Purpose: This study evaluated the effect of lung volume at the catch position to force and power outputs during single maximal effort strokes in rowing. Responses were compared when the participants were ‘fresh’ and following specific inspiratory muscle fatigue (IMF). In addition, a single subject pilot study was performed to characterise the changes in intra-thoracic (ITP), intra-abdominal (IAP) and trans-diaphragmatic (Pdi) pressures during a 30 second maximal effort piece on a rowing ergometer. Methods: Nine male rowers of international standard participated in the research. Static force, as well as the power produced during a single stroke were assessed at residual volume (RV), 25%TLC, 50%TLC, 75%TLC, total lung capacity (TLC), and a self-selected lung volume (S-S). Lung volumes were derived from maximal flow-volume loops (MFVLs) and achieved using online real-time feedback. Inspiratory muscle fatigue (IMF) was induced by breathing against an inspiratory load equivalent to 80% baseline maximal inspiratory pressure (MIP), at a breathing frequency (fB) of 15 breaths per minute, and a duty cycle of 0.6. Expiration was unimpeded. The single subject pilot study was undertaken using balloon catheters to measure ITP, IAP, and Pdi during a 30 second maximal effort free-rating piece on the ergometer. Results: There was no significant effect of lung volume upon either force or power production. The RMF protocol induced a significant reduction in MIP (159.9 ± 70.8 vs. 106.8 ± 58.7 cmH2O; p = 0.000), but not maximal expiratory pressure (MEP; 159.9 ± 79.2 vs. 166.6 ± 53.0 cmH2O; p = 0.376). RMF induced a significant reduction in force output with increasing lung volume, across all lung volumes (mean force 1313.4 ± 31.9 vs. 1209.6 ± 45.0N; p < 0.008), but not power (mean power 598.6 ± 31.9 vs. 592.7 ± 45.0W; p > 0.05). Self-selected lung volumes were consistent across all tests for force and power (mean 38.1 ± 6.9% [Force] vs. 28.2 ± 0.6% [Power]; p > 0.017). The pilot study indicated that internal pressures fluctuate markedly during maximal effort rowing (pressure, [max, min, average] cmH2O; IAP [144.69, 7.46, 73.59], ITP [75, -22.65, 15.34], Pdi [111.84, 7.09, 58.83]), suggesting that the trunk muscles play an active role in power production during rowing. Conclusion: The present study suggests that there is no significant effect of lung volume on force or power when athletes are in a fresh condition. However, a decrement in force production is present with inspiratory muscle fatigue. Combined with evidence of high internal pressures during maximal effort rowing, these data may indicate a role for the inspiratory muscles in force production during rowing.

O sistema estuarino-lagunar do Rio São Francisco, litoral norte da zona costeira de Sergipe, é uma região que apresenta vastas áreas de manguezal, apesar da incidência de tensores antrópicos. O presente estudo realizou um diagnóstico ambiental dos manguezais dessa zona costeira, considerando-se os níveis hierárquicos setting (paisagem), stand (unidade de paisagem) e site (parcela ou árvore), adaptado da proposta de Schaeffer-Novelli et al. (2000; 2005). Imagens de satélites e fotografias aéreas coloridas da área de estudo foram processadas em SIG e foi gerado um mapa de uso e cobertura da terra para 2008. Verdade de campo foi realizada e características qualitativas da composição da vegetação e da estrutura de bosques de mangue foram registradas. Atualmente 93% (179 km2) da zona costeira em estudo é ocupada por áreas de vegetação natural: manguezal (30 Km2, 16%), apicum (1,4 Km2,0,7%) e formações pioneiras de influência marinha (14 Km2, 77%); enquanto que 7% (13,56 km2) é ocupada por áreas antrópicas: aquicultura (4,6 Km2, 2,4%) e culturas de coco e arroz (9 Km2, 4,7%). Manguezais vêm a pelo menos 40 anos sendo pressionados por diferentes formas de uso da terra, destacando-se atualmente a carcinocultura e culturas de coco e arroz, que ocupam 25% da área total dessa vegetação, o que pode indicar que ¼ dos manguezais foram alterados ou convertidos para usos antrópicos. Esses resultados indicam que estado de conservação dos manguezais do sistema estuarino-lagunar do Rio São Francisco encontra-se bastante vulnerável demandando plano de gestão costeira que considere como prioridade a conservação dos mesmos diante da expansão da carcinocultura, o manejo das atividades locais de forma a considerar a capacidade de suporte do ecossistema manguezal e dos corpos dágua e a segurança das populações locais frente às alterações geradas pelos intensos processos erosivos na região da foz. / The estuarine