This thesis focuses on the development of a novel polymer based housing for power thyristor devices typically used in long distance high voltage direct current (HVDC) transmission. Power thyristor devices used in HVDC power conversion stations are typically packaged in a hermetically sealed ceramic housing and have demonstrated an excellent history of reliability and performance. However, to avoid increasing the number of thyristors in future higher powered HVDC schemes thyristors having higher power ratings at 8.5 kV and sizes at 125 mm and 150 mm diameters are sought for implementation to achieve higher transmission ratings of, for example, 4000 A at +/- 800 kV. The main disadvantages of such large ceramic-based packages are higher processing cost and weight whilst robustness is also a concern. To overcome these issues, replacing the current ceramic housing with a polymeric material has been investigated in this project. The advantages it is anticipated such packages will provide include lower cost, less weight, robustness, recyclability, etc. However, some challenges it will also offer are: non-hermeticity i.e. polymers are moisture and gas permeable, potentially more complex manufacturing routes, and different electrical, mechanical and thermal properties compared to ceramic materials. The work presented in this thesis was part of a larger project where these challenges have been addressed by developing and testing a prototype polymeric thyristor housing. The prototype is aimed at demonstrating that polymer packages can deliver performance and reliability comparable to, if not better than, current ceramic packages. In this thesis, it is the package development and reliability related studies that are discussed. Because the housings will experience severe electrical stresses and various thermal excursions during their service life, the electrical and thermo-mechanical behaviour of the polymer housing was studied using finite element analysis to gain an understanding of the effects of various design variables and materials properties on performance and the tradeoffs between performance and manufacturability. From these modelling studies, design guidelines have been established for the future development of polymer housings. On the other hand, to identify the physics-of-failure of the prototype that was manufactured as part of the project, accelerated life tests were performed to study its reliability. The knowledge gained from the polymer prototype development was then applied to the design of a larger 125 mm diameter housing using the Taguchi method of experimental design.

Microelectronics integration continuously follows the trend of miniaturisation for which the technologies enabling fine pitch interconnection are in high demand. The recent advancement in the assembly of Hybrid Pixel Detectors, a high resolution detecting and imaging device, is an example of where novel materials and processes can be applied for ultra-fine pitch interconnections. For this application, indium is often used for the fine pitch bump bonding process due to its unique properties that make it especially suitable, in particular in a cryogenic environment where some types of detector have to serve. Indium bumps are typically fabricated through vacuum evaporation at the wafer level; however, this thesis investigates an alternative low cost manufacturing process at the wafer scale for the deposition of indium micro-bumps through electroplating. The work has placed its emphasis on the requirements of future technologies which will enable a low temperature (<150oC), high density interconnection (> 40,000 IOs/cm2) with a high throughput and high production yield. This research is a systematic investigation of the wafer-scale indium bumping process through electrodeposition using indium sulphamate solution. An intensive experimental study of micro-bump formation has been carried out to elaborate the effects of two of the main electroplating factors that can significantly influence the quality of bumps in the course of electrodeposition, namely the current distribution and mass transport. To adjust the current density distribution, various waveforms of current input, including direct current (DC), unipolar pulse current and bipolar pulse reverse current, were employed in the experiments. To assist mass transportation prior to or during electroplating, acoustic agitation including ultrasonic agitation at 30 kHz frequency as well as megasonic agitation at 1 MHz, were utilised. The electrochemical properties of the indium sulphamate solution were first investigated using non-patterned plain substrates prior to indium bumping trials. This provided understanding of the microstructural characteristics of indium deposits produced by electroplating and, through cathodic polarisation measurements, the highest current density suitable for electrodeposition was achieved as approximately 30 mA/cm2 when electroplating was carried out at room temperature and with no agitation applied. The typical surface morphology of DC electroplated indium contained a granular structure with a surface feature size as large as 10 µm. Pulse and pulse reverse electroplating significantly altered the surface morphology of the deposits and the surface became much smoother. By introducing acoustic agitation, the current density range suitable for electrodeposition could be significantly expanded due to the greater mass transfer, which led to a higher speed of deposition with