Harmônicos e desequilíbrios podem causar uma série de problemas a equipamentos conectados a rede elétrica. Este trabalho propõe um método de extração em tempo real das componentes de seqüência positiva, negativa e/ou harmônicos que não requer transformações de coordenadas ou filtragem de sinais. O método proposto é verificado via simulação numérica e implementado experimentalmente em um DSP. Como exemplos de aplicação apresentam-se: a simulação de um Filtro Ativo de Potência utilizando-se um conversor do tipo fonte de tensão operando em PWM e um Relé de Seqüência Negativa. / Harmonics and unbalances cause several problems to equipments connected to AC mains. This work proposes a real time method to obtain the positive and negative sequence components and/or harmonics that requires no coordinate transformation neither signal filtering. Numerical simulation and experimental results are shown to validate the proposed method. As examples of application an Active Power Filter using a voltage source converter operating with PWM and an Negative Sequence Power Relay are presented.

A literatura sobre o desamparo aprendido utilizando humanos como participantes de pesquisa, tem encontrado dificuldades metodologicas. O presente experimento teve como objetivo geral estabelecer um procedimento que permitisse controle experimental suficiente para verificacao do efeito de uma historia de incontrolabilidade, com e sem feedback de erro, sobre a aprendizagem de uma nova resposta operante em sujeitos humanos. Estudantes universitarios foram divididos em quatro grupos (n=10), denominados Nao-tratado (N), Controlavel (C), Incontrolavel (I) e Incontrolavel feedback (If). Na primeira fase (tratamento), com excecao dos sujeitos do grupo N, os demais foram expostos a estimulos aversivos (som) que poderiam ser desligados contingentes ao seu comportamento de teclar sequencias variaveis (grupo C) ou independente dele (grupos I e If). No final da sessao, foi perguntado aos sujeitos a que atribuiam o termino do som: as respostas mostraram correspondencia entre a contingencia a qual estavam submetidos e o comportamento verbal para 100% dos participantes do Grupo C, 70% do Grupo If e 60% do Grupo I. Na segunda fase (teste), todos os participantes foram submetidos a resolucao de anagramas: os sujeitos dos grupos C e N apresentaram menores latencias e maior numero de acertos, sendo maiores as latencias e falhas obtidas no grupo If; o grupo I mostrou resultados intermediarios. Esses resultados sao consistentes com o esperado no estudo do desamparo aprendido, sugerindo que o procedimento proposto e adequado para esse estudo. Foram discutidas as contingencias acidentais que possivelmente se estabeleceram no grupo I, a funcao do feedback de erro no controle dessas contingencias, o controle pela regra e as implicacoes metodologicas do procedimento empregado. / The literature on learned helplessness in human has been fraught with methodological difficulties. The present research has the general objective of establishing a procedure that permits sufficient experimental control to verify the effect of a history of uncontrollability with or without feedback of failure on learning a new operant response by humans. College students were divided into four groups (n=10), deemed Non-treated (N), Controllable (C), Uncontrollable (I) and Uncontrollable with feedback (If). In the first phase (treatment), except for Group N, the participants were exposed to an aversive stimulus (tones) that could be controllable (i.e., turned off contingent upon making variable sequences using the keyboard) or independent of behavior (Groups I and If). At the end of the session, participants were asked to what they attributed the end of the tones: the correspondence between their answers and the situation to which they were exposed was 100% for Group C, 70% for Group If and 60% for Group I. In the second phase (test), all participants were asked to solve some anagrams. Groups C and N showed lower latencies and a greater number of correct responses. Latencies and rate of failure were higher in Group If; Group I presented intermediate results. These results were in agreement with the learned helplessness effect, suggesting that the procedure is adequate for its study. The possible accidental contingences established in Group I, the function of the feedback of failure in these accidental contingencies, the role of instructions and some methodological implications are discussed.