system of the São Francisco River, the coastal zone of Sergipe State, Northeast Brazil is a region with large areas of mangrove despite they are strongly pressured by human activities. This study performed an environmental assessment of mangrove areas of the São Francisco River Estuary, considering the hierarchical levels: setting (landscape), stand (landscape unit) and site (plot or tree), adapted from the framework proposed by Schaeffer-Novelli et al. (2000, 2005). Satellite images and digital colour aerial photographs of the study area were processed in GIS and a land use and cover map was produced for 2008. Ground-truth was performed and characteristics of vegetation composition and structure were recorded. Currently 93% (179 km2) of the coastal zone in question is occupied by natural vegetation: mangrove (30 km2, 16%), apicum (1.4 km2, 0.7%) and sand coast plain (14 Km2 , 77%), while 7% (13.56 km2) is occupied by disturbed areas: aquaculture (4.6 km2, 2.4%) and coconut and rice plantations (9 km2, 4.7%). Mangroves have been pressured by different land uses for at least 40 years. Now the land use for aquaculture (mainly shrimp farms) and coconut and rice plantations occupy 25% of the total area of mangrove, which may indicate that ¼ of mangroves have been changed or converted to man-made uses. These results show that the conservation status of mangroves in the study area is vulnerable, requiring a coastal management plan which considers as priority the preservation of mangroves before the expansion of aquaculture, management of local activities to consider the carrying capacity of the mangrove ecosystem and water bodies and the security of local populations in the face of changes generated by intense erosion in the region of the mouth of the São Francisco River.

O sistema estuarino-lagunar do Rio São Francisco, litoral norte da zona costeira de Sergipe, é uma região que apresenta vastas áreas de manguezal, apesar da incidência de tensores antrópicos. O presente estudo realizou um diagnóstico ambiental dos manguezais dessa zona costeira, considerando-se os níveis hierárquicos setting (paisagem), stand (unidade de paisagem) e site (parcela ou árvore), adaptado da proposta de Schaeffer-Novelli et al. (2000; 2005). Imagens de satélites e fotografias aéreas coloridas da área de estudo foram processadas em SIG e foi gerado um mapa de uso e cobertura da terra para 2008. Verdade de campo foi realizada e características qualitativas da composição da vegetação e da estrutura de bosques de mangue foram registradas. Atualmente 93% (179 km2) da zona costeira em estudo é ocupada por áreas de vegetação natural: manguezal (30 Km2, 16%), apicum (1,4 Km2,0,7%) e formações pioneiras de influência marinha (14 Km2, 77%); enquanto que 7% (13,56 km2) é ocupada por áreas antrópicas: aquicultura (4,6 Km2, 2,4%) e culturas de coco e arroz (9 Km2, 4,7%). Manguezais vêm a pelo menos 40 anos sendo pressionados por diferentes formas de uso da terra, destacando-se atualmente a carcinocultura e culturas de coco e arroz, que ocupam 25% da área total dessa vegetação, o que pode indicar que ¼ dos manguezais foram alterados ou convertidos para usos antrópicos. Esses resultados indicam que estado de conservação dos manguezais do sistema estuarino-lagunar do Rio São Francisco encontra-se bastante vulnerável demandando plano de gestão costeira que considere como prioridade a conservação dos mesmos diante da expansão da carcinocultura, o manejo das atividades locais de forma a considerar a capacidade de suporte do ecossistema manguezal e dos corpos dágua e a segurança das populações locais frente às alterações geradas pelos intensos processos erosivos na região da foz. / The estuarine system of the São Francisco River, the coastal zone of Sergipe State, Northeast Brazil is a region with large areas of mangrove despite they are strongly pressured by human activities. This study performed an environmental assessment of mangrove areas of the São Francisco River Estuary, considering the hierarchical levels: setting (landscape), stand (landscape unit) and site (plot or tree), adapted from the framework proposed by Schaeffer-Novelli et al. (2000, 2005). Satellite images and digital colour aerial photographs of the study area were processed in GIS and a land use and cover map was produced for 2008. Ground-truth was performed and characteristics of vegetation composition and structure were recorded. Currently 93% (179 km2) of the coastal zone in question is occupied by natural vegetation: mangrove (30 km2, 16%), apicum (1.4 km2, 0.7%) and sand coast plain (14 Km2 , 77%), while 