high current efficiency. Wafer-scale indium bumping (15 µm to 25 µm diameter) at a minimum pitch size of 25 µm was successfully developed through electroplating trials with 3 inch test wafers and subsequently applied onto the standard 4 inch wafers. The results demonstrate the capability of electroplating to generate high quality indium bumps with ultrafine pitch at a high consistency and yield. To maximise the yield, pre-wetting of the ultrafine pitch photoresist patterns by both ultrasonic or megasonic agitation is essential leading to a bumping yield up to 99.9% on the wafer scale. The bump profiles and their uniformity at both the wafer and pattern scale were measured and the effects of electrodeposition regimes on the bump formation evaluated. The bump uniformity and microstructure at the feature scale were also investigated by cross-sectioning the electroplated bumps from different locations on the wafers. The growth mechanism of indium bumps were proposed on the basis of experimental observation. It was found that the use of a conductive current thief ring can homogenise the directional bump uniformity when the electrical contact is made asymmetrically, and improve the overall uniformity when the electrical contact is made symmetrically around the periphery of the wafer. Both unipolar pulse electroplating and bipolar pulse reverse electroplating improved the uniformity of the bump height at the wafer scale and pattern scale, and the feature scale uniformity could be significantly improved by pulse reverse electroplating. The best uniformity of 13.6% for a 4 inch wafer was achieved by using pulse reverse electroplating. The effect of ultrasonic agitation on the process was examined, but found to cause damage to the photoresist patterns if used for extended periods and therefore not suitable for use throughout indium bumping. Megasonic agitation enabled high speed bumping without sacrifice of current efficiency and with little damage to the photoresist patterns. However, megasonic agitation tended to degrade some aspects of wafer scale uniformity and should therefore be properly coupled with other electroplating parameters to assist the electroplating process.

O crescente interesse por sistemas de transmissão do tipo VSC-based HVDC (VSCHVDC) como alternativa aos atuais tem levado à necessidade de estudos sobre o principal desafio associado à sua implantação, que é o desenvolvimento de um esquema de proteção que seja rápido e que identifique a zona de proteção na qual uma eventual falta tenha ocorrido, respeitando-se assim o princípio de seletividade. Para estudo de um sistema de proteção que atenda a estes requisitos, foi utilizada neste trabalho uma rede com quatro terminais e transmissão High-Voltage Direct Current (HVDC), implementada com conversores modulares multiníveis (Modular Multilevel Converter (MMC)) e simulada em situações de contingência. Grandezas medidas nos elos de Corrente Contínua (CC) ligados a um dos terminais foram utilizadas para identificar a ocorrência de uma contingência na rede e então para decidir se trata-se de uma falta interna à zona de proteção considerada na análise. Para classificar as faltas em interna ou externa, observaram-se os espectros dos sinais de tensão CC em um terminal, calculados sobre uma janela do sinal através de Fast Fourier Transform (FFT), para várias situações de falta. Destes espectros, notou-se que uma característica varia de acordo com a distância da falta até o terminal, com o fato de a falta ser interna ou externa e com a resistência de falta. Através desta característica, denominada aqui \"frequência de centro de massa\", foi possível distinguir as faltas internas com resistências de falta baixas do restante dos eventos testados. Considerando-se apenas este parâmetro, não foi possível classificar corretamente faltas internas com resistência de falta muito alta. / The growing interest in VSC-based HVDC (VSC-HVDC) transmission systems as an alternative to the current ones has required studies about the the main challenge associated with its application, which is the development of a protection scheme that is able to both fast and efficiently determine the protection zone where a fault may have happened so as to achieve selectivity. In order to study a protection system that complies with those requirements, a High-Voltage Direct Current (HVDC) transmission system with four terminals implemented with Modular Multilevel Converter (MMC) converters was simulated under contingency condition. Electrical quantities measured in one of the terminal\'s Direct Current (DC) links were used to determine the occurrence of a fault event in the system, as well as to decide whether that event belonged to the protection zone considered in the analysis. Spectra obtained via Fast Fourier Transform (FFT) over a window of the DC voltage measured in one of the terminals were observed in order to discriminate between internal and external fault events. From these observations, it was noticed that a certain characteristic, named here \"center of mass frequency\", varies according to the distance between the fault location and the terminal, fault resistance, as well as whether that the fault is either internal or external to the analysed protection zone. By using this characteristic, it was possible to tell internal faults with low resistance fault from other events. Considering this parameter only, it was not possible to correctly classify internal faults with high fault resistance.

