<div>Charge degree of freedom has been successfully manipulated in the semiconductor industry over the past few decades. The trend of doubling the number of transistors every two years in each chip was observed by Gordon Moore at 1965 and this observation was named after him, Moores law. People have kept up with the prediction fairly well till very recently when the fundamental physics limitations has reached in the conventional Si-based devices. All variety of materials and different degrees of freedom are being explored intensively to make novel device designs to overcome this challenge. In this dissertation, we will focus on two-dimensional transition metal dichalcogenides (TMDs) materials and explore not only charge but also valley and spin degrees of freedom. 2D TMDs have attracted a lot of attention for many reasons and one of them is their superior electrostatic control due to the lowering of dimensionality from 3D to 2D. Such reduction of the dimensionality besides the easiness of doping, on the other hand, makes good metal contact harder to achieve due to its inert surface comparing to the existing Si technology. To evaluate the possibility of being one of the promising candidates of post-CMOS (complementary metal oxide semiconductor) devices, the access to both electrons (conduction band) and holes (valence band) is required in order to make CMOS devices. Fermi-level pinning in these materials, however, severely limits the tunability of the Fermi level alignment between metal and semiconductor by choosing different metal work functions. In Chapter 2, we will discuss our results on making good contact by lowering the Schottky barrier height and having atomically precise doping layer control and its associated doping level where we also achieved the record high hole branch current at the bias volt- age of -1V. Besides the manipulation of charge degree of freedom, we also explored and demonstrated the unique valley degree of freedom that can be electrically generated and detected for the first time in Chapter 3. Many fascinating properties of valley physics can be analogized to spin physics, such as, zero dissipation pure spin/valley current and binary nature (spin +1/2 and -1/2, valley K and K’). Due to the unique lattice structure in TMDs, monolayer particularly, the inversion symmetry is intrinsically broken which lifts the Kramers degeneracy and leads to non-zero Berry curvature. As a result, it possesses valley Hall effect. Even more interestingly, when the transport carriers are in the valence band of monolayer TMDs, spin and valley are locked and it is called spin-locked valley Hall effect. Owing to the nature of being 2D materials, these spins’ polarization is out-of-plane unlike the conventional spin Hall effect materials, such as Pt, Ta, and W, where spins are polarized in the surface plane. This out-of-plane polarization is particularly favorable in the SOT-magnetic random access memory (SOT-MRAM) applications due to the lowering of critical switching current and consequently the reducing of power consumption. We directly observed this spin-locked valley Hall effect for the first time and we will discuss it in Chapter 4.</div>

A população moderna tem sido frequentemente acometida por problemas como disfunção e colapso dos componentes do sistema estomatognático. O estudo de populações primitivas é importante para verificar se os hábitos de vida adotados pela população moderna realmente são fatores interferentes na função deste sistema. Desta forma, este estudo visou: comparar os dados coletados de 38 índios do Parque Indígena do Xingu e 38 brancos urbanizados referentes à avaliação clínica de medidas faciais, dimensão vertical de oclusão (DVO), palpação muscular, desgaste oclusal fisiológico (DOF), limite de abertura bucal máximo (ABM), hábitos de vida, índice Clínico de Fonseca; e referentes à avaliação eletromiográfica (EMG) dos músculos da mastigação durante atividades posturais e dinâmicas. Foi realizada a correlação entre estes dados em índios e brancos. Os