7% (13.56 km2) is occupied by disturbed areas: aquaculture (4.6 km2, 2.4%) and coconut and rice plantations (9 km2, 4.7%). Mangroves have been pressured by different land uses for at least 40 years. Now the land use for aquaculture (mainly shrimp farms) and coconut and rice plantations occupy 25% of the total area of mangrove, which may indicate that ¼ of mangroves have been changed or converted to man-made uses. These results show that the conservation status of mangroves in the study area is vulnerable, requiring a coastal management plan which considers as priority the preservation of mangroves before the expansion of aquaculture, management of local activities to consider the carrying capacity of the mangrove ecosystem and water bodies and the security of local populations in the face of changes generated by intense erosion in the region of the mouth of the São Francisco River.

A radiação térmica é frequentemente considerada um mecanismo de transferência de calor muito importante em processos de combustão em alta pressão, devido à presença de meios participantes e às altas temperaturas envolvidas. Resolver a radiação térmica em meios participantes é um problema complexo devido à natureza integro-diferencial da equação governante e à dependência espectral altamente irregular das propriedades de radiação. Atualmente, o método mais preciso para resolver a integração espectral é o método linha-porlinha (LBL), que possui um custo computacional muito elevado. Para contornar essa dificuldade, o problema espectral é geralmente resolvido usando modelos espectrais e, consequentemente, a equação da transferência radiativa (RTE) é simplificada. Um destes modelos é o da soma-ponderada-de-gases-cinza (WSGG), que substitui o comportamento espectral altamente irregular do coeficiente de absorção, por bandas de coeficientes de absorção uniforme e tem mostrado um bom desempenho em diversas aplicações, mesmo sendo um modelo bastante simplificado. Entretanto, recentemente alguns autores não obtiveram bons resultados ao tentar aplicar o WSGG a problemas de combustão em alta pressão. Este artigo desenvolve um modelo WSGG para CO2 e H2O em condições de alta pressão. Para validar o modelo, a emitância total é calculada usando os coeficientes WSGG e comparada à solução do LBL obtida usando o banco de dados espectrais HITEMP 2010. Os resultados mostraram grande convergência entre os valores de emitância de ambos os métodos, mesmo para valores de alta pressão, tanto para o CO2 quanto para H2O, provando que o método WSGG é aplicável a condições de alta pressão. O modelo também foi validado pelo cálculo do fluxo de calor e termo fonte radiativo, e comparando-os com os obtidos através do método LBL. O H2O teve melhores resultados para baixas pressões, enquanto o CO2 apresentou melhores resultados para pressões mais altas. O efeito da pressão total sobre a solução de LBL foi maior para o H2O, o que pode ser um dos motivos pelo qual os desvios foram maiores para os casos de alta pressão. / Thermal radiation is often a very important heat transfer mechanism in high pressure combustion processes due to the presence of participating media and the high temperatures involved. Solving thermal radiation in participating media is a tough problem due to the integro-differential governing equation and the complex spectral dependence of radiation properties. Currently, the most accurate method to solve the spectral integration is the line-byline (LBL) method, which has a very high computational cost. In order to avoid this drawback the spectral problem is usually solved using spectral models, and as a consequence the radiative transfer equation (RTE) is simplified. One of the models is the weighted-sum-ofgray- gases (WSGG) which replaces the highly irregular spectral behavior of the absorption coefficient by bands of uniform absorption coefficients, and has shown great performance a lot of applications even though it is a very simple model. However, recently some authors didn’t have good results when trying to apply the WSGG to high pressure combustion problems. This thesis develops a WSGG model for both CO2 and H2O on high pressure conditions. In order to validate the model the total emittance is calculated using the WSGG coefficients and compared to the LBL solution which was obtained using the HITEMP 2010 spectral emissivity database. The results showed that the emittance values from both methods were very close even for high pressure values for both CO2 and H2O proving that the WSGG method is applicable to high pressure conditions. The model was also validated by calculating the radiative heat flux and source, and comparing them with the LBL method. H2O had better results for low pressures while CO2 had better results for higher pressures. The effect of total pressure on the LBL solution was higher for H2O, which might be the reason why deviations were higher at high pressure values.