O desenvolvimento da estimulação magnética transcraniana (EMT) permitiu o estudo de potenciais evocados motores eliciados pela estimulação direta do córtex cerebral de forma não-invasiva. Foi observado que diferentes paradigmas de estimulação cortical por EMT apresentam diferentes padrões de resposta, que posteriormente foram associados ao funcionamento de circuitos corticais GABAérgicos e glutamatérgicos do córtex motor, compondo assim índices de excitabilidade cortical motora (ECM). Ademais, desvios da normalidade de tais índices foram encontrados em diversas condições clínicas, incluindo transtornos mentais como a esquizofrenia. O uso dessas medidas também auxiliou o desenvolvimento da estimulação transcraniana por corrente contínua (ETCC), técnica que se mostrou capaz de produzir efeitos neuromodulatórios no sistema nervoso central de forma segura e com mínimos efeitos adversos. Tal técnica vem apresentando possibilidades terapêuticas promissoras, como por exemplo, tendo sido observado sua eficácia no alívio de alucinações auditivas de indivíduos com esquizofrenia. O uso de ETCC para tratamento de sintomas negativos da esquizofrenia também pode vir a se mostrar uma abordagem eficaz, e a análise da ECM pode auxiliar no entendimento dos seus mecanismos de ação e atuar como possível preditor de resposta terapêutica. O objetivo do presente estudo é avaliar o perfil de ECM em um grupo de indivíduos com esquizofrenia, e as possíveis influências de um protocolo terapêutico utilizando ETCC sobre essas medidas. Com esse objetivo, foi selecionada uma coorte de sujeitos com esquizofrenia que participou em ensaio clínico randomizado e controlado com placebo (estimulação sham), tendo a ETCC como intervenção ativa alvo. A ECM foi mensurada na avaliação inicial dos sujeitos, assim como após a primeira sessão de ETCC, e quando da avaliação de desfecho primário. O protocolo terapêutico de ETCC envolveu a colocação de 2 eletrodos de área 5x7 cm, pólo anódico aplicado sobre região correspondente ao córtex pré-frontal dorsolateral esquerdo e pólo catódico aplicado sobre córtex de transição temporoparietal esquerdo; com intensidade de corrente de 2 mA, aplicada por 20 minutos. Cada sujeito foi submetido a 10 sessões no total. Encontramos que idade se correlacionou com diminuição da inibição intracortical, reproduzindo resultado previamente encontrado em indivíduos saudáveis. Acerca da modulação da ECM após sessão de ETCC, observamos que sujeitos submetidos à intervenção ativa apresentaram aumento da inibição intracortical no hemisfério estimulado, em oposição à ausência de mudança significativa da ECM nos sujeitos que receberam estimulação placebo. Os resultados sugerem que sessão de ETCC, utilizando os parâmetros aplicados neste estudo, levou ao aumento da inibição intracortical. Devido a evidências prévias de déficit de inibição intracortical em pessoas com esquizofrenia, é possível que o fenômeno observado represente mecanismo terapêutico da ETCC. É necessário verificar se tal efeito sobre a ECM acompanha medidas objetivas de resposta clinica. Caso isto se comprove, a ECM pode se tornar um valioso marcador de resposta terapêutica e evolução clinica em pacientes com esquizofrenia / The development of transcranial magnetic stimulation allowed the study of motor evoked potentials by applying direct stimuli to the brain cortex in a non-invasive fashion. Different stimulation protocols were observed to yield different response patterns, which were later associated with the functioning of cortical GABAergic and glutamatergic circuits, assembled as motor cortex excitability indices. Also, deviations from normality of such indices were observed in several clinical conditions, including mental disorders such as schizophrenia. The use of these measurements also helped the development of transcranial direct current stimulation (tDCS), a technique which was shown to promote neuromodulatory effects in central nervous system, with potential treatment applications. This technique has been used with success in the treatment of auditory hallucinations in patients with schizophrenia. The use of tDCS might also be effective in the treatment of negative symptoms of schizophrenia, and motor cortex excitability analysis might be used to clarify its physiological effects and act as a possible treatment response predictor. The aim of the present study is to evaluate the motor cortical excitability profile of individuals with schizophrenia, as well as possible influences of tDCS over these measurements. With this aim, we selected a cohort of subjects with schizophrenia who participated in a randomized placebo controlled