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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

Diagnóstico fitossanitário da cultura do inhame (Dioscorea spp.) em áreas produtoras do Nordeste do Brasil

ANDRADE, Genira Pereira de 20 March 2007 (has links)
Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-17T12:25:45Z No. of bitstreams: 1 Genira Pereira de Andrade.pdf: 531734 bytes, checksum: 9dc28c82bfccaa852aa4dbc98b012e2d (MD5) / Made available in DSpace on 2017-03-17T12:25:45Z (GMT). No. of bitstreams: 1 Genira Pereira de Andrade.pdf: 531734 bytes, checksum: 9dc28c82bfccaa852aa4dbc98b012e2d (MD5) Previous issue date: 2007-03-20 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The yam (Dioscorea spp.) is affected by several diseases and pests occurring in field and/or during transport and storage. It is a crop with a high social economic importance in Northeast of Brazil, showing a good expansion potential by tuber export, especially to Europe. An evaluation of disease and pest development in important producing areas was undertaken, as well as a study on the quality of tuber seed used by the growers. Visits to seven counties of Pernambuco and three of Paraíba, totaling 30 farms were done. In order to evaluate the occurrence of diseases and the damages caused by pests under field conditions, in each field five lines of 10 plants were marked, while for virus evaluation, 30 plants were randomly selected. The plants were analyzed 30 days before and at the harvest day. The nematodes were extracted by association the Jenkins method and identified by their structures under light microscope. For fungus identification, isolation and inoculation were doneand the structures were observed under light microscope. For the viruses, observation under electron microscopy, triple antibody sandwich enzyme-linked immunosorbent assay” (TAS-ELISA), with polyclonal and monoclonal antibodies specific to Yam mosaic virus (YMV), from IITA, Nigeria, and a polymerase chain reaction (PCR) with degenerated primers for detecting badnavirus and duplex reverse transcription (RT-PCR) with specific primers to YMV and Yam mild mosaic virus (YMMV) were used. The PCR and RT-PCR products were purified and sequenced in order to validate the tests used for detecting badnavirus andidentification of the potyviruses by the comparative analyses of the sequences available in the GenBank. It was observed the leaf spot caused by Curvularia eragrostidis in all areas studied, with a higher intensity on cv. Inhame-da-Costa of D. cayennensis-D. rotundata complex, whereas the damages caused by leaf wor (Pseudoplusia oo), present in all fields, were higher on cv. São Tomé of D. alata plants. The seed tubers of both yam species, collected in five farms representative of the growing areas of Pernambuco and Paraíba, after 60 days of storage, presented serious problems of green rot caused by Penicilium sclerotigenum, mealybugs (Planoccocus sp.) and tuber worms (Araecerus fasciculatus). It was identified the potyviruses YMV and YMMV, occurring in single and mixed infections with badnavirus, consisting the first detailed report with molecular information on theseviruses in Brazil. / O inhame (Dioscorea spp.) tem sido afetado por a vários problemas fitossanitários, que se manifestam na lavoura e durante o transporte e/ou armazenamento. É uma cultura de elevada importância sócio-econômica para a região Nordeste do Brasil, inclusive com potencial de expansão via exportação de túberas, especialmente para a Europa. Foi efetuada uma avaliação do desenvolvimento de doenças e pragas em importantes áreas produtoras, bem como um estudo da qualidade do material de propagação utilizado pelos produtores. Foram visitados sete municípios de Pernambuco e três da Paraíba, totalizando 30 propriedades. Para avaliação da ocorrência das doenças da parte aérea e danos causados por lagarta, foram marcadas em cada campo, 5 fileiras de 10 plantas e mais 30 plantas, escolhidas aleatoriamente, para análise de viroses, as quais foram avaliadas um mês antes e no período da colheita. Para extração dos nematóides foi usado método de centrifugação rápida associadoao de Jenkins, os quais foram identificados por suas estruturas observadas ao microscópio ótico. Os fungos detectados foram isolados e identificados e observando-se suas estruturas reprodutivas. Para identificação dos vírus foram efetuadas observações ao microscópio eletrônico de transmissão, teste “triple antibody sandwich enzyme-linked immunosorbent assay” (TAS-ELISA), com anti-corpos policlonais e monoclonais específicos para Yam mosaic virus (YMV), obtidos do IITA, Nigéria e reaçaão de PCR (“polimerase chain reaction”) com oligonucleotídeos degenerados paradetecção de badnavírus e duplex reverse transcription (RT)-PCR com oligonucleotídeos específicos para YMV e Yam mild mosaic virus (YMMV). Os produtos de PCR e RT-PCR foram purificados e seqüenciados para validação dos testes usados na detecção de badnavírus e identificação dos potyvírus, por análise comparativa com as seqüências disponíveis no GenBank. Ficou comprovada a ocorrência de pinta preta, causada por Curvularia eragrostidis em todas as áreas estudadas, com maior intensidade na cv. Inhame-da-Costa do complexo D. cayennensis-D. rotundata, enquanto que o ataque de lagarta das folhas (Pseudoplusia oo), presente em todos os campos, teve maior severidade na cv. São Tomé de D. alata. As túberas-semente de ambas as espécies de inhame, coletadas em cinco propriedades representativas das áreas de cultivo em Pernambuco eParaíba, após 60 dias de armazenamento, apresentaram sérios problemas de Podridão Verde, causada por Penicillium sclerotigenum, cochonilhas (Planoccocus sp.) e brocas das túberas (Araecerus fasciculatus). Foram identificados os potyvírus YMV e YMMV, ocorrendo em infecção simples e mista com badnavírus, constituindose o primeiro registro detalhado com informações moleculares destes vírus no Brasil.
142