dados referentes à avaliação clínica revelaram semelhança entre medidas faciais e DVO em índios e brancos, maior sensibilidade dolorosa a palpação muscular nos brancos, índices mais elevados de desgaste oclusal fisiológico nos índios, limite de abertura bucal reduzido nos índios, hábitos de vida mais saudáveis nos índios, e maior índice de Fonseca nos brancos. Os dados referentes à avaliação eletromiográfica revelaram atividade reduzida no grupo dos índios que no grupo dos brancos. A correlação entre os dados revelou que no grupo dos brancos a presença de facetas de desgaste está relacionada com a diminuição da DVO e nos índios esta correlação não existe, a presença de facetas de desgaste está relacionada com a idade nos dois grupos, os brancos relataram aumento de dor a palpação enquanto que a atividade EMG era menor e nos índios esta correlação foi inversa; a correlação entre a EMG e a abertura bucal máxima foi inversamente proporcional para os brancos e não existiu nos índios; não houve correlação entre EMG e índice de Fonseca em nenhum dos grupos. Pode-se concluir que os indígenas do Parque Nacional do Xingu recrutam menor quantidade de unidades motoras e fibras musculares para desempenharem suas funções quando comparados com os brancos e revelam menores indícios de disfunção do sistema estomatognático que os brancos. Este fato está relacionado com um treinamento saudável e eficiente desta musculatura realizado por meio de uma alimentação rica em fibras e proteínas e ausência de estresse. O trabalho nas aldeias indígenas do Xingu é um modo de subsistência e o respeito mútuo existente por toda a vida dos índios xinguanos proporciona condições mais favoráveis para um sistema estomatognático mais saudável. / Modern population has been frequently suffered by problems like stomatognatic system´s dysfunction and collapse. Primitive populations study could be important to evaluate the real interference that modern habits of life have on this system functioning. This study aims at comparing data measured in 38 Xingu Villages indigenous people and 38 render urban concerning at clinical evaluation of facial measurement, vertical dimension occlusion, muscular palpation, physiological occlusal erosion, maximal opening mouth limit, habits of life, Fonseca Clinical Index; and referring at electromyographic (EMG) assessment of masticatory muscles during postural and dynamic activities. A correlation assessment of these data between indigenous and white people was realized. Clinical assessment data showed be facial measurements similar in indigenous and white volunteers, high pain to muscle palpation in white people, high levels of physiological occlusal erosion in indigenous than white, maximal opening mouth limit reduced in indigenous, life habits more health in indigenous, higher Fonseca Clinical Index in white volunteers. Electromyographic data revealed reduced activity in indigenous group than white people. Correlation between data revealed that in white group the wearing facets is related to vertical dimension occlusion reducing and in indigenous this correlation do not exist, the facets wearing is related to age in both groups, white people revealed a muscle palpation pain increasing while EMG reduced and in indigenous this correlation was inverted, the correlation between EMG and maximal opening mouth limit was conversely proportional to white and do not occurred in indigenous, there was no correlation between EMG and Fonseca Index in both groups. Is possible to conclude that Xingu Villages indigenous recruiting less motor units and muscle fibers to acquit their functions when compared to white people, and revealed less signals of stomatognatic system dysfunction than white. This fact is being related to health and efficient training of this musculature enable by a feed based on fibers and proteins and absence of stress. Job in Xingu villages is simply subsistence life way, and respect among the people during all Xingu indigenous life provides longing model health of stomatognatic system.