A literatura sobre o desamparo aprendido utilizando humanos como participantes de pesquisa, tem encontrado dificuldades metodologicas. O presente experimento teve como objetivo geral estabelecer um procedimento que permitisse controle experimental suficiente para verificacao do efeito de uma historia de incontrolabilidade, com e sem feedback de erro, sobre a aprendizagem de uma nova resposta operante em sujeitos humanos. Estudantes universitarios foram divididos em quatro grupos (n=10), denominados Nao-tratado (N), Controlavel (C), Incontrolavel (I) e Incontrolavel feedback (If). Na primeira fase (tratamento), com excecao dos sujeitos do grupo N, os demais foram expostos a estimulos aversivos (som) que poderiam ser desligados contingentes ao seu comportamento de teclar sequencias variaveis (grupo C) ou independente dele (grupos I e If). No final da sessao, foi perguntado aos sujeitos a que atribuiam o termino do som: as respostas mostraram correspondencia entre a contingencia a qual estavam submetidos e o comportamento verbal para 100% dos participantes do Grupo C, 70% do Grupo If e 60% do Grupo I. Na segunda fase (teste), todos os participantes foram submetidos a resolucao de anagramas: os sujeitos dos grupos C e N apresentaram menores latencias e maior numero de acertos, sendo maiores as latencias e falhas obtidas no grupo If; o grupo I mostrou resultados intermediarios. Esses resultados sao consistentes com o esperado no estudo do desamparo aprendido, sugerindo que o procedimento proposto e adequado para esse estudo. Foram discutidas as contingencias acidentais que possivelmente se estabeleceram no grupo I, a funcao do feedback de erro no controle dessas contingencias, o controle pela regra e as implicacoes metodologicas do procedimento empregado. / The literature on learned helplessness in human has been fraught with methodological difficulties. The present research has the general objective of establishing a procedure that permits sufficient experimental control to verify the effect of a history of uncontrollability with or without feedback of failure on learning a new operant response by humans. College students were divided into four groups (n=10), deemed Non-treated (N), Controllable (C), Uncontrollable (I) and Uncontrollable with feedback (If). In the first phase (treatment), except for Group N, the participants were exposed to an aversive stimulus (tones) that could be controllable (i.e., turned off contingent upon making variable sequences using the keyboard) or independent of behavior (Groups I and If). At the end of the session, participants were asked to what they attributed the end of the tones: the correspondence between their answers and the situation to which they were exposed was 100% for Group C, 70% for Group If and 60% for Group I. In the second phase (test), all participants were asked to solve some anagrams. Groups C and N showed lower latencies and a greater number of correct responses. Latencies and rate of failure were higher in Group If; Group I presented intermediate results. These results were in agreement with the learned helplessness effect, suggesting that the procedure is adequate for its study. The possible accidental contingences established in Group I, the function of the feedback of failure in these accidental contingencies, the role of instructions and some methodological implications are discussed.

Nos estudos do desamparo aprendido em humanos os resultados experimentais tem sido inconsistentes. Isso provavelmente devido a ocorrencia, na sessao de incontrolabilidade, entre outras variaveis, de contiguidades sistematicas entre o termino do estimulo aversivo e a resposta imediatamente precedente, mimetizando uma condicao de controle, embora acidental. Com o objetivo geral de estabelecer um procedimento que permitisse controle experimental suficiente para que fosse analisado o efeito de uma historia de incontrolabilidade sobre a aprendizagem de uma nova resposta operante em sujeitos humanos, bem como a prevencao (imunizacao) desse efeito, foram realizados tres experimentos. O primeiro deles demonstrou o controle operante sob tres contingencias de reforcamento negativo (sequencias variaveis, labirinto e discriminacao de formas geometricas), o que permitiu verificar o efeito da ausencia de controle sobre uma nova aprendizagem operante (Experimento 2 desamparo aprendido) e o efeito da ausencia de controle, apos historia de controle, sobre uma nova aprendizagem operante (Experimento 3 imunizacao). No Experimento 2, dois grupos de participantes foram expostos a sons aversivos (Grupos C e I) e um nao foi manipulado (Grupo N). Para os participantes do Grupo C, a interrupcao de um som agudo era contingente a emissao de sequencias variaveis; para os participantes do Grupo I, a duracao do som era independente das respostas emitidas. Os sujeitos do Grupo Incontrolavel foram divididos em dois subgrupos de acordo com a presenca ou a ausencia de indicacoes na tela (Ip e I). Na sessao de incontrolabilidade foram manipuladas algumas variaveis a fim de evitar a selecao acidental da resposta mensurada (duracao do estimulo; numero de tentativas; custo da resposta e instrucao