Avaliação neuropsicológica da tomada de decisão no comprometimento cognitivo leve / Neuropsychological assessment of decision-making in the mild cognitive impairment

Rodolfo Santos Flaborea 27 March 2015 (has links)
Introdução: o aumento da população idosa traz uma demanda significativa sobre as ciências da saúde para lidar com os problemas característicos do envelhecimento. Neste contexto, as demências são as desordens neuropsiquiátricas de maior impacto atualmente. Poucas pesquisas acerca do CCL foram dedicadas a analisar a função neuropsicológica da tomada de decisão. Esta é definida como o processo de escolher uma ação específica, dentro de um rol de alternativas possíveis, que produza o resultado mais vantajoso para o sujeito. Logo, ela possui papel clínico fundamental, pois subsidia importante espectro da funcionalidade. Objetivo: avaliar se idosos com CCL amnéstico de múltiplos domínios ou de único domínio apresentam prejuízos na tomada de decisão sob risco, quando comparados a idosos saudáveis. Métodos: foram analisados os desempenhos de 20 sujeitos (9 CCL e 11 controles) no teste de tomada de decisão Cambridge Gambling Task (CGT). Utilizou-se modelo linear geral acompanhado de análise de covariância para idade, anos de escolaridade e escore do Mini Exame do Estado Mental. Resultados: Foi verificado efeito de grupo e da idade sobre a aversão ao atraso, proporção global de aposta e assunção de risco. Conclusão: pacientes com CCL demonstraram maior impulsividade nas escolhas das apostas, além de terem apostado menos ao longo de todo o CGT. O déficit no controle da impulsividade pode ser um indicador de maior risco para conversão para demência, hipótese esta que necessita ser mais investigada. Apostas menores podem constituir estratégia compensatória em reação à impulsividade ou, ainda, ser resultado da menor confiança do paciente com CCL em suas capacidades para lidar com o teste / Introduction: The increase in elderly population brings a significant demand upon the health sciences to deal with aging-specific issues. In this context, dementia is currently the group of neuropsychiatric disorders with the greatest impact. Research on cerebral reserve shows the importance of early treatment in these syndromes, highlighting the need for comprehension about Mild Cognitive Impairment (MCI), classically defined by literature as a prodromic stage for dementia. Few existing studies on MCI aimed at investigating the neuropsychological function of decision-making, which is defined as the process of choosing a specific action among several options in order to achieve the most advantageous outcome. Therefore, this function has a fundamental clinical role, since it grants the basis for the individual functionality. Objective: investigate possible deficits in the decision-making of a sample of elderly patients diagnosed with amnestic MCI of multiple or single domain by comparing their performance with that of healthy ones. Methods: the performances of a sample 20 subjects (9 MCI and 11 controls) in the Cambridge Gambling Task (CGT) were analysed. General linear model with covariance analysis for age, years of schooling and the Mini Mental State Examination scores was used for the statistical analyses. Results: it was found that group and age effect on delay aversion, overall proportion bet, and risk taking. Conclusion: MCI patients showed higher impulsivity on bet choices and made smaller bets throughout the CGT run. The impulsivity control deficit can be an indicator of the conversion risk from MCI to dementia, hypothesis that needs further investigation. Smaller bets may be a compensatory strategy for the increased impulsivity or the result of MCI patients less confidence in their own cognitive ability to deal with the test
143

