Fatty-acids and their C-13 signatures in seep carbonates from hydrocarbon seeps on the upper (GC 185) and lower (AC 645) continental slope of the Gulf of Mexico

Here we reported the fatty-acids and their δ 13C values in seep carbonates collected from Green Canyon lease block 185 (GC 185; Sample GC-F) at upper continental slope (water depth: ∼540 m), and Alaminos Canyon lease block 645 (GC 645; Sample AC-E) at lower continental slope (water depth: ∼2200 m) of the Gulf of Mexico. More than thirty kinds of fatty acids were detected in both samples. These fatty acids are maximized at C16. There is a clear even-over-odd carbon number predominance in carbon number range. The fatty acids are mainly composed of n-fatty acids, iso-/anteiso-fatty acids and terminally branched odd-numbered fatty acids (iso/anteiso). The low δ 13C values (−39.99‰ to.32.36‰) of n-C12:0, n-C13:0, i-C14:0and n-C14:0 suggest that they may relate to the chemosynthetic communities at seep sites. The unsaturated fatty acids n-C18:2 and C18:1Δ9 have the same δ 13C values, they may originate from theBeggiatoa/Thioploca. Unlike other fatty acids, the terminally branched fatty acids (iso/anteiso) show lowerδ 13C values (as low as −63.95‰) suggesting a possible relationship to sulfate reducing bacteria, which is common during anaerobic oxidation of methane at seep sites.

Propulsion characteristics of wing-in-ground effect dual-foil propulsors

Propulsion characteristics of wing-in-ground effect propulsors were investigated using a comparative analysis of thrust and powering characteristics between wing-in-ground (WIG) effect thrusters and traditional screw propellers. WIG thrusters were found to have constant thrust production and efficiency, nearly independent of speed of advance, as contrary to screw propellers, whose optimum efficiency occurs at only one speed point. To produce the same amount of thrust as equivalent screw propellers, WIG thrusters have to work under heavily loaded operating conditions. WIG thrusters were also found to produce a relatively lower but nearly constant efficiency and thrust, independent of speed. Another distinguishing propulsion characteristic revealed for WIG thrusters is that they are capable of operating at much higher speeds, in a range of three to six times that of screw propellers of the same size. While the speed range of screw propellers is mainly limited by their geometric pitch, the speed range of WIG thrusters has no speed limit in ideal fluid. In reality, the speed range is only limited by viscous drag and cavitation, or compressibility, in water or air, respectively. This suggests a potential for WIG thrusters of higher speed application than screw propellers. An experimental investigation and validation of the propulsion system is warranted. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

Spatial variability in water quality and surface sediment diatom assemblages in a complex lake basin,lake of the woods,ontario,canada

Lake of the Woods (LOW) is an international waterbody spanning the Canadian provinces of Ontario and Manitoba, and the U.S. state of Minnesota. In recent years, there has been a perception that water quality has deteriorated in northern regions of the lake, with all increase in the frequency and intensity of toxin-producing cyanobacterial blooms. However, given the lack of long-term data these trends are difficult to verify. As a first step, we examine spatial and seasonal patterns in water quality in this highly complex lake on the Canadian Shield. Further, we examine surface sediment diatom assemblages across multiple sites to determine if they track within-take differences in environmental conditions. Our results show that there are significant spatial patterns in water quality in LOW. Principal Component Analysis divides the lake into three geographic zones based primarily on algal nutrients (i.e., total phosphorus, TP), with the highest concentrations at sites proximal to Rainy River. This variation is closely tracked by sedimentary diatom assemblages, with [TP] explaining 43% of the variation in diatom assemblages across sites. The close correlation between water quality and the surface sediment diatom record indicate that paleoecological models could be used to provide data on the relative importance of natural and anthropogenic sources of nutrients to the lake.

Relationship between precipitation and the infiltration depth over the middle and lower reaches of the Yellow River and Yangtze-Huaihe River Valley

National Natural Science Foundation of China [40701021, 40625002, 40331013]; National Knowledge Innovation Program of Chinese Academy of Sciences [KZCX2-YW-315-2]