Disfunção temporomandibular (DTM) é um termo coletivo que engloba um largo espectro de alterações articulares e musculares no sistema estomatognático. Estas disfunções são caracterizadas por dor, ruídos articulares e funções irregulares da mandíbula, e representam a principal causa de dor não dentária da região orofacial. A prevalência de indivíduos com necessidade de tratamento está entre 5 e 12%, calcula-se que no Brasil 8,5 milhões de brasileiros precisariam ter algum tipo de intervenção. Estudos epidemiológicos sobre DTM têm se apresentado deficientes quanto à padronização de índices e classificações. Conscientes disso realizou-se um levantamento de prontuários dos pacientes atendidos no Serviço de Oclusão, Disfunção Temporomandibular e Dor Orofacial, do projeto DAPE da Faculdade de Odontologia de Ribeirão Preto USP, que realiza atendimento na área de DTM para população encaminhada pelo Sistema Único de Saúde (SUS), entre os anos de 2010 e 2011. Avaliou-se 117 prontuários de indivíduos, que foram submetidos à classificação do Índice Anamétido de Helkimo, divididos de acordo com a severidade de sinais e sintomas, em dois grupos : AiI (leves a moderados) e AiII (severos). Posteriormente os grupos foram subdivididos com relação ao gênero e faixa etária. Os dados foram coletados por meio de entrevista, onde os indivíduos foram questionados quanto à presença de hábitos parafuncionais, alterações otológicas, oftalmológicas, sistêmicas e comportamentais. Os dados foram tabulados em planilha de Excel, e submetidos à Análise Estatística, utilizando o Teste de Kruskal-Wallis e Teste de Miller, ambos com significância de 0,05. A prevalência de cada alteração também foi avaliada. Os resultados evidenciaram que indivíduos com DTM apresentaram altas prevalências nas alterações locais e sistêmicas pesquisadas. / Temporomandibular (DTM) is a collective term that encompasses a broad spectrum of clinical problems and deformations in orofacial area. These disorders are characterized by pain, joint noises and irregular functions of the jaw, and represent the leading cause of orofacial pain not dental. The prevalence of individuals in need of treatment is between 5% and 12%, it is estimated that in Brazil 8.5 million Brazilians would have some kind of intervention. Epidemiological studies on TMD have presented handicapped on the standardization of indexes and ratings. Aware of this was done a survey of medical records of patients seen in Orofacial Pain service of special Patients clinic FORP-USP, who performs service in the area of TMD for population forwarded by the Central regulating (SUS), the city of Ribeirão Preto, between the years 2010 and 2011. Assessed-if medical records of individuals, these 117 were subjected to the classification of the Anamétido Index of Helkimo, and divided according to the severity of symptoms and signs, in two groups AiI (mild to moderate) and AiII (severe). Later groups were sub-divided in relation to gender and age group. The data were collected through interview, where individuals were questioned as to the presence of parafunctional habits, changes otologicals, ophthalmologicals, systemic and behavioral. The data were tabulated into Excel spreadsheet, and subjected to statistical analysis, using the Kruskal-Wallis test, and Miller\'s Test, both with significance of 0.05. The prevalence of each change was also evaluated. The results showed that TMD patients showed a high prevalence in the surveyed local and systemic changes.

Este trabalho teve por objetivo avaliar o efeito do tratamento com placa interoclusal estabilizadora como terapia única ou pós terapia miofuncional orofacial prévia em portadores de disfunção temporomandibular articular (Grupos II e III) associada ou não ao diagnóstico de DTM muscular (Grupo I) de acordo com Research Diagnostic Criteria for TMD (RDC/TMD), a fim de determinar os efeitos desta terapia para a redução dos sinais e sintomas de DTM, como também melhora no limiar de dor à pressão com algômetro, dor à palpação, redução da dor subjetiva pela VAS e alteração da atividade muscular avaliada através da eletromiografia. A amostra foi composta por 33 pacientes, do sexo feminino com idade entre 18 a 45 anos que já haviam sido submetidos, há menos de 12 meses, à Terapia Miofuncional Orofacial (TMO), ou não, e que apresentavam indicação para complementar o tratamento por meio do uso de placa. Os indivíduos foram divididos em dois grupos, Grupo T (n = 21), grupo que passou por tratamento prévio com TMO e Grupo P (n = 12), grupo que não se submeteu a terapias prévias. Ambos os grupos foram tratados com placa interoclusal estabilizadora com