inicial). Apos essa fase, todos os participantes foram submetidos a uma contingencia de resolucao de um labirinto associado a um som. No Experimento 3, um Grupo Precontrole (P) foi acrescido a triade do Experimento 2. A contingencia de fuga discriminação foi realizada na fase pre-tratamento sendo associada a um som. Na fase de teste os participantes dos Grupos C, N e P apresentaram menor latencia e maior numero de respostas corretas em comparacao aos grupos incontrolaveis. Entre esses ultimos, foi verificada uma correlacao negativa entre a frequencia de contiguidades no tratamento e o desempenho no teste. Os participantes do Grupo I apresentaram baixa frequencia de contiguidades no tratamento e latencias e falhas mais elevadas no teste; os do Grupo Ip mostraram padrao intermediario. Esses resultados replicam o desamparo aprendido e a imunizacao desse efeito em humanos, sugerindo que os pocedimentos estabelecidos foram adequados para o estudo desses dois efeitos e demonstram o papel da selecao acidental, durante a sessao de incontrolabilidade, como impeditivo da verificacao do efeito no teste (Grupo Ip). O papel das indicacoes na tela, os parametros utilizados e a presenca de contiguidades sistematicas foram discutidos / The results of learned helplessness studies with humans have been inconsistent. This is probably due to the systematic contiguity between the end of the aversive stimulus and the immediately preceding response during the uncontrollability session, which mimics an accidental control condition. Three experiments were conducted to establish a procedure with adequate experimental control to analyze the effects of an uncontrollability history upon learning of a new operant response in humans, as well as the prevention (immunization) of this effect. The first experiment demonstrated operant control under three negative reinforcement contingencies (variable sequences, maze, and discrimination of geometric forms), which allowed verifying the effect of the absence of control upon learning of a new operant response (Experiment 2 learned helplessness) and the effect of the absence of control, after a history of controllability, upon learning of a new operant response (Experiment 3 immunization). During the uncontrollability session, a number of variables were manipulated to avoid the accidental selection of the response being measured (duration of the stimulus, number of trials, response cost, and initial instructions). In Experiment 2, two groups were exposed to aversive tones (groups C and U) and one group was not (group N). For group C, the interruption of a high-pitch tone was contingent on the emission of variable sequences; for group U, the duration of the tone was response independent. Group U was further divided into two subgroups, according to the presence or absence of a hint on the screen (Up and U). After this manipulation, all participants had to solve a maze that was presented along with a tone. In Experiment 3, a pre-control group (P) was added to the ones in Experiment 2. The escape contingency for discriminating geometric forms was presented in the pre-treatment phase along with a tone. The results of the test phase indicated shorter latencies and a greater number of responses for groups C, N, and P, in comparison to the uncontrollable groups. For the latter groups, there was a negative correlation between the frequency of contiguities in the treatment phase and performance during the test phase. There was a low frequency of contiguities during treatment, and longer latencies and more errors during the test for Group U; an intermediate pattern was observed for Group Up. These results replicate the learned helplessness and immunization effects in humans, and suggest that this procedure is adequate to study these phenomena. The results also indicate that accidental selection during the uncontrollability session may eliminate the learned helplessness effect during the test (Group Up). The effects of the hints on the screen, the schedule parameters, and the presence of systematic contiguities are further discussed

Harmônicos e desequilíbrios podem causar uma série de problemas a equipamentos conectados a rede elétrica. Este trabalho propõe um método de extração em tempo real das componentes de seqüência positiva, negativa e/ou harmônicos que não requer transformações de coordenadas ou filtragem de sinais. O método proposto é verificado via simulação numérica e implementado experimentalmente em um DSP. Como exemplos de aplicação apresentam-se: a simulação de um Filtro Ativo de Potência utilizando-se um conversor do tipo fonte de tensão operando em PWM e um Relé de Seqüência Negativa. / Harmonics and unbalances cause several problems to equipments connected to AC mains. This work proposes a real time method to obtain the positive and negative sequence components and/or harmonics that requires no coordinate transformation neither signal filtering. Numerical simulation and experimental results are shown to validate the proposed method. As examples of application an Active Power Filter using a voltage source converter operating with PWM and an Negative Sequence Power Relay are presented.

