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排序方式: 共有410条查询结果,搜索用时 15 毫秒
401.
Kaminski Abigail Bauer Dana Marie Bell Kathleen P. Loftin Cynthia S. Nelson Erik J. 《Landscape Ecology》2021,36(10):2937-2956
Landscape Ecology - Urban-rural gradients are useful tools when examining the influence of human disturbances on ecological, social and coupled systems, yet the most commonly used gradient... 相似文献
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Jennifer E. Horner James W. Castle John H. Rodgers Jr. Cynthia Murray Gulde James E. Myers 《Water, air, and soil pollution》2012,223(5):1945-1957
Pilot-scale constructed wetland treatment systems (CWTSs) were designed and built to decrease concentrations of constituents of concern in water simulated to match characteristics of water produced from specific oilfields in sub-Saharan Africa. The oilfield produced water has low ionic strength (704?C1,370?mg?L?1 total dissolved solids) and contains Fe, Mn, Ni, Zn, and oil and grease (O&G). To treat these constituents, biogeochemical pathways were targeted in the design of two subsurface flow (SSF) CWTS series planted with Phragmites australis and a free-water surface (FWS) series planted with Typha latifolia. These systems were designed for prevailing conditions at the sub-Saharan site studied. Concentrations of O&G, Fe, Mn, Ni, and Zn in outflow from the SSF series met use criteria for irrigation and livestock watering. For the FWS series, outflow concentrations of O&G, Fe, and Mn met use criteria for irrigation and livestock watering, and Ni concentrations met use criteria for livestock watering. Both SSF and FWS series were effective in reducing concentrations of O&G in the produced water investigated with >98% efficiency. The high-removal efficiency is attributed to achieving aerobic conditions in the wetland cells. Both SSF and FWS series reduced concentrations of Fe and Mn but with a wider range of efficiency compared with O&G removal. The removal of Ni and Zn could be increased by the addition of organic matter, such as plant detritus, to wetland cells to promote reducing conditions and dissimilatory sulfate reduction. 相似文献
406.
Kim HJ Graham DW DiSpirito AA Alterman MA Galeva N Larive CK Asunskis D Sherwood PM 《Science (New York, N.Y.)》2004,305(5690):1612-1615
Siderophores are extracellular iron-binding compounds that mediate iron transport into many cells. We present evidence of analogous molecules for copper transport from methane-oxidizing bacteria, represented here by a small fluorescent chromopeptide (C45N12O14H62Cu, 1216 daltons) produced by Methylosinus trichosporium OB3b. The crystal structure of this compound, methanobactin, was resolved to 1.15 angstroms. It is composed of a tetrapeptide, a tripeptide, and several unusual moieties, including two 4-thionyl-5-hydroxy-imidazole chromophores that coordinate the copper, a pyrrolidine that confers a bend in the overall chain, and an amino-terminal isopropylester group. The copper coordination environment includes a dual nitrogen- and sulfur-donating system derived from the thionyl imidazolate moieties. Structural elucidation of this molecule has broad implications in terms of organo-copper chemistry, biological methane oxidation, and global carbon cycling. 相似文献
407.
Dillin A Hsu AL Arantes-Oliveira N Lehrer-Graiwer J Hsin H Fraser AG Kamath RS Ahringer J Kenyon C 《Science (New York, N.Y.)》2002,298(5602):2398-2401
To explore the role of mitochondrial activity in the aging process, we have lowered the activity of the electron transport chain and adenosine 5'-triphosphate (ATP) synthase with RNA interference (RNAi) in Caenorhabditis elegans. These perturbations reduced body size and behavioral rates and extended adult life-span. Restoring messenger RNA to near-normal levels during adulthood did not elevate ATP levels and did not correct any of these phenotypes. Conversely, inhibiting respiratory-chain components during adulthood only did not reset behavioral rates and did not affect life-span. Thus, the developing animal appears to contain a regulatory system that monitors mitochondrial activity early in life and, in response, establishes rates of respiration, behavior, and aging that persist during adulthood. 相似文献
408.
Virginia B. Sinnott DVM Cynthia M. Otto DVM PhD DACVECC 《Journal of Veterinary Emergency and Critical Care》2009,19(5):484-488
Objective – To analyze thromboelastograms (TEGs) of naturally occurring cases of immune-mediated hemolytic anemia (IMHA) in order to identify whether a hypercoagulable state was present and whether its presence was associated with differences in survival.
