RESUMO
We present an experimental protocol for fast determination of hydrate stability in porous media for a range of pressure and temperature (P, T) conditions. Using a lab-on-a-chip approach, we gain direct optical access to dynamic pore-scale hydrate formation and dissociation events to study the hydrate phase equilibria in sediments. Optical pore-scale observations of phase behavior reproduce the theoretical hydrate stability line with methane gas and distilled water, and demonstrate the accuracy of the new method. The procedure is applicable for any kind of hydrate transitions in sediments, and may be used to map gas hydrate stability zones in nature.
RESUMO
This article presents the life stories of three individuals who lived in Trondheim, Norway, during the 13th century. Based on skeletal examinations, facial reconstructions, genetic analyses, and stable oxygen isotope analyses, the birthplace, mobility, ancestry, pathology, and physical appearance of these people are presented. The stories are discussed within the relevant historical context. These three people would have been ordinary citizens, without any privileges out of the ordinary, which makes them quite rare in the academic literature. Through the study of individuals one gets a unique look into the Norwegian medieval society.
Assuntos
Fósseis , Antropometria , DNA Mitocondrial/genética , Feminino , História Medieval , Humanos , Masculino , NoruegaRESUMO
Two 1-D phase-encode sequences for T2 mapping, namely CPMG-prepared SPRITE and spin-echo SPI, are presented and compared in terms of image quality, accuracy of T2 measurements and the measurement time. The sequences implement two different approaches to acquiring T2-weighted images: in the CPMG-prepared SPRITE, the T2-weighting of magnetization precedes the spatial encoding, while in the spin-echo SPI, the T2-weighting follows the spatial encoding. The sequences are intended primarily for T2 mapping of fluids in porous solids, where using frequency encode techniques may be problematic either due to local gradient distortions or too short T2. Their possible applications include monitoring fluid-flow processes in rocks, cement paste hydration, curing of rubber, filtering paramagnetic impurities and other processes accomplished by changing site-specific T2.
Assuntos
Algoritmos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Teste de Materiais/métodos , Processamento de Sinais Assistido por Computador , Análise Numérica Assistida por ComputadorRESUMO
Magnetic resonance imaging was used to monitor and quantify methane hydrate formation and exchange in porous media. Conversion of methane hydrate to carbon dioxide hydrate, when exposed to liquid carbon dioxide at 8.27 MPa and approximately 4 degrees C, was experimentally demonstrated with MRI data and verified by mass balance calculations of consumed volumes of gases and liquids. No detectable dissociation of the hydrate was measured during the exchange process.