Made available in DSpace on 2016-04-28T20:17:24Z (GMT). No. of bitstreams: 1 2007- Lidiane de Castro Soares.pdf: 1336181 bytes, checksum: 47680a74331a705e5ecd649c1639aa3f (MD5) Previous issue date: 2007-02-28 / Funda??o Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / Coagulasenegative staphylococci (SCN) take part of normal microbiota. Although it has been considered saprophytic, nowadays there is a concern about its pathogenic potential.Nevertheless, all advance in SCN identification assays, these microorganisms are continually neglected in laboratorial routine of infectious diseases, because of the wide range of species. In spite of the difficulties, it is necessary to make an appropriated species identification in order to differentiate the potential pathogenic agents and to determine its antimicrobial susceptibility pattern. Resistance in SCN is related to the presence of mecA gene, which expresses a heterogeneous pattern that can be detected through diverse phenotypics tests. In this study, 72 SCN isolates obtained from external ear conducts of dogs, bovine mastitis and human nosocomial infections were evaluated. Staphylococcus xylosus was the most prevalent microorganism in animal and S. cohnii subsp.urealyticus in human sample. The antimicrobial resistance patterns were evaluated through disc diffusion test, and a high level of resistance to penicillin and ampicillin were detected. The most efficient antibiotics evaluated were gentamicin, vancomicin and the association ampicillin+sulbactam. Oxacillin resistance was phenotypically detected by modified disc diffusion test, agar screen, broth microdilution and agar dilution. Presence of mecA gene where detected in 5,55% of the isolates by Polimerase Chain Reaction (PCR). Correlation with the detection of mecA gene was used as gold standard for evaluation of sensitivity and specificity of phenotypical assays. The low number of mecA positives isolates did not allowed the association between cefoxitin and oxacillin resistance as a test to detect the presence this gene. The broth microdilution and agar dilution tests presented the best accuracy in phenotypic detection of the oxacillin resistance. / Os estafilococos coagulasenegativos (ECN) fazem parte da microbiota normal da pele e apesar de terem sido considerados sapr?fitas por muito tempo, o seu significado cl?nico como agente etiol?gico tem aumentado com o passar dos anos. No entanto, apesar de todo avan?o nas t?cnicas de identifica??o dos ECN e do conhecimento destes como agentes etiol?gicos em diversos processos infecciosos, estes microrganismos muitas vezes s?o negligenciados na rotina laboratorial, devido a enorme diversidade de esp?cies encontradas. A identifica??o das esp?cies de ECN, embora de dif?cil realiza??o para a maioria dos laborat?rios cl?nicos, ? necess?ria para diferenciar o potencial patog?nico e o perfil de resist?ncia de cada isolado. A resist?ncia ? oxacilina em ECN ? mediada pelo gene mecA e usualmente heterog?nea, sendo detectada por v?rios m?todos fenot?picos. Neste estudo, foram avaliados 72 isolados de ECN provenientes de amostras do conduto auditivo de c?es da ra?a Beagles, de mastite bovina e de infec??es humanas. Staphylococcus xylosus foi o microrganismo mais isolado, nas amostras animais, e S. cohnii subsp.urealyticus em humanos, dentro de uma ampla gama de esp?cies identificadas. O perfil de resist?ncia aos antimicrobianos em isolados de animais e humanas foi avaliado atrav?s da t?cnica de difus?o em disco, na qual detectouse um elevado n?vel de resist?ncia ? penicilina e ampicilina. A gentamicina, vancomicina e associa??o ampicilina+sulbactam foram eficientes frente aos isolados testados. A avalia??o da resist?ncia ? oxacilina foi realizada atrav?s da difus?o em disco modificada, ?gar screen, microdilui??o em caldo e em ?gar. A presen?a do gene mecA foi determinada pelo m?todo da Rea??o em Cadeia de Polimerase (PCR), sendo 5,55% dos isolados mecA positivos. Os resultados fenot?picos de resist?ncia a cefoxitina e a oxacilina foram correlacionados com a detec??o do gene mecA, que foi utilizado como padr?o ouro para avalia??o da sensibilidade e especificidade das t?cnicas utilizadas. O reduzido n?mero de isolados mecA + n?o permitiu estabelecer o grau de correla??o entre a cefoxitina e a oxacilina como m?todo de predi??o do gene, embora ambas tenha apresentado o mesmo percentual de resist?ncia. O teste fenot?pico que apresentou melhor acur?cia na detec??o da resist?ncia ? oxacilina foi a microdilui??o em caldo.