Design – Retrospective study spanning January 2000 to June 2008. Medical records of dogs were evaluated. Endpoints were considered death or discharge from the hospital.
Setting – Academic teaching hospital.
Animals – Thirty-nine dogs with a diagnosis of IMHA and at least one TEG performed during hospitalization were included.
Interventions – None.
Measurements and Main Results – Four values were evaluated from the TEG: the R time (R), K time (K), alpha angle (α), and maximum amplitude. From these values, a coagulation index (CI) was calculated to classify patients as normocoagulable, hypercoagulable, or hypocoagulable. Thirty-three of 39 patients were hypercoagulable based on the CI. The 6 remaining dogs were normocoagulable. The patients with a normocoagulable CI had an increased mortality rate (100%) when compared with the hypercoagulable patients using Fisher's exact test ( P =0.02). Additionally, prolongation of partial thromboplastin time did not preclude hypercoagulable TEG values.
Conclusions – The majority of dogs with IMHA were hypercoagulable as measured by TEG. A normal CI was associated with a worse outcome in this patient population. TEG may provide additional and complementary information to prothrombin time and partial thromboplastin time relating to coagulation status in dogs with IMHA and may help predict prognosis and potentially guide clinical decisions to utilize anticoagulant drugs. 相似文献
Design – Retrospective study spanning January 2000 to June 2008. Medical records of dogs were evaluated. Endpoints were considered death or discharge from the hospital.
Setting – Academic teaching hospital.
Animals – Thirty-nine dogs with a diagnosis of IMHA and at least one TEG performed during hospitalization were included.
Interventions – None.
Measurements and Main Results – Four values were evaluated from the TEG: the R time (R), K time (K), alpha angle (α), and maximum amplitude. From these values, a coagulation index (CI) was calculated to classify patients as normocoagulable, hypercoagulable, or hypocoagulable. Thirty-three of 39 patients were hypercoagulable based on the CI. The 6 remaining dogs were normocoagulable. The patients with a normocoagulable CI had an increased mortality rate (100%) when compared with the hypercoagulable patients using Fisher's exact test ( P =0.02). Additionally, prolongation of partial thromboplastin time did not preclude hypercoagulable TEG values.
Conclusions – The majority of dogs with IMHA were hypercoagulable as measured by TEG. A normal CI was associated with a worse outcome in this patient population. TEG may provide additional and complementary information to prothrombin time and partial thromboplastin time relating to coagulation status in dogs with IMHA and may help predict prognosis and potentially guide clinical decisions to utilize anticoagulant drugs. 相似文献
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Paul M. Chittaro Jens C. Hegg Brian P. Kennedy Laurie A. Weitkamp Lyndal L. Johnson Cynthia Bucher Richard W. Zabel 《Ecology of Freshwater Fish》2019,28(3):396-410
An animal's performance during its early life stage can greatly influence its survival to adulthood. Therefore, understanding aspects of early life history can be informative, particularly when designing management plans to rebuild a population. For a threatened population of fall Chinook salmon (Oncorhynchus tshawytscha) in the Snake River of Idaho, we reconstructed the early life history for 124 returning wild and hatchery adults using information recorded in their otoliths. Of our sampled wild adults (n = 61), 43% and 49% reared within the Snake River and Clearwater/Salmon rivers. We also found that only 21% of our sampled wild adults exhibited the historically common subyearling out‐migration strategy, in which juveniles exit freshwater shortly after hatching, while the remaining wild adults exhibited the yearling out‐migration strategy (i.e., individuals delay their freshwater exit). As expected, yearlings had, on average, a significantly larger body size than subyearlings at ocean entry. However, 35% of wild yearlings overlapped in size with wild subyearlings suggesting that spending more time in freshwater might not necessarily result in a larger body size. Lastly, we observed that variability in fork length at Snake River egress and ocean entry were best explained by migration strategy and where it reared, followed by hatch year and sex. Results from this study highlight the utility of adult otoliths in providing details about early life history, an understanding of which is critical to the conservation of Snake River fall Chinook salmon. 相似文献