Treino de memória para idosos saudáveis e com comprometimento cognitivo leve: benefícios sobre parâmetros cognitivos / Memory training in healthy elderly and seniors with mild cognitive impairment: benefits on cognitive parameters

Paula Schimidt Brum 28 June 2012 (has links)
As intervenções cognitivas voltadas a idosos saudáveis ainda encontram-se pouco estudadas na literatura nacional, apesar de terem sido investigadas em outros países. O treino de memória oferecido a idosos com Comprometimento Cognitivo Leve (CCL) tem recebido cada vez mais atenção de pesquisadores e parece também beneficiar esta população. Não se sabe se o treino tem efeito a longo prazo e nem se os benefícios são os mesmos para idosos saudáveis e com CCL. Esta pesquisa teve como intuito avaliar o impacto do treino de memória de oito sessões oferecido a idosos controles normais (CN) e com CCL com alta escolaridade em parâmetros cognitivos. Para isso, contamos com a participação de 61 idosos acompanhados pela equipe multidisciplinar do Laboratório de Neurociências LIM 27 do Instituto de Psiquiatria da FMUSP aleatoriamente divididos em grupo experimental - GE (sendo 17 CN e 18 com CCL) e grupo controle - GC (sendo 12 CN e 14 com CCL). Estes grupos foram avaliados em quatro momentos diferentes, a saber, antes da intervenção (T0), uma semana após o término da intervenção (T1), um mês após a última avaliação (T2) e seis meses após T1 (T3). O GE recebeu treino de memória com ênfase na categorização e grifos entre T0 e T1. O GC realizou todas as avaliações no mesmo tempo de GE, mas o treino foi lhes oferecido depois de T3. Observou-se melhora em ambos os grupos GE de T0 para T1 quando comparados ao grupo GC em testes de atenção, velocidade de processamento, estratégias mnemônicas, e em testes de memória. Estes efeitos parecem se manter a curto e a longo prazo, mostrando, de maneiras diferentes, os benefícios do treino e a existência de plasticidade cognitiva em ambas as populações estudadas / The cognitive interventions aimed at elderly healthy are little studied in the national literature, despite having been investigated in other countries. The memory training offered to seniors with mild cognitive impairment (MCI) has received increasing attention from researchers and also seems to benefit this population. It is not known whether the training has long-term effect, nor whether the benefits are the same for healthy elderly and MCI. This study was aimed to evaluate the impact of eight memory training sessions offered to elderly normal controls (NC) and seniors with MCI in cognitive parameters. For this, we had the participation of 61 older people accompanied by a multidisciplinary team of the Laboratory of Neurosciences LIM 27, Institute of Psychiatry, FMUSP randomly divided into experimental group - EG (including 17 NC and 18 with MCI) and control group - CG (being 12 NC and 14 with MCI). These groups were evaluated at four different times, namely before the intervention (T0), one week after the intervention (T1), one month after the last assessment (T2) and six months after T1 (T3). EG received memory training with emphasis on categorization and underline words between T0 and T1. The CG performed all the assessments at the same time EG, but the training was offered to them after T3. Improvement was observed in both groups EG from T0 to T1 when compared to the CG on tests of attention, processing speed, mnemonic strategies, and memory tests. These effects seem to keep the short and long term, showing, in different ways, the benefits of training and the existence of cognitive plasticity in both populations studied
144