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-04-10T18:18:36Z No. of bitstreams: 1 2012 - Marcus Andr? Ferreira S?.pdf: 393876 bytes, checksum: 9d184a085854acf9828da371a7e2b732 (MD5) / Made available in DSpace on 2017-04-10T18:18:36Z (GMT). No. of bitstreams: 1 2012 - Marcus Andr? Ferreira S?.pdf: 393876 bytes, checksum: 9d184a085854acf9828da371a7e2b732 (MD5) Previous issue date: 2012-07-17 / CAPES / The present experiment aimed to verify if different vacuum pump negative pressures (150, 280 e 400 mmHg) can influence the oocyte recovery rate per preovulatory follicle aspirated. Hence, 21 estrous cycles from regularly cycling mares were subject to OPU. The estrous cycles were sorted in three groups (G150=150 mmHg; G280=280 mmHg; G400=400 mmHg) in the following sequence: G150= 150mmHg (n=6); G280= 280mmHg (n=7); G400= 400mmHg (n=6). During the estrus, the ovarian activity of the mares was daily monitored using the transrectal ultrasound technique until the largest follicle reached at least a diameter of 35mm and endometrial edema secore 2.5 was identified on ultrasonographic evaluation, when 1000UI of hCG administered intravenuous. Approximately 24 hours after the hCG administered, the mares were monitored by rectal palpation and ultrasonography every six hours to follicle evaluation. In the case of imminent indication of ovulation or formation of hemorrhagic follicle, the follicle would be immediately aspirate. The aspirations occurred in 32,45?1,92h after the hCG administration. The transvaginal aspirations were performed with ultrasound apparatus equipped with a convex transducer of 5,0mHz with polyethylene guide containing a double lumen needle of 12G. The follicular fluid collected from each follicle was frozen and the aspirated content was transferred to a Petri Dishes and thoroughly examined on the stereomicroscope to identify the oocytes presence. In order to statistically evaluate the influence of different pressures on the oocyte recovery, were used Chi-Squared test (a 5% significance) and Fisher Exact Test, when recommended. The recovery rate was 31,57% (6/19), being 16,66 % (1/6) in G150, 42,85 % (3/7) in G280 and 33,33 % (2/6) in G400. There was no difference among groups (p>0,05). From the results of the current study, it is possible to conclude that the negative pressure of the vacuum pump is not a determining factor to increase the oocyte recovery and other aspects would possibly have more significant influence . / O presente experimento visou investigar se diferentes press?es negativas da bomba de v?cuo (150, 280 e 400mmHg) podem influenciar a taxa de recupera??o oocit?ria por fol?culo preovulat?rio aspirado. Para tanto, foram submetidos a ovum pick up 21 ciclos estrais de ?guas ciclando regularmente, distribu?dos em tr?s grupos (G150= 150 mmHg; G280= 280 mmHg; G400= 400 mmHg), na seguinte ordem: G150= 150 mmHg (n=6); G280= 280 mmHg (n=7); G400= 400 mmHg (n=6), definida por meio de sorteio. Durante estro, a atividade ovariana das ?guas foi monitorada diariamente atrav?s da t?cnica ultrassonogr?fica transretal at? que o maior fol?culos atingisse pelo menos 35mm de di?metro e edema endometrial grau 2,5 durante a avalia??o ultrassonogr?fica, quando ent?o administrou-se 1000UI de hCG, por via endovenosa. Aproximadamente 24 horas ap?s a administra??o de hCG as ?guas foram submetidas a exame ultrassonogr?fico a cada seis horas para avalia??o folicular. Caso houvesse indica??o iminente de ovula??o ou forma??o de fol?culo hemorr?gico, o mesmo seria imediatamente aspirado. As aspira??es ocorreram em 32,45?1,92h ap?s a aplica??o do hCG fazendo uso de ultrassom equipado com um transdutor convexo de 5,0mHz com guia de polietileno contendo uma agulha de duplo l?men de 12G. O fluido folicular coletado de cada fol?culo foi congelado e o conte?do aspirado transferido para uma Placa de Petri e examinado minuciosamente ao estereomicrosc?pio para localiza??o dos o?citos. Para avaliar estatisticamente o efeito das diferentes press?es sobre a recupera??o oocit?ria, foi utilizado o teste Qui-Quadrado (a 5% de signific?ncia) e Fisher Exato, quando recomendado. A taxa de recupera??o foi de 31,57% (6/19), sendo 16,66 % (1/6) no G150, 42,85 % (3/7) no G280 e 33,33 % (2/6) no G400. N?o houve diferen?a entre os grupos (p>0,05). Atrav?s dos resultados obtidos no presente estudo ? poss?vel concluir que a press?o negativa da bomba de v?cuo utilizada n?o ? o determinante para elevar a recupera??o oocit?ria, possivelmente havendo outros fatores atuando de modo mais importante.