guias (protrusiva e canina) e acompanhamento por 120 dias. Todos os sujeitos foram avaliados antes da instalação do dispositivo interoclusal (A1) e após os 120 dias de uso (A2). Os resultados mostraram que: houve aumento significante nas medidas de movimentos excursivos quanto ao movimento de protrusão para o Grupo P, entretanto, para os outros movimentos os grupos se comportaram de maneira semelhante; houve redução significante em relação ao aspecto subjetivo da dor por meio da VAS nos dois grupos estudados, sem diferença entre eles; não se observou diferença entre os grupos em relação à alteração do limiar de dor com algômetro; para o ProDTMmulti; foi observado uma diminuição na presença de sinais e sintomas para a maioria dos parâmetros avaliados e um decréscimo na severidade de dor articular e dor muscular apenas para o grupo P e na sensibilidade dentária e plenitude apenas para o grupo T e ruídos articulares para os dois grupos. Não houve mudanças na atividade muscular avaliada por meio de eletromiografia de superfície. / This study aimed to evaluate the effect of the treatment with stabilization splint as a single therapy or after prior orofacial myofunctional therapy in TMJ patients (Groups II and III) with or without the diagnosis of myofascial pain (Group I) according to Research Diagnostic Criteria for TMD (RDC / TMD) in order to determine the effects of this therapy to reducing TMD signs and symptoms, as well as improvement in pain threshold algometer pressure, pain to palpation, reduction of subjective pain by VAS and changes in muscle activity assessed by electromyography (EMG). A total of 33 patients, female, aged from 18 to 45, were divided into two groups: T Group (n = 21), a group that underwent to prior therapy (Orofacial Myofunctional Therapy-OMT) and P Group (n = 12), a group that hadnt undergone to prior therapies. Both groups were treated with stabilization splint with guides (canine and protrusive) and were evaluated before (A1) and after (A2) the splint therapy (120 days). The results showed that there was a significant increase in measures on protrusive movement for Group P, however, for the other movements the groups behaved similarly; there was significant reduction in relation to the subjective aspect of pain by VAS in both groups, without differences between them; there wasnt any differences between groups regarding the change in pain threshold by algometer; for ProDTMmulti, a decrease was observed in the presence of signs and symptoms for most of the evaluated parameters and a decrease in the severity of joint pain and muscle pain only to the P Group; tooth sensitivity and fullness only to the T Group; and joint sounds to both groups. There werent changes in muscle activity assessed by surface electromyography (EMG).

A população moderna tem sido frequentemente acometida por problemas como disfunção e colapso dos componentes do sistema estomatognático. O estudo de populações primitivas é importante para verificar se os hábitos de vida adotados pela população moderna realmente são fatores interferentes na função deste sistema. Desta forma, este estudo visou: comparar os dados coletados de 38 índios do Parque Indígena do Xingu e 38 brancos urbanizados referentes à avaliação clínica de medidas faciais, dimensão vertical de oclusão (DVO), palpação muscular, desgaste oclusal fisiológico (DOF), limite de abertura bucal máximo (ABM), hábitos de vida, índice Clínico de Fonseca; e referentes à avaliação eletromiográfica (EMG) dos músculos da mastigação durante atividades posturais e dinâmicas. Foi realizada a correlação entre estes dados em índios e brancos. Os dados referentes à avaliação clínica revelaram semelhança entre medidas faciais e DVO em índios e brancos, maior sensibilidade dolorosa a palpação muscular nos brancos, índices mais elevados de desgaste oclusal fisiológico nos índios, limite de abertura bucal reduzido nos índios, hábitos de vida mais saudáveis nos índios, e maior índice de Fonseca nos brancos. Os dados referentes à avaliação eletromiográfica revelaram atividade reduzida no grupo dos índios que no grupo dos brancos. A correlação entre os dados revelou que no grupo dos brancos a presença de facetas de desgaste está relacionada com a diminuição da DVO e nos índios esta correlação não existe, a presença de facetas de desgaste está relacionada com a idade nos dois grupos, os brancos relataram aumento de dor a palpação enquanto que a atividade EMG era menor e nos índios esta correlação foi inversa; a correlação entre a EMG e a abertura bucal máxima foi inversamente proporcional para os brancos e não existiu nos índios; não houve correlação