Epigenetic Dysregulation in the Basocortical Cholinergic Projection System During the Progression of Alzheimer's Disease

January 2018 (has links)
abstract: Alzheimer’s disease (AD) is characterized by the degeneration of cholinergic basal forebrain (CBF) neurons in the nucleus basalis of Meynert (nbM), which provides the majority of cholinergic input to the cortical mantle and together form the basocortical cholinergic system. Histone deacetylase (HDAC) dysregulation in the temporal lobe has been associated with neuronal degeneration during AD progression. However, whether HDAC alterations play a role in cortical and cortically-projecting cholinergic nbM neuronal degeneration during AD onset is unknown. In an effort to characterize alterations in the basocortical epigenome semi-quantitative western blotting and immunohistochemistry were utilized to evaluate HDAC and sirtuin (SIRT) levels in individuals that died with a premortem clinical diagnosis of no cognitive impairment (NCI), mild cognitive impairment (MCI), mild/moderate AD (mAD), or severe AD (sAD). In the frontal cortex, immunoblots revealed significant increases in HDAC1 and HDAC3 in MCI and mAD, followed by a decrease in sAD. Cortical HDAC2 levels remained stable across clinical groups. HDAC4 was significantly increased in prodromal and mild AD compared to aged cognitively normal controls. HDAC6 significantly increased during disease progression, while SIRT1 decreased in MCI, mAD, and sAD compared to controls. Basal forebrain levels of HDAC1, 3, 4, 6 and SIRT1 were stable across disease progression, while HDAC2 levels were significantly decreased in sAD. Quantitative immunohistochemistry was used to identify HDAC2 protein levels in individual cholinergic nbM nuclei immunoreactive for the early phosphorylated tau marker AT8, the late-stage apoptotic tau marker TauC3, and Thioflavin-S, a marker of mature neurofibrillary tangles (NFTs). HDAC2 nuclear immunoreactivity was reduced in individual cholinergic nbM neurons across disease stages, and was exacerbated in tangle-bearing cholinergic nbM neurons. HDAC2 nuclear reactivity correlated with multiple cognitive domains and with NFT formation. These findings identify global HDAC and SIRT alterations in the cortex while HDAC2 dysregulation contributes to cholinergic nbM neuronal dysfunction and NFT pathology during the progression of AD. / Dissertation/Thesis / Doctoral Dissertation Neuroscience 2018
145

Brain networks involved in decision making: an electroencephalography and magnetic resonance imaging study