<p>In contrast-enhanced magnetic resonance angiography (CE-MRA),vascular signal is produced by the acquisition of a T1-weighted magnetic resonance imaging scan while the presence of a contrast agent induces a low T1 in blood. In this thesis,CE-MRA of the aortoiliac arteries was evaluated.Different contrast agents and techniques for synchronisation of the scan with the contrast bolus passage were assessed.</p><p>In 30 patients with clinically suspected iliac artery stenoses,contrast-enhanced magnetic resonance angiography was compared with duplex ultrasound scanning and digital subtraction x-ray angiography (DSA),with intraarterial pressure measurements as reference method. No statistically significant differences in sensitivity or specificity were observed between the techniques regarding the detection of hemodynamically significant iliac stenoses. The use of multiplanar reformats and source images in the MRA examinations was of value for the differentiation between high-grade stenoses and occlusions. With DSA as reference method, MRA had significantly higher sensitivity and specificity than duplex for the detection of ≥50% stenoses.</p><p>In fourteen patients examined with iliac artery MRA, differences in contrast arrival time of up to 7 s was observed between the aorta and the common femoral artery.A dual-station timing technique adjusting for this difference was found feasible. Compared with a fluoroscopically triggered technique (n=13),which is used in clinical rotine, the dual-station technique was more reliable for the visualisation of distal vessels.</p><p>In a clinical phase II study comparing different doses of t he contrast agent gadobenate dimeglumine for the enhancement of iliac artery MRA, a significant improvement in subjective diagnostic quality compared with time-of-flight MRA was found at all doses from 0.025 mmol/kg.An increasing trend with dose was observed up to a dose level of 0.05-0.1 mmol/kg.</p><p>In a phase I clinical study on the intravascular, iron oxide contrast agent NC100150 Injection, a positive dose response was observed for abdominal vascular enhancement, with the highest contrast-to-noise ratio observed at 4.0 mg Fe/kg bw at 1.5 T and at 2.5-4 mg Fe/kg bw at 0.5 T.At 1.5 T higher R2*values were calculated for the aorta than for the IVC.</p>

In contrast-enhanced magnetic resonance angiography (CE-MRA),vascular signal is produced by the acquisition of a T1-weighted magnetic resonance imaging scan while the presence of a contrast agent induces a low T1 in blood. In this thesis,CE-MRA of the aortoiliac arteries was evaluated.Different contrast agents and techniques for synchronisation of the scan with the contrast bolus passage were assessed. In 30 patients with clinically suspected iliac artery stenoses,contrast-enhanced magnetic resonance angiography was compared with duplex ultrasound scanning and digital subtraction x-ray angiography (DSA),with intraarterial pressure measurements as reference method. No statistically significant differences in sensitivity or specificity were observed between the techniques regarding the detection of hemodynamically significant iliac stenoses. The use of multiplanar reformats and source images in the MRA examinations was of value for the differentiation between high-grade stenoses and occlusions. With DSA as reference method, MRA had significantly higher sensitivity and specificity than duplex for the detection of ≥50% stenoses. In fourteen patients examined with iliac artery MRA, differences in contrast arrival time of up to 7 s was observed between the aorta and the common femoral artery.A dual-station timing technique adjusting for this difference was found feasible. Compared with a fluoroscopically triggered technique (n=13),which is used in clinical rotine, the dual-station technique was more reliable for the visualisation of distal vessels. In a clinical phase II study comparing different doses of t he contrast agent gadobenate dimeglumine for the enhancement of iliac artery MRA, a significant improvement in subjective diagnostic quality compared with time-of-flight MRA was found at all doses from 0.025 mmol/kg.An increasing trend with dose was observed up to a dose level of 0.05-0.1 mmol/kg. In a phase I clinical study on the intravascular, iron oxide contrast agent NC100150 Injection, a positive dose response was observed for abdominal vascular enhancement, with the highest contrast-to-noise ratio observed at 4.0 mg Fe/kg bw at 1.5 T and at 2.5-4 mg Fe/kg bw at 0.5 T.At 1.5 T higher R2*values were calculated for the aorta than for the IVC.