clinical trial using transcranial direct current stimulation (and sham stimulation for placebo), and measuring motor cortical excitability during baseline evaluation, after the first stimulation session, and at the time of the primary outcome evaluation. The transcranial direct current stimulation protocol used in the present study involved the use of 2 electrodes of area 5x7 cm, anode placed over the region corresponding to the left dorsolateral prefrontal cortex, and cathode over the left cortical temporoparietal juntion. A current of 2 mA intensity was applied for 20 minutes. Each subject underwent a total of 10 sessions. We found that age was correlated to reduced intracortical inhibition, as has been previously found in healthy subjects. Regarding changes of motor cortical excitability following a transcranial direct current stimulation session, we observed that subjects that received the active stimulation displayed an increase in intracortical inhibition, as opposed to those who received sham stimulation, which did not present with any significant change. Results suggest that transcranial direct current stimulation session, using the parameters described in this study, led to an increase in intracortical inhibition. Given previous evidence of intracortical inhibition deficit in individuals with schizophrenia, it is possible that the observed phenomenon corresponds to a treatment mechanism of the electrical stimulation in this population. This need to be confirmed by comparing such changes in cortical excitability to objective measurements of clinical improvement. In case that is confirmed, measurement of motor cortical excitability may have a valuable application as a marker of treatment response and clinical outcome for patients with schizophrenia

A transmissão de energia em corrente contínua, a partir de conversores fonte de tensão, é oportuna ao progresso do sistema elétrico de potência e tem permitido vantajosas aplicações. Muito se dá, devido ao emprego na conexão de sistemas com frequências distintas, além da redução de perdas na transmissão, provida pelas características operacionais destes. VSCs também promovem o controle do fluxo de potência, possibilitando uma efetiva contextualização no âmbito das redes inteligentes. Diante deste cenário, este estudo pretende construir um perfil de corrente através do Cálculo de Curto-Circuito Probabilístico, que emprega a Simulação de Monte Carlo, para prover as informações ao desenvolvimento de projetos de equipamentos, ajustes da proteção e controle de sistemas de transmissão em corrente contínua. A Simulação de Monte Carlo requer muitas iterações, tendo um custo computacional elevado. Se forem executadas em programas comerciais, exige um tempo elevado para leitura dos sinais em arquivos. Devido a isso, um programa de código livre usando linguagem C++, foi desenvolvido para possibilitar acesso aos sinais de interesse ainda em memória, reduzindo desta forma o tempo computacional. Além disso, para melhorar a performance, foram usadas técnicas de processamento paralelo e de computação em nuvem. Desta forma, este estudo contribui com informações indispensáveis ao projeto de equipamentos de proteção dos sistemas de transmissão em corrente contínua de forma a cooperar com o desenvolvimento consistente desta tecnologia. / Transmitting electrical power in direct current using a VSC is suitable for the progress of these systems and has remarkable and advantageous applications. This happens in order to connect two systems with distinct frequencies. This type of line is also used in the reduction of losses in transmission over long distances, provided by their operating characteristics. These converters also promote the control of power flow between distinct generation units, making them effective in the context of Smart Grids. Based on this, the purpose of this research is to construct a profile of a current using a Probabilistic Short-Circuit Analysis by Monte Carlo Simulation to provide basic data to the optimum development of design equipment in protection and control. The Monte Carlo Simulation requires many iterations to find an optimal result. An open source program using C++ language was developed to describe all the system models variables in order to decrease the computation time, as it is time consuming to read signals stored on a disk using commercial software. Moreover, in order to lower computation costs, parallel process techniques and cloud computing were used. Therefore, this study contributes to the literature by providing essential information for designing equipment for Direct Current transmission protection systems.