entre EMG e índice de Fonseca em nenhum dos grupos. Pode-se concluir que os indígenas do Parque Nacional do Xingu recrutam menor quantidade de unidades motoras e fibras musculares para desempenharem suas funções quando comparados com os brancos e revelam menores indícios de disfunção do sistema estomatognático que os brancos. Este fato está relacionado com um treinamento saudável e eficiente desta musculatura realizado por meio de uma alimentação rica em fibras e proteínas e ausência de estresse. O trabalho nas aldeias indígenas do Xingu é um modo de subsistência e o respeito mútuo existente por toda a vida dos índios xinguanos proporciona condições mais favoráveis para um sistema estomatognático mais saudável. / Modern population has been frequently suffered by problems like stomatognatic system´s dysfunction and collapse. Primitive populations study could be important to evaluate the real interference that modern habits of life have on this system functioning. This study aims at comparing data measured in 38 Xingu Villages indigenous people and 38 render urban concerning at clinical evaluation of facial measurement, vertical dimension occlusion, muscular palpation, physiological occlusal erosion, maximal opening mouth limit, habits of life, Fonseca Clinical Index; and referring at electromyographic (EMG) assessment of masticatory muscles during postural and dynamic activities. A correlation assessment of these data between indigenous and white people was realized. Clinical assessment data showed be facial measurements similar in indigenous and white volunteers, high pain to muscle palpation in white people, high levels of physiological occlusal erosion in indigenous than white, maximal opening mouth limit reduced in indigenous, life habits more health in indigenous, higher Fonseca Clinical Index in white volunteers. Electromyographic data revealed reduced activity in indigenous group than white people. Correlation between data revealed that in white group the wearing facets is related to vertical dimension occlusion reducing and in indigenous this correlation do not exist, the facets wearing is related to age in both groups, white people revealed a muscle palpation pain increasing while EMG reduced and in indigenous this correlation was inverted, the correlation between EMG and maximal opening mouth limit was conversely proportional to white and do not occurred in indigenous, there was no correlation between EMG and Fonseca Index in both groups. Is possible to conclude that Xingu Villages indigenous recruiting less motor units and muscle fibers to acquit their functions when compared to white people, and revealed less signals of stomatognatic system dysfunction than white. This fact is being related to health and efficient training of this musculature enable by a feed based on fibers and proteins and absence of stress. Job in Xingu villages is simply subsistence life way, and respect among the people during all Xingu indigenous life provides longing model health of stomatognatic system.

Orientador: Araildo Lima da Silva / Banca: Mauro Pedro Peres / Banca: Libório José Faria Júnior / Resumo: O presente trabalho tem por objetivos, analisar a intensidade e freqüência dos ruídos articulares da articulação temporomandibular (A.T.M.) de indivíduos saudáveis e patológicos, auxiliar nos procedimentos clínicos e em futuras pesquisas. Para a análise dos sinais coletados foi desenvolvido um sistema para aquisição de dados, composto por um conjunto estetoscópio/microfone, equipamentos para condicionamento e aquisição de sinais e aplicativos computacionais para registro, análise e apresentação dos dados. A identificação das freqüências dominantes e o cálculo dos parâmetros considerados no domínio do tempo (valor médio, valor eficaz, desvio padrão e nível da pressão sonora - NPS) foram realizados por meio de programas computacionais específicos. Os resultados decorrentes dos cálculos e das observações em relação aos sinais obtidos, possibilitaram a determinação das faixas de freqüência, o nível da pressão sonora em decibéis (dB)* da população em estudo, além de proporcionar algumas diferenças entre os grupos patológicos e não-patológicos. Pode-se concluir que a presença da patologia influiu na amplitude dos sinais coletados, diferenciando dessa forma os casos patológicos dos não patológicos. Outra contribuição desse trabalho foi o desenvolvimento de um exame não invasivo para as Disfunções das Articulações Temporomandibulares (D.T.Ms.) / Abstract: This word has the objective of analyzing the amount and frequency of articular noise in temporomandibular joint (TMJ) of both healthy and