Syftet med den här avhandlingen är att förbättra möjligheter till miljöledning av järnvägens infrastruktur genom att utveckla en metod för att rikta in ansträngningar på att minska miljöpåverkan från infrastrukturens produkter. Metodens används i ett byggprojekt och dess robusthet blir testad. Den använder den materialrelaterade energianvändningen för att studera miljöpåverkan från infrastrukturen. Vidare studeras vilka förutsättningar och hinder det finns för att införa ett livscykelperspektiv i Banverkets organisation. Först analyserades de miljömässiga försättningarna genom en jämförande studie med vägtransportsystemet. Fokus låg även på infrastrukturens del i miljöpåverkan i jämförelse med själva transporterna i de bägge systemen. Sedan presenterades metoden och analyserades med avseende på användbarhet och robusthet. I de senare testen gavs materialtransporternas del av miljöpåverkan samt energiindikatorns miljörelevans extra utrymme.Slutligen studerades de organisatoriska förutsättningarna för att introducera metoden och införa ett livscykelperspektiv vid materialhanteringen. De organisatoriska förutsättningarna präglas mycket av Banverket miljöhistoria som främst handlar om miljögifter kopplade till lokala eller regionala miljöproblem. Dessutom finns det få miljörelaterade krav utifrån, vilket delvis kan förklara att livscykelperspektivet i mångt och mycket saknats inom organisationens materialhantering. Miljökraven på Banverkets inköp av produkter är oftast lagkrav, men eftersom de lagkrav som har anknytning till de globala miljöproblemen, vilka främst kan kopplas till uppströms produktframställning, inte är tillräckligt specifika, har organisationen svårt att översätta dessa till relevanta miljökrav vid upphandling. De avdelningar inom Banverket som är mest berörda av upphandlingen och arbetet med kravspecifikationer kräver mer stöd och kunskap för att kunna införa livscykelperspektivet i materialhanteringen. De upplevda miljöfördelar som järnvägen tycks ha över vägtrafiken är inte helt självklara. Vikten av indirekt miljöpåverkan från infrastrukturen är större för järnvägstrafiken än för vägtrafiken och detta i kombination med att den materialrelaterade energianvändningen är nästan uteslutande fossilbaserad leder till att miljöförsprånget minskar jämfört med trafikens miljöpåverkan. Om vägtrafiken minskar sitt fossilberoende i användningsfasen så måste järnvägssektorn antingen minska energianvändningen eller fossilberoendet i produktionen av järnvägsprodukter för att fortfarande kunna sägas ha miljöfördelar. För att kunna göra det senare måste nya perspektiv introduceras i Banverkets organisation. Metoden som presenteras i denna avhandling kan användas för att introducera dessa nya livscykelperspektiv och bidra till att Banverkets ansträngningar fokuseras på att minska infrastrukturens miljöpåverkan. Denna nya kunskap kan användas vid design av nya järnvägsprodukter och vid upphandlingen av dessa. Dessutom visar avhandlingen på var utförligare miljöanalyser av produkter kan behövas. Metoden använder en energiindikator för att uppskatta miljöpåverkan från materialanvändningen. Denna indikator är lätt att använda för miljöanalysen vilket gör det möjligt att enkelt introducera och inrikta livscykeltänkandet i organisationens miljöledning. Något som annars kan ligga utanför dess expertis, budget och tidsresurser. Metoden identifierar de tre produkter som är absolut viktigast att fokusera på om man vill minska miljöpåverkan från materialanvändningen i infrastrukturen. Dessa är räl, slipers och ballastmaterial där räl har överlägset störst användning av uppströms materialrelaterad energi. Genom att introducera miljökrav tidigt i designprocessen vid införande av dessa produkter kan stora miljövinster göras. Teknikavdelningarna samt upphandlarna behöver därför stöd för att introducera dessa starkare krav på uppströms miljöpåverkan. / The aim of this thesis has been to develop an approach for the scoping of environmental aspects regarding material use in the Swedish railway infrastructure in order to contribute to strategic environmental management. This is done through the development of a method based on the concepts of embodied energy and material flows, which is then tested for its robustness. Furthermore, a study has