Farrar, Danielle 03 November 2016 (has links)
Executive function describes high-level cognitive-abilities including planning, decision-making, set switching and response inhibition. Impairments of the executive functions in disease states may be subtle but can greatly reduce the quality of life and independence. The overarching theme of this project was to investigate the network of brain regions that are needed to support executive function. This was undertaken using a two-fold approach: one, to apply network analysis to resting state functional Magnetic Resonance Imaging (rs-fMRI) and Diffusion Tensor Imaging (DTI) data in order to describe how differences in morphometry and connectivity correlate to executive function differences of individuals with Mild Cognitive Impairment (MCI), and two, to describe the brain networks involved in one form of executive function, decision-making under uncertain conditions, in young, healthy individuals. Impaired decision-making can dramatically impact day-to-day functioning and understanding the underlying network of regions that support this task can provide a target for future intervention studies. Data from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) were used in the studies of MCI. Individuals were grouped by their executive abilities. A regions-of-interest approach was used to parcel and label various brain regions and a network of connections was constructed out of these regions. Differences between the networks were then compared between the MCI subjects with good and poor executive functions. Those with high executive abilities showed decreased functional network connectivity and increased structural network connectivity. The second arm of these studies was based an original decision-making paradigm that was used to compare of networks involved in decision-making at times of uncertainty in healthy young individuals using both electroencephalography (EEG) and task-based functional magnetic resonance imaging (fMRI). Overall we found greater network connectivity in the uncertain condition of the task than in the certain condition. This suggests that with increased uncertainty comes increased organized connectivity. Taken together, the results of this study re-iterate the notion that cognition depends upon the efficient communication between a network of brain regions rather than on isolated regions. They also highlight the importance of having a well-defined network of nodes and connections for optimal executive functioning.
146

Vestibular, Balance, Microvascular and White Matter Neuroimaging Characteristics of Blast Injuries and Mild Traumatic Brain Injury: Four Case Reports

Gattu, Ramtilak, Akin, Faith W., Cacace, Anthony T., Hall, Courtney D., Murnane, Owen D., Haacke, E. Mark, Furman, Joseph M. 14 October 2016 (has links)
Background: Case reports are presented on four Veterans, aged 29–46 years, who complained of chronic dizziness and/or postural instability following blast exposures. Two of the four individuals were diagnosed with mild traumatic brain injury and three of the four were exposed to multiple blasts. Comprehensive vestibular, balance, gait, audiometry and neuroimaging procedures were used to characterize their injuries.Case report: Vestibular assessment included videonystagmography, rotary chair and cervical and ocular vestibular evoked myogenic potentials. Balance and gait testing included the sensory organization test, preferred gait speed and the dynamic gait index. Audiometric studies included pure tone audiometry and middle-ear measurements. Neuroimaging procedures included high resolution structural magnetic resonance imaging, susceptibility-weighted imaging and diffusion-tensor imaging.Findings: Based on the neuroimaging and vestibular and balance test results, it was found that all individuals had diffuse axonal injuries and all had one or more micro-hemorrhages or vascular anomalies. Three of the four individuals had abnormal vestibular function, all had abnormally slow walking speeds and two had abnormal gait and balance dysfunction.Conclusion: The use of contemporary neuroimaging studies in conjunction with comprehensive vestibular and balance assessment provided a better understanding of the pathophysiology and pathoanatomy of dizziness following blast exposures than standard vestibular and balance testing alone.
147

Diagnosis and Treatment of Vestibular Disorders in mTBI

Akin, Faith W., Serrador, Jorge M. 01 November 2013 (has links)
The purpose of this session is to examine the vestibular consequences of mild traumatic brain injury (TBI) and blast exposure. Preliminary data will be presented showing characteristics of vestibular dysfunction and postural instability related to mild TBI and blast exposure. Also reviewed will be the latest findings including recent data collected at the War Related Illness & injury Center showing vestibular impairments in those with mTBI. The target audience is audiologists, physical therapists, neurologists, otolaryngologists. This session will cover intermediate level of content.
148

The Effects of Hand Fidgets on the On-Task Behaviors of A Middle School Student With Disabilities in an Inclusive Academic Setting