pathological individuals and aid in clinical procedures as well as in future researches. For the proposed analysis, a dada collecting system was developed comprising a stethoscope/microphone set, equipment for the signal conditioning and capturing, and computer software for data recording, analysis and presentation. The identification of dominating frequencies and the parameter calculation considered in the time period (average amount, efficient amount, linear fit, and sound pressure level) were performed through specific computer softwares. The results found through the calculations and observations in relation to the signals obtained made the determination of the frequency, the level of sound pressure (in dB) of the studied population possible besides differentiating the pathological and non-pathological groups. It can be concluded that the presence of the pathology influenced in the amplitude of the collected signals, differentiating of this form the pathological cases of the not pathological ones. Another contribution of this work was the development of a not invasive examination for the temporomandibular dysfunction (TMD) / Mestre

Disfunção temporomandibular (DTM) é um termo coletivo que engloba um largo espectro de alterações articulares e musculares no sistema estomatognático. Estas disfunções são caracterizadas por dor, ruídos articulares e funções irregulares da mandíbula, e representam a principal causa de dor não dentária da região orofacial. A prevalência de indivíduos com necessidade de tratamento está entre 5 e 12%, calcula-se que no Brasil 8,5 milhões de brasileiros precisariam ter algum tipo de intervenção. Estudos epidemiológicos sobre DTM têm se apresentado deficientes quanto à padronização de índices e classificações. Conscientes disso realizou-se um levantamento de prontuários dos pacientes atendidos no Serviço de Oclusão, Disfunção Temporomandibular e Dor Orofacial, do projeto DAPE da Faculdade de Odontologia de Ribeirão Preto USP, que realiza atendimento na área de DTM para população encaminhada pelo Sistema Único de Saúde (SUS), entre os anos de 2010 e 2011. Avaliou-se 117 prontuários de indivíduos, que foram submetidos à classificação do Índice Anamétido de Helkimo, divididos de acordo com a severidade de sinais e sintomas, em dois grupos : AiI (leves a moderados) e AiII (severos). Posteriormente os grupos foram subdivididos com relação ao gênero e faixa etária. Os dados foram coletados por meio de entrevista, onde os indivíduos foram questionados quanto à presença de hábitos parafuncionais, alterações otológicas, oftalmológicas, sistêmicas e comportamentais. Os dados foram tabulados em planilha de Excel, e submetidos à Análise Estatística, utilizando o Teste de Kruskal-Wallis e Teste de Miller, ambos com significância de 0,05. A prevalência de cada alteração também foi avaliada. Os resultados evidenciaram que indivíduos com DTM apresentaram altas prevalências nas alterações locais e sistêmicas pesquisadas. / Temporomandibular (DTM) is a collective term that encompasses a broad spectrum of clinical problems and deformations in orofacial area. These disorders are characterized by pain, joint noises and irregular functions of the jaw, and represent the leading cause of orofacial pain not dental. The prevalence of individuals in need of treatment is between 5% and 12%, it is estimated that in Brazil 8.5 million Brazilians would have some kind of intervention. Epidemiological studies on TMD have presented handicapped on the standardization of indexes and ratings. Aware of this was done a survey of medical records of patients seen in Orofacial Pain service of special Patients clinic FORP-USP, who performs service in the area of TMD for population forwarded by the Central regulating (SUS), the city of Ribeirão Preto, between the years 2010 and 2011. Assessed-if medical records of individuals, these 117 were subjected to the classification of the Anamétido Index of Helkimo, and divided according to the severity of symptoms and signs, in two groups AiI (mild to moderate) and AiII (severe). Later groups were sub-divided in relation to gender and age group. The data were collected through interview, where individuals were questioned as to the presence of parafunctional habits, changes otologicals, ophthalmologicals, systemic and behavioral. The data were tabulated into Excel spreadsheet, and subjected to statistical analysis, using the Kruskal-Wallis test, and Miller\'s Test, both with significance of 0.05. The prevalence of each change was also evaluated. The results showed that TMD patients showed a high prevalence in the surveyed local and systemic changes.