been made on which preconditions for life-cycle considerations there are for the manager of the Swedish railway infrastructure and how this relates to the actual environmental pressures from the product. The study has used the Swedish National Rail Authority, Banverket, as a case. First the environmental context was studied by an analysis of how the environmental pressure from material use compares to the operations phase and to other transport systems. Secondly, a scoping method for environmental pressure from material use in a large organization was developed and tests performed on its use and its robustness. Special focus was on the importance of materials transports and the environmental relevance of the energy indicator used. Finally, an organizational context was presented which showed the possibilities and hindrances to implementing life-cycle considerations in the environmental management of the Swedish railway infrastructure. It seems difficult to incorporate life-cycle considerations in an organization whose history is characterized by its work on solving specific local environmental issues. In addition, there seem to be limited pressures either from outside or inside the organization to adopt life-cycle environmental management. There is a need for clearer and more specific policy instruments governing many of the global environmental issues pertaining to upstream environmental pressures in order to make it easier for organizations to translate these into something useful in their environmental management. The departments with the most capacity to influence the environmental pressures from material use are demanding support and more knowledge about life-cycle considerations in order to set more relevant environmental requirements on the products. The perceived environmental advantage of the rail transport sector over road transports should not be taken for granted. The importance of the indirect environmental pressures for the rail infrastructure decreases this advantage, since its material-related energy use is almost entirely from non-renewable sources. Thus the rail transport sector needs to start decreasing the use of energy for production of railway infrastructure products or its reliance on nonrenewable energy sources for production. In order to start working with the environmental management of the railway products there is a need to adopt and introduce new perspectives. The approach developed in this thesis can be used to introduce these new perspectives, such as upstream environmental pressures, to the organization’s environmental management. It can also be employed to identify hot spots in the organization’s material use. Consequently, this new knowledge can be used in the design of new products, to set environmental demands in purchasing, and to focus further environmental analyses of the hot spots. It can also be used to broaden the perspectives in, for instance, environmental impact assessments, strategic environmental assessments and environmental reviews. The relative ease with which this indicator is collected and calculated can make it possible for the organization to include new environmental dimensions in their environmental management, which could otherwise be outside their expertise, budget or time frame. The scoping of environmental pressures, by using the approach presented in the thesis, pointed to three important railway infrastructure products. These are the products that Banverket needs to focus on first. One of the most important tasks in incorporating life-cycle considerations for products is to set environmental requirements when introducing new products to the material supply process. The requirements should already be present in the design phase of the products. Thus it is essential that the product developers get the support needed in finding relevant environmental criteria for the new product. One way to accomplish this is to employ an environmental coordinator with sufficient knowledge in the technical departments to work together with the design teams as an integral part of the design process. The overall environmental pressures from the railway transport system depend substantially on the upstream environmental pressures generated by the production of the infrastructure products. These pressures are totally dominated by three products. There is a large improvement potential in focusing the environmental management on these products by posing environmental requirements on their suppliers, in order to decrease the overall environmental pressures generated by the railway transport system.