Les Troubles Obsessionnels et Compulsifs (TOC) sont un trouble mental sévère et fréquemment résistant. La physiopathologie du trouble se caractérise par des anomalies au sein des boucle cortico-striato-thalamo-cortical entrainant une hyper-activité du cortex orbito-frontal, du cortex cingulaire antérieur, du putamen. Au cours des dernières années, des anomalies structurales et fonctionnelles du cervelet ont de plus été mise en évidence dans les TOC venant compléter le modèle existant.Nous avons mise au point un protocole de traitement par tDCS ciblant le cortex orbito-frontal gauche et le cervelet droit pour les TOC résistants. Dans une première étude, nous avons étudié la faisabilité de ce protocole de traitement dans une étude ouverte. Cette étude a mis en évidence une réduction significative des symptômes dans une population de patient à haut niveau de résistance. Dans une deuxième étude, nous avons évaluer l’effet de ce traitement dans un protocole randomisé, contrôlé et parallèle contre placebo. Cette étude n’a pas confirmé l’efficacité de ce protocole de traitement. Dans cette même population, nous avons au cours du protocole mesuré les paramètres d’excitabilité corticale au niveau du cortex moteur par stimulation magnétique transrânienne. Nous avons ainsi mis en évidence que la tDCS provoquait une augmentation significative des processus d’inhibition (Short Interval Cortical Inhibition : SICI ) et une diminution non significative des processus de facilitation (Intra Cortical Facilitation : ICF). L’étude des effets cliniques et électro-physiologiques de cette approche thérapeutique novatrice dans les TOC résistants n’a pas permis de confirmer son intérêt clinique malgré un impact de ce protocole sur les modifications de l’excitabilité corticale inhérentes aux troubles. Ces données ont été mise en relation avec la littérature afin de proposer des perspectives d’évolution dans l’utilisation de la tDCS dans les TOC résistants / Obsessive-compulsive disorder (OCD) is a severe mental illness. OCD symptoms are often resistant to available treatments. Neurobiological models of OCD are based on an imbalance between the direct (excitatory) and indirect (inhibitory) pathway within this cortico-striato-thalamo-cortical loops, which causes hyperactivation in the orbito-frontal cortex, the cingular anterior cortex, the putamen. More recently, the role of cerebellum in the OCD physiopathology has been brought to light by studies showing structural and functional abnormalities. We proposed to use tDCS as a therapeutic tool for resistant OCD by targeting the hyperactive left orbito-frontal cortex with cathodal tDCS (assumed to decrease cortical excitability) coupled with anodal cerebellar tDCS. In a first study, we studied the feasibility of this treatment protocol in an open-trial. This study found a significant reduction in symptoms in a population with a high level of resistance. In a second study, we evaluated the effect of this treatment in a randomized-controlled trial. This study did not confirm the effectiveness of this intervention. We have assessed motor cortex cortical excitability parameters by transcranial magnetic stimulation. We thus demonstrated that the tDCS caused a significant increase of inhibition processes (Short Interval Cortical Inhibition: SICI) and a nonsignificant decrease in the facilitation processes (Intra Cortical Facilitation (ICF)). In addition, clinical improvement assessed by Clinical Global Impression at the end of the follow-up period (3 months) was positively correlated with SICI at baseline.tDCS with the cathode placed over the left OFC combined with the anode placed over the right cerebellum decreased hyper-excitability in the motor cortex but was not significantly effective in SSRI- resistant OCD patients. These works were discussed in light of the available literature to create future prospect in the field of tDCS treatment for OCD resistant patients

INTRODUÇÃO: Os episódios depressivos são bastante prevalentes e, potencialmente, incapacitantes ao longo do curso do transtorno bipolar (TB). Todavia, ainda não se dispõe de opções terapêuticas com eficácia e tolerabilidade satisfatórias. A estimulação transcraniana por corrente contínua (ETCC) é uma nova modalidade de estimulação cerebral não-invasiva com poucos eventos adversos, que mostrou resultados promissores na depressão unipolar. OBJETIVO: Avaliar a eficácia e a segurança da ETCC como tratamento aditivo aos psicofármacos na depressão bipolar (DB). MÉTODOS: Foi realizado um ensaio clínico, duplo-cego, randomizado, em ambiente acadêmico. 