Objectives: Previous studies in the Oral Neurophysiology Laboratories in Dundee have defined the electromyographic properties of the inhibitory jaw reflex that can be evoked in human subjects by electrical stimulation of the lip. This reflex, in contrast with the more widely studied biphasic inhibitory reflexes evoked by stimulation of intra-oral nerves, consists of just a single phase of inhibition and usually requires the application of stimuli which excite nociceptive nerves. The aims of the present studies were to define the mechanical manifestations of this reflex in the form of changes in biting forces, and to investigate whether the mechanical manifestation of the inhibitory jaw reflex evoked by stimulation of the human upper lip, can be modulated by experimentally-controlled conditions that mimic symptoms of a myogenous temporomandibular disorder. Methods: Three series of experiments were performed on 49 volunteer subjects in total. The experiments involved recording bite forces between the anterior teeth and electromyograms (EMGs) from the masseter muscles. Transcutaneous electrical stimuli were applied to the hairy skin of upper lip while the subjects maintained a biting force of around 50N with the aid of visual feedback. In the first series of experiments, a range of electrical stimuli below and above the nociceptive threshold was delivered. In the second set of experiments, double stimuli with a range of different inter-stimulus intervals were applied. Finally in a third series of experiments, electrical stimulation was repeated before, immediately after, and 5 and 10 minutes following a 3-minute accelerated chewing task. This task consisted of chewing 1.5g of a tough chewing gum at 1.5 times the subject’s natural chewing rate and in 18 cases, muscle fatigue and/or pain were reported by the subjects. Results: Following stimulation at intensities that were described as sharp or painful, all the subjects showed both a suppression of the masseter EMG and a reduction of biting force. When analysing the maximum responses in each subject, the mean reduction in the EMG inhibition was to 15.78 ± 14.4% and 10.39 ± 7.92% of the baseline (for the ipsi- and contra-lateral EMGs respectively), whereas the biting force was reduced only to 83.98 ± 11.04% of baseline (+ S.D.). The latencies of onset of these responses were: 38.17 ± 3.58ms, 38.97 ± 4.49ms and 51.83 ± 6.23ms respectively. The response observed in the force record was weaker than in that observed in either EMG (Paired t tests, P < 0.005 in both cases). When applying double stimuli, it was found that the prolongation of the EMG inhibitory jaw reflex (to 144.70 ± 46.93% of the control level) evoked by double stimulation of the upper lip (with a 10 ms inter-stimulus interval) resulted in a greater increase in the depth of the accompanied relaxation (to 223.63 ± 70.88% of that seen in the control responses) compared to a relatively smaller increase in the duration of the relaxation (to 128.32 ± 27.23% of that seen in the control responses). Following the accelerated chewing task, 17 out of 22 subjects reported pain and/or fatigue in one or both of the masseter muscles. The integral for the bite force relaxation significantly decreased in size immediately following the conditioning procedure (to 76.04 ± 35.63% of the control level, P = 0.014; single sample t-test with Bonferroni correction, test value 100). Conclusion: The inhibitory jaw reflex evoked by stimulation of the human lip can be demonstrated mechanically as well as electromyographically although the mechanical version of the response appears less marked. In addition to that, the onset of reflex relaxation in bite force lags several milliseconds behind the corresponding reductions in electromyographic activity. The depth of force relaxation can be increased by increasing the duration of EMG recorded inhibitory reflex. Finally, the results from a chewing task suggest that induced acute pain and/or fatigue cause clear changes in the mechanical manifestation of this inhibitory jaw reflex.