Voytecki, Karen S 11 March 2005 (has links)
Many students with mild disabilities display off-task behaviors during academic content classes. The off-task behaviors can negatively impact their academic progress. In primarily clinical settings, specific interventions derived from the theory of sensory integration have been shown to increase on-task behaviors in students with mild disabilities. Using a single subject A-B-A-B withdrawal design, the researcher investigated the effects of hand fidgets on on-task behaviors demonstrated by a middle school student with mild disabilities who typically displayed off-task behaviors when participating in an inclusive, academic content class (language arts). Social validity was assessed to evaluate student and teacher perceptions regarding the intervention. During baseline and withdrawal (A phases) participants followed their typical classroom routine and were not exposed to the intervention - hand fidgets. During the intervention (B phases) participants were provided with a hand fidget for use during the class period. Results indicated substantial increases in the percentage of on-task behaviors demonstrated by the participant, when presented with the opportunity to use a hand fidget, during activities in which listening to a lecture was the primary task expectation. Social validity findings indicated that both the students and classroom teacher preferred the use of hand fidgets to the condition of no hand fidget present. This study provides preliminary support for the use of hand fidgets to increase on-task behaviors by students with mild disabilities who present tendencies for off-task behaviors during classroom lecture situations.
149

Laser diagnostics in MILD combustion.

Medwell, Paul R. January 2007 (has links)
Despite mounting concerns of looming global warming and fuel shortages, combustion will remain the predominant source of fulfilling the world’s ever-increasing demand for energy in the foreseeable future. In light of these issues, the combustion regime known as Moderate and Intense Low oxygen Dilution (MILD) combustion has the potential of offering increased efficiency whilst lowering pollutant emissions. Essentially, MILD combustion relies on the reuse of the exhaust gases from the combustion process to simultaneously dilute the oxygen concentration of the oxidant stream, and increase its temperature. The benefit of this technique is that it results in a vast reduction in emissions, especially oxides of nitrogen. In addition, the thermal efficiency of the combustion process is increased, reducing fuel demands, as well as producing a more uniform heating profile and subsequently better product quality for many applications. The recirculation of exhaust gas and heat has been utilised for applications in the past. MILD combustion aims to extend the advantages of heat recovery and exhaust gas recirculation beyond the boundaries that are otherwise possible using conventional techniques. The relatively new concept of MILD combustion is a major advancement to the previous technology, and many fundamental issues have not yet been resolved. In a furnace environment, the dilution and preheating of the reactants generate a unique “distributed” reaction zone. There is a need to better understand the structure of this combustion regime and the parameters which control it. To emulate MILD combustion conditions in a controlled experimental environment, a Jet in Hot Coflow (JHC) burner is used in this study. The MILD combustion regime is examined using laser diagnostic techniques. The two key flame intermediates hydroxyl radical (OH) and formaldehyde (H2CO), as well as temperature, are imaged simultaneously to reveal details relating to the reaction zone. Simultaneous imaging enables not only the spatial distribution of each scalar to be investigated, but also the combined effect of the interactions of the three measured scalars. The role of four key variables are investigated as part of this work, namely; the coflow oxygen (O2) level, the jet Reynolds number, fuel dilution and fuel type. Also considered is the effect of surrounding air entrainment into the hot and diluted coflow, which causes a deviation from MILD combustion conditions. The local oxygen (O2) concentration is a key parameter in the establishment of MILD combustion conditions. The effect of lowering the O2 level is to lead to reductions in the OH and temperature in the reaction zone, in effect leading to a less intense reaction. When comparatively high oxygen laden, cold surrounding air mixes with the hot and low O2 coflow, MILD combustion conditions no longer exist. In this case, the flame front can become locally extinguished and subsequent premixing with the high O2 concentrations can lead to increased reaction rates and hence higher temperatures. It is therefore essential that fresh air must be excluded from a MILD combustor to maintain the stable reaction which typifies MILD combustion. It is found that the flame structure is relatively insensitive to both the type of hydrocarbon fuel and the Reynolds number. Each of these parameters can lead to changes in some intermediate species, namely formaldehyde, yet the OH and temperature measurements show comparatively minor variation. Nevertheless, fuel type and Reynolds number, in the form of increased flow convolution, can lead to striking differences in the flame structure. One of the most prominent effects is noted with the dilution of the fuel with various diluents. Some of the flames visually appear lifted, whereas the measurements reveal the occurrence of pre-ignition reactions in the “lifted” region. The unique characteristics of the stabilisation for these particular cases has lead to the term transitional flames. The fundamental aspects discovered by this study shed new light on the reaction zone structure under MILD combustion conditions. By advancing understanding of MILD combustion, future combustion systems will be able to better utilise the efficiency increases and lower pollutant benefits it offers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1293788 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007.
150

Laser diagnostics in MILD combustion.