ABSTRACT Numerous studies have examined the development of body image among people, especially girls and young women. Many factors have been associated with the development of body image dissatisfaction. Especially important are exposure to mass media and its relationship with three theoretical constructs: Awareness of a thin ideal, internalization of a thin ideal, and perceived pressures to be thin. Extending existing research, this study examined through experimentation the relationships among exposure to American media content and the awareness and internalization of the American norms and expectations for thinness, pressures to adopt these norms, and Trinidadian female adolescents' body image satisfaction. Based on previous findings, this study hypothesized that the three risk factors in the development of body image disturbance (awareness, internalization and pressures) would mediate the relationship between American media exposure and body image satisfaction among Trinidadian female adolescents. The results indicated that American media exposure and all three risk factors had statistically significant relationships with Trinidadian female adolescents' body image satisfaction. The more hours Trinidadian female adolescents spent watching American sitcoms, the less satisfied they are with their body image. An increase in American media exposure also resulted in the increase in the adolescents' awareness and internalization of the American norms and expectations for thinness, as well as the pressures to adopt those norms and expectations. Results also revealed that the three risk factors in the development of body image disturbance (awareness, internalization and pressures) were negatively correlated with body image satisfaction among Trinidadian female adolescents. Taken as a whole, the study supported the sociocultural model for the development of body image dissatisfaction.

Pas de résumé en anglais

Applications of natural gases that contain high levels of hydrogen have become a primary interest in the gas turbine market. For reheat gas turbines, understanding of the ignition delay times of high-hydrogen natural gases is important for two reasons. First, if the ignition delay time is too short, autoignition can occur in the mixer before the primary combustor. Second, the flame in the secondary burner is stabilized by the ignition delay time of the fuel. While the ignition delay times of hydrogen and of the individual hydrocarbons in natural gases can be considered well known, there have been few previous experimental studies into the effects of different levels of hydrogen on the ignition delay times of natural gases at gas turbine conditions. In order to examine the effects of hydrogen content at gas turbine conditions, shock-tube experiments were performed on nine combinations of an L9 matrix. The L9 matrix was developed by varying four factors: natural gas higher-order hydrocarbon content of 0, 18.75, or 37.5%; hydrogen content of the total fuel mixture of 30, 60, or 80%; equivalence ratios of 0.3, 0.5, or 1; and pressures of 1, 10, or 30 atm. Temperatures ranged from 1092 K to 1722 K, and all mixtures were diluted in 90% Ar. Correlations for each combination were developed from the ignition delay times and, using these correlations, a factor sensitivity analysis was performed. It was found that hydrogen played the most significant role in ignition delay time. Pressure was almost as important as hydrogen content, especially as temperature increased. Equivalence ratio was slightly more important than hydrocarbon content of the natural gas, but both were less important than pressure or hydrogen content. Further analysis was performed using ignition delay time calculations for the full matrix of combinations (27 combinations for each natural gas) using a detailed chemical kinetics mechanism. Using these calculations, separate L9 matrices were developed for each natural gas. Correlations from the full matrix and the L9 matrix for each natural gas were found to be almost identical in each case, verifying that a thoughtfully prepared L9 matrix can indeed capture the major effects of an extended matrix.