Tese de mestrado integrado. Mestrado Integrado em Engenharia Civil. Especialização em Estruturas. Faculdade de Engenharia. Universidade do Porto. 2012

As far as we know, we only have one planet to live on, with a delicate atmospheric system providing us safety and life. Global CO2 emissions continue to plague the environment of Earth, primarily due to the processing of fossil fuels, deforestation, and industrialization. There are several avenues of pursuing CO2 reutilization, each having their own benefits and limitations. Direct and indirect thermochemical approaches of CO2 conversion boast of efficient CO2 conversion rates but have limitations associated with the use of renewable hydrogen and high temperatures of operation. The work in this dissertation investigates low temperature photocatalytic CO2 conversion, a simple principle, which provides opportunity for fuel production while harvesting solar energy. Large scale implementation of this process has been plagued by limitations such as fast electron/hole recombination rates, poor quantum efficiency, product selectivity, catalyst stability, and the band gap energy (Eg) being too large to harvest solar light. Our long term goals and applications look to utilize sustainable fuel generation in-situ on Mars for human exploration. We must use available Mars resources to generate fuel to save launch and resource costs from Earth, utilizing the Sun, Mars atmospheric CO2 (95%), and H2O that can be harvested from subsurface ice. Visible light activated catalysts are needed for applications of CO2 conversion on Earth and Mars due to the intensity and abundance of visible light available in the solar spectrums. The dissertation presents the development of photocatalysts for CO2 reduction in the presence of H2O under visible light irradiation. Detailed chemical analysis and characterization were performed on the photocatalysts for improved understanding of material design, including optical and elemental properties, charge transport, stability, catalytic function and scalability. Induced defects and impurities were implemented to understand Eg tunability. Introducing defects through impurities reduced the electron confinement effects in some cases, increasing the photocatalytic activity. Three material regimes were synthesized, tuned, and tested for catalytic function. The first was a series of (ZnO)1-x(AlN)x, materials that had not been synthesized previously, nor ever demonstrated in CO2 and H2O under solar irradiation. The Zn:Al materials were derived from layered double hydroxides. The second material set was (ZnO)1-x(GaN)x, also derived from layered double hydroxides. To the best of our knowledge, these Zn:Ga materials were demonstrated for the first time in CO2 reduction to CO under visible light without the use of any noble metal co-catalysts or dopants. The third set of materials were MoS2 nanoflowers synthesized via chemical vapor deposition that, to our pleasant surprise, produced thinly stacked sheets in the form of nanoflowers that contained large edge-site exposure, which was vastly different from the morphology of commercially purchased MoS2. The preliminary results from this work have demonstrated that tunable band gap energy is achievable. The (ZnO)1-x(AlN)x Eg ranged from 2.84 to 3.25 eV. The Zn:Al solid solution materials were tuned by increasing nitridation time, and varying the cationic ratio. Increasing the cationic ratio in this study more than tripled CO production under solar light irradiation compared to lower cationic ratios. The (ZnO)1-x(GaN)x, materials had a Eg range from 2.33 eV to 2.59 eV. The Eg was also easily tunable from varying nitriding time and cationic ratio. The highest CO production rate was the Zn:Ga cationic ratio of 3:1 at 20 min of nitriding time at 100 °C, which produced 1.06 µmol-g-1-h-1. This production was higher than both of our controlled TiO2 experiments, and other reported pure TiO2 solar photoreaction experiments. The results indicate a delicate balance of nitridation and Zn:M3+ ratio should be selected, along with precursor material cation ratios in order to obtain the desired final product and crystal structure. The controlled introduction of imperfections or crystal defects through MoS2 synthesis variations also revealed the tuning ability of flake edge morphology, nanoflower diameter, stacked-sheet thickness, optical Eg and catalytic activity. The nanoflower Eg ranged from 1.38 to 1.83 eV, and the production rates of CO nearly doubled when post treating the nanoflowers in a reduction step. These developments support tunable gas phase photocatalytic activity and can be enhanced further for further photocatalytic reactions, optoelectronics and field emitter applications. The photoreactor studies indicated that careful tuning of the parent material is imperative to understand before adding a co-catalyst or doping process, as the edge site morphology, crystal phase stability, and strain-induced defects impact the photocatalytic performance.