O presente trabalho teve como objetivo investigar se padrões variáveis de respostas podem ser instalados e mantidos por reforçamento negativo intermitente em um procedimento de esquiva em tentativas discretas. Seis ratos machos Wistar foram submetidos à modelagem e fortalecimento da resposta de pressão à barra com reforçamento positivo em uma caixa de condicionamento operante com duas barras (direita, D, e esquerda, E). Em seguida, essa resposta passou a ser reforçada negativamente em um procedimento de esquiva em tentativas discretas no qual um estímulo elétrico (US) de 0,5 s e 0,5 mA (em média) podia ocorrer ao final de um período de luz (CS). A emissão da resposta de pressão à barra durante o CS produzia o seu desligamento e um tom de 0,5 s e 10 Hz, cancelando o próximo US programado e iniciando um período de blackout sem qualquer contingência programada, após o qual um novo CS era apresentado. Duzentos US foram programados a cada sessão. O procedimento de esquiva se iniciou com reforçamento em FR 1 e FR 2 (com alternação das barras a cada 50 US programados). Posteriormente, sequências de três respostas foram reforçadas (com as duas barras disponíveis). Inicialmente, o reforçamento era contingente à variabilidade na emissão das sequências, avaliada pela disposição das respostas que as compõem entre as barras D e E: DDD, EED, DED etc. O variar foi reforçado de acordo com uma contingência Lag n, na qual apenas as sequências que diferiam das n anteriormente emitidas pelo sujeito evitavam o US, sendo o valor de n igual a 1, 2 ou 3. Uma vez que o desempenho se mostrou estável nessas fases, os sujeitos foram expostos ao procedimento Aco, no qual a distribuição de reforços foi acoplada àquela obtida na última sessão de Lag n, porém sem exigência de variação. Alguns sujeitos foram reexpostos à contingência Lag n após essa fase. Os resultados mostraram que todos os sujeitos apresentaram esquiva e altos índices variabilidade na emissão de sequências nas fases Lag n (medida pelo valor U), havendo queda sistemática desses índices sob o procedimento Aco. Os sujeitos reexpostos à Lag n mostraram recuperação dos altos índices de variação. Esses resultados sugerem que a variabilidade comportamental foi controlada pelo reforçamento negativo na contingência de esquiva proposta / This study aimed to investigate if variable patterns of responses can be acquired and maintained by intermittent negative reinforcement under a discrete-trial avoidance contingency. Six male Wistar rats were submitted to a lever-press response shaping session in an operant conditioning chamber with two levers (right, R, and left, L). Then, that response was negatively reinforced in a discrete-trial avoidance procedure in which a 0.5 s and 0.5 mA (average) shock (US) could occur after a light period (CS). Lever-press response emission during CS presentation turned off the CS, produced a 0.5 s and 10 Hz tone, canceled the next programmed US, and initiated a blackout period with no programmed contingency, after which a new CS was presented. Two hundred US were programmed per session. Initially, negative reinforcement occurred under FR 1 and FR 2 schedules (with levers alternation each 50 programmed US). Following, three response sequences were reinforced (with the two levers available). Reinforcement was contingent to behavioral variability, which was examined by comparing three-response sequences across R and L levers: RRR, LLR, RLR etc. Varying was reinforced according to a Lag contingency, in which only sequences that differed from n previous sequences avoided US (n was equal to 1, 2 or 3). After steady states were obtained in those contingencies, subjects were submitted to a yoke procedure, in which reinforcer distribution was yoked to the last Lag session, but without varying exigency. Some subjects were re-exposed to the Lag contingency after yoke procedure. Results showed that all the subjects avoided shocks and presented high levels of behavioral variability under the Lag contingency (measured by U value). During the yoke procedure, behavioral variability decreased systematically. Subjects that were re-exposed to the Lag contingency after yoke procedure recovered high levels of variation. These results suggest that behavioral variability was controlled by negative reinforcement under the proposed avoidance contingency

This thesis investigates the relationship between conflict, economic growth, state capacity and natural resources in Sub-Saharan Africa. It contributes to the limited research in this area and empirically examines these relationships using different econometric models. The first empirical chapter uses a panel dataset that covers the period 1997 - 2013 to analyse the effects of economic growth on conflict in Nigeria using the negative binomial model. The findings support the direct relationship between economic growth and conflict in Nigeria. Controlling for other factors, the results indicate that increase in growth rate - measured by annual growth rate of GDP per capita - decreases the expected number of conflicts. The study finds no evidence of a relationship between levels of wealth in a state and the incidence of conflicts. The analysis controls for factors such as spill-over effects from other states and year and state effects. Finally, to address potential concerns that economic growth could be a cause of conflict or that other unobserved factors could confound the relationship between economic growth and conflict, the chapter employs instrumental variable (IV) estimation using percentage change in rainfall as an instrument. The results with the IV estimation are similar to the results without IV in terms of both sign and significance, indicating that the negative effect of economic growth on conflicts is not due to reverse causality or omitted variables. For robustness checks, a Panel Autoregressive model (PVAR) is also employed. The second empirical chapter analyses the effect of conflict on state capacity in Sub-Saharan Africa. State capacity is measured in terms of fiscal and legal capacity. It also looks at the effects of internal and external conflicts on state capacity. The chapter adopts the Ordinary least squared (OLS) and the system generalised methods of moments (GMM) estimation methods to analyse the panel data consisting of 49 Sub-Saharan countries over the period 2000 - 2015. The results suggest that conflicts have a negative and significant effect on state capacity. However, when military expenditure is used as a proxy for state capacity it is found that conflict strengthens state capacity. The results are consistent with theoretical argument that internal conflicts polarise societies and make it more difficult for governments to reach a consensus in investing in state capacity, while external conflicts mobilise domestic population against a common enemy thereby helping in state capacity building. Finally, the third empirical chapter examines the effect of natural resources on conflict onset and duration using discrete choice models with a dataset covering the period 1980 -2016. The results on the duration analysis show that natural resources prolong duration of conflicts. However, it is found that not all natural resources prolong duration of conflicts. Oil production does not seem to affect duration, whereas oil reserves and gas production lengthens the duration. The findings from the onset analysis show that both production and reserves of natural resources increase the risk of conflict onset.

Many reports, scientific papers, patents, and scientific news investigate the feasibility and affordability of direct carbon dioxide capture from the atmospheric air (DAC). Since carbon dioxide (CO2) is extremely diluted in the atmosphere, large volumes of air have to be handled to capture comparable amounts of CO2. Therefore, both the energy consumption and the plant size are expected to be 'prohibitive'. On the other hand, some analyses have shown that DAC is feasible and can become affordable with essential research and development. DAC has been regarded as an optional bridging or a transitional technology for mitigating CO2 emissions in the medium-term. Priorities include investing in renewable and low-carbon technologies, efficiency and integration of energy systems, and realisation of additional environmental benefits. A heavy reliance on negative emission technologies (NETs), and consequently DAC, may be extremely risky as NETs interact with a number of societal challenges, i.e. food, land, water and energy security. Although, "... capturing carbon from thin air may turn out to be our last line of defence, if climate change is as bad as the climate scientists say, and if humanity fails to take the cheaper and more sensible option that may still be available today" MacKay (2009). Certainly, more research is necessary to bring down both cost and energy requirements for DAC. This work firstly predicts the adsorption equilibrium behaviour of a novel temperature swing adsorption process, which captures carbon dioxide directly from the air, concentrates, and purifies it at levels compatible to geological storage. The process consists of an adsorption air contactor, a compression and purification train, which is a series of packed beds reduced in size and connected in-line for the compression and purification purposes, and a final storage bed. The in-line beds undergo subsequent adsorption and desorption states. The final desorbed stream is stored in a storage bed. This cyclic process is repeated for a number of times imposed by the required purity and pressure in the final bed. The process is been thermodynamically verified and optimised. Since, the overall performance of this process does not only depend on the design of the process cycle and operating conditions but also on the chosen adsorbent material, further optimisation of the adsorptive and physical properties of the solid adsorbent is investigated. Thus, the optimal parameters of the potentially used porous materials is identified. Continuing the research on different adsorbent materials, an experimental investigation on the equilibrium properties of two competitive adsorbents is also performed. Besides the thermodynamic analysis, a dynamic model is presented for the investigation of the mass and heat transfer and its influence on the adsorption rate and consequently on the overall process performance. Since the initial stream is very dilute, it is expected that the adsorption rate will be low compared to other temperature swing processes and the capture rate will be affected by the heat transfer. Finally, the design and development of an experimental laboratory-scale apparatus is presented and analysed. Future design improvements are also discussed.