Medwell, Paul R. January 2007 (has links)
Despite mounting concerns of looming global warming and fuel shortages, combustion will remain the predominant source of fulfilling the world’s ever-increasing demand for energy in the foreseeable future. In light of these issues, the combustion regime known as Moderate and Intense Low oxygen Dilution (MILD) combustion has the potential of offering increased efficiency whilst lowering pollutant emissions. Essentially, MILD combustion relies on the reuse of the exhaust gases from the combustion process to simultaneously dilute the oxygen concentration of the oxidant stream, and increase its temperature. The benefit of this technique is that it results in a vast reduction in emissions, especially oxides of nitrogen. In addition, the thermal efficiency of the combustion process is increased, reducing fuel demands, as well as producing a more uniform heating profile and subsequently better product quality for many applications. The recirculation of exhaust gas and heat has been utilised for applications in the past. MILD combustion aims to extend the advantages of heat recovery and exhaust gas recirculation beyond the boundaries that are otherwise possible using conventional techniques. The relatively new concept of MILD combustion is a major advancement to the previous technology, and many fundamental issues have not yet been resolved. In a furnace environment, the dilution and preheating of the reactants generate a unique “distributed” reaction zone. There is a need to better understand the structure of this combustion regime and the parameters which control it. To emulate MILD combustion conditions in a controlled experimental environment, a Jet in Hot Coflow (JHC) burner is used in this study. The MILD combustion regime is examined using laser diagnostic techniques. The two key flame intermediates hydroxyl radical (OH) and formaldehyde (H2CO), as well as temperature, are imaged simultaneously to reveal details relating to the reaction zone. Simultaneous imaging enables not only the spatial distribution of each scalar to be investigated, but also the combined effect of the interactions of the three measured scalars. The role of four key variables are investigated as part of this work, namely; the coflow oxygen (O2) level, the jet Reynolds number, fuel dilution and fuel type. Also considered is the effect of surrounding air entrainment into the hot and diluted coflow, which causes a deviation from MILD combustion conditions. The local oxygen (O2) concentration is a key parameter in the establishment of MILD combustion conditions. The effect of lowering the O2 level is to lead to reductions in the OH and temperature in the reaction zone, in effect leading to a less intense reaction. When comparatively high oxygen laden, cold surrounding air mixes with the hot and low O2 coflow, MILD combustion conditions no longer exist. In this case, the flame front can become locally extinguished and subsequent premixing with the high O2 concentrations can lead to increased reaction rates and hence higher temperatures. It is therefore essential that fresh air must be excluded from a MILD combustor to maintain the stable reaction which typifies MILD combustion. It is found that the flame structure is relatively insensitive to both the type of hydrocarbon fuel and the Reynolds number. Each of these parameters can lead to changes in some intermediate species, namely formaldehyde, yet the OH and temperature measurements show comparatively minor variation. Nevertheless, fuel type and Reynolds number, in the form of increased flow convolution, can lead to striking differences in the flame structure. One of the most prominent effects is noted with the dilution of the fuel with various diluents. Some of the flames visually appear lifted, whereas the measurements reveal the occurrence of pre-ignition reactions in the “lifted” region. The unique characteristics of the stabilisation for these particular cases has lead to the term transitional flames. The fundamental aspects discovered by this study shed new light on the reaction zone structure under MILD combustion conditions. By advancing understanding of MILD combustion, future combustion systems will be able to better utilise the efficiency increases and lower pollutant benefits it offers. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1293788 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007.

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