Comparison of the physical and geotechnical properties of gas-hydrate-bearing sediments from offshore India and other gas-hydrate-reservoir systems

This paper is not subject to U.S. copyright. The definitive version was published in Marine and Petroleum Geology 58A (2014): 139-167, doi:10.1016/j.marpetgeo.2014.07.024.The sediment characteristics of hydrate-bearing reservoirs profoundly affect the formation, distribution, and morphology of gas hydrate. The presence and type of gas, porewater chemistry, fluid migration, and subbottom temperature may govern the hydrate formation process, but it is the host sediment that commonly dictates final hydrate habit, and whether hydrate may be economically developed. In this paper, the physical properties of hydrate-bearing regions offshore eastern India (Krishna-Godavari and Mahanadi Basins) and the Andaman Islands, determined from Expedition NGHP-01 cores, are compared to each other, well logs, and published results of other hydrate reservoirs. Properties from the hydrate-free Kerala-Konkan basin off the west coast of India are also presented. Coarser-grained reservoirs (permafrost-related and marine) may contain high gas-hydrate-pore saturations, while finer-grained reservoirs may contain low-saturation disseminated or more complex gas-hydrates, including nodules, layers, and high-angle planar and rotational veins. However, even in these fine-grained sediments, gas hydrate preferentially forms in coarser sediment or fractures, when present. The presence of hydrate in conjunction with other geologic processes may be responsible for sediment porosity being nearly uniform for almost 500 m off the Andaman Islands. Properties of individual NGHP-01 wells and regional trends are discussed in detail. However, comparison of marine and permafrost-related Arctic reservoirs provides insight into the inter-relationships and common traits between physical properties and the morphology of gas-hydrate reservoirs regardless of location. Extrapolation of properties from one location to another also enhances our understanding of gas-hydrate reservoir systems. Grain size and porosity effects on permeability are critical, both locally to trap gas and regionally to provide fluid flow to hydrate reservoirs. Index properties corroborate more advanced consolidation and triaxial strength test results and can be used for predicting behavior in other NGHP-01 regions. Pseudo-overconsolidation is present near the seafloor and is underlain by underconsolidation at depth at some NGHP-01 locations.This work was supported by the Coastal and Marine Geology, and Energy Programs of the U.S. Geological Survey. Partial support for this research was provided by Interagency Agreement DE-FE0002911 between the USGS Gas Hydrates Project and the U.S. Department of Energy's Methane Hydrates R&D Program

Track D Social Science, Human Rights and Political Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

Phylogenomics and the rise of the angiosperms

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1,2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3,4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5,6,7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade

Effects of Environmental Lighting Conditions on Operating Speeds on Urban Arterials

Driver behavior is certainly influenced by the environmental lighting conditions on roads; in literature, many studies report the reduced night/day accident ratio following improvements to lighting on different types of roads, with the results classified by severity and type of accident. Few studies, however, report the influence of lighting conditions on driver speed. In this work the authors investigate the principal factors which influence driver speed on arterial roads in Turin (Italy). The aim of this study is to analyze, in particular, driver speed under different daylight and nighttime lighting conditions. Six arterial roads were selected for observation and the measurement of speeds and illuminance on the pavement surface. The results show that illuminance, in addition to other factors such as lane position, lane width and the relevant speed limit, should be considered a variable that can influence driver speed. In the paper, a regression equation for the prediction of operating speeds (V85) on urban arterials is presented: from a sensitivity analysis thereof, it has been possible to quantify the effects of the above mentioned variables on operating speed under different environmental lighting condition