59 pacientes com transtorno bipolar (TB) tipos I ou II em episódio depressivo maior, em regime farmacológico estável, com escores Hamilton (HDRS-17) superiores a 17. Os dados foram analisados por intenção de tratamento. A ETCC foi aplicada em 2 mA/25cm2, sendo o ânodo e o cátodo posicionados sobre as áreas correspondentes ao córtex dorsolateral pré-frontal esquerdo e direito, respectivamente, por 30 minutos, diários, por dez dias consecutivos, exceto aos finais de semana. Após este período, duas estimulações adicionais foram aplicadas, em semanas alternadas, até o final do estudo (6a semana). A alteração na escala de HDRS -17, na 6a semana, foi o desfecho primário. RESULTADOS: Cinquenta e nove pacientes (40 mulheres), com média de idade de 45,9 anos participaram; 36 (61%) com transtorno bipolar tipo I e 23 (39%) com tipo II foram randomizados e 52 finalizaram o ensaio. Na análise por intenção de tratamento, os pacientes do grupo ETCC ativa apresentaram melhora estatisticamente significativa relação àqueles que receberam ETCC simulada (número necessário para tratar [NNT], 5,8; intervalo de confiança [IC] 95%, 3,3-25,8; p = 0,01). A taxa de resposta cumulativa foi maior no grupo ativo em relação ao simulado (67,6% vs 30,4%, NNT, 2,69; IC 95%, 1,84-4,99; p = 0,01), mas não para taxa de remissão (37,4% vs 19,1%; NNT, 5,46; IC 95%, 3,38-14,2; p = 0,18). Os eventos adversos, incluindo virada maníaca, foram semelhantes entre os grupos; com exceção de vermelhidão na pele, maior no grupo ativo (54% vs 19%; P = 0,01). CONCLUSÃO: Nesse estudo, a ETCC foi uma intervenção eficaz, segura e tolerável para esta pequena amostra de pacientes com depressão bipolar. Todavia, outros estudos são necessários para que se possa examinar a eficácia da ETCC em amostras maiores / INTRODUCTION: More effective, tolerable interventions for bipolar depression treatment are needed. Transcranial direct current stimulation (tDCS) is a novel therapeutic modality virtually devoid of severe adverse effects that showed promising results for unipolar depression. OBJECTVE: To determine the efficacy and safety of tDCS as an add-on treatment for bipolar depression. METHODS: A randomized, sham-controlled, double-blind trial was conducted at an academic setting. Participants included 59 adults with type I or II bipolar disorder in a major depressive episode and receiving a stable pharmacologic regimen with 17-item Hamilton Depression Rating Scale (HDRS-17) scores higher than 17. Data were analyzed in the intention-to-treat sample. Ten daily 30-minute, 2-mA, anodal-left and cathodal-right prefrontal sessions of active or sham tDCS on weekdays and then 1 session every fortnight until week 6. The main outcome was the change in HDRS-17 scores at week 6. RESULTS: 59 patients (40 women), with a mean age of 45.9 years participated; 36 (61%) with bipolar I and 23 (39%) with bipolar II disorder were randomized and 52 finished the trial. In the intention-to-treat analysis, patients in the active tDCS condition showed significantly superior improvement compared with those receiving sham (number needed to treat [NNT], 5.8; 95% confidence interval [CI], 3.3-25.8; p = .01). Cumulative response rates were higher in the active vs sham groups (67.6% vs 30.4%; NNT, 2.69; 95% CI, 1.84-4.99; p = .01), but not remission rates (37.4% vs 19.1%; NNT, 5.46; 95% CI, 3.38-14.2; p = .18). Adverse events, including treatment-emergent affective switches, were similar between groups, except for localized skin redness that was higher in the active group (54% vs 19%; p = .01). CONCLUSION: In this trial, tDCS was an effective, safe, and tolerable add-on intervention for this small bipolar depression sample. Further trials should examine tDCS efficacy in a larger sample

O desenvolvimento da estimulação magnética transcraniana (EMT) permitiu o estudo de potenciais evocados motores eliciados pela estimulação direta do córtex cerebral de forma não-invasiva. Foi observado que diferentes paradigmas de estimulação cortical por EMT apresentam diferentes padrões de resposta, que posteriormente foram associados ao funcionamento de circuitos corticais GABAérgicos e glutamatérgicos do córtex motor, compondo assim índices de excitabilidade cortical motora (ECM). Ademais, desvios da normalidade de tais índices foram encontrados em diversas condições clínicas, incluindo transtornos mentais como a esquizofrenia. O uso dessas medidas também auxiliou o desenvolvimento da estimulação transcraniana por corrente contínua (ETCC), técnica que se mostrou capaz de produzir efeitos neuromodulatórios no sistema nervoso central de forma segura e com mínimos efeitos adversos. Tal técnica vem apresentando possibilidades terapêuticas promissoras, como por exemplo, tendo sido observado sua eficácia no alívio de alucinações auditivas de indivíduos com esquizofrenia. O uso de ETCC para tratamento de sintomas negativos da esquizofrenia também pode vir a se mostrar uma abordagem eficaz, e a análise da ECM pode auxiliar no entendimento dos seus mecanismos de ação e atuar como possível preditor de resposta terapêutica. O objetivo do presente estudo é avaliar o perfil de ECM em um grupo de indivíduos com esquizofrenia, e as possíveis influências de um protocolo terapêutico utilizando ETCC sobre essas medidas. Com esse objetivo, foi selecionada uma coorte de sujeitos com esquizofrenia que participou em ensaio clínico randomizado e controlado com placebo (estimulação sham), tendo a ETCC como intervenção ativa alvo. A ECM foi mensurada na avaliação inicial dos sujeitos, assim como após a primeira sessão de ETCC, e quando da avaliação de desfecho primário. O protocolo terapêutico de ETCC envolveu a colocação de 2 eletrodos de área 5x7 cm, pólo anódico aplicado sobre região correspondente ao córtex pré-frontal dorsolateral esquerdo e pólo catódico aplicado sobre córtex de transição temporoparietal esquerdo; com intensidade de corrente de 2 mA, aplicada por 20 minutos. Cada sujeito foi submetido a 10 sessões no total. Encontramos que idade se correlacionou com diminuição da inibição intracortical, reproduzindo resultado previamente encontrado em indivíduos saudáveis. Acerca da modulação da ECM após sessão de ETCC, observamos que sujeitos submetidos à intervenção ativa apresentaram aumento da inibição intracortical no hemisfério estimulado, em oposição à ausência de mudança significativa da ECM nos sujeitos que receberam estimulação placebo. Os resultados sugerem que sessão de ETCC, utilizando os parâmetros aplicados neste estudo, levou ao aumento da inibição intracortical. Devido a evidências prévias de déficit de inibição intracortical em pessoas com esquizofrenia, é possível que o fenômeno observado represente mecanismo terapêutico da ETCC. É necessário verificar se tal efeito sobre a ECM acompanha medidas objetivas de resposta clinica. Caso isto se comprove, a ECM pode se tornar um valioso marcador de resposta terapêutica e evolução clinica em pacientes com esquizofrenia / The development of transcranial magnetic stimulation allowed the study of motor evoked potentials by applying direct stimuli to the brain cortex in a non-invasive fashion. Different stimulation protocols were observed to yield different response patterns, which were later associated with the functioning of cortical GABAergic and glutamatergic circuits, assembled as motor cortex excitability indices. Also, deviations from normality of such indices were observed in several clinical conditions, including mental disorders such as schizophrenia. The use of these measurements also helped the development of transcranial direct current stimulation (tDCS), a technique which was shown to promote neuromodulatory effects in central nervous system, with potential treatment applications. This technique has been used with success in the treatment of auditory hallucinations in patients with schizophrenia. The use of tDCS might also be effective in the treatment of negative symptoms of schizophrenia, and motor cortex excitability analysis might be used to clarify its physiological effects and act as a possible treatment response predictor. The aim of the present study is to evaluate the motor cortical excitability profile of individuals with schizophrenia, as well as possible influences of tDCS over these measurements. With this aim, we selected a cohort of subjects with schizophrenia who participated in a randomized placebo controlled clinical trial using transcranial direct current stimulation (and sham stimulation for placebo), and measuring motor cortical excitability during baseline evaluation, after the first stimulation session, and at the time of the primary outcome evaluation. The transcranial direct current stimulation protocol used in the present study involved the use of 2 electrodes of area 5x7 cm, anode placed over the region corresponding to the left dorsolateral prefrontal cortex, and cathode over the left cortical temporoparietal juntion. A current of 2 mA intensity was applied for 20 minutes. Each subject underwent a total of 10 sessions. We found that age was correlated to reduced intracortical inhibition, as has been previously found in healthy subjects. Regarding changes of motor cortical excitability following a transcranial direct current stimulation session, we observed that subjects that received the active stimulation displayed an increase in intracortical inhibition, as opposed to those who received sham stimulation, which did not present with any significant change. Results suggest that transcranial direct current stimulation session, using the parameters described in this study, led to an increase in intracortical inhibition. Given previous evidence of intracortical inhibition deficit in individuals with schizophrenia, it is possible that the observed phenomenon corresponds to a treatment mechanism of the electrical stimulation in this population. This need to be confirmed by comparing such changes in cortical excitability to objective measurements of clinical improvement. In case that is confirmed, measurement of motor cortical excitability may have a valuable application as a marker of treatment response and clinical outcome for patients with schizophrenia

O transtorno do déficit de atenção e hiperatividade (TDAH) é um transtorno do neurodesenvolvimento e sua prevalência na vida adulta é em torno de 2,5%. O tratamento farmacológico, apesar de efetivo, possui importantes limitações, justificando a busca por outras estratégias terapêuticas. A estimulação elétrica transcraniana (EETC) é uma técnica não invasiva de neuroestimulação que tem apresentado resultados promissores em melhorar o desempenho cognitivo em vários distúrbios neuropsiquiátricos, no entanto, poucos estudos avaliaram a sua eficácia e tolerabilidade no TDAH. Foi realizado um ensaio clínico randomizado, duplo-cego e controlado, com estimulação falsa para avaliar a eficácia da EETC nos sintomas de TDAH. Dezessete adultos com TDAH foram randomizados em dois grupos, nove receberam EETC verdadeira e oito, falsa. No grupo da EETC verdadeira foi aplicada estimulação com intensidade de corrente de 2 mA, durante 20 minutos, em cinco dias consecutivos. O ânodo foi posicionado sobre o córtex pré-frontal dorsolateral (CPFDL) direito e o cátodo sobre o CPFDL esquerdo. O grupo controle recebeu estimulação falsa durante o mesmo período. Os sintomas do TDAH foram mensurados por meio da escala Adult ADHD Self-Report Scale (ASRS) e a incapacidade com a escala Sheehan Disability Scale (SDS). As duas escalas foram aplicadas nos seguintes momentos: antes de iniciar (t0) as estimulações, ao final do protocolo (t1) e uma (t2), duas (t3) e quatro semanas (t4) após a intervenção. Observamos redução, estatisticamente significativa, na pontuação das escalas ASRS desatenção (p = 0,02) e SDS (p = 0,04) entre t0 e t1 após a intervenção em comparação ao grupo controle. Na ASRS total também observamos essa tendência, mas não se mostrou estatisticamente significativa (p = 0,07). Ampliando a análise dos dados observamos interação positiva entre tempo e tratamento na pontuação da ASRS total (p = 0,003), ASRS desatenção (p = 0,0001) e SDS (p = 0,001). Os dados deste estudo apontam que a EETC é eficaz para melhorar a atenção em adultos com TDAH. Contudo, mais pesquisas são necessárias para avaliar a eficácia clínica da ETCC nessa população. / Attention Deficit Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder with 2,5% prevalence in adulthood. Pharmacological treatment, although effective, has important limitations, justifying the search for other therapeutic strategies. Transcranial direct-current stimulation (tDCS) is a non-invasive neurostimulation technique which has show promising results to improve cognitive performance in several neuropsychiatric disorders, nonetheless few studies have evaluated their efficacy and tolerability in ADHD. A randomized, double-blind, sham-controlled trial was conducted to examine the efficacy of tDCS on ADHD symptoms. in adults with ADHD. Seventeen adults with ADHD were randomized into two groups, nine received active EETC eight, false. In the active group was applied EETC with 2mA current intensity, for 20 minutes, in five consecutive days. Anode was positioned on the right dorsolateral prefrontal cortex (DLPFC) and cathode over the left DLPFC. Control group received false stimulation during the same period. ADHD symptoms were measured using the scale Adult ADHD Self-Report Scale (ASRS) and the disability with Sheehan Disability Scale Scale (SDS). Both scales were applied at the following times: before starting the stimulation, the end of the protocol, and one, two and four weeks after the intervention. Subjects in the active group achieved significant reduction in ASRS inattention (p = 0,02) and SDS (p = 0,04) scores after intervention compared to control group. At ASRS total score was also observed this trend, without statistical significance (p = 0.07). Extending data analysis shows there are positive interaction between time and treatment on ASRS total score (p = 0,003), ASRS inattention (p = 0,0001) and SDS (p = 0,001). These data indicate that tDCS is effective to improving attention in adults with ADHD. However, further research is needed to assess the clinical efficacy of tDCS in this population.

<p>U okviru doktorske disertacije, realizovane su podešljive feritne komponente sa jezgrima koja su proizvedena od komercijalno dostupnih ESL 40011 feritnih traka čije se induktivnosti podešavaju primenom jednosmerne struje. Rad realizovanih podešljivih feritnih komponenti je verifikovan u kolu DC-DC konvertora podizača napona. U disertaciji je predložena merna metoda koja omogućava ispitivanje uticaja jednosmerne struje na karakteristike SMD induktora postavljenih u realnom okruženju. Metoda je verifikovana na komercijalno dostupnim SMD induktorima.</p> / <p>As part of this thesis variable ferite components with cores produced from comercialy available ESL 40011 ferite tapes manufactured in Low Temperature Co-fired Ceramic technology are implemented. Inductivity of the components is varied by applying DC current. Functionality of the implemented ferite components is verified in a circuit of DC-DC boost converter. This thesis proposes a measurement method which enables examining the influence of DC current on the characteristics of SMD inductors in real environment. The method is verified on comercialy available SMD inductors</p>