\\gamma$ descreve a intensidade do potencial. Estabelecemos a existência e unicidade das soluções do problema de Cauchy associado em um espaço de funções adequado. No caso do potencial atrativo ($\\gamma>0$), calculamos de forma explícita o seu único ground state e mostramos a sua estabilidade orbital.\\\\ A segunda parte trata detalhadamente da equação de Schrödinger logarítmica com um delta derivada potencial; $V(x)=-\\gamma\\, \\delta^{\\prime}(x)$. A boa colocação global para o problema de Cauchy é verificada em um espaço de funções adequado. No caso do potencial atrativo ($\\gamma>0$), o conjunto dos ground states é completamente determinado. Mais precisamente: se $0<\\gamma\\leq2$, então há um único ground state e é uma função ímpar; se $\\gamma>2$, então existem dois ground states não-simétricos. Em adição, provamos que cada ground state é orbitalmente estável através de uma abordagem variacional. Finalmente, usando a teoria de extensão de operadores simétricos, também mostramos um resultado de instabilidade para $\\gamma>2$. / The first part of this thesis deals with the logarithmic Schrödinger equation with a delta potential; $V(x)=-\\gamma \\,\\delta(x)$, where $\\delta$ is the Dirac distribution at the origin and the real parameter $\\gamma$ is interpreted as the strength of the potential. We establish the existence and uniqueness of the solutions of the associated Cauchy problem in a suitable functional framework. In the attractive potential case ($\\gamma>0$), we explicitly compute the unique ground state and we show their orbital stability .\\\\ The second part deals with the case of the logarithmic Schrödinger equation with a delta prime potential; $V(x)=-\\gamma\\, \\delta^{\\prime}(x)$. Global well-posedness is verified for the Cauchy problem in a suitable functional space. In the attractive potential case ($\\gamma>0$), the set of the ground state is completely determined. More precisely: if $0<\\gamma\\leq2$, then there is a single ground state and it is an odd function; if $\\gamma>2$, then there exist two non-symmetric ground states. Moreover, we show that every ground state is orbitally stable via a variational approach. Finally, by applying the theory of extensions of symetric operators, we also prove a result of instability for $\\gamma>2$.

A doença de Chagas, parasitose causada pelo Trypanosoma cruzi, é doença prevalente na América Latina. Estima-se que cerca de 10 milhões de pessoas estão sob o risco de infecção e, em 2008, registraram-se mais de 10 mil óbitos devido à doença. Os únicos dois fármacos disponíveis na terapêutica, nifurtimox e benznidazol, são mais eficazes no tratamento da doença no início da fase aguda. Entretanto, a fase crônica da doença não possui tratamento. O nitrofural (NF), fármaco antimicrobiano, destaca-se por possuir atividade contra o T. cruzi, porém, apresenta toxicidade. Seu derivado hidroximetilado, o hidroximetilnitrofural (NFOH), por sua vez, mostrou maior atividade antichagásica e menor toxicidade. Ante a necessidade de novos fármacos antichagásicos, a existência de alvos terapêuticos promissores como a 14&#945;-esterol desmetilase (CYP51) e a cruzaína e mediante utilização do bioisosterismo como ferramenta de modificação molecular, realizou-se a triagem virtual de 144 ligantes análogos do NFOH pelo método de docking com o programa GOLD para a CYP51 de T. cruzi. Adicionalmente, realizou-se estudo qualitativo dos campos de interação moleculares (MIFs) com o programa GRID para a enzima humana e do parasita, homólogas entre si, estudo que revelou 9 resíduos de aminoácidos no sítio ativo da enzima parasitária que podem ser explorados no planejamento de inibidores seletivos. Neste trabalho, obtiveram-se 5 compostos inéditos, caracterizados por determinação da faixa de fusão, análise elementar, técnicas de espectroscopia no infravermelho, espectroscopia de ressonância magnética nuclear de 1H,13C, HSQC, HMBC, HETCOR e NOESY, e a atribuição dos sinais foi realizada com o auxílio de técnicas de modelagem molecular. Testaram-se 4 compostos contra a forma amastigota de T. cruzi em células da linhagem U2OS. Todos os compostos apresentaram atividade da ordem de micromolar e índices de seletividade satisfatórios. O composto LAPEN-2901 teve sua estrutura elucidada por cristalografia de raios X, apresentou toxicidade duas vezes menor que o NFOH e potência semelhante à do composto de referência benznidazol, porém menor eficácia. Os resultados obtidos ressaltam a importância de grupos nitro, 1,2,4-triazólicos e tiossemicarbazônicos para o planejamento de derivados eficazes no tratamento da fase crônica da doença de Chagas. / Chagas disease, parasitosis caused by Trypanosoma cruzi, is a disease that predominates in Latin America. It is estimated that 10 million people are under the risk of infection and, in 2008, more than 10 thousand deaths were registered. The only two drugs available in the therapeutics, nifurtimox and benznidazole, showed to be more effective in the acute phase of the disease. However, there is no choice for the chronic phase. Nitrofurazone (NF), an antimicrobial drug, has activity against T. cruzi, although being toxic. Its hydroxymethyl derivative, the hydroxymethylnitrofurazone (NFOH), showed to be more active and less toxic than the prototype. Considering the need for new antichagasic drugs, the existence of promising new therapeutic targets, as 14&#945;-esterol demethylase and cruzain, and by employing the bioisosterism approach, a virtual screening using T. cruzi CYP51 was performed for 144 NFOH analogues. Additionaly, a qualitative molecular interaction field study was performed, revealing 9 aminoacids in the parasitic enzyme relevant for selectivity. Five novel compounds were synthesized, characterized by melting range, elemental analysis, IR spectroscopy, 1H and 13C NMR as well as HSQC, HMBC, HETCOR and NOESY experiments, in which the signal assigning were aided using molecular modeling techniques Four compounds were tested against T. cruzi amastigotes in infected U2OS cells. All compounds were sufficiently selective towards T. cruzi and showed trypanomicidal activity in low micromolar range. The compound LAPEN-2901 had its structure determined using X-ray crystallography and showed lower toxicity than NFOH and potency similar to benznidazole, but lower efficacy. These results highlight the importance of the 1,2,4-triazolic, thiosemicarbazonic and nitro group moieties for designing new efficient compounds for the chronic phase of Chagas disease.

A integridade da via auditiva e a investigação do respectivo limiar eletrofisiológico podem ser avaliadas por meio da observação, no domínio do tempo, dos potenciais evocados auditivos de tronco encefálico. Atualmente, nova técnica de análise dos potenciais evocados auditivos, no domínio das freqüências, tem sido utilizada para uma observação particular desses limiares. Assim, com a aplicação da transformada rápida de Fourier, é possível realizar a análise das freqüências comprometidas na audição, de maneira eficiente e rápida. O objetivo com este trabalho, então, foi desenvolver, caracterizar e realizar testes preliminares com um dispositivo único capaz de avaliar os potenciais evocados auditivos nos dois domínios, por meio de uma placa de som, que ainda não havia sido implementada para tal fim. Desse modo, foi produzido um aparelho capaz de registrar sinais biológicos da ordem de 0,5 ?V. Após a caracterização e o estudo simulado, foram conduzidos testes-piloto com doze seres humanos, ouvintes normais (n = 24 orelhas), divididos em dois grupos com o mesmo número de participantes. No grupo 1, os potenciais evocados auditivos de tronco encefálico adquiridos por meio de um instrumento padrão-ouro e de instrumento desenvolvido foram comparados entre si. Em seguida, os achados foram relacionados com o exame no domínio das freqüências formatado no novo aparelho. O grupo 2 foi submetido à avaliação dos potenciais miogênicos vestibulares, também com os dois instrumentos, e suas latências absolutas comparadas. Os resultados demonstraram não haver diferenças significativas entre os dois instrumentos para as amplitudes e latências do potencial evocado auditivo de tronco encefálico. Constatou-se, ainda, que as ondas presentes no domínio do tempo davam respostas equivalentes no domínio das freqüências. Por fim, também não foram encontradas diferenças significativas entre os dois aparelhos para as latências do potencial miogênico vestibular. / The integrity of the auditory pathway and the investigation of the respective electrophysiological threshold can be assessed by observation, in the time domain, of brainstem auditory evoked potentials. This assessment is usually evoked by clicks, which have a wide acoustic spectrum, and consequently serious limitations with respect to frequency specificity, in determining electrophysiological thresholds. New techniques for analyzing auditory evoked potentials in the frequency domain are currently being used for a closer observation of these thresholds. Thus, by applying the fast Fourier transform, one can analyzed the compromised auditory frequencies efficiently and rapidly. This method, on the other hand, does not investigate the integrity of specific auditory pathway structures, as the other method does. Although both types of assessment require similar biological amplifier architecture and are, to a certain extent, complementary, they are performed with two distinct devices. The first, which makes the observation in the time domain, is quite well known and several manufacturers have been producing it for a long time. The second, which inspects the potentials in the frequency domain, was introduced into the market only a few years ago. The aim of this study, therefore, was to develop, characterize and conduct preliminary tests with a single device capable of evaluating the auditory evoked potentials in both domains, by means of a sound card that had not been previously used for this purpose. Thus, a device was produced with biological amplifiers, filters, electrical protection apparatus and a logic control system capable of recording biological signals around 0.5 µV. After characterization and the simulated study, pilot tests were carried out with 12 normal- hearing subjects (n = 24 ears), allocated to two groups of 6 participants. In group 1, we observed the latencies and amplitudes of waves I, III and V of the brainstem auditory evoked potentials, using a gold standard instrument and a developed instrument and later compared them. The findings were then correlated to those of the frequency domain examination formatted on the new device. Group 2 was submitted to an assessment of components p13 and n23 of the vestibular myogenic potentials to observe the most delayed biological signals, also with both instruments, and their absolute latencies were compared. The results showed no significant differences between the two instruments for the amplitudes (p = 0.379; p = 0.301; p = 0.605, waves I, III and V, respectively) and latencies (p = 0.381; p = 0.140; p = 0.255) of the brainstem auditory evoked potentials. It was also found that the waves present in the time domain gave equivalent responses in the frequency domain. Finally, no significant differences were observed between the two devices for the absolute latencies of components p13 and n23 of the vestibular myogenic potentials, with p values of 0.102 and 0.078, respectively. Thus, it was concluded that the new instruments were efficient for the functions tested.

Introdução: O P300 é um potencial evocado auditivo que ocorre aproximadamente 300 milissegundos (ms) após a apresentação do estímulo. Geralmente, é evocado ao se utilizar o paradigma tradicional, no qual são apresentados dois estímulos perceptivelmente diferentes: um estímulo frequente (85%) e um estímulo raro (15%). Os indivíduos são orientados a indicar, de alguma maneira, a quantidade de estímulos raros que perceberam durante a realização do exame. O P300 é considerado um potencial endógeno, pois ocorre devido a um evento cognitivo (decisão da ocorrência do estímulo raro). Contudo, alguns estudos mostraram que as características acústicas do estímulo podem interferir no potencial, evidenciando uma contribuição exógena ou sensorial para evocar a resposta. Essas implicações endógenas e exógenas para evocar o P300 ainda não foram totalmente definidas. A avaliação desses aspectos específicos pode ajudar a identificar os geradores desse potencial. Objetivo: verificar o efeito da contribuição endógena e exógena para obtenção do P300, utilizando paradigma tradicional e o paradigma de omissão. Métodos: participaram desse estudo 30 indivíduos jovens adultos, normo-ouvintes sem alteração neurológica ou psiquiátrica aparente. Os indivíduos foram avaliados com o paradigma tradicional (estímulo frequente: 800 Hz; estímulo raro 1200 Hz) e com o paradigma de omissão (estímulo frequente: 800 Hz; estímulo raro: ausência de som). Cada orelha foi avaliada separadamente por ambos os paradigmas na intensidade de 80 dBNPS. Foram apresentados 300 estímulos (45 raros) em cada estimulação. Para a obtenção do P300, foi utilizado o equipamento \"Neuroscan Stim2\" com 12 eletrodos ativos no escalpo, colocados nas seguintes posições: FPz, F4, Fz, F3, C4, Cz, C3, CP6, CP5, P4, Pz e P3. O maior pico após o complexo N1-P2-N2 foi considerado como P300. A amplitude foi medida considerando a linha de base do intervalo pré-estímulo, enquanto a latência foi medida no maior pico positivo. Nesse estudo, foi utilizada a Análise de Variância (ANOVA) com medidas repetidas. Foram realizados mapas topográficos do escalpo para ambas as estimulações. Resultados: para todos os 12 eletrodos analisados nesse estudo, a média da latência em milissegundos foi significantemente menor, e a média da amplitude foi significantemente maior para o paradigma tradicional quando comparado ao paradigma de omissão. Além disso, a morfologia da onda foi mais bem definida para o paradigma tradicional. Os mapas topográficos para ambos os paradigmas mostraram uma ativação mais generalizada e mais positiva na região centro-parietal, indicando que as mesmas áreas foram ativadas em ambos os paradigmas. Conclusão: o presente estudo demonstrou que o estímulo acústico, ausente no paradigma de omissão, influencia a latência, amplitude e morfologia da onda, evidenciando uma contribuição exógena/sensorial para obtenção do potencial / Introduction: The P300 is an auditory evoked potential that occurs approximately 300 ms after the stimulus presentation. It is usually elicited by a traditional paradigm in which two perceptually different stimuli are randomly presented with different proportions - one is frequent (85%) and the other is rare (15%). The tested individual is instructed to somehow indicate the amount of rare stimuli heard. According to the literature, P300 is considered an endogenous potential since it occurs in response to a cognitive event (i.e. decision of the occurrence or not of the rare stimulus). However, few studies have shown that the acoustic characteristics of the stimuli might influence the potential, evidencing some exogenous or sensorial contribution to the response formation. The implications that endogenous and exogenous contributions have to eliciting the P300 are not fully understood yet. The assessment of their specific roles would help to identify the P300 generators. Objective: To verify the effects of the endogenous and exogenous contribution to obtain/elicit the P300 using both the traditional and the omission paradigms. Methods: Thirty normal hearing young adults, without known neurological or psychiatric disorders, participated in this study. The individuals were assessed using P300 elicited by the traditional paradigm (frequent stimulus: 800 Hz; rare stimulus: 1200Hz) and by the omission paradigm (frequent stimulus: 800 Hz; rare stimulus: absence of sound). Both paradigms were presented to one ear at a time, at 80dBSPL, and 300 stimuli (45 rare) were presented in each stimulation. The \"Neuroscan Stim2\" was used to obtain the P300 with 12 active electrodes fixed at the following positions: FPz, F4, Fz, F3, C4, Cz, C3, CP6, CP5, P4, Pz e P3. The largest peak after the N1-P2-N2 complex was considered the P300. Its amplitude was measured considering the pre-stimulation response baseline, while its latency was measured at the most positive peak. The Analysis of Variance (ANOVA) with repeated measures was used in this study. Topographic maps from the scalp to both paradigms were also analyzed. Results: To all 12 electrodes positions analyzed in this study, the mean latency (ms) was significantly earlier and the mean amplitude (?V) was significantly larger for the traditional paradigm compared to the omission paradigm. Also, better wave morphology was obtained for the traditional paradigm. The topographic maps to both paradigms has shown more generalized and positive activation at the centro-parietal region, indicating that the same brain areas were involved in both paradigms. Conclusion: The current study has demonstrated that the acoustic stimulus, absent on the omission paradigm, have an impact on the wave formation in respect to its latency, amplitude and morphology, evidencing the influence of sensorial information to the P300

A doença de Chagas, parasitose causada pelo Trypanosoma cruzi, é doença prevalente na América Latina. Estima-se que cerca de 10 milhões de pessoas estão sob o risco de infecção e, em 2008, registraram-se mais de 10 mil óbitos devido à doença. Os únicos dois fármacos disponíveis na terapêutica, nifurtimox e benznidazol, são mais eficazes no tratamento da doença no início da fase aguda. Entretanto, a fase crônica da doença não possui tratamento. O nitrofural (NF), fármaco antimicrobiano, destaca-se por possuir atividade contra o T. cruzi, porém, apresenta toxicidade. Seu derivado hidroximetilado, o hidroximetilnitrofural (NFOH), por sua vez, mostrou maior atividade antichagásica e menor toxicidade. Ante a necessidade de novos fármacos antichagásicos, a existência de alvos terapêuticos promissores como a 14&#945;-esterol desmetilase (CYP51) e a cruzaína e mediante utilização do bioisosterismo como ferramenta de modificação molecular, realizou-se a triagem virtual de 144 ligantes análogos do NFOH pelo método de docking com o programa GOLD para a CYP51 de T. cruzi. Adicionalmente, realizou-se estudo qualitativo dos campos de interação moleculares (MIFs) com o programa GRID para a enzima humana e do parasita, homólogas entre si, estudo que revelou 9 resíduos de aminoácidos no sítio ativo da enzima parasitária que podem ser explorados no planejamento de inibidores seletivos. Neste trabalho, obtiveram-se 5 compostos inéditos, caracterizados por determinação da faixa de fusão, análise elementar, técnicas de espectroscopia no infravermelho, espectroscopia de ressonância magnética nuclear de 1H,13C, HSQC, HMBC, HETCOR e NOESY, e a atribuição dos sinais foi realizada com o auxílio de técnicas de modelagem molecular. Testaram-se 4 compostos contra a forma amastigota de T. cruzi em células da linhagem U2OS. Todos os compostos apresentaram atividade da ordem de micromolar e índices de seletividade satisfatórios. O composto LAPEN-2901 teve sua estrutura elucidada por cristalografia de raios X, apresentou toxicidade duas vezes menor que o NFOH e potência semelhante à do composto de referência benznidazol, porém menor eficácia. Os resultados obtidos ressaltam a importância de grupos nitro, 1,2,4-triazólicos e tiossemicarbazônicos para o planejamento de derivados eficazes no tratamento da fase crônica da doença de Chagas. / Chagas disease, parasitosis caused by Trypanosoma cruzi, is a disease that predominates in Latin America. It is estimated that 10 million people are under the risk of infection and, in 2008, more than 10 thousand deaths were registered. The only two drugs available in the therapeutics, nifurtimox and benznidazole, showed to be more effective in the acute phase of the disease. However, there is no choice for the chronic phase. Nitrofurazone (NF), an antimicrobial drug, has activity against T. cruzi, although being toxic. Its hydroxymethyl derivative, the hydroxymethylnitrofurazone (NFOH), showed to be more active and less toxic than the prototype. Considering the need for new antichagasic drugs, the existence of promising new therapeutic targets, as 14&#945;-esterol demethylase and cruzain, and by employing the bioisosterism approach, a virtual screening using T. cruzi CYP51 was performed for 144 NFOH analogues. Additionaly, a qualitative molecular interaction field study was performed, revealing 9 aminoacids in the parasitic enzyme relevant for selectivity. Five novel compounds were synthesized, characterized by melting range, elemental analysis, IR spectroscopy, 1H and 13C NMR as well as HSQC, HMBC, HETCOR and NOESY experiments, in which the signal assigning were aided using molecular modeling techniques Four compounds were tested against T. cruzi amastigotes in infected U2OS cells. All compounds were sufficiently selective towards T. cruzi and showed trypanomicidal activity in low micromolar range. The compound LAPEN-2901 had its structure determined using X-ray crystallography and showed lower toxicity than NFOH and potency similar to benznidazole, but lower efficacy. These results highlight the importance of the 1,2,4-triazolic, thiosemicarbazonic and nitro group moieties for designing new efficient compounds for the chronic phase of Chagas disease.

Binding-sites which facilitate the transport of substrates across membranes are ubiquitous in membrane proteins. To understand this fundamental process in cells, we build up a synthetic membrane system consisting of microfluidic channels and colloidal particles. Holographic optical tweezers are used to modulate the potential energy landscape in those channels. We show how to extract the underlying energy potential by analysing local transition probabilities. Our method is applicable both to equilibrium systems and non-equilibrium steady states. Our method offers improved robustness when dealing with fragmented trajectories or small ensembles of data compared to other established approaches, such as probability density function and splitting probability. Meanwhile, we utilise the intensity distribution of the optical traps generated by holographic optical tweezers to estimate energy landscapes featuring high energy barriers where transitions rarely occur. We use this newly developed experimental system to mimic the functionality of membrane protein transporters that are known to alternate their substrate-binding sites between the extracellular and cytosolic side of the membrane. We study particle transport through a channel coupled with an energy well that oscillates its position between the two entrances of the channel deterministically and stochastically. Optimised particle transport across the channel is obtained by adjusting the oscillation frequency. At the optimal oscillation frequency, the translocation rate of particles through the channel is a hundred times higher with respect to free diffusion across the channel. Our findings reveal the effect of time dependent potentials on particle transport across a channel. This work adds a new tool for the investigation of highly controlled membrane transport processes at the micron scale. Our results are relevant for improving our understanding